Co-reporter:Lifu Xu, Teng Han, Jiang Li, Ying Xiong, Shaoyun Guo
Composites Science and Technology 2017 Volume 145(Volume 145) pp:
Publication Date(Web):16 June 2017
DOI:10.1016/j.compscitech.2017.03.037
The lightweight flexible poly(vinyl chloride) (PVC)/mica composite foams with low density (0.51 g/cm3) which is 40–60% reduction and high sound insulation performance (an average STL of 28.3 dB) were prepared in this work. And the influences of mica content and foaming time on the cell morphology, mica distribution, and sound transmission loss (STL) were investigated. It was observed that the PVC/mica foams not only showed good sound insulation properties, but also maintained ultra-light in weight when the mica content was below 10 wt%. In addition, as the foaming time became longer, the cell density increased and the cell-wall thickness decreased. As a result, the bi-axial stretching induced by the cell growth would drive the mica platelets to orient along the thin cell walls, which significantly increased the sound insulation properties. Simultaneously, the flexibility and reusability of the foams were tested by cyclic compression. When the mica content was below 10 wt%, the PVC/mica composite foams showed low compressive stress and low permanent strain.
Co-reporter:Yu Zheng, Renqiong Dong, Jiabin Shen, and Shaoyun Guo
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 2) pp:1371
Publication Date(Web):December 29, 2015
DOI:10.1021/acsami.5b10246
Shape memory materials containing alternating layers of thermoplastic polyurethane (TPU) and polycaprolactone (PCL) were fabricated through layer-multiplying extrusion. As a type of special co-continuous morphology, the multilayer structure had stable and well-defined continuous layer spaces and could be controlled by changing the number of layers. Compared with conventional polymer blends, the multilayer-assembled system with the same compositions had higher shape-fixing and -recovery ratios that could be further improved by increasing the number of layers. By analyzing from a viscoelastic model, the deformation energy preserved in elastic TPU layers would be balanced by adjacent PCL layers through interfacial shearing effect so that each component in the multilayer structure was capable of endowing the maximum contribution to both of the shape-fixing and -recovery stages. Besides, the influence of the hardness of TPU layers and the morphology of PCL layers were respectively concerned as well. Results revealed that choosing low-hardness TPU or replacing neat PCL layers by TPU/PCL blend with co-continuous morphology were beneficial to achieving outstanding shape memory performances.Keywords: co-continuous; interface; multilayer structure; polycaprolactone; polyurethane; shape memory polymer
Co-reporter:Lichao Xia, Min Wang, Hong Wu, Shaoyun Guo
International Journal of Hydrogen Energy 2016 Volume 41(Issue 4) pp:2887-2895
Publication Date(Web):30 January 2016
DOI:10.1016/j.ijhydene.2015.12.043
•FKM gaskets with different ingredients are chemical aged in simulated PEMFC solution.•Effects of cure system and filler on chemical aging behavior are investigated.•FKM recipe that shows good chemical stability is optimized.•The insert filler BaSO4 reduces the blister but deteriorates the chemical stability of the gaskets.The chemical aging behavior of gaskets especially the chemical stability is crucial to the overall performance of PEMFC stack. The chemical stability of gaskets not only depends on the polymer but also heavily depends on the other ingredients. In this paper, we have studied the properties of fluoroelastomer with different amount of the cure agent, acid-acceptor and filler in the simulated PEMFC environment. The weight and volume change of samples was monitored. The surface conditions of the virgin and aged samples were observed using optical microscopy. Leachants in the soaking solution were detected using atomic emission spectrometry. ATR-FTIR was employed to determine the chemical change of samples. These results show that FKM cured with bisphenol system has the best comprehensive properties when the amount of bisphenol AF is set as 2.5 phr and the amount of Ca(OH)2 is 6 phr. The inert filler BaSO4 is not suitable for FKM because it has inferior effect on the compression resistance and chemical stability of FKM in this system.
Co-reporter:Guansong He, Fengshun Zhang, Huaning Yu, Jiang Li and Shaoyun Guo
RSC Advances 2016 vol. 6(Issue 16) pp:12744-12752
Publication Date(Web):22 Jan 2016
DOI:10.1039/C5RA23333J
This paper presents the studies of the puncture resistances of conventional blend and multilayered structure sheets. The polypropylene homopolymer (HPP)/ethylene 1-octene copolymer (POE) alternating multilayered sheets were prepared though multilayered coextrusion. Polarized optical microscope (POM) photographs revealed that HPP and POE layers aligned alternately vertical to the interfaces and continuously parallel to the extrusion direction, indicating a better laminate structure. Puncture results demonstrated the conventional blend was less puncture-resistant than the multilayered samples. Obvious interfacial delamination occurred in the multilayered structure during crack propagation, causing the puncture behavior to develop into a staged rupture behavior. Hence the puncture resistance was enhanced by the special energy absorbing mechanisms including the plastic deforming independently, interfacial delamination and ductile tearing of the layers.
Co-reporter:Xiao Liu;Xianming Dong;Ying Xiong;Ping Yi;Yikun Ren
Journal of Applied Polymer Science 2016 Volume 133( Issue 43) pp:
Publication Date(Web):
DOI:10.1002/app.44156
ABSTRACT
Traditionally, the morphologies of the dispersed phase in Polycarbonate (PC)/poly(styrene-co-acrylonitrile) (SAN) blends were strongly influenced if AN content in SAN changed significantly even under constant processing conditions. This would hinder the pure research intended to study the effect of the refractive index difference between the polymer host and the polymeric dispersed particles on the optical properties tough. Therefore, we respectively prepared different PC/SAN light diffusion sheets with four types of SAN containing different AN content ranging just from 20 to 25 wt %, a narrow range that sufficiently ensures the relatively stable morphology of different SAN in PC matrix. The results suggest that the refractive index of SAN increases with an decreasing AN content, thus narrowing the refractive index difference between PC and SAN and producing PC/SAN(70/30) light diffusion sheets with an increasing transmittance and decreasing haze. The interesting phenomenon is further analyzed using Mie scattering theory. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44156.
Co-reporter:Shanshan Luo;Ping Yi;Ying Xiong;Jiabin Shen
Journal of Applied Polymer Science 2016 Volume 133( Issue 34) pp:
Publication Date(Web):
DOI:10.1002/app.42844
ABSTRACT
Light-scattering materials were fabricated by the melt blending of polypropylene with an ethylene–vinyl acetate copolymer (EVA) to prevent the glare effect of light-emitting diodes. The results show that the light-scattering capacity was remarkably dependent on the phase morphologies of EVA. (1) When EVA was dispersed as spherical droplets, the transmittance and haze gradually increased with the enrichment of EVA, and the half-peak width of the light-scattering pattern reached a maximum when 30 wt % EVA was loaded. On the basis of the analysis of Mie scattering theory, the enlargement of scattering particles promoted light transmittance, and more incoming light was deflected at the arclike interfaces. This induced a distinct antiglare effect. (2) When scattering particles deformed and expanded vertically in the light-transmitting direction, the light-scattering capacity turned out to be weakened by further enrichment of the EVA phase. The planelike interfaces reduced the deflection of incoming light, and this led to decreases in the scattering angles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42844.
Co-reporter:Lichao Xia, Hong Wu, Shaoyun Guo, Xiaojie Sun, Wenbin Liang
Composites Part A: Applied Science and Manufacturing 2016 Volume 81() pp:225-233
Publication Date(Web):February 2016
DOI:10.1016/j.compositesa.2015.11.023
In this work, the composites with multilayered distribution of the mica were fabricated by a multilayer coextrusion technique. The influence of layer number on sound insulation and mechanical properties of multilayered composites was investigated. The distribution, dispersion and orientation of mica particulates in composites were characterized by PLM and SEM. The sound insulation property of composites was measured by four microphone impedance tube. PLM and SEM images showed that the mica was distributed as the multilayered structure along the thickness direction of the composites. With the increase of layer number, more mica aggregates delaminated into thin flakes and aligned parallel to the flow direction. Compared to the conventional composites, the multilayered composites showed the enhanced sound insulation efficiency and mechanical properties. The discontinuity of sound impedance and the improved stiffness were considered to play a crucial role in the improvement of sound transmission loss.
Co-reporter:Rong Chen, Haibo Qu, Shaoyun Guo and Paul Ducheyne
Journal of Materials Chemistry A 2015 vol. 3(Issue 16) pp:3141-3149
Publication Date(Web):04 Mar 2015
DOI:10.1039/C4TB01622J
Conventional silica xerogels prepared through sol–gel processing are regarded as suitable materials for the long-term release of proteins due to the mild processing conditions. However, they fall short of short-time release of these large molecules because of their small pore size and a slow dissolution rate. With the goal of achieving controlled release of large molecules (such as proteins) in a very short time (several days), herein we focus on the co-hydrolysis and co-condensation of different precursors to synthesize composite xerogels (co-xerogels) with adjustable degradation rates. Tetraethoxysilane and 3-(triethoxysilyl) propylsuccinic anhydride were employed to prepare the co-xerogels. Succinic anhydride was chosen due to its potential to crosslink with Si–OH and to integrate into the silica network under acidic conditions. Using the trypsin inhibitor (TI) as a model drug to characterize the release properties of co-xerogels, we obtained tailored release behavior of TI (2–7 days). It is demonstrated that the co-hydrolysis and co-condensation of different precursors is an easy technique that further expands the applicability of sol–gel materials as excellent carriers for the controlled release of a variety of drugs.
Co-reporter:Wanli Gao, Yu Zheng, Jiabin Shen, and Shaoyun Guo
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 3) pp:1541
Publication Date(Web):December 30, 2014
DOI:10.1021/am506773c
Materials consisting of alternating layers of pure polypropylene (PP) and carbon black filled polypropylene (PPCB) were fabricated in this work. The electrical behaviors of the multilayered composites were investigated from two directions: (1) Parallel to interfaces. The confined layer space allowed for a more compact connection between CB particles, while the conductive pathways tended to be broken up with increasing number of layers leading to a distinct enhancement of the electrical resistivity due to the separation of insulated PP layers. (2) Vertical to interfaces. The alternating assemblies of insulated and conductive layers like a parallel-plate capacitor made the electrical conductivity become frequency dependent. Following the layer multiplication process, the dielectric permittivity was significantly enhanced due to the accumulation of electrical charges at interfaces. Thus, as a microwave was incident on the dielectric medium, the interfacial polarization made the main contribution to inherent dissipation of microwave energy, so that the absorbing peak became strengthened when the material had more layers. Furthermore, the layer interfaces in the multilayered system were also effective to inhibit the propagation of cracks in the stretching process, leading to a larger elongation at the break than that of the PP/CB conventional system, which provided a potential route to fabricate electrical materials with optimal mechanical properties.Keywords: conductive polymer composites; electrical properties; interface; microwave absorption; multilayered structure
Co-reporter:Jiaming Zhu, Jiabin Shen, Shaoyun Guo, Hung-Jue Sue
Carbon 2015 Volume 84() pp:355-364
Publication Date(Web):April 2015
DOI:10.1016/j.carbon.2014.12.031
Polyvinylidene fluoride (PVDF)-based multilayered dielectrics containing alternating layers of confined carbon black (CB) were fabricated using a layer-multiplying extrusion. For a given film thickness, a large enhancement of dielectric permittivity occurred following the increase of CB containing layers. When the number of total layers reached 256, the permittivity at 103 Hz became 3 times higher than that predicted by the series model. A frequency dependence in the dielectric loss curves caused by the layer multiplication process was also observed. The differences in capacitance and conductivity between neat PVDF and CB containing layers resulted in charge accumulation at their interfaces, leading to an increase in the permittivity and the dielectric loss peak intensity. Furthermore, the presence of PVDF between the CB containing layers distinctly improved the breakdown strength of the multilayered films by at least two orders of magnitude higher than that of the PVDF/CB conventional composite at a similar CB loading or conductivity level. The present approach for the preparation of high-k dielectrics with high breakdown strength would significantly broaden the choices of dielectric materials for pulse powered, high field electronics and a new generation of clean energy applications.
Co-reporter:Kangming Xu, Fengshun Zhang, Xianlong Zhang, Jiwei Guo, Hong Wu and Shaoyun Guo
RSC Advances 2015 vol. 5(Issue 6) pp:4200-4209
Publication Date(Web):28 Nov 2014
DOI:10.1039/C4RA06644H
The fundamental mechanism of the improved damping properties of poly(vinyl acetate) (PVAc), contributed by the introduction of hindered phenols, was systematically elucidated by two-dimensional infrared (2D IR) spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimeter (DSC), X-ray diffraction (XRD) and molecular dynamics (MD) simulation. The 2D IR results revealed the evolution of hydrogen bonds (H-bonds) from intermolecular H-bonds to H-bond networks of PVAc/hindered phenols. Note that subsequent DMA results revealed that the damping properties of PVAc exhibited two different degrees of improvement due to the addition of hindered phenol. Moreover, DSC results showed that all hybrids were miscible, as concentration fluctuations changed irregularly. In accordance with the XRD observation of only amorphous hindered phenols existing in the PVAc matrix, further MD simulation, based on an amorphous cell, characterized the number of H-bonds, the binding energy and the fractional free volume (FFV) of the hybrids. It was observed that the variation tendency of the simulation data was in accordance with the experimental results. Therefore, the damping mechanism of PVAc/hindered phenol hybrids was proposed through a detailed analysis on the synergistic effect of the number of intermolecular H-bonds and the binding energy between PVAc and the hindered phenol, as well as the FFV or dynamic heterogeneity.
Co-reporter:Jiaming Zhu, Shanshan Luo, Bo Cao, Jiabin Shen and Shaoyun Guo
RSC Advances 2015 vol. 5(Issue 81) pp:65927-65931
Publication Date(Web):28 Jul 2015
DOI:10.1039/C5RA11596E
Polyvinylidene fluoride (PVDF)-based multilayer dielectrics containing alternating layers of carbon black (CB) were fabricated through layer-multiplying extrusion. Benefits from the presence of PVDF between CB-containing layers, the breakdown strength and hysteresis behaviors of the multilayer specimens were investigated. The multilayered distribution of conductive particles was considered to be preferred for controlling the energy conversion and storage of dielectric materials.
Co-reporter:Fengshun Zhang;Guansong He;Kangming Xu;Hong Wu
Journal of Applied Polymer Science 2015 Volume 132( Issue 2) pp:
Publication Date(Web):
DOI:10.1002/app.41259
ABSTRACT
The alternating multilayered damping composites, which were consisted of chlorinated butyl rubber (CIIR) layers and poly(vinyl chloride) (PVC) layers, were first prepared through multilayered coextrusion technology. The multilayered structure was controlled by adjusting the layer number or the thickness ratio of CIIR layer and PVC layer. The damping and flame-retardant properties of the CIIR/PVC multilayered damping composites were investigated by dynamic mechanical analysis, the limiting oxygen index, and thermogravimetric analyzer, respectively. The results showed that the effective damping temperature range was broadened with increasing the layer number, since multilayered structure resulted in partial overlap of the loss peaks of CIIR and PVC. Meanwhile, the flame-retardant properties of the multilayered composites were also enhanced with increasing the layer number. Less surface area of CIIR contacting oxygen in the confined burning space, rather than the formation of char residue, could effectively retard the combustion of the material. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41259.
Co-reporter:Huijun Su;Juan Xue;Peiling Cai;Jiang Li
Journal of Applied Polymer Science 2015 Volume 132( Issue 27) pp:
Publication Date(Web):
DOI:10.1002/app.42211
ABSTRACT
Ethylene–vinyl alcohol copolymer (EVOH) and linear low-density polyethylene (LLDPE) blends with 5% LLDPE grafted with 1% maleic anhydride (MAH; EVOH/LLDPE/LLDPE-g-MAH), created to increase the interfacial compatibility, were coextruded with pure LLDPE through the microlayer coextrusion technology. The phase morphology and gas-barrier properties of the alternating-layered (EVOH/LLDPE/LLDPE-g-MAH)/LLDPE composites were studied by scanning electron microscopy observation and oxygen permeation coefficient measurement. The experimental results show that the EVOH/LLDPE/LLDPE-g-MAH and LLDPE layers were parallel to each other, and the continuity of each layer was clearly evident. This structure greatly decreased the oxygen permeability coefficient compared to the pure LLDPE and the barrier percolation threshold because of the existence of the LLDPE/EVOH/LLDPE-g-MAH blend layers, and the LLDPE layers diluted the concentration of EVOH in the whole composites. In addition, the effects of the layer thickness ratio of the EVOH/LLDPE/LLDPE-g-MAH and LLDPE layers and the layer number on the barrier properties of the layered composites were investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42211.
Co-reporter:Ming Wang;Jiabin Shen;Jiang Li
Polymer International 2015 Volume 64( Issue 1) pp:105-112
Publication Date(Web):
DOI:10.1002/pi.4762
Abstract
Three semicrystalline polymers with different molecular structure and crystallinity were investigated to analyze the Mullins effect therein. The polymers exhibited time-dependent stress resistance and stress softening. Recoverable network alteration in both crystalline and amorphous domains was proposed to explain the cyclic loading deformation and relaxation. The crystallites and the entanglements acted as the joints in the network where stress was transferred. The maximum stress first rapidly decreased and the balance stress was reached after ca 50 cycles. The balance stress was higher than the quasi-static stress obtained by normal stress relaxation. However, the balance stress could be eliminated by the following stress relaxation and the residual stress was very close to the quasi-static stress. The different network strength between the strain before and after yielding is also discussed by comparing the balance stress and the quasi-static stress. The stress resistance of the network before yielding was stronger than that after yielding mainly due to crystallite slip. © 2014 Society of Chemical Industry
Co-reporter:Xian-long Zhang;Hong Wu 吴宏;Shao-yun Guo 郭少云
Chinese Journal of Polymer Science 2015 Volume 33( Issue 7) pp:988-999
Publication Date(Web):2015 July
DOI:10.1007/s10118-015-1645-8
The molecular structure of SEBS grafted with maleic anhydride (SEBS-g-MAH) through ultrasound initiation was investigated by nuclear magnetic resonance (NMR). It can be confirmed that the grafting groups mainly exist on the terminus of the ultrasound initiated SEBS-g-MAH. However, it was difficult to detailedly confirm the block of the SEBS on which MAH is grafted through characterization of 1H-NMR due to the complex structure of the SEBS. Moreover, the temperature-dependent infrared spectra of the ultrasound initiated SEBS-g-MAH were also analyzed by the perturbation correlation moving window 2D (PCMW2D) correlation spectroscopy. It could confirm that the broken point existed at the joint between poly(ethylene-co-1-butene) (EB block) and polystyrene block (S block). Therefore, the grafting groups were attached to not only the S block but also the EB block. In addition, in order to well understand the aggregation structure of the ultrasound initiated SEBS-g-MAH, the possible grafting mechanism and aggregation model of the ultrasound initiated SEBS-g-MAH at room temperature were also proposed.
Co-reporter:Kangming Xu, Fengshun Zhang, Xianlong Zhang, Qiaoman Hu, Hong Wu and Shaoyun Guo
Journal of Materials Chemistry A 2014 vol. 2(Issue 22) pp:8545-8556
Publication Date(Web):06 Mar 2014
DOI:10.1039/C4TA00476K
In this study, a polyurethane/hindered phenol system was prepared as a melt in order to study the yet unclear mechanism of the formation of hydrogen bonds (H-bonds) in analogous systems. The evolution of intermolecular H-bonds between ester carbonyl/phenolic hydroxyl groups and urethane carbonyl/phenolic hydroxyl groups was detected, for the first time, by infrared analysis. Subsequent dynamic mechanical analysis combined with thermal analysis showed the fluctuation of the glass transition temperatures and the damping properties of the hybrids. From X-ray diffraction analysis the existence was observed of only amorphous hindered phenol in the polyurethane, further molecular dynamic simulation, based on an amorphous cell, characterized the number of H-bonds, the H-bond predominant binding energy and the fractional free volume in a quantitative manner. It was observed that the variation of the simulation data was in accordance with the fluctuation change of the damping properties, thus a relationship was established between the evolution of the H-bonds and the damping properties.
Co-reporter:Fengshun Zhang, Guansong He, Kangming Xu, Hong Wu and Shaoyun Guo
RSC Advances 2014 vol. 4(Issue 40) pp:20620-20625
Publication Date(Web):24 Apr 2014
DOI:10.1039/C4RA00976B
The relaxation behavior and different modes of molecular motion in the miscible blends of asymmetric chlorinated butyl rubber (CIIR) and petroleum resin (PR) were investigated by dynamic mechanical spectroscopy (DMS) and dielectric spectroscopy (DS). The different modes of CIIR molecular motion, attributed to local segmental motion, sub-Rouse modes and Rouse mode relaxation, have been detected from both of the DMS and DS results, and the relaxation times of local segmental motion and Rouse modes could be fitted by the Vogel–Fulcher–Tammann equation. Due to the increased activation energy with increasing PR content, local segmental motion of CIIR is slightly confined, however, Rouse modes of CIIR, which contain more backbone bonds and need a larger free volume than the local segmental motion, are greatly confined. As a result, the relaxation temperature of local segmental motion moves slightly to high temperature but that of Rouse modes moves to high temperature more significantly.
Co-reporter:Jiabin Shen, Baoshu Chen, Jiaming Zhu, Shaoyun Guo, Yuzhong Wang
Polymer Degradation and Stability 2014 Volume 102() pp:74-80
Publication Date(Web):April 2014
DOI:10.1016/j.polymdegradstab.2014.02.006
Polycarbonate (PC)/phosphorus-containing thermotropic liquid crystalline copolyester (PHDDT) composites were prepared through a novel multistage stretching extrusion. The morphology of the PHDDT phase was controlled by combining an assembly of force-assembling elements (FAEs) with an extruder. SEM observation revealed that morphological evolution of PHDDT from platelets to microfibrils occurred by applying different number of FAEs. The dynamic rheological and thermogravimetric results showed that the increased interfacial area between PHDDT and PC led to a drastic reduction of the complex viscosity and a lower temperature of the maximum loss. Accompanied with the elongation of the PHDDT along flowing direction, the storage modulus and glass transition temperature of the composite were enhanced. However, compared with the system dispersed with the platelet-like phase, the micro-fibrillation of the flame-retarding PHDDT resulted in the decrease of the temperature of the heat release rate curve starting to rise up and the value of the limiting oxygen index. The confined space formed between the platelet-like PHDDT phase was considered to effectively retard the combustion of the whole material.
Co-reporter:Guansong He;Fengshun Zhang;Liang Huang;Jiang Li
Journal of Applied Polymer Science 2014 Volume 131( Issue 15) pp:
Publication Date(Web):
DOI:10.1002/app.40574
ABSTRACT
As one of the most appropriate techniques for evaluating the fracture behavior, the essential work of fracture (EWF) was introduced to investigate the fracture toughness of multilayered composites. Propylene–ethylene copolymer (CPP)/polypropylene homopolymer (HPP) alternating multilayered composites with 2–128 layers were prepared though multilayered coextrusion. Polarized optical microscopy photographs revealed that the CPP and HPP layers aligned alternately vertical to the interfaces and continuously parallel to the extrusion direction. The dichroic Fourier transform infrared spectroscopy results showed that the coextrusion sheet had a preferential orientation parallel to the melt flow direction (MD); this caused crack propagation along the blunted MD and the necking ligament section. After heat treatment, the orientation parallel to the MD could been largely eliminated, and the crack propagated in a stable manner. The specific essential work of fracture (we) of the multilayered composite was higher than that of the blend; this indicated a higher resistance of crack propagation. The number of layers had little effect on the toughness of the multilayered composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40574.
Co-reporter:Jianfeng Wang;Xianlong Zhang;Tianbao Zhao;Liyuan Shen;Hong Wu
Journal of Applied Polymer Science 2014 Volume 131( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/app.40108
ABSTRACT
The sheets of polycarbonate (PC)/polyethylene (PE) in situ microfibrillar composites are successfully prepared directly through multistage stretching extrusion with an assembly of laminating-multiplying elements (LMEs) instead of the secondary processing. The morphological development of the PC dispersed phase in PE matrix with increasing the number of LMEs during multistage stretching extrusion investigated by scanning electron microscope shows that core-skin structure of the microfibrillar PC/PE composites during multistage stretching extrusion with 4 LMEs is weakened, and the diameter of the PC microfibrils is relatively more uniform, indicating that the shear field in LMEs greatly affects the morphology of PC dispersed phase in PE matrix. The tensile, crystalline, melting, orientation and rheological behavior of the PC/PE microfibrillar composites are also investigated. The results show that the PC microfibrils are helpful to increase complex viscosity and yield stress of the PE/PC composites. In addition, it is found that the glass transition temperature of PC in PE matrix reduced with increasing the number of LMEs during dynamic rheological testing. It is coincided with the results of DSC analysis of the PC/PE composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40108.
Co-reporter:Jiaming Zhu;Jiabin Shen
Journal of Applied Polymer Science 2014 Volume 131( Issue 9) pp:
Publication Date(Web):
DOI:10.1002/app.40221
ABSTRACT
The morphological evolution of ethylene–vinyl alcohol copolymer (EVOH) and its effect on the gas-barrier properties of high-density polyethylene (HDPE) were investigated. HDPE/EVOH blends were prepared through a multistage stretching extrusion, which combined an assembly of force-assembling elements (FAEs) with an extruder. Scanning electron microscopy confirmed that with an increasing number of FAEs, the biaxial-stretching field existing in each FAE transformed the dispersed EVOH phase into well-defined platelets along the flowing plane. Dynamic rheological results further revealed that the formation of the platelets enlarged the interfaces between the dispersed barrier phase and the matrix; this not only led to the decline of the complex viscosity but also created more tortuous paths for the diffusion of gas molecules. Compared with that of the non-FAE specimen blended with 25 wt % EVOH, the oxygen permeability coefficient decreased more than one order of magnitude when one FAE was applied. The structural model for permeability indicated that the enhanced barrier resulted from the increased tortuosity of the diffusion pathway, which was provided by the aligned high-aspect-ratio platelets. Compared with the previous biaxial-stretching method, multistage stretching extrusion provided a simple and economical way to generate a laminar structure of the dispersed phase in the matrix phase without the application of an external stretching force. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40221.
Co-reporter:Wanli Gao;Jiabin Shen
Polymer Engineering & Science 2014 Volume 54( Issue 6) pp:1471-1476
Publication Date(Web):
DOI:10.1002/pen.23663
Composite materials consisting of alternating layers of carbon black/polypropylene (PPCB) and polypropylene (PP) were fabricated by layer-multiplying coextrusion. A negative effect of the layer-multiplying process on the conducting percolation of CB in PPCB layers was revealed by electrical resistivity measurements. When polyamide 6 (PA6) was introduced into pure PP layers, the resistivity was less than that of a system without the nylon phase. Morphological and crystalline examinations demonstrated that with increasing the number of layers, PA6 was elongated along the extrusion direction and adhered to by some CB particles. This was considered to be beneficial for the formation of new conducting pathways that compensated for the negative effect of the layer-multiplying process on conductivity. POLYM. ENG. SCI., 54:1471–1476, 2014. © 2013 Society of Plastics Engineers
Co-reporter:Feng Qiu, Ming Wang, Yongbo Hao, Shaoyun Guo
Composites Part A: Applied Science and Manufacturing 2014 Volume 58() pp:7-15
Publication Date(Web):March 2014
DOI:10.1016/j.compositesa.2013.11.011
The isotactic polypropylene/talc composites with talc stratified distribution were prepared by a multilayered co-extrusion technology. The talc orientation in polypropylene matrix was studied by scanning electronic microscopy and polarized light microscopy. The crystallization behavior of the composites was investigated by differential scanning calorimeter and polarized light microscopy. The mechanical properties and thermal stability of the composites were compared with the conventional blends by tensile machine and thermogravimetric analyzer, respectively. The composites with talc stratified distribution exhibited better mechanical properties and thermal stability than that of the conventional blends, which were related to the transcrystals in the unfilled polypropylene layers and the high orientation of talc particles in the filled polypropylene layers.
Co-reporter:Guansong He, Jiang Li, Fengshun Zhang, Fan Lei, Shaoyun Guo
Polymer 2014 Volume 55(Issue 6) pp:1583-1592
Publication Date(Web):24 March 2014
DOI:10.1016/j.polymer.2014.01.039
The multilayered propylene–ethylene copolymer (CPP)/low density polyethylene (LDPE) composite sheets were prepared by the microlayered coextrusion system. The essential work of fracture (EWF) method was firstly used to quantitatively evaluate the fracture behavior of layered materials. The experimental results indicated that the two-dimensional layered interfaces in the multilayered materials could play an important role in the fracture behavior. The specific essential work of fracture, we, increased with the layers due to interfacial delamination. Additionally, the different testing speeds had a dual effect on the increscent trend of the specific essential work of fracture, we, with increasing layers.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Fan Lei;Shuo Yang;Mingtao Yang;Jiang Li
Polymer Bulletin 2014 Volume 71( Issue 12) pp:3261-3273
Publication Date(Web):2014 December
DOI:10.1007/s00289-014-1254-7
Polypropylene (PP)/organic montmorillonite (OMMT) nanocomposites were first prepared through twin-screw extruder and then subjected to multistage stretching extrusion with an assembly of laminating-multiplying elements (LMEs, which divide and recombine polymer melts). The exfoliated efficiency of LMEs on OMMT dispersed in PP matrix was investigated by optical microscopy, scanning electron microscope, transmission electron microscopy and X-ray diffraction. Because of the absence of compatibilizer, molecular chains of PP were not intercalated into the galleries of OMMT during the multistage stretching extrusion. The exfoliation of OMMT was induced by the strong force occurred in LMEs, which can destruct van der Waal’s interaction between the laminate OMMT platelets. The exfoliation degree of OMMT has been improved with the increase of number of LMEs used. The dispersion morphology of OMMT was thermodynamically stable after secondary melt processing. As a result, the mechanical properties of composites have been enhanced with increasing LME number. We realized the exfoliation of OMMT by the function of strong shear field without the incorporation of compatibilizer.
Co-reporter:Rong Chen;Haibo Qu;Ashwin Agrawal
Journal of Materials Science: Materials in Medicine 2013 Volume 24( Issue 1) pp:137-146
Publication Date(Web):2013 January
DOI:10.1007/s10856-012-4783-3
Conventional sol–gel processing requires several distinct steps involving hydrolysis, condensation and drying to obtain a highly porous, glassy solid material. With the goal of achieving controlled release of small molecules, herein we focus on the acceleration of the condensation and drying steps by casting the hydrolyzed sol on a large open surface to achieve a denser 100 % silica xerogel structure. Thus, cast xerogel with a more limited porosity was prepared. The effect of synthesis parameters during sol–gel synthesis on the release kinetics of bupivacaine, vancomycin and cephalexin was investigated. The release kinetics fitted well with the Higuchi model, suggesting a diffusional release mechanism. Combining the release and nanostructure data, the formation mechanism of cast xerogel is described. Without introducing additional precursors or additives into sol–gel systems, sol–gel casting is an easy technique that further expands the applicability of sol–gel materials as excellent carriers for the controlled release of a variety of drugs.
Co-reporter:Ming Wang;Jiabin Shen;Jiang Li
Rheologica Acta 2013 Volume 52( Issue 10-12) pp:963-972
Publication Date(Web):2013 November
DOI:10.1007/s00397-013-0725-3
The interfacial slip of the immiscible isotactic polypropylene/polystyrene (PS) blends with different morphologies was studied. The morphologies were obtained by choosing different PS contents (7, 21, and 55 vol%) and different processing methods (multilayered co-extrusion and conventional blending). The interfacial slip was obviously found in the multilayered morphology and the co-continuous morphology, but did not occur in the sea-island morphology. Besides, it was observed that the slip velocity of the multilayered system was higher than that of the conventional blends with co-continuous morphology and could be promoted with the increase of layer numbers. However, the interfacial slip in the multilayered system would be suppressed by the layer deformation and breaking during the test, when the thickness of layers was thin enough. The effect of composition on the interfacial slip velocity was also discussed in the multilayered composites.
Co-reporter:Jiabin Shen, Michel F. Champagne, Richard Gendron, Shaoyun Guo
European Polymer Journal 2012 Volume 48(Issue 5) pp:930-939
Publication Date(Web):May 2012
DOI:10.1016/j.eurpolymj.2012.03.005
The development of electronic conducting networks during the simultaneous biaxial stretching of isotactic polypropylene/carbon nanotube (iPP/CNT) composites was investigated. During the stretching process, the electrical resistivity of the composites was found to be very sensitive to the draw ratios. This was especially true at CNT concentration close to the percolation threshold, ca. 2.2 vol.%. The resistivity–draw ratio dependence was divided into two stages. In the first stage, the stretching was taken by the amorphous zones and only led to the enlargement of the distance between CNT aggregates. This resulted in the breaking of the conductive network and, consequently, a sharp increase in resistivity. As the turning point was approached, individual nanotubes started to disentangle from CNT aggregates. Meanwhile, the resistivity of the stretched films was dramatically decreased by 7 orders of magnitude, indicating a rebuilding of the conducting network during the biaxial stretching process.Graphical abstractHighlights► The development of CNT network in PP during biaxial stretching is studied. ► Higher stretching temperature is beneficial to recovering the CNT network. ► A deforming mechanism of CNTs during biaxial stretching is proposed.
Co-reporter:Jiabin Shen, Jiang Li, Shaoyun Guo
Polymer 2012 Volume 53(Issue 12) pp:2519-2523
Publication Date(Web):25 May 2012
DOI:10.1016/j.polymer.2012.04.004
An additional damping transition at −25 °C, which has never been reported in blended system, is observed in dynamic mechanical spectra (DMS) of isotactic polypropylene/ethylene 1-octene copolymer (iPP/POE) composites with alternating multilayered structure. With increasing layer number, this additional transition becomes larger followed by the decrease of the damping peak of iPP. Through mechanical analysis, the maximum of interfacial stress is found at −25 °C, where the new damping peak appears coincidentally. Hence, the origin of the additional transition is ascribed to the advanced defreezing of chain segments of iPP for balancing difference of the mechanical response between adjacent layers.Graphical abstract
Co-reporter:Jiabin Shen, Michel F. Champagne, Zhi Yang, Qin Yu, Richard Gendron, Shaoyun Guo
Composites Part A: Applied Science and Manufacturing 2012 Volume 43(Issue 9) pp:1448-1453
Publication Date(Web):September 2012
DOI:10.1016/j.compositesa.2012.04.003
Two developing stages of conducting network in carbon nanotube (CNT)/polypropylene composite films were found during simultaneous biaxial (SIB) stretching and sequential biaxial (SEB) stretching. The electrical resistivity was first increased up to 1011 Ω cm with the extension of the films, regardless of the stretching modes. Once further stretched to 3.5 × 3.5, the SIB- and SEB-stretched films showed reduction of their resistivity of six and eight orders of magnitude, respectively. Microscopic observations revealed that specimens stretching in SEB mode promoted the elongation of CNTs and their clusters, which was apparently more effective for reconnecting adjacent particles and fabricating a new conducting network.
Co-reporter:Ming Wen, Xiaojie Sun, Lin Su, Jiabin Shen, Jiang Li, Shaoyun Guo
Polymer 2012 Volume 53(Issue 7) pp:1602-1610
Publication Date(Web):22 March 2012
DOI:10.1016/j.polymer.2012.02.003
We reported the design of a grape-cluster-like conductive network in a polypropylene (PP) matrix, where oriented multi-walled carbon nanotubes (MWCNTs) served as branches and provided charge transport over large distances while grape-like carbon black (CB) aggregates enriched around MWCNTs and linked these conductive tubes through charge transport over small distances. The key for construction of this grape-cluster-like conductive network was the extension and orientation of MWCNTs, which was achieved in this work by multistage stretching extrusion with an assembly of laminating-multiplying elements (LMEs, which divide and recombine polymer melts). The highest efficient grape-cluster-like conductive network was obtained at a CB:MWCNT weight ratio of 6. The experimental results showed that this novel grape-cluster-like conductive network provided a low percolation threshold for PP/CB/MWCNT composites due to the synergistic effect of CB and oriented MWCNTs. When the combined CB and MWCNT content was about 6.9 vol%, the electrical resistivity of PP/CB/MWCNT composites prepared by multistage stretching extrusion with 6 LMEs decreased to only 0.63 Ω cm.This novel grape-cluster-like conductive network provided a low percolation threshold for PP/CB/MWCNT composites due to the synergistic effect of CB and oriented MWCNTs.
Co-reporter:Bo Peng, Hong Wu, Wenting Bao, Shaoyun Guo, Yong Chen, Hua Huang, Hongyu Chen, Shih-Yaw Lai and Jinder Jow
Polymer Journal 2011 43(1) pp:91-96
Publication Date(Web):November 3, 2010
DOI:10.1038/pj.2010.95
Propylene-based plastomer/nanosilica composites, with a filler content of 1–4 wt%, were prepared by a specially designed ultrasound-assisted extrusion system that was developed in our laboratory. The effects of ultrasound on the morphology, as well as the rheological and mechanical properties of the composites, were studied in this paper. In spite of slight ultrasound-induced degradation of the polymeric matrix, the results showed that the strength and elongation of the composites at break, in most cases, still improve in the presence of ultrasound because of ultrasound-induced homogeneous dispersion of nanoparticles in the polymeric matrix (as confirmed by scanning electron microscope, transmission electron microscope and differential scanning calorimetry studies). Dynamic rheological measurements also indicate that ultrasound-induced compatibilization has a more predominant role than does degradation. From dynamic mechanical measurements, it was found that ultrasound-induced degradation results in a drop in the dynamic storage modulus and glass transition temperature for composites with 4 wt% filler content, whereas ultrasound-induced compatibilization enhances their loss factor values.
Co-reporter:Bowen Yan, Hong Wu, Genjie Jiang, Shaoyun Guo, and Jian Huang
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 11) pp:3023
Publication Date(Web):October 13, 2010
DOI:10.1021/am1003574
This paper describes interfacial crystalline structures found in injection overmolded polypropylene components and the relationship of these structures to bond strength between the components. The combined effects of the development of hierarchical gradient structures and the particular thermomechanical environment near the interface on the interfacial crystalline structures were investigated in detail by PLM, SEM, DSC, WAXD, and infrared dichroism spectroscopy. The experimental results showed that during molding there was competitive formation of interfacial crystalline structures consisted of “shish-kebab” layer (SKL) and a transcrystalline layers (TCL). Variation in shear stress (controlled by injection pressure and injection speed) plays an important role in the formation of the SKL. The formation of TCL is influenced by the thermal environment, namely melt temperature and mold temperature. Increasing within certain limits, interfacial temperature and the thermal gradient near the interface promotes β-iPP growth. The relationship between interfacial crystalline structures and interfacial bond strength was established by lap shear measurement. The interfacial bond strength is improved by enhancing the formation of TCL, but reduced if SKL predominates.Keywords: bond strength; crystalline structure; injection overmolding; interface; polypropylene
Co-reporter:Rong Chen, Chuanbin Yi, Hong Wu, Shaoyun Guo
Carbohydrate Polymers 2010 Volume 81(Issue 2) pp:188-195
Publication Date(Web):11 June 2010
DOI:10.1016/j.carbpol.2010.02.012
The mechanochemical degradation behavior of hydroxyethyl cellulose (HEC) during vibratory ball milling and its induced morphological and structure development of HEC were studied through intrinsic viscosity measurement and scanning electron microscope (SEM), particle size analysis, wide-angle X-ray diffractometry (WAXD) and thermal gravimetry analysis (TG). A degradation kinetic model was proposed to evaluate the effects of ball-milling time on degradation rate of HEC with different initial molecular weights. The fragmentation mechanism is proposed based on the results of FTIR and 13C NMR measurements. The experimental results indicated that the molecular weight decreased sharply with the increase of ball-milling time, charge ratio of steel ball/HEC and the rotational speed. Meanwhile, the fibriform morphology of original HEC was damaged observably and the crystallinity of HEC decreased sharply during the milling, which induced the decrease of the thermal stability.
Co-reporter:Tingting Xie;Hong Wu;Wenting Bao;Yong Chen;Hua Huang;Hongyu Chen;Shih-Yaw Lai;Jinder Jow
Journal of Applied Polymer Science 2010 Volume 118( Issue 3) pp:1846-1852
Publication Date(Web):
DOI:10.1002/app.32547
Abstract
The effects of POE-g-MAH, prepared through different methods, on morphology and properties of PA6/POE/POE-g-MAH blends are summarized in this article. The grafting degree of POE-g-MAH can be increased through the ultrasound-assisted extrusion. Experimental results showed that the addition of POE-g-MAH can increase the mechanical properties of the PA6/POE blend and decrease the particle size of POE dispersed phase in PA6 matrix due to the compatibilization by POE-g-MAH. The PA6/POE blend compatibilized by POE-g-MAH prepared through the ultrasound-assisted extrusion has smaller particle size of POE dispersed phase and higher notched Izod impact strength than that by POE-g-MAH with similar grafting degree initiated only by peroxide. This result is ascribed to some anhydride rings attached to the chain terminus of POE due to ultrasound initiation. Rheological and Molau test results also showed enhanced compatibilization of POE-g-MAH prepared through the ultrasound-assisted extrusion on the PA6/POE blend due to a structural difference of POE-g-MAH. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Genjie Jiang;Hong Wu
Polymer Engineering & Science 2010 Volume 50( Issue 12) pp:2273-2286
Publication Date(Web):
DOI:10.1002/pen.21686
Abstract
Polymer blending is a common and effective way to develop new materials with desirable physical and mechanical properties. Since most polymer pairs are immiscible, reactive compatibilization has been extensively studied to stabilize morphology of polymer blends and improve their mechanical properties. In the past several years, considerable interest has been expressed in understanding the fundamental kinetics and mechanisms of the interfacial reaction, investigating the reinforcement of the interfacial adhesion and the development of morphological structure at polymer–polymer interface induced by the interfacial reaction. The present review focused on some theoretical and experimental results that include the formation and growth of copolymers at the interface, and also the major factors such as reaction conditions, the concentration and bulk properties of the functionalized polymer, the thermodynamic interaction between the functionalized polymer and the matrix, which can influence the interfacial adhesion and morphological development. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Co-reporter:Jiabin Shen, Ming Wang, Jiang Li, Shaoyun Guo, Shuangxi Xu, Yuqing Zhang, Ting Li, Ming Wen
European Polymer Journal 2009 Volume 45(Issue 11) pp:3269-3281
Publication Date(Web):November 2009
DOI:10.1016/j.eurpolymj.2009.07.013
Multilayered propylene–ethylene copolymer (PPE)/ethylene 1-octene copolymer (POE) composites were prepared by a microlayered coextrusion system. Static and dynamic tensile results showed that yield strengths and storage moduli of the multilayered samples were distinctly larger than those of conventional blends. The equivalent box model (EBM) proposed by Kolarik was used to explain the effect of morphology on mechanical properties. Experimental and theoretical results indicated that the excellent mechanical properties of multilayered composites were ascribed to the phase continuity. The effects of interfacial layers in multilayered composites on mechanical properties were also discussed. The existence of interfaces between POE and PPE layers not only led to the invalidation of EBM for prediction of mechanical properties of multilayered composites with larger number of layers, but also induced a new absorbing peak in loss modulus-temperature spectrum because of the shearing friction between POE and PPE layers through interfaces.
Co-reporter:Lijuan Zhao;Zhigang Sun;Jacques Tatibouët
Journal of Applied Polymer Science 2009 Volume 114( Issue 5) pp:2731-2739
Publication Date(Web):
DOI:10.1002/app.30668
Abstract
On the basis of the previous observations that the ultrasonic signals are sensitive to the crystallization of polymers (Tatibouet and Piché, Polymer 1991, 32, 3147), we have expanded our efforts to study the detail relationship between the ultrasonic signals and crystallization process in this work. The nonisothermal and isothermal crystallization of virgin poly(ethylene terephthalate) (PET) and PET samples after degradation were studied by using a specially designed pressure-volume-temperature (PVT) device, with which an ultrasonic detector was combined. The results showed that the evolution of the ultrasonic signals not only can be used to probe the crystallization process but also can qualitatively characterize the crystallization rate, crystallinity, crystallite size, and amorphous. DSC measurement was used to verify such results. Ultrasonic signals could be as a complementary tool to polymer chain movement and well be applied to characterize the crystallization behavior. Furthermore, the ultrasonic measurement has the potential use to characterize crystallization of products in-line during processing (i.e., injection molding, micromoulding). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Guangshun Chen;Bo Yang
Journal of Applied Polymer Science 2009 Volume 114( Issue 3) pp:1848-1855
Publication Date(Web):
DOI:10.1002/app.30684
Abstract
In this study, a polar conductive filler [carbon black (CB)], a nonpolar polymer [polypropylene (PP)], and a polar polymer [nylon 6 (PA6)] were chosen to fabricate electrically conductive polymer composites by melt blending and compression molding. The morphological developments of these composites were studied. Scanning electron microscopy results showed that in a CB-filled PP/PA6 (CPA) composite, CB particles were selectively dispersed in PA6 phases and could make the dispersed particles exist as microfiber particles, which could greatly improve the electrical conductivity. The PA6 and CB contents both could affect the morphologies of these composites. The results of electrical resistivity measurements of these composites proved the formation of conductive networks. The resistivity–temperature behaviors of these composites were also studied. For CB-filled PP (CP) composites, there were apparent positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects and an unrepeatable resistivity–temperature characteristic. However, for CPA composites, there were no PTC or NTC effects from room temperature to 180°C, and the resistivity–temperature behavior showed a repeatable characteristic; this proved that CB particles were selectively dispersed in the PA6 phase from another point of view. All experimental results indicated that the addition of PA6 to a CP composite could lead to an expected morphological structure and improve the electrical conductivity of the CP composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Rong Chen;Chuanbin Yi;Hong Wu
Journal of Applied Polymer Science 2009 Volume 112( Issue 6) pp:3537-3542
Publication Date(Web):
DOI:10.1002/app.30098
Abstract
The effects of mechanochemical treatment on hydroxyethyl cellulose (HEC) and its grafting reaction with acrylic acid (AA) under solvent-free conditions were studied through a vibratory ball-milling machine, which was developed in our laboratory. Fourier transform infrared (FTIR) spectroscopy and 13C-NMR analysis were used to investigate the structural development of HEC during vibromilling and the grafting mechanism. Further development of the structure and properties of the graft copolymer was characterized by viscosity measurement, wide-angle X-ray diffraction (WAXD), and thermal gravity (TG) analysis. The FTIR results showed a new peak at 1720 cm−1, corresponding to the CO absorbance peak of AA, which indicated that AA was successfully grafted onto HEC during the high-energy vibromilling of the HEC/AA mixture at ambient temperature in the absence of a solvent and a catalyst. The WAXD showed the destruction of crystals of HEC during the milling, and the TG analysis demonstrated the improvement of the thermal stability of the copolymer. The effects of the processing conditions on the grafting rate and grafting efficiency were studied by chemical titration to determine the optimum grafting conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Xiaofeng Yu;Hong Wu;Jiang Li;Jianhui Qiu
Polymer Engineering & Science 2009 Volume 49( Issue 4) pp:703-712
Publication Date(Web):
DOI:10.1002/pen.21302
Abstract
The structure and mechanical properties of injection-molded polypropylene along the flow direction were investigated in this article. A remarkable difference was found in morphology and mechanical properties of the injection-molded parts along the flow direction. The three-layered structure (namely the skin, subskin, and core layer) showed a gradient distribution along the flow direction. The IR and WAXD results showed that the orientation of the subskin layer in the gate part is much higher than that in the far part. DSC analysis results indicated that the two parts (gate part and far part) of injection-molded bar has the same degree of crystallinity that should not be responsible for the mechanical difference of the two parts. According to the measurement of residual internal stress, there is large difference between the gate part and far part, which is the main reason leading to the difference of impact behavior. The annealing treatment eliminated the internal stress, so the mechanical difference between the two parts decreased and the fracture type of the far part changed from brittle to ductile. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Co-reporter:Guangshun Chen;Bo Yang
Journal of Polymer Science Part B: Polymer Physics 2009 Volume 47( Issue 18) pp:1762-1771
Publication Date(Web):
DOI:10.1002/polb.21778
Abstract
The experimental data reveal that the addition of ethylene–acrylic acid copolymer (EAA) into carbon black (CB)/polypropylene (PP) composites can improve the electrical conductivity of CB/PP composites by two to six orders of magnitude at a comparatively low CB content (φ), and when φ = 2.5 vol %, 60/40 of PP/EAA is an optimum for electrical conductivity improvement. The dynamic rheological data show that with increasing φ there are apparent rheological percolations for CB/PP composites. A modified Kerner–Nielson equation can be used to describe the correlation between electrical percolation and dynamic viscoelastic percolation. The addition of EAA into CB/PP composites leads to apparent changes in dynamic rheological behaviors. When φ = 2.5 vol %, a rheological percolation appears in CB/PP/EAA (CPE) composites with increasing EAA content. The similar rheological behaviors correspond to the similar morphological structures for CPE composites with φ = 5.0 vol %. The appearance of bumps in the van-Gurp–Palmen plots corresponds to the formation of network structure in CB/PP and CPE composites, and the more perfect the networks, the higher the amplitude of the bumps. All data indicate that the van-Gurp–Palmen plot is sensitive to the formation of filler particle networks or cocontinuous phase which spans the whole composite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1762–1771, 2009
Co-reporter:Xiong Ying;Chen Guangshun ;Guo Shaoyun
Journal of Polymer Science Part B: Polymer Physics 2008 Volume 46( Issue 10) pp:938-948
Publication Date(Web):
DOI:10.1002/polb.21428
Abstract
In this article, a solid mechanochemical route to prepare core-shell structured particles was introduced. X-ray photoelectron spectrum, transmission electron microscope and dissolving experimental results indicated the formation of [(inorganic particle)/(elastomer)] core-shell structured particles. The thermal stable experiments showed that untreated SiO2 can cause dehydrochlorination of poly(vinyl chloride) (PVC) and discoloration of PVC/SiO2 composites and the formation of core-shell structured SiO2 particles will improve the thermal stability of PVC/SiO2 composites. The mechanical properties and rheological results showed that the formation of core-shell structured SiO2 particles can both improve the mechanical and processing properties of PVC/SiO2 composite. ACR in PVC/(SiO2-PMMA-ACR) composites acted not only as toughener for PVC matrix but also as cushion breaker if the content of ACR is enough. Meanwhile compared with other SiO2 particles the formation of core-shell structured SiO2 particles can decrease the apparent viscosity, increase the critical shear rate and improve the appearance of extrudes of PVC/SiO2 composites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 938–948, 2008
Co-reporter:Bo Peng, Hong Wu, Shaoyun Guo, Shih-Yaw Lai, Jinder Jow
Polymer Degradation and Stability 2007 Volume 92(Issue 8) pp:1632-1639
Publication Date(Web):August 2007
DOI:10.1016/j.polymdegradstab.2007.03.025
The ultrasonic degradation of novel propylene based plastomer (DP) melts with different melt viscosities was conducted in a “static” ultrasonic device where the samples were taken from various distances from the tip of an ultrasonic probe. The effects of ultrasonic time, oscillation temperature, ultrasonic intensity and the distance from the ultrasonic probe tip on the degradation behavior of DP melts as well as the ultrasonic degradation effect on the linear rheological behavior of DP melts were studied. The results show that the increase of initial melt viscosity of DP (higher molecular weight) has greater impact on the ultrasonic degradation of DP melt. The molecular weight and intrinsic viscosity of DP decrease with the increase of ultrasonic oscillation time and they approach to a limiting value. The molecular weight distribution of DP increases after ultrasonic degradation. Decreasing oscillation temperature and distance from probe tip and increasing ultrasonic intensity lead to an increase in the degradation of DP melt. The linear rheological behavior measurements of the samples obtained near the ultrasonic probe tip show that ultrasonic oscillations decrease the complex viscosity, zero shear viscosity, viscoelastic moduli, cross modulus, relaxation time and the slope of log G′ − log G″ for DP melts.
Co-reporter:Xiaolang Chen;Jie Yu
Journal of Applied Polymer Science 2007 Volume 103(Issue 3) pp:1978-1984
Publication Date(Web):8 NOV 2006
DOI:10.1002/app.24965
The thermal stability and thermal oxidative degradation kinetics of polypropylene (PP) and flame-retardant PP composites filled with untreated and treated magnesium hydroxide (MH) in air were studied by thermogravimetric analysis (TGA). The effect of the heating rate in dynamic measurements (5°C–30°C/min) on kinetic parameters such as activation energy was also investigated. The Kissinger and Flynn–Wall–Ozawa methods were used to determine the apparent activation energy for the degradation of neat PP and flame-retardant PP composites. The results of TGA showed that the addition of untreated or treated MH improved the thermal oxidative stability of PP in air. The kinetic results showed that the apparent activation energy for degradation of flame-retardant PP composites was much higher than that of neat PP, suggesting that the flame retardant used in this work had a great effect on the mechanisms of pyrolysis and combustion of PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1978–1984, 2007
Co-reporter:Bo Peng;Hong Wu;Jinder Jow;Shih-Yaw Lai
Journal of Applied Polymer Science 2007 Volume 106(Issue 3) pp:1725-1732
Publication Date(Web):17 JUL 2007
DOI:10.1002/app.26765
The effects of ultrasonic oscillations on the die pressure, productivity of extrusion, melt apparent viscosity, melt surface appearance, and die swell of novel propylene-based plastomers were studied in a specially designed ultrasonic oscillations extrusion system developed in our laboratory. The effects of ultrasonic oscillations on molecular weights, tensile strength, and dynamic mechanical properties of extrudates were also studied. The experimental results showed that the presence of ultrasonic oscillations during extrusion could significantly increase the productivity of plastomers at the same die pressure, and reduce die swell and melt fracture such as sharkskin at a given screw rotation speed. The die pressure and apparent viscosity of plastomers remarkably decreased with increasing ultrasonic intensity. Introduction of ultrasonic oscillations into plastomer melts can improve their processibility. The possible mechanism for ultrasonic improvement of rheological behavior was also proposed in this article. Under certain conditions, ultrasound-assisted extrusion could slightly decrease the glass transition temperature (Tg) and storage modulus of plastomers due to the minor reduction in molecular weights, but showed no significant impact on yield strength and strength at break. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Jiang Li;Xiaofeng Yu
Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 2) pp:184-195
Publication Date(Web):1 DEC 2006
DOI:10.1002/polb.20998
The structure and mechanical properties of injection-molded bars of high-density polyethylene (HDPE)/PA6 blends were studied in this article. The experimental results showed that the morphologies of injection-molded bars change gradually along the flow direction, which is tightly related to the melt viscosity and processing conditions. The higher melt viscosity, lower mold temperature, and shorter packing time, restricting the macromolecular relaxation, enhance the difference in morphologies and properties at near and far parts of a mold. An injection-molded bar (namely H2C5), consisting of 75 wt % of HDPE, 20 wt % of PA6, and 5 wt % of compatibilizer (HDPE-g-MAH), showed a greater difference in mechanical properties at near and far parts because of its higher melt viscosity. A clear interface between the skin and core layers of near part in it leads to a much higher impact strength than that of far part. And tensile tests show that its tensile strength of near part is higher than that of far part due to the higher orientation degrees of HDPE matrix and PA6 dispersed phase in near part. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 184–195, 2007
Co-reporter:Lijuan Zhao;Qin Du;Genjie Jiang
Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 16) pp:2300-2308
Publication Date(Web):2 JUL 2007
DOI:10.1002/polb.21235
In this article, the effect of ultrasonic oscillation on the dispersed morphology of attapulgite in polypropylene (PP) and crystallizing kinetics of PP/attapulgite composites prepared through extrusion in the presence and the absence of ultrasonic oscillation were studied. X-ray diffraction analysis results showed that ultrasonic oscillation did not change attapulgite crystal structure during extrusion in PP/attapulgite composites. On the other hand, scanning electron microscopy and transmission electron microscope photographs indicated that ultrasonic oscillation promoted the dispersion of attapulgite particles in PP matrix. The dispersed morphology of attapulgite and ultrasound oscillation affected the crystalline form, nucleation rate, crystallization temperature, crystallinity, and spherulite size of PP crystals. PP transcrystals were formed on the attapulgite particle surface. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2300–2308, 2007
Co-reporter:Ming Wang, Jiayou Xu, Hong Wu, Shaoyun Guo
Polymer Degradation and Stability 2006 Volume 91(Issue 9) pp:2101-2109
Publication Date(Web):September 2006
DOI:10.1016/j.polymdegradstab.2006.01.011
The stabilization effect of calcium and zinc stearates (CaSt2/ZnSt2) combined with pentaerythritol (PeE) and organic tin on poly(vinyl chloride) was investigated. The results show that the addition of calcium/zinc stearates combined with PeE and organic tin can improve thermal and colour stability of poly(vinyl chloride) in both static and dynamic tests. Mechanisms for improving stability of PVC are also discussed. The increase of stabilizing effectiveness of calcium/zinc stearates is ascribed to the synergistic effect between CaSt2/ZnSt2 and PeE and the interaction between organic tin and double bonds formed during the degradation of PVC. There is no synergistic action between organic tin and PeE or organic tin and calcium/zinc stearates.
Co-reporter:Jiang Li;Mei Liang
Journal of Applied Polymer Science 2006 Volume 100(Issue 3) pp:1856-1863
Publication Date(Web):30 JAN 2006
DOI:10.1002/app.23037
In this study, the extrusion processing behaviors of polystyrene (PS), ethylene–propylene–diene terpolymer (EPDM), and their blend (PS/EPDM, 80/20) were studied by using a special ultrasonic oscillation extrusion system developed in our laboratory. The die pressure and volume flow rate were measured at different ultrasonic intensities and screw rotation speeds. The dependences on ultrasonic intensity of die pressure, volume flow rate, and apparent viscosity of polymers, as well as die swell at the same screw rotation speed were investigated. The effects of screw rotation speed on the processing behaviors of polymers and their blend at the same ultrasonic intensity were also studied. The experimental results showed that in the presence of ultrasonic irradiation, the processibilities of polymers and their blend were improved. Their possible mechanism is discussed in this article. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1856–1863, 2006
Co-reporter:Shaoyun Guo;Guangshun Chen;Ying Xiong
Journal of Applied Polymer Science 2006 Volume 102(Issue 2) pp:1084-1091
Publication Date(Web):28 JUL 2006
DOI:10.1002/app.24262
In this study, a novel mechanochemical route to prepare core-shell structured particles was introduced. XPS, TEM, and dissolving experimental results indicate the formation of [(inorganic particle)/(elastomer)] core-shell structured particles, and several kinds of calcium carbonate (nano-CaCO3) particles with various interfaces were obtained. The mechanical properties and morphological results indicate that the surface treatment of nano-CaCO3 particles and the existence of outer elastic layer will strengthen the interfacial interaction between nano-CaCO3 particles and PVC matrix, which results in improvement of mechanical properties of PVC/CaCO3 composites. The theoretical calculations of the interfacial interaction and DMA results confirm these especially when the surface of nano-CaCO3 particles was treated by MMA and coated in succession by ACR through vibro-milling. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1084–1091, 2006
Co-reporter:Xiaofeng Yu;Hong Wu;Chang Lu
Journal of Applied Polymer Science 2006 Volume 102(Issue 3) pp:2990-2997
Publication Date(Web):23 AUG 2006
DOI:10.1002/app.24632
The effect of ultrasonic oscillations on the weld line strength of amorphous polystyrene (PS), polymethyl methacrylate (PMMA), and PS/PMMA (20/80, 50/50, 80/20) blends at various temperatures was investigated. By facilitating the molecular diffusion across the weld line, the introduction of ultrasonic oscillations could evidently improve the weld line strength of PS, PMMA, and their blends. The different effects on the weld line strength of PS/PMMA (20/80, 50/50, 80/20) blends were investigated. The ultrasonic oscillations could greatly increase the weld line strength of PS/PMMA (80/20) by ∼ 70%, but was less efficient to PS/PMMA (50/50, 20/80) blends, due to the great difference of weld line morphologies of these blends. The dispersed phase of PS/PMMA (80/20) in the weld line was spherical while two different morphologies in the weld line of PS/PMMA (50/50) were observed. And the stripe-like morphology of PS perpendicular to the flow direction in the weld line of PS/PMMA (20/80) is responsible for the little effect of ultrasonic oscillations. The fractured surfaces of PS, PMMA, and PS/PMMA (80/20) with weld line became much rougher due to the introduction of ultrasonic oscillations. The morphology study of PS/PMMA (80/20) showed that the spherical dispersed phase of PS/PMMA at the skin turned smaller under ultrasonic oscillations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2990–2997, 2006
Co-reporter:Xiaolang Chen;Jie Yu
Journal of Applied Polymer Science 2006 Volume 102(Issue 5) pp:4943-4951
Publication Date(Web):28 SEP 2006
DOI:10.1002/app.24938
Silane and silicone oil modified superfine magnesium hydroxide (MH) was filled into polypropylene (PP) as a flame retardant. The PP and flame-retarded PP composites were studied for their mechanical properties and rheological behaviors by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), limiting oxygen index (LOI), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the addition of MH improved flame retardancy of PP/MH composites, but seriously deteriorated mechanical properties of the composites. Surface treatment of MH could significantly improve tensile and impact strength of PP/MH composite because of its enhanced interfacial adhesion between MH and PP matrix. DSC results showed that MH had heterogeneous nucleation effect on PP. Surface treatment of MH weakened its heterogeneous nucleation effect. POM results showed that the dispersion of MH particles played an important role in the crystalline morphology and spherulite size of PP crystals. TGA indicated that MH greatly enhanced the thermal stability of PP. The introduction of treatment agent further improved the thermal oxidative stability of the composite. According to LOI, silane-treated MH greatly enhanced flame retardancy of PP/MH composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4943–4951, 2006
Co-reporter:Chang Lu;Xiaofeng Yu
Journal of Polymer Science Part B: Polymer Physics 2006 Volume 44(Issue 10) pp:1520-1530
Publication Date(Web):13 APR 2006
DOI:10.1002/polb.20795
The effect of ultrasonic oscillations and ultrasonic oscillation-induced modes on weld line strength of polystyrene(PS) and polystyrene/polyethylene(PS/HDPE) blend was investigated. And the mechanism of ultrasonic improvement of weld line strength of PS and PS/HDPE blend was also studied. The presence of ultrasonic oscillations can enhance the weld line strength of PS and PS/HDPE blend. Compared with mode I(ultrasonic oscillations were induced into mold at the whole process of injection molding), the induced ultrasonic oscillations as mode II(ultrasonic oscillations were induced into mold after injection mold filling) is more effective to increase weld line strength of PS and PS/HDPE blend. The mechanism for ultrasonic improvement of weld line strength of PS and PS/HDPE blend is that the ultrasonic oscillations can improve the molecular diffusion across weld line of the melt at the core, and make against the fusion of melt at the skin. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1520–1530, 2006
Co-reporter:Yuntao Li, Jiang Li, Shaoyun Guo, Huilin Li
Ultrasonics Sonochemistry 2005 Volume 12(Issue 3) pp:183-189
Publication Date(Web):February 2005
DOI:10.1016/j.ultsonch.2003.10.011
In this paper, the effect of ultrasonic intensity on the degradation of high-density polyethylene (HDPE) melt, degradation mechanism, ultrasonic degradation kinetics of HDPE melt as well as the development of molecular weight distribution of HDPE melt during ultrasonic degradation were studied. In the initial stage, the ultrasonic degradation of HDPE melt shows a random scission process, and the molecular weight distribution broadens. After that, the ultrasonic degradation of HDPE melt shows a nonrandom scission process, and the molecular weight distribution of HDPE melt narrows with ultrasonic irradiation time. The average molecular weight of HDPE decreases with the increase of ultrasonic intensity and increases and trends forward that of undegraded HDPE with the increase of distance from ultrasonic probe tip, indicating that attenuation of ultrasonic intensity in HDPE melt is very quick. Ultrasonic degradation kinetics of HDPE melt obeys the equation: Mt=M∞+Ae−kt. The theoretic calculation by this equation accords well with the experimental results. The plausible ultrasonic degradation mechanism of polymer melt based on molecular relaxation was also proposed in this paper.
Co-reporter:Shaoyun Guo;Manhong Tian;Guangshun Chen
Macromolecular Materials and Engineering 2005 Volume 290(Issue 9) pp:927-932
Publication Date(Web):31 AUG 2005
DOI:10.1002/mame.200400375
Summary: The effects of interfacial interaction between nano-CaCO3 and PVC on mechanical properties and morphology of PVC/nano-CaCO3 composites were studied. Nano-CaCO3 was treated with vibromilling in the presence of PVC and coupling agents. The mechanical properties of PVC/treated nano-CaCO3 are remarkably improved. Transmission electron microscopy results revealed that vibromilled nano-CaCO3 particles are well dispersed in PVC matrix with good homogeneity and well adhered to PVC matrix. Molau test indicated that chemical reaction between newly formed surface of nano-CaCO3 and PVC or coupling agent took place. Theoretical calculation results show that the interfacial interaction between PVC and nano-CaCO3 are substantially improved through vibromilling treatment of nano-CaCO3 in the presence of PVC and coupling agent.
Co-reporter:Yuntao Li;Guangshun Chen;Huilin Li
Journal of Applied Polymer Science 2005 Volume 96(Issue 2) pp:379-384
Publication Date(Web):10 FEB 2005
DOI:10.1002/app.21440
The effects of ultrasonic oscillations on the rheological and viscoelastic properties and morphology of high-density polyethylene (HDPE)/Illite (70/30) composites were studied. The experimental results showed that the die pressure and apparent viscosity of the HDPE/Illite (70/30) composites were reduced greatly, and so the mass-flow rate significantly increased in the presence of ultrasonic oscillations during the extrusion. Scanning electron microscopy and linear viscoelasticity tests showed that ultrasonic oscillations improved the dispersion of the Illite particles into the HDPE matrix. The aggregation of the Illite particles disappeared on the fractured surfaces of HDPE/Illite (70/30) composites extruded in the presence of ultrasonic oscillations, and this indicated that ultrasonic oscillations promoted the homogeneous dispersion of Illite particles into the HDPE matrix. Ultrasonic oscillations caused the permanent reduction of the dynamic viscosity and zero-shear viscosity of HDPE/Illite (70/30) composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 379–384, 2005
Co-reporter:Shaoyun Guo;Jiang Li;Radek Slezák;Berenika Hausnerová
Macromolecular Chemistry and Physics 2005 Volume 206(Issue 24) pp:2429-2439
Publication Date(Web):5 DEC 2005
DOI:10.1002/macp.200500311
Summary: In this paper, high power ultrasound was introduced into polystyrene (PS)/ethylene-propylene diene monomer (EPDM) (80/20) blend melts during extrusion. The structure and properties of PS/EPDM blends treated ultrasonically, such as their mechanical properties, phase morphology, dynamic rheological behavior and the size distribution fractal dimension of dispersed particles, as well as the interfacial tension between the PS and EPDM phases, were studied. The experimental results indicated that ultrasonic treatment could improve the compatibility of PS/EPDM blends. This is attributed to the formation of a copolymer of PS and EPDM by the combination of different macroradicals, resulting from the homolytic cleavage of polymer chains induced by ultrasonic irradiation. The disproportional termination of the macroradicals leads to the degradation of PS and EPDM. Some properties, like mechanical and linear viscoelastic characteristics, were affected by both ultrasonic compatibilization and degradation. These properties depended strongly on the ultrasonic intensity, ultrasonic treatment time and number of extrusions (repeated extruded times).
Co-reporter:Radek Slezák;Berenika Hausnerová;Jiang Li
Macromolecular Chemistry and Physics 2005 Volume 206(Issue 24) pp:
Publication Date(Web):19 DEC 2005
DOI:10.1002/macp.200590048
Co-reporter:Shaoyun Guo;Hong Wu;Zhen Li
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 21) pp:3030-3043
Publication Date(Web):19 SEP 2005
DOI:10.1002/polb.20603
The effects of ultrasonic oscillations on linear viscoelastic behaviors of metallocene-catalyzed linear low density polyethylene (mLLDPE) and its blends with low density polyethylene (LDPE) were investigated in this article. The experimental results showed that ultrasonic oscillations can increase the cross modulus, characteristic time, plateau modulus, complex viscosity, zero shear viscosity, and flow activation energy of mLLDPE. Molecular weight of mLLDPE increases but molecular polydispersity index decreases in the presence of ultrasonic oscillations. It has been found for mLLDPE/LDPE blends that the addition of LDPE as well as ultrasonic oscillations can decrease the cross modulus but increase the characteristic time of the blends. The complex viscosity, zero shear viscosity, and flow activation energy of the blends increase by the addition of LDPE, but decrease in the presence of ultrasonic oscillations. Shear thinning effect of the blends is improved because of the addition of LDPE. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3030–3043, 2005
Co-reporter:Hong Wu;Zhen Li;Hong Wu;Zhen Li
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 15) pp:2121-2129
Publication Date(Web):27 JUN 2005
DOI:10.1002/polb.20501
In this work, the effect of ultrasonic irradiation on molecular structure development of metallocene-catalyzed linear low density polyethylene (mLLDPE) was studied. GPC results show that ultrasonic irradiation have influence on molecular weight and molecular weight distribution of mLLDPE. Molecular weight of mLLDPE decreases slightly at the initial 30 s of ultrasonic irradiation and then increases obviously; its distribution becomes wider with the increase of ultrasonic irradiation time. The power and frequency of ultrasonic irradiation have the distinct influence on molecular weight and its distribution of mLLDPE. DSC results show that ultrasonic irradiation has distinct influence on multiple step crystallizing behaviors of mLLDPE because of the change of branched chain in mLLDPE molecules. Thermal stability of mLLDPE is improved greatly because of micro-crosslinking structure in mLLDPE molecule, which is formed in the presence of ultrasonic irradiation. A possible mechanism for molecular structure development of mLLDPE in the presence of ultrasonic irradiation is also proposed in this paper. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2121–2129, 2005
Co-reporter:Chang Lu;Xiaofeng Yu
Polymer Engineering & Science 2005 Volume 45(Issue 12) pp:1666-1672
Publication Date(Web):26 OCT 2005
DOI:10.1002/pen.20456
The effect of melt temperature, ultrasonic oscillations, and induced ultrasonic oscillations modes on weld line strength of polystyrene (PS) and polystyrene/polyethylene (PS/HDPE) (90/10) blend was investigated. The results show that the increase of melt temperature is beneficial to the increase of weld line strength of PS and PS/HDPE blend. Compared with PS, the increase of melt temperature can greatly enhance the strength of PS/HDPE blends. For PS, the presence of ultrasonic oscillations can enhance the weld line strength of PS at different melt temperatures. But for PS/HDPE blends, the presence of ultrasonic oscillations can improve the weld line strength when the melt temperature is 230°C, but when the melt temperature is 195°C, the induced ultrasonic oscillations hardly enhance the weld line strength. Compared with Mode I (ultrasonic oscillations were induced into the mold at the whole process of injection molding), the induced ultrasonic oscillations as Mode II (ultrasonic oscillations were induced into the mold after injection mold filling) is more effective at increasing the weld line strength of PS and PS/HDPE blends. The mechanism for ultrasonic improvement of weld line strength was also studied. POLYM. ENG. SCI., 45:1666–1672, 2005. © 2005 Society of Plastics Engineers
Co-reporter:Jiang Li, Mei Liang, Shaoyun Guo, Ying Lin
Polymer Degradation and Stability 2004 Volume 86(Issue 2) pp:323-329
Publication Date(Web):November 2004
DOI:10.1016/j.polymdegradstab.2004.04.021
The ultrasonic degradation of polyamide 6 (PA6) melt was conducted in a specially designed reactor. The effects of initial molecular weight of PA6, irradiation time, ultrasonic intensity as well as ultrasonic irradiation distance on the ultrasonic degradation of PA6 melt were investigated. Some surprising experimental results show that for low molecular weight PA6 (LPA6), the viscosity-average molecular weight of LPA6 increases in the presence of ultrasonic oscillations due to extension reaction of end groups (COOH and NH2), while for high molecular weight PA6 (HPA6), the viscosity-average molecular weight of HPA6 decreases with irradiation time, and passes through a minimum, then increases with irradiation time, up to a limiting molecular weight. Ultrasonic degradation kinetics of HPA6 melt obey the equation: Mt=M∞+Ae−kt. FTIR analysis and a microtitration method confirm that the chain scission of HPA6 under ultrasonic irradiation occurs at CN bonds. A plausible ultrasonic degradation model of the polymer melt based on molecular movement is proposed.
Co-reporter:Hong Wu;Huaigu Shi;Guangshun Chen
Journal of Applied Polymer Science 2004 Volume 94(Issue 6) pp:2522-2527
Publication Date(Web):25 OCT 2004
DOI:10.1002/app.21214
The influences of ultrasonic oscillations on rheological behavior and mechanical properties of metallocene-catalyzed linear low-density polyethylene (mLLDPE)/low-density polyethylene (LDPE) blends were investigated. The experimental results showed that the presence of ultrasonic oscillations can increase the extrusion productivity of mLLDPE/LDPE blends and decrease their die pressure and melt viscosity during extrusion. Incorporation of LDPE increases the critical shear rate for sharkskin formation of extrudate, crystallinity, and mechanical properties of mLLDPE. The processing behavior and mechanical properties of mLLDPE/LDPE blends were further improved in the presence of ultrasonic oscillations during extrusion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2522–2527, 2004
Co-reporter:Guangshun Chen;Yuntao Li
Journal of Applied Polymer Science 2004 Volume 92(Issue 5) pp:3153-3158
Publication Date(Web):23 MAR 2004
DOI:10.1002/app.20282
The linear rheological properties of high-density polyethylene (HDPE), polystyrene (PS), and HDPE/PS (80/20) blends were used to characterize their structural development during extrusion in the presence of ultrasonic oscillations. The master curves of the storage shear modulus (G′) and loss shear modulus (G″) at 200°C for HDPE, PS, and HDPE/PS (80/20) blends were constructed with time–temperature superposition, and their zero shear viscosity was determined from Cole–Cole plots of the out-of-phase viscous component of the dynamic complex viscosity (η″) versus the dynamic shear viscosity. The experimental results showed that ultrasonic oscillations during extrusion reduced G′ and G″ as well as the zero shear viscosity of HDPE and PS because of their mechanochemical degradation in the presence of ultrasonic oscillations; this was confirmed by molecular weight measurements. Ultrasonic oscillations increased the slopes of log G′ versus log G″ for HDPE and PS in the low-frequency terminal zone because of the increase in their molecular weight distributions. The slopes of log G′ versus log G″ for HDPE/PS (80/20) blends and an emulsion model were used to characterize the ultrasonic enhancement of the compatibility of the blends. The results showed that ultrasonic oscillations could reduce the interfacial tension and enhance the compatibility of the blends, and this was consistent with our previous work. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3153–3158, 2004
Co-reporter:Guangshun Chen;Xiangrong Chen;Hong Wu
Polymer Composites 2003 Volume 24(Issue 3) pp:456-463
Publication Date(Web):15 APR 2004
DOI:10.1002/pc.10044
The effect of high-energy mechanical milling of CaCO3 (calcium carbonate) and STC (a mixture of sericite, tridymite and cristobalite) on mechanical properties, rheological and dynamical mechanical behavior of high-density polyethylene (HDPE)/CaCO3 and HDPE/STC was studied through SEM (scanning electron microscope), DMTA (dynastic mechanical test analysis), mechanical and melt rheological properties tests. The experimental results show that addition of fillers treated by coupling agent and vibromilling to HDPE makes the impact strength of HDPE greatly increased. The impact strength of HDPE/treated CaCO3 (60/40) and HDPE/treated STC (60/40) is ca. 4 and 3 times respectively as high as that of HDPE. The SEM micrographs of impact fractured surfaces of treated fillers filled HDPE show extensive plastic deformation of HDPE matrix, indicating that the plastic deformation of matrix induced by the treated fillers is the main contribution for absorbing a great amount of impact energy. This is the reason why the impact strength of HDPE greatly increases with addition of coupling agent and vibromilling treated fillers. The intensity of γ relaxation peak of HDPE in HDPE/treated CaCO3 on tanδ vs. temperature curve increases and the peak shifts to higher temperature due to its stronger interface interaction as compared with that of HDPE/untreated CaCO3.
Co-reporter:Hong Pi;Yong Ning
Journal of Applied Polymer Science 2003 Volume 89(Issue 3) pp:753-762
Publication Date(Web):2 MAY 2003
DOI:10.1002/app.12202
In this study, the effect of the high-energy mechanical milling of a mixture of poly(vinyl chloride) (PVC) with zinc borate (ZB) or ZB–aluminum trihydrate (ATH), a mixture of ZB and ATH, on the flame-retardant and mechanical properties of ZB and ZB–ATH filled PVC was examined. The high-energy mechanical milling of PVC/ZB and the PVC/ZB–ATH mixture produced chemical bonding between PVC and ZB or ZB–ATH, increasing the interfacial interaction of PVC/ZB and PVC/ZB–ATH blends, which resulted in a great increase in the limiting oxygen index, the impact and yield strengths, and the elongation at break of PVC/ZB and PVC/ZB–ATH blends. The results from ultraviolet spectroscopy and gas chromatography–mass spectroscopy show that mechanochemical modification of ZB and ZB–ATH much more effectively suppressed the release of aromatic compounds in PVC/ZB and PVC/ZB–ATH blends during burning. Mechanochemical modification provided an excellent route for the improvement of the flame-retardant and mechanical properties of flame-retardant-additive-filled PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 753–762, 2003
Co-reporter:Hong Wu;Jia Lin;Guangshun Chen;Hongtao Wang;Wei Chen
Journal of Applied Polymer Science 2003 Volume 90(Issue 7) pp:1873-1878
Publication Date(Web):16 SEP 2003
DOI:10.1002/app.12859
The effects of ultrasonic oscillations and die materials on die pressure, productivity of extrusion, melt viscosity of metallocene-catalyzed linear low density polyethylene (mLLDPE), as well as their mechanism were studied in a special ultrasonic oscillations extrusion system developed in our lab. Die materials used in our experiment included steel, brass, and polytetrafluoroethylene (PTFE). The experimental results showed that ultrasonic oscillations as well as die materials have great influence on the rheological and processing behavior of mLLDPE. Ultrasonic oscillations can greatly increase the productivity of mLLDPE melt extruded through different dies, and can decrease the die pressure and the melt viscosity of mLLDPE. Compared with steel or brass die, mLLDPE melt extruded through PTFE die is more sensitive to ultrasonic oscillations. A possible mechanism for the improved processability of mLLDPE is proposed in this article. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1873–1878, 2003
Co-reporter:Shaoyun Guo;A. Ait-Kadi
Journal of Applied Polymer Science 2002 Volume 84(Issue 10) pp:1856-1865
Publication Date(Web):11 MAR 2002
DOI:10.1002/app.10450
In this work, the mechanical strength and weld line morphology of injection molded polystyrene/poly(methyl methacrylate) (PS/PMMA) blends were investigated by scanning electron microscopy (SEM) and mechanical property test. The experimental results show that the tensile strength of PS/PMMA blends get greatly decreased due to the presence of the weld line. Although the tensile strength without the weld line of PS/PMMA (70/30) is much higher than that of the PS/PMMA (30/70) blend, their tensile strength with weld line shows reversed change. The viscosity ratio of dispersed phase over matrix is a very important parameter for control of weld-line morphology of the immiscible polymer blend. In PS/PMMA (70/30) blend, the PMMA dispersed domains at the core of the weld line are spherically shaped, which is the same as bulk. While in the PS/PMMA (30/70) blend, the viscosity of the dispersed PS phase is lower than that of the PMMA matrix, the PS phase is absent at the weld line, and PS particles are highly oriented parallel to the weld line, which is a stress concentrator. This is why weld line strength of PS/PMMA (30/70) is lower than that of PS/PMMA (70/30) blend. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1856–1865, 2002; DOI 10.1002/app.10450
Co-reporter:Shanshan Luo, Longfei Yi, Yu Zheng, Jiabin Shen, Shaoyun Guo
European Polymer Journal (April 2017) Volume 89() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.eurpolymj.2017.02.013
•1D confined layer spaces can be continuously fabricated through layer-multiplying coextrusion.•The growth of spherulites can be confined in 1D layer spaces.•The layer multiplication leads to the increase of yielding strength.•A higher transmittance can be directly collected by increasing the layer numbers.In this work, multilayer materials containing alternating layers of polypropylene (PP) and ethylene vinyl acetate copolymer (EVA) were fabricated through layer-assembly coextrusion. With increasing the number of layers, the growth of spherulites distributed in PP layers was gradually confined along the thickness direction leading to the slowdown of crystallization rate. Owing to the formation of the anisotropic spherulitic morphology, its influence on mechanical and optical behaviors of the multilayer specimens was investigated, respectively. Results revealed that the layer multiplication induced the increase of yielding strength and promoted the propagation of necking zone in a stretching process. When a beam of light passed through the specimen with more layers, a higher transmittance could be directly collected along the incident direction. It was recognized that the confined spherulites with high aspect ratios played a crucial role in weakening the light deflection, which provided a potential route to massively fabricate the transparent PP without filling nucleating agents.
Co-reporter:Liyuan Shen, Lichao Xia, Teng Han, Hong Wu, Shaoyun Guo
International Journal of Hydrogen Energy (28 December 2016) Volume 41(Issue 48) pp:23164-23172
Publication Date(Web):28 December 2016
DOI:10.1016/j.ijhydene.2016.11.006
Co-reporter:Rong Chen, Haibo Qu, Shaoyun Guo and Paul Ducheyne
Journal of Materials Chemistry A 2015 - vol. 3(Issue 16) pp:NaN3149-3149
Publication Date(Web):2015/03/04
DOI:10.1039/C4TB01622J
Conventional silica xerogels prepared through sol–gel processing are regarded as suitable materials for the long-term release of proteins due to the mild processing conditions. However, they fall short of short-time release of these large molecules because of their small pore size and a slow dissolution rate. With the goal of achieving controlled release of large molecules (such as proteins) in a very short time (several days), herein we focus on the co-hydrolysis and co-condensation of different precursors to synthesize composite xerogels (co-xerogels) with adjustable degradation rates. Tetraethoxysilane and 3-(triethoxysilyl) propylsuccinic anhydride were employed to prepare the co-xerogels. Succinic anhydride was chosen due to its potential to crosslink with Si–OH and to integrate into the silica network under acidic conditions. Using the trypsin inhibitor (TI) as a model drug to characterize the release properties of co-xerogels, we obtained tailored release behavior of TI (2–7 days). It is demonstrated that the co-hydrolysis and co-condensation of different precursors is an easy technique that further expands the applicability of sol–gel materials as excellent carriers for the controlled release of a variety of drugs.
Co-reporter:Kangming Xu, Fengshun Zhang, Xianlong Zhang, Qiaoman Hu, Hong Wu and Shaoyun Guo
Journal of Materials Chemistry A 2014 - vol. 2(Issue 22) pp:NaN8556-8556
Publication Date(Web):2014/03/06
DOI:10.1039/C4TA00476K
In this study, a polyurethane/hindered phenol system was prepared as a melt in order to study the yet unclear mechanism of the formation of hydrogen bonds (H-bonds) in analogous systems. The evolution of intermolecular H-bonds between ester carbonyl/phenolic hydroxyl groups and urethane carbonyl/phenolic hydroxyl groups was detected, for the first time, by infrared analysis. Subsequent dynamic mechanical analysis combined with thermal analysis showed the fluctuation of the glass transition temperatures and the damping properties of the hybrids. From X-ray diffraction analysis the existence was observed of only amorphous hindered phenol in the polyurethane, further molecular dynamic simulation, based on an amorphous cell, characterized the number of H-bonds, the H-bond predominant binding energy and the fractional free volume in a quantitative manner. It was observed that the variation of the simulation data was in accordance with the fluctuation change of the damping properties, thus a relationship was established between the evolution of the H-bonds and the damping properties.
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4_b.png)
