Co-reporter:Shiyu Yu, Xiaodong Wang, and Dezhen Wu
Energy & Fuels 2014 Volume 28(Issue 5) pp:3519-3529
Publication Date(Web):April 15, 2014
DOI:10.1021/ef5005539
Novel microencapsulated phase-change materials based on an n-eicosane core and calcium carbonate (CaCO3) wall have been synthesized through a self-assembly method. The resultant microcapsules presented rhombohedral and spherical morphologies when the synthesis was performed at different concentrations of surfactant. These two types of the n-eicosane microcapsules also exhibited a well-defined core–shell structure. X-ray diffraction patterns and Fourier transform infrared spectra confirmed that the rhombohedral microcapsules achieved a calcite CaCO3 shell, whereas the shell of spherical microcapsules were composed of the vaterite CaCO3. The crystalline phase of the CaCO3 shell could be controlled by the concentration of surfactant, sodium dodecylbenzenesulfonate, and a crystalline transition from calcite to vaterite occurred when the synthesis was carried out at the surfactant concentration of 3.0 mmol/L. The investigation of phase-change behaviors demonstrated that the encapsulation of n-eicosane enhanced its crystallinity in the α-form and thus led to an increase in crystallization temperature. The spherical microcapsules also exhibited higher encapsulation efficiency and energy-storage efficiency than the rhombohedral ones. The thermal conductivity of the n-eicosane microcapsules was significantly enhanced due to the fabrication of a highly thermally conductive CaCO3 shell, and accordingly, the supercooling of n-eicosane was suppressed. Considering the easy availability and low cost of CaCO3, this synthetic technology is worthy extending to the encapsulation of other PCMs with a CaCO3 shell, and it also exhibits a good prospect in the industrial manufacture of microencapsulated PCMs with inorganic shells.
Co-reporter:Huan Liu, Xiaodong Wang, Dezhen Wu
Polymer Degradation and Stability 2014 Volume 103() pp:96-112
Publication Date(Web):May 2014
DOI:10.1016/j.polymdegradstab.2013.02.008
A novel cyclotriphosphazene-based epoxy compound (PN-EPC) as a halogen-free reactive-type flame retardant was synthesized via a two-step synthetic route. The chemical structures and compositions of the cyclotriphosphazene precursor and the final product were characterized by 1H, 13C, and 31P NMR spectroscopy, Fourier transform infrared spectroscopy, mass spectroscopy, and elemental analysis. A series of thermosetting systems based on a conventional epoxy resin and PN-EPC were prepared, and their thermal curing behaviors were investigated. These epoxy thermosets achieved a significant improvement in glass transition temperature and also gained the good thermal stability with a high char yield. The incorporation of PN-EPC could impart an excellent nonflammability to the epoxy thermosets due to a synergistic flame retarding effect as a result of the unique combination of phosphorus and nitrogen from the phosphazene rings, and these epoxy thermosets achieved the high limiting oxygen indexes and the UL-94 V-0 rating when 20 wt.% of PN-EPC was added. The study on flame-retardant mechanism indicates that the pyrolysis products of phosphazene rings acted in both the condensed and gaseous phases to promote the formation of intumescent phosphorus-rich char on the surface of the epoxy thermosets. Such a char layer can supply a much better barrier for underlying thermosets to inhibit gaseous products from diffusing to the flame, to shield the surface of the thermosets from heat and air, and to prevent or slow down oxygen diffusion. As a result, the resulting epoxy thermosets obtained an excellent nonflammability.
Co-reporter:Hongyan Han;Dezhen Wu
Journal of Chemical Technology and Biotechnology 2013 Volume 88( Issue 7) pp:1200-1211
Publication Date(Web):
DOI:10.1002/jctb.3956
Abstract
Background
Bio-based thermoplastic composites with high-performance and low cost have attracted much interest due to their sustainability and their potential applications. The reinforcement of poly(butylene succinate) (PBS) with recycled carbon fiber (RCF) not only gives this biodegradable material excellent physical properties to compete with conventional composites, but also provides a new route to the use of RCF with well controlled cost.
Results
Bio-based PBS/RCF composites were prepared by simple melt extrusion through a twin-screw extruder. The evaluation of mechanical properties confirms a significant enhancement effect of RCF on PBS as a result of surface treatment of RCF with silane coupling agent. Morphological study indicates a homogeneous dispersion of RCF in the matrix due to the good interfacial interaction between fibers and PBS. The investigation of crystallinity verifies that RCF plays the role of nucleation agent in the crystallization process of PBS matrix and remarkably accelerates its crystallization rate.
Conclusion
The incorporation of RCF is advantageous for the enhancement of mechanical properties, heat resistance, and processability of PBS-based materials. PBS/RCF composites can be used to many fields as a low-cost biodegradable material having high performance. © 2012 Society of Chemical Industry.
Co-reporter:Yong Chen;Dezhen Wu
Polymers for Advanced Technologies 2013 Volume 24( Issue 4) pp:364-375
Publication Date(Web):
DOI:10.1002/pat.3088
The thermoplastic composites based on poly(butylene terephthalate) (PBT) and recycled carbon fiber (RCF) were prepared through simple melt compounding by a twin-screw extruder. An effective approach was utilized to clean and treat the RCF surface with a concentrated solution of nitric acid and then a solution of diglycidyl ether of bisphenol A as macromolecular coupling agent so as to improve the interfacial adhesion between the RCF and PBT matrix. As a result, the reinforcing potential of the RCF was enhanced substantially, and the mechanical properties, heat distortion temperature, and thermal stability of PBT could be significantly improved by incorporating this surface-treated RCF. The morphologies of fracture surfaces indicated that the RCF achieved a homogeneous dispersion in the PBT matrix due to a good interfacial interaction between fiber and PBT. The investigations on the crystallization behaviors and kinetics demonstrated that the RCF acted as a nucleation agent for the crystallization of PBT, and the crystallization rate and nucleation density of PBT were increased remarkably due to the heterogeneous nucleating effect of RCF in the matrix. These features may be advantageous for the enhancement of mechanical properties, heat resistance, and processability of PBT-based composites. This study may provide a design guide for carbon fiber-reinforced PBT composites with a great potential as well as a low cost for industrial and civil applications. Copyright © 2012 John Wiley & Sons, Ltd.
Co-reporter:Guotao Yan;Dezhen Wu
Journal of Applied Polymer Science 2013 Volume 129( Issue 6) pp:3502-3511
Publication Date(Web):
DOI:10.1002/app.39105
Abstract
Thermoplastic composites of polycarbonate (PC)/acrylonitrile–butadiene–styrene copolymer (ABS) alloys reinforced with recycled carbon fiber (RCF) were prepared by melt extrusion through a twin-screw extruder. The RCF was first cleaned and activated with a concentrated solution of nitric acid and was then surface-coated with diglycidyl ether of bisphenol A as a macromolecular coupling agent. Such an approach is effective to improve the interfacial bonding between the fibers and the PC/ABS matrix. As was expected, the reinforcing potential of the RCF was enhanced substantially, and furthermore, the mechanical properties, heat distortion temperature, and thermal stability of PC/ABS alloys were significantly improved by incorporating this surface-treated RCF. The composites also obtained a reduction in electrical resistivity. The morphologies of impact fracture surfaces demonstrated that the RCF achieved a homogeneous dispersion in the PC/ABS matrix due to good interfacial adhesion between the fibers and the matrix. In addition, the introduction of RCF into PC/ABS alloys also resulted in an increase in the storage moduli of the composites but a decrease in the loss factors. It is prospective that, with such good performance in mechanical data, heat resistance, and electrostatic discharge, the RCF-reinforced PC/ABS composites exhibit a potential application in industrial and civil fields as high-performance and lightweight materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Jian Sun, Xiaodong Wang, and Dezhen Wu
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 8) pp:4047
Publication Date(Web):July 25, 2012
DOI:10.1021/am300843c
A novel halogen-free fire resistant epoxy resin with pendent spiro-cyclotriphosphazene groups was designed and synthesized via a three-step synthetic pathway. The chemical structures and compositions of spiro-cyclotriphosphazene precursors and final product were confirmed by 1H, 13C, and 31P NMR spectroscopy, mass spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. The thermal curing behaviors of the synthesized epoxy resin with 4,4′-diamino-diphenylmethane, 4,4′-diamino-diphenyl sulfone, and novolac as hardeners were investigated by differential scanning calorimetry (DSC), and the curing kinetics were also studied under a nonisothermal condition. The evaluation of the thermal properties demonstrated that these thermosets achieved a good thermal resistance due to their high glass transition temperatures more than 150 °C, and also gained high thermal stabilities with high char yields. The flammability characteristics of the spirocyclic phosphazene-based epoxy thermosets cured with these three hardeners were investigated on the basis of the results obtained from the limiting oxygen index (LOI) and UL–94 vertical burning experiments as well as the analysis of the residual chars collected from the vertical burning tests. The high LOI values and UL–94 V–0 classification of these epoxy thermosets indicated that the incorporation of phosphazene rings into the backbone chain imparts nonflammability to the epoxy resin owing to the unique combination of phosphorus and nitrogen following by a synergistic effect on flame retardancy. The epoxy resin obtained in this study is a green functional polymer and will become a potential candidate for fire- and heat-resistant applications in electronic and microelectronic fields with more safety and excellent performance.Keywords: characterization; curing kinetics; flammability characteristics; spirocyclic phosphazene-based epoxy resin; synthesis; thermal properties;
Co-reporter:Yongwei Bai, Xiaodong Wang, and Dezhen Wu
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 46) pp:15064
Publication Date(Web):October 31, 2012
DOI:10.1021/ie300962a
A novel halogen-free flame-retardant epoxy resin was designed by introducing phosphazene rings into the backbone in a cyclolinear-linked mode, and then it was synthesized through a three-step synthetic route. The chemical structures and compositions of all the cyclotriphosphazene precursors and the final product were confirmed by 1H and 31P NMR spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. The thermal curing behaviors of the synthesized epoxy resin with dicyandiamide, 4,4′-diaminodiphenylmethane, and novolak as hardeners were investigated by differential scanning calorimetry (DSC), and the thermal properties were also evaluated by DSC and thermogravimetric analysis. These thermosets achieved high glass transition temperatures over 150 °C and simultaneously displayed good thermal stability with high char yields. Moreover, these thermosets have higher tensile and flexural strength but lower impact toughness in comparison with the conventional epoxy thermosets. The flammability characteristics of the thermosets obtained by curing this epoxy with three hardeners were studied on the basis of the limiting oxygen index (LOI) and UL–94 vertical burning experiments as well as the analysis of residual chars of the tested bars after vertical burring. The high LOI values and the V–0 classification for these epoxy thermosets indicate that the incorporation of phosphazene rings into the molecular backbone imparts flame retardancy on the epoxy resin. This may result from a unique combination of phosphorus and nitrogen in the phosphazene ring. The epoxy resin synthesized in this study is a green functional polymer and may become a potential candidate for fire- and heat-resistant applications in electronic and microelectronic fields.
Co-reporter:Hongyan Han, Xiaodong Wang, and Dezhen Wu
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 43) pp:14047-14060
Publication Date(Web):October 12, 2012
DOI:10.1021/ie3012352
The biocomposites of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3,4HB)] and recycled carbon fiber (RCF) were prepared via a melting extrusion. The crystallization behaviors and kinetics of the P(3,4HB) matrix in composites were exclusively studied under both nonisothermal and isothermal conditions. The corresponding results indicated that the P(3,4HB) either neat or compositing with RCF had a dual-peak cold crystallization behavior in the nonisothermal condition, and the isothermal crystallization rate of P(3,4HB) in composites was jointly determined by the rates of the nucleation and the crystal growth and integrity. However, it was reduced with the incorporation of RCF. Wide-angle X-ray scattering investigation demonstrated that the presence of RCF did not change the crystallization mechanism and crystalline structure of the P(3,4HB) matrix, but the crystallinity of the P(3,4HB) either neat or compositing with RCF was enhanced with an increase of crystallization temperature. Dynamic mechanical analysis revealed that the storage moduli of P(3,4HB)-based composites were significantly improved with increasing the RCF loadings, and the dual internal friction peaks corresponding to the thermal motion of surface molecule of crystalline zone and the glass transfer of whole macromolecules were observed on the thermograms of the P(3,4HB) either neat or compositing with RCF. The mechanical properties including tensile, flexural, and notched Izod impact strength were significantly improved in the presence of RCF, and such reinforcing and toughening effects were due to the good interfacial adhesion between RCF and P(3,4HB) as a result of bonding effect of silane coupling agent. Scanning electronic microscopy further confirmed a good dispersion of RCF in P(3,4HB) matrix and a strong interfacial interaction between fibers and matrix.
Co-reporter:Jia Liu, Jiuying Tang, Xiaodong Wang and Dezhen Wu
RSC Advances 2012 vol. 2(Issue 13) pp:5789-5799
Publication Date(Web):23 May 2012
DOI:10.1039/C2RA20739G
A novel cyclolinear phosphazene-based epoxy resin has been synthesized through a four-step synthetic route. The curing behaviors of this epoxy resin with methyl tetrahydrophthalic anhydride, 4,4′-diaminodiphenylmethane, and novolak as hardeners were investigated by differential scanning calorimetry (DSC). The thermal behaviors and stabilities were also evaluated with DSC and thermogravimetric analysis. These thermosets achieved high glass transition temperatures over 150 °C and also gained good thermal stabilities with high char yields. The flammability characteristics of the cyclolinear phosphazene-based epoxy thermosets were investigated by limiting oxygen index (LOI) and UL-94 vertical burning experiments. The high LOI values and UL-94 V-0 classification of these epoxy thermosets indicate that the incorporation of phosphazene rings into the molecular backbone imparts non-flammability to the epoxy resin as a result of the unique combination of phosphorus and nitrogen following by a synergistic effect on flame retardancy. The analysis of the residual chars collected from the UL-94 test demonstrates that cyclotriphosphazene moieties of this epoxy resin can enhance char formation during combustion serving as a barrier against heat and oxygen diffusion, and consequently the flame retardancy of the thermosets is improved significantly.
Co-reporter:Shiwen Lin;Shuangyue Sun;Yadong He;Dezhen Wu
Polymer Engineering & Science 2012 Volume 52( Issue 5) pp:927-936
Publication Date(Web):
DOI:10.1002/pen.22159
Abstract
Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based compounds containing resorcinol bis(diphenyl phosphate) (RDP) and poly(dimethyl-diphenyl siloxane) (PDMDPS) were prepared through melt extrusion, and their flammability characteristics and mechanical properties were evaluated. The incorporation of RDP enhanced the flame retardancy of PPO compounds, but hardly made them obtain the UL 94 V-0 rating unless RDP and PDMDPS were combined. Studies on the residual chars after vertical burning test suggested that the excellent flame retardancy be correlated with the retention from the combination effects of silica and phosphate in the char, whose cross-linked silica enhanced the formation of a compact char to retard combustion. Thermogravimetric analysis indicated that the presence of PDMDPS and RDP improved the char yielding as well as the decomposition temperature of PPO compounds. Moreover, the Izod impact strength was improved significantly in the presence of RDP and PDMDPS, and this toughening effect was attributed to the deformation and multiple cracks induced by PDMDPS, which enhances the impact energy absorption of the matrix. This work provides a very effective flame retarding formulation for PPO compounds with improved impact toughness. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers
Co-reporter:Chunling Xin;Yadong He;Qingchun Li;Yingzhu Huang;Baorui Yan
Journal of Applied Polymer Science 2011 Volume 119( Issue 3) pp:1275-1286
Publication Date(Web):
DOI:10.1002/app.30717
Abstract
In this study, a systematic investigation on the nonisothermal crystallization kinetics of conversional polypropylene (PP) containing various amounts of ultra-high molecular weight polyethylene (UHMWPE) was reported, and the effects of UHMWPE on crystallization behavior of these PP materials and their foaming properties were also presented. The kinetic studies revealed that the incorporation of UHMWPE into PP led to an increase in the crystallization temperature and temperature range during the crystallization process as well as the relative crystallinity. This behavior was attributed to a comprehensive effect of the nucleation and entanglement of the UHMWPE chains. The kinetic models based on Ozawa's and Mo's methods were used to analyze the nonisothermal crystallization behaviors. It was found that the latter succeeded in describing the nonisothermal crystallization behavior of the PP containing UHMWPE, while the former was not appropriate. The activation energy for the nonisothermal crystallization determined by Kissinger's method also indicated that the crystallization ability of PP was improved with the addition of UHMWPE. Owing to the modification of the crystallization kinetics of the PP materials by introduction of UHMWPE, the foaming properties (i.e., cell uniformity and expandability etc.) were improved significantly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Shuangyue Sun;Yadong He;Dezhen Wu
Journal of Applied Polymer Science 2011 Volume 121( Issue 1) pp:541-553
Publication Date(Web):
DOI:10.1002/app.33662
Abstract
This work is focused on a facile route to prepare a new type of nylon 6-based nanocomposites with both high fracture toughness and high strength. A series of nylon 6-matrix blends were prepared via melting extrusion by compounding with poly (methyl methacrylate-co-butadiene-co-styrene) (MBS) or poly(methyl methacrylate-co-methylphenyl siloxane-co-styrene) (MSIS) latices as impact modifier and diglycidyl ether of bisphenol-A (DGEBA) as compatibilizer. Layered organic clay was also incorporated into above nylon 6 blends for the reinforcement of materials. Morphology study suggests that the MBS or MSIS latex particles could achieve a mono-dispersion in nylon 6 matrix with the aid of DGEBA, which improves the compatibilization and an interfacial adhesion between the matrix and the shell of MBS or MSIS. High impact toughness was also obtained but with a corresponding reduction in tensile strength and stiffness. A moderate amount of organic clay as reinforcing agent could gain a desirable balance between the strength, stiffness and toughness of the materials, and tensile strength and stiffness could achieve an improvement. This suggests that the combination of organic clay and core-shell latex particles is a useful strategy to optimize and enhance the properties of nylon 6. Morphology observation indicates that the layered organic clay was completely exfoliated within nylon 6 matrix. It is found that the core-shell latex particles and the clay platelets were dispersed individually in nylon 6 matrix, and no clay platelets were present in MBS or MSIS latex particles. So the presence of the clay in nylon 6 matrix does not disturb the latex particles to promote high fracture toughness via particle cavitation and subsequent matrix shear yielding, and therefore, provides maximum reinforcement to the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Huanzhi Zhang, Shuangyue Sun, Xiaodong Wang, Dezhen Wu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2011 Volume 389(1–3) pp:104-117
Publication Date(Web):20 September 2011
DOI:10.1016/j.colsurfa.2011.08.043
In order to enhance the thermal transfer and phase change properties of microencapsulated phase change materials (micro-PCMs), a new micro-PCM based on n-octadecane core and silica shell was synthesized through interfacial polycondensation in different conditions. Fourier transform infrared spectra confirm the successful encapsulation of n-octadecane with inorganic silica. The silica microcapsules show a pronounced dependence of morphology and microstructure on the acidity of reaction solution in terms of the scanning electric microscopy observation, although all of them exhibit a well-defined core–shell structure. It is found that the microcapsules formed at pH 2.89 achieve a compact silica shell with fairly smooth surface as well as a large mean particle size of about 17.0 μm. Wide-angle X-ray scattering patterns indicate that the crystalline nature of the microencapsulated n-octadecane is maintained despite the confinement of silica shell. Thermogravimetric analysis shows that the silica microcapsules perform a typical two-step degradation process and present a good thermal stability. Differential scanning calorimetry investigation indicates that the silica-microencapsulated n-octadecane can achieve good phase change properties and high encapsulation efficiency by controlling the acidity of the reaction solution as well as the loading content of core material in synthesis. The thermal conductivity of the silica microcapsules is also significantly improved due to the presence of high thermal conductive silica shell. Encapsulation of n-octadecane with the silica shell material through interfacial polycondensation can be a perspective way to prepare the micro-PCMs with enhanced thermal transfer and phase change properties for potential applications to thermal-regulating textiles and fibers.Graphical abstractHighlights► We synthesize microencapsulated n-octadecane with silica wall via self-assembly. ► The microstructure of microcapsules depends strongly on the acidity of reaction. ► Compact silica shell is achieved when synthesis is carried out at pH 2.89. ► Good phase change properties can be achieved by controlling the pH value. ► The microcapsules obtain higher thermal conductivity due to their silica shell.
Co-reporter:Yang Gao, Shuangyue Sun, Yadong He, Xiaodong Wang, Dezhen Wu
Composites Part B: Engineering 2011 Volume 42(Issue 7) pp:1945-1955
Publication Date(Web):October 2011
DOI:10.1016/j.compositesb.2011.05.044
A novel type of polyoxymethylene (POM)-based composites with polytetrafluoroethylene (PTFE) fiber and poly(ethylene oxide) (PEO) was prepared via melt extrusion in order to enhance the friction lubrication and wear resistance of POM. The tribological experiments demonstrated that the coefficient of friction and wear rate of POM were both reduced by the incorporation of PTFE fiber, and furthermore, the higher the loading of PTFE fiber the better the tribological properties. The wear mechanism is derived from the thin film of PTFE formed on the contact-surfaces during sliding. The addition of PEO into POM/PTFE fiber composites can enhance the formation of transfer film on the mating surfaces during sliding contact, and thus further improves the friction and wear performance. The wear behaviors also depend on the normal loading and sliding duration, under which the transfer film could form appropriately. In addition, the abrasion of the dispersed PEO domains in matrix is also helpful to the heat dissipation when the counter-surface exerts oscillating forces on the POM surface. It should be emphatically mentioned that the use of PTFE fiber as tribological additive can improve the notched impact strength of POM, and the subsequent incorporation of PEO leads to a more significant toughening effect for POM. The morphological investigation reveals that the toughening effect is attributed to the dissipation of impact energy through the pullout of PTFE fiber and the plastic deformation of the POM matrix induced by PEO. Polarized optical microscopy demonstrates that the presence of PEO can interfere in the crystallization of POM and reduced the size of spherulites, and consequently weakened the sensitivity to notch. Although the POM-based composites underwent a different mode of thermal degradation from neat POM with a slight reduction in the temperature at rapid weight loss, their thermal stabilities were maintained well enough to meet the requirement for its application.
Co-reporter:Huanzhi Zhang, Xiaodong Wang, Dezhen Wu
Journal of Colloid and Interface Science 2010 Volume 343(Issue 1) pp:246-255
Publication Date(Web):1 March 2010
DOI:10.1016/j.jcis.2009.11.036
A novel microencapsulated phase-change material (PCM) based on an n-octadecane core and an inorganic silica shell was designed to enhance thermal conductivity and phase-change performance. These silica microcapsules were synthesized by using TEOS as an inorganic source through a sol–gel process. Fourier transform infrared spectra confirm that the silica shell material was successfully fabricated onto the surface of the n-octadecane core. Scanning electronic microscopy images suggest that the silica microcapsules exhibit a spherical morphology with a well-defined core–shell microstructure. Furthermore, the silica microcapsules synthesized at pH 2.45 display a smooth and compact surface. These microcapsules also present a large particle size range of 7–16 μm. Wide-angle X-ray scattering patterns indicate that the n-octadecane inside the silica microcapsules still retains a good crystallinity. Thermogravimetric analysis shows that these silica microcapsules are degraded in two distinct steps, and have good thermal stability. The silica-microencapsulated n-octadecane can achieve good phase-change performance, high encapsulation efficiency, and good antiosmosis property by controlling the loading of core material and acidity of the reaction solution during the sol–gel process. The thermal conductivity of the microencapsulated n-octadecane is also significantly enhanced due to the presence of the high thermal conductive silica shell.A novel microencapsulated phase-change material based on an n-octadecane core and a silica shell was synthesized via a sol–gel process for enhancement of thermal conductivity and performance.
Co-reporter:Shuangyue Sun;Yadong He;Dezhen Wu
Journal of Applied Polymer Science 2010 Volume 116( Issue 4) pp:2451-2464
Publication Date(Web):
DOI:10.1002/app.31860
Abstract
Two types of core-shell structured latexes, poly(methyl methacrylate-co-butadiene-co-styrene) (MBS) and poly(methyl methacrylate-co-methylphenyl siloxane-co-styrene) (MSiS) were used to modify recycled polycarbonate (PC) for the enhancement of toughness and flame retardancy. The impact strength of the modified PC blends was not improved after melt-blending recycled PC with these two kinds of latexes, probably because the latex particles were not evenly dispersed in the PC matrix because of the incompatibility between PC and PMMA shell of the latexes. Addition of a compatibilizer, e.g. diglycidyl ether of bisphenol-A or poly(styrene-co-maleic anhydride), can effectively enhance the toughening effect of recycled PC with core-shell structured modifiers. The presence of compatibilizer in the blends reduces the interfacial tension and introduces a steric hindrance to coalescence, and thus enhances the interfacial adhesion between PC domain and PMMA shell, and improves the dispersion of core-shell structured particles in the PC matrix. The ternary blends achieve a high impact resistance by cavitation of the particles, which relieves the triaxial stress and promotes massive shear yielding of the matrix, and then enables the matrix to fracture by the plane stress ductile tearing mode. Additionally, MSiS has a silicone-based core and can effectively retard the combustion of recycled PC. The blends containing 7 wt % MSiS and 3 wt % compatibilizer can achieve a UL94 V-0 rating in vertical burning test. We proposed that, during combustion, a fine dispersion of MSiS particles in the PC matrix facilitates the rapid migration of MSiS and formation of a uniform and highly flame resistant char barrier on the surface of the modified PC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Shuangyue Sun;Yadong He;Dezhen Wu
Journal of Applied Polymer Science 2010 Volume 118( Issue 1) pp:611-622
Publication Date(Web):
DOI:10.1002/app.32465
Abstract
The flammability characteristics and thermal stability of a novel halogen-free flame-retardant compounding system based on polyoxymethylene (POM) were studied, and a very effective flame retarding formulation for POM was developed from a combination of ammonium polyphosphate (APP), melamine cyanurate (MC), novolak, and dipentaerythritol. The decomposition behavior of POM compounds was evaluated by thermogravimetric analysis. The compound shows optimal flame retardancy with a limiting oxygen index of 52.8 and flammability rating of UL94 V-0, when 27 wt % APP, 9 wt % MC, 4 wt % novolak, and 4 wt % dipentaerythritol are simultaneously incorporated into POM. The presence of novolak and dipentaerythritol as char-forming agents results in a dense and compact multicellular char residue for the test bar after combustion, while Fourier transform infrared spectra confirm a characteristic phosphorous- and carbon-rich char resulting from the APP/MC formulation. The pyrolysis–gas chromatography/mass spectrometry analysis indicates that highly flammable formaldehyde gas, the main pyrolysis product of POM, is annihilated by amide derivatives produced by the pyrolysis of MC, imparting better flame retardancy. The comprehensive flame-retardant mechanisms based on phosphorus–nitrogen synergism promote the high flame retardancy of POM to reach the nonflammability of V-0 rating. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Ran Liu, Xiaodong Wang
Polymer Degradation and Stability 2009 Volume 94(Issue 4) pp:617-624
Publication Date(Web):April 2009
DOI:10.1016/j.polymdegradstab.2009.01.008
Hexakis(4-hydroxyphenoxy)-cyclotriphosphazene (PN–OH) was synthesized through nucleophilic substitution of the chloride atoms of hexachlorocyclotriphosphazene and reduction of the aldehyde groups, and its chemical structure was characterized by elemental analysis, 1H and 31P NMR, and Fourier transform infrared (FTIR) spectroscopy. A new phosphazene-based epoxy resin (PN-EP) was successfully synthesized through the reaction between diglycidyl ether of bisphenol-A (DGEBA) and PN–OH, and its chemical structure was confirmed by FTIR and gel permeation chromatography. Four PN-EP thermosets were obtained by curing with 4,4′-diaminodiphenylmethane (DDM), dicyandiamide (DICY), novolak and pyromellitic dianhydride (PMDA). The reactivity of PN-EP with the four curing agents presents an increase in the order of DDM, PMDA, novolak and DICY. An investigation on their thermal properties shows that the PN-EP thermosets achieve higher glass-transition and decomposition temperatures in comparison with the corresponding DGEBA ones while their char yields increase significantly. The PN-EP thermosets also exhibit excellent flame retardancy. The thermosets with novolak, DICY and PMDA achieve the LOI values above 30 and flammability rating of UL94 V-0, whereas the one with DDM reaches the V-1 rating. The nonflammable halogen-free epoxy resin synthesized in this study has potential applications in electric and electronic fields in consideration of the environment and human health.
Co-reporter:Min Ma, Xiaodong Wang
Materials Chemistry and Physics 2009 Volume 116(Issue 1) pp:191-197
Publication Date(Web):15 July 2009
DOI:10.1016/j.matchemphys.2009.03.009
In present work, we prepared a series of the epoxy-based composite materials containing multi-walled carbon nanotubes (CNTs) and piezoceramic complex of lead magnesium niobate and lead zirconate titanate (PMN-PZT), and their properties were studied. The composites exhibited a percolation threshold in the range of 1–1.5 g CNTs per 100 g epoxy, and under this circumstance, a continuous electro-conductive network was formed. Dynamic mechanical loss factors of the composites were improved when PMN-PZT and CNTs were incorporated at above critical electrical percolation loading, which indicates a good piezo-damping performance. In these composite materials, the PMN-PZT contributes to the transformation of mechanical noise and vibration energies into electric energy, while the CNTs serve in shorting of the generated electric current to the external circuit. Thermal stabilities and mechanical properties were also improved by incorporating these two fillers. A new type of the rigid piezo-damping materials was designed on the basis of the results in this study.
Co-reporter:Huanzhi Zhang, Xiaodong Wang
Solar Energy Materials and Solar Cells 2009 93(8) pp: 1366-1376
Publication Date(Web):
DOI:10.1016/j.solmat.2009.02.021
Co-reporter:Huanzhi Zhang, Xiaodong Wang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 332(2–3) pp:129-138
Publication Date(Web):15 January 2009
DOI:10.1016/j.colsurfa.2008.09.013
A series of microencapsulated phase change materials (micro-PCMs) based on n-octadecane core and resorcinol-modified melamine–formaldehyde shell were synthesized by in situ polymerization method using different emulsifiers. The Fourier transform infrared spectra confirmed that the resorcinol-modified melamine–formaldehyde shell was successfully fabricated on the surface of the core material; however, the morphology investigation suggested that the sodium salt of styrene-maleic anhydride copolymer as an anionic emulsifier is optimal for the fabrication of the microcapsules in this study. And the microcapsules fabricated with a core/shell weight ratio of 75/25 have a compact surface of the shell and a mean particle size of below 20 μm with the centralized size distribution. The sample under this condition has much better phase change properties and a higher efficiency of encapsulation (about 92%) than the others through the evaluation of the differential scanning calorimetry, while it also exhibits an excellent stability from the anti-osmosis measurement. In addition, the confinement effect of n-octadecane inside the microcapsules also results in a significant decrease in both the melting and crystallization temperatures of the micro-PCMs.
Co-reporter:Zhengwei Jin, Xiaodong Wang, Xiuguo Cui
Microporous and Mesoporous Materials 2008 Volume 108(1–3) pp:183-192
Publication Date(Web):1 February 2008
DOI:10.1016/j.micromeso.2007.03.042
Well-ordered mesoporous silica materials were synthesized by using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer as template through two-step pathway under mildly acidic conditions (pH 2.2–4.1). The highly ordered cage-like mesoporosity of the prepared materials having cubic Fm3m mesostructure was evidenced by the well-defined small angle X-ray diffraction patterns combined with transmission electron microscopy. Scanning electron microscopy observation exhibits a macron-sized spherical morphological structure for the prepared materials at pH 2.2, and a variation trend to small amount of spheres on the surface of randomly shaped agglomerations with increasing the pH value. The nitrogen adsorption–desorption analysis reveals that the prepared mesoporous silica materials have a uniform moderate-sized pore diameter (5.6–6.5 nm) and a very thick pore wall (4.96–6.10 nm). These features may lead to a much higher thermal, hydrothermal, and mechanical stability. The mesoporous silica materials synthesized in this study will favor the incorporation of catalytically active heteroatoms in silica frameworks, and the functionalization of organic groups for applications in catalysis, sensor and separation. The two-step synthetic method under mildly acidic conditions can also be extended to the production in the industrial scale as an environmentally friendly way.
Co-reporter:Huanzhi Zhang, Xiaodong Wang
Journal of Non-Crystalline Solids 2008 Volume 354(45–46) pp:5068-5073
Publication Date(Web):15 November 2008
DOI:10.1016/j.jnoncrysol.2008.07.022
Novel lamellar-mesostructured poly(ethylene glycol) distearate (PEGDS)/silica hybrids have been synthesized successfully through self-assembly with a sol–gel technology, in which the PEGDS is imbedded within silica interlayers through a micelle-templating technique by seeding rod micelles of the PEGDS as surfactant aggregate during the condensation of the silica sol performed by the hydrolysis of organosilane precursor. The well-ordered lamellar mesostructure was confirmed by X-ray diffraction patterns, transmission electronic microscopy, and N2 adsorption–desorption isotherms. Studies on confined behaviors of the PEGDS within silica matrix indicated that the molecular chains of the PEGDS with two-dimensional degree of freedom could still crystallize, though they were stranded one-dimensionally between the silica interlayers. However, the confinement effects of the lamellar mesostructure caused a significant decrease in both the melting and crystallization temperatures of the PEGDS.
Co-reporter:Zhengwei Jin, Xiaodong Wang, Xiuguo Cui
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2008 Volume 316(1–3) pp:27-36
Publication Date(Web):5 March 2008
DOI:10.1016/j.colsurfa.2007.08.013
Finely ordered SBA-15-type mesoporous silica materials were synthesized by templating with an amphiphilic block copolymer under various conditions, and their internal two-dimensional hexagonal mesostructures were confirmed by X-ray diffraction patterns, transmission electronic microscopy and nitrogen adsorption–desorption isotherms. Evaluation on morphological dependence of the synthetic conditions demonstrated that, for the samples synthesized through a one-step route, a variety of morphologies (e.g. short columns, spheres, hexagonal platelets, etc.) were achieved by means of adjusting acid species, reaction temperature, acidity and the concentration of inorganic salt. For the samples synthesized through a two-step route under mildly acidic conditions, the morphologies can be controlled by acidity of the solutions, and exhibits the irregularly faceted particles, the spherical ones, and the aggregated spheres by varying the pH from 1.02 to 2.61.
Co-reporter:Zhengwei Jin, Xiaodong Wang, Xiuguo Cui
Journal of Colloid and Interface Science 2007 Volume 307(Issue 1) pp:158-165
Publication Date(Web):1 March 2007
DOI:10.1016/j.jcis.2006.11.006
Highly ordered SBA-16-type mesoporous silica materials were synthesized by using poly(ethylene oxide–b–propylene oxide–b–ethylene oxide) triblock copolymer (EO132–PO50–EO132, Pluronic F108) as template through a two-step pathway under mildly acidic conditions (pH 2.15–4.50). The highly ordered cage-like mesoporosity of the prepared SBA-16-type mesoporous silica materials having Im3m cubic mesostructure was proved by the well-defined X-ray diffraction patterns combined with transmission electron microscopy. Scanning electron microscopy shows a variation from the spherical agglomerations to the randomly shaped ones with an increase of pH value. The nitrogen adsorption–desorption analysis reveals that the prepared SBA-16-type mesoporous silica materials have a uniform small-sized pore diameter (3.37–4.24 nm) and very thick pore wall (8.84–10.2 nm). These features may make the SBA-16-type mesoporous silica materials synthesized in this study favor the incorporation of catalytically active heteroatoms in silica frameworks, and the functionalization of organic groups for applications in catalysis, sensor and separation. The two-step synthetic method under the mildly acidic conditions can also be extended to the production in the industrial scale as an environmentally friendly way.Small-pored and thick-walled SBA-16-type mesoporous silica materials were synthesized by templating with an amphiphilic triblock copolymer through a two-step pathway under mildly acidic conditions. This new synthetic method is friendly to the environment, and is possible to be extended to preparation of a wide family of the mesoporous silica materials as well as their industrial products.
Co-reporter:Zhengwei Jin, Xiaodong Wang, Xiuguo Cui
Journal of Non-Crystalline Solids 2007 Volume 353(Issue 26) pp:2507-2514
Publication Date(Web):1 August 2007
DOI:10.1016/j.jnoncrysol.2007.05.003
Highly ordered mesoporous silica materials have been synthesized under mildly acidic conditions by templating with a nonionic triblock copolymer (Pluronic P104) in a two-step process. It was found that a transformation from the SBA-15 type 2-dimensional (2D) hexagonal channel mesostructure (p6mm symmetry) to the MSU-X type 3-dimensional (3D) worm-like mesostructure could be induced by varying the pH whilst keeping all other conditions constant. The transformation between two types of mesoporous silica materials can be attributed to the effect of varying proton concentration on the interaction between organic micelles and inorganic species. Both types of mesoporous materials have high surface areas, large pore volumes, thick pore walls, large mean pore sizes, and narrow pore size distribution.
Co-reporter:Zhengwei Jin;Xiuguo Cui
Journal of Materials Science 2007 Volume 42( Issue 2) pp:465-471
Publication Date(Web):2007 January
DOI:10.1007/s10853-006-1170-9
Ordered and cubic mesoporous silica materials were synthesized by using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer as template under a moderately acidic condition of 0.5 mol/l HCl solution. These mesoporous materials were characterized by Fourier transform (FT) IR spectroscopy, thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption measurements. The three-dimensional cage-like microporosity of the prepared mesoporous silica having ordered hexagonal mesoporous structure was evidenced by the well-defined XRD patterns combined with TEM photographs. SEM observation shows a highly regular cubic crystal structure for the prepared mesoporous silica. The size of these crystallites was maintained within the range between 4 and 6 μm, which is fairly important for the application to the stationary phase for separation. The nitrogen adsorption–desorption analysis reveals that the prepared mesoporous silica possesses a small pore diameter of 3.68 nm, a total surface area of 363.648 m2/g, a total pore volume of 0.379 cm3/g, and a pore-wall thickness of 6.63 nm. These features may lead to higher thermal and hydrothermal stability, excellent microporosity, and good connectivity. The mesoporous silica prepared in this study exhibits potential applications to catalysis, sensoring, and separation.
Co-reporter:Xiuguo Cui
Journal of Applied Polymer Science 2006 Volume 101(Issue 6) pp:3791-3799
Publication Date(Web):27 JUN 2006
DOI:10.1002/app.24040
The multilamellar barrier materials based on the blends of high-density polyethylene (HDPE) and copolyester (PETG) were prepared via melt extrusion, and poly(ethylene-co-acrylic acid) (EAA) as a compatibilizer was incorporated into the blends. A systematic investigation was carried out, with regard to morphology and properties. Scanning electron microscopy observation displayed the laminar morphology for the blends with the whole compositions, and the thinner laminas of the PETG phase formed in the HDPE matrix by incorporating EAA into the blends. In addition, the number and the size of the laminas of the dispersed phases were also dependant on the die temperature and screw speed, respectively. Evaluation of the mechanical properties demonstrated that incorporation of the EAA resulted in an improvement of the mechanical properties. These behaviors are attributed mainly to better adhesion and compatibility between HDPE and PETG, which has been confirmed by thermal analysis and the rheological properties. On the basis of these premises, it is reasonable to suggest that the improved barrier properties of the ternary blends with increasing concentration of the EAA be attributed to both the increase in the number of the laminas of the PETG and the decrease in their thickness, which prohibits the organic solvent molecules from entering into and permeating through the amorphous regions of the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3791–3799, 2006
Co-reporter:Xin Luo;Lei Wu
Journal of Applied Polymer Science 2006 Volume 102(Issue 6) pp:5472-5482
Publication Date(Web):28 SEP 2006
DOI:10.1002/app.25171
In the present work, we extend the investigation on the influence of processing conditions on the morphology, the mechanical properties, and the rheology of the blends of thermoplastic polyurethane (TPU) and ethylene–propylene–diene monomer elastomer (EPDM). Scanning and transmission electron microscopies show that the dual-phase continuous morphology of the blends was strongly dependant on the EPDM composition, processing temperature, and the shear rates. The network structure of the EPDM domain in TPU matrix became finest and most regular for the blends containing 7 wt % EPDM. It was also found that high shear rate favored the formation of the perfect network structure. Furthermore, the blends prepared at 180°C present finer and more perfect network structure than those at the other processing temperatures. The competition of compatible and incompatible segments of TPU with EPDM during melt blending plays an important role in development of the dual-phase continuous morphology. This was reflected through the influence of processing conditions on the rheological properties, and was also verified by the Davies equation's prediction. The tensile properties present a significant improvement with addition of EPDM, and obtained the optimum value for the blends containing 7 wt % EPDM. The influence of different processing parameters on the mechanical properties is associated with their influence on the morphology, and better tensile properties are obtained in the processing conditions, in which, the finer and more perfect network structure of EPDM domain is presented. These facts confirm that the dual-phase continuous morphology is the main advantage for higher tensile strength, elongation at break, and Young's modulus can be well controlled by different processing conditions for the improvement of mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5472–5482, 2006
Co-reporter:Xiaodong Wang, Xiuguo Cui
European Polymer Journal 2005 Volume 41(Issue 4) pp:871-880
Publication Date(Web):April 2005
DOI:10.1016/j.eurpolymj.2004.10.046
Two ionomers, ethylene–methacrylic acid copolymer ionized with sodium cation (EMA-Na) and zinc cation (EMA-Zn), were employed as impact modifiers to prepare blends with polyoxymethylene (POM) via a melt extrusion. A copolymer of methyl methacrylate–styrene–butadiene (MBS) used as a co-impact modifier was also incorporated into the blends. The mechanical properties, thermal properties, morphology, and rheology were studied. A moderate toughening was observed for POM/ionomer binary blends, which was attributable to the rubbery natural and good adhesion of the ionomers. EMA-Zn exhibited a much better toughening effect than EMA-Na because of its higher elasticity and stronger interaction with POM. The incorporation of the ionomers into POM/MBS blends resulted in an improvement of mechanical properties, which was attributable to the compatibilizing effect of ionomer on POM/MBS blending system. The observation of scanning electron microscopy demonstrated that the finer phase domains were caused by incorporation of ionomers, which, acting as a compatibilizer as well as an impact modifier, reduced the interfacial tension and improved the interfacial adhesion between the phases. Differential scanning calorimetry investigation indicated that the presence of ionomer in the blends disturbed the crystallization of POM and resulted in a decrease in the crystallinity of POM. The evaluation of melt flow index revealed an increase in viscosity of the blends by incorporation of the ionomers, which was caused the ionic interaction between POM and the ionomers.
Co-reporter:Xiaodong Wang, Xin Luo, Xinfeng Wang
Polymer Testing 2005 Volume 24(Issue 1) pp:18-24
Publication Date(Web):February 2005
DOI:10.1016/j.polymertesting.2004.08.003
Blends of Estane® thermoplastic polyurethane (TPU) and aliphatic polyester were prepared via melt blending and blend films were prepared via blow molding. The morphology, thermal properties and rheology of the blends, and the properties as moisture vapor permeable films were studied. Differential scanning calorimetry and Fourier transformed infrared spectroscopy investigation indicated that the TPU was compatible with the aliphatic polyester. Scanning electron microscopy (SEM) micrographs exhibited a particle-dispersed type of the morphology, in which the aliphatic polyester was finely dispersed as regular spherical particles in the TPU matrix when the content of the aliphatic polyester was below 30 wt%; however, the dispersed domain presented an irregular form owing to aggregation when the content of the aliphatic polyester reached 40 wt%. Evaluation of the properties of the blend films demonstrated that incorporation of the aliphatic polyester could significantly enhance the adhesive strength and the tensile properties of the TPU film, but the moisture vapor permeability and the waterproofness deteriorated. The blend films will still have a balance of comfort and laminating processability as long as the aliphatic polyester content is controlled to an appropriate level, i.e. below 20 wt%.
Co-reporter:Xiaodong Wang, Qiang Zhang
European Polymer Journal 2004 Volume 40(Issue 2) pp:385-395
Publication Date(Web):February 2004
DOI:10.1016/j.eurpolymj.2003.09.023
An organophosphorus compound, 10-(2,5-dihydroxyl phenyl)-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DHPDOPO), was synthesized through the reaction of 9,10-dihydro-9-oxa-10-phosphaphnanthrene-10-oxide (DOPO) and p-benzoquinone, and characterized by elemental analysis, Fourier transform infrared spectrum (FTIR), and 1H-NMR and 31P-NMR spectroscopes. Consequently, the phosphorus-containing epoxy resins with phosphorus content of 1 and 2 wt.% were prepared via the reaction of diglycidyl ether of bisphenol-A with DHPDOPO and bisphenol-A, and confirmed with FTIR and gel permeation chromatography (GPC). Phenolic melamine, novolak, and dicyanodiamide (DICY) were used as curing agents to prepare the thermosetted resins with the control and the phosphorus-containing epoxy resins. Thermal properties and thermal degradation behaviors of these the thermosetted resins were investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Phenolic melamine-cured resins exhibited higher glass transition temperatures than the other cured resins due to the high rigidity of their molecular chain. TGA studies demonstrated that the decomposition temperatures of the novolak-cured resins were higher than those of the others. A synergistic effect from the combination of the phosphorus-containing epoxy resin and the nitrogen-containing curing agent can result in a great improvement of the flame retardance for their thermosetted resins.
Co-reporter:Xiaodong Wang, Xin Luo
European Polymer Journal 2004 Volume 40(Issue 10) pp:2391-2399
Publication Date(Web):October 2004
DOI:10.1016/j.eurpolymj.2004.06.008
Blends of thermoplastic polyurethane (TPU) and ethylene–propylene–diene elastomer (EPDM) were prepared via a melt blending, and morphology, mechanical properties, and rheology were studied. Scanning electron microscopy (SEM) micrographs demonstrated that a network of EPDM domain was formed in TPU matrix, and became finer and more perfect with addition of 8 wt% EPDM into TPU. Dynamic mechanical analysis (DMA) and Fourier transformed infrared spectroscopy (FTIR) investigation indicated that EPDM was thermodynamically miscible with the soft segments of TPU and incompatible with the hard segments. The formation of the network was resulted from the competition of compatible and incompatible segments of TPU with EPDM. The tensile strength and elongation at break achieved a significant improvement with addition of EPDM, and obtained the optimum values of 39.21 MPa and 2659%, respectively, when EPDM content was 8 wt%. PEO-g-MA as a compatibilizer was employed to improve the compatibilization between EPDM and the hard segments of EPDM, and consequently, the network became finer and more perfect. The evaluation of rheological properties revealed that the introduction of EPDM into TPU resulted in a reduction of the viscosity at high shear rate and a decrease of the flow activation energy; thus the processability of the blends was improved.
Co-reporter:Xiaodong Wang;Qiang Zhang
Polymer International 2004 Volume 53(Issue 6) pp:
Publication Date(Web):15 APR 2004
DOI:10.1002/pi.1482
Compounds of poly(vinyl chloride) (PVC) and hydrotalcite were prepared via melt blending, and the thermal stability, mechanical properties, rheology and flame retardance were studied. Transmission electron microscopy showed that the hydrotalcite achieved an optimal dispersion in PVC compounds when surface-treated with titanate coupling agent. The Congo Red test and thermogravimetric analysis demonstrated that the thermal stability of PVC was improved significantly only in the presence of a complex of the hydrotalcite and the organotin stabilizer. Such a significantly positive thermal stabilizing effect was attributable to the stabilizing mechanisms that the electrostatic interaction generated between the electron cloud of chlorine atoms in PVC chain and the positive lay charge of hydrotalcite, which resulted in a decrease in electronic cloud density of chlorine atoms. This weakened the activity of chloride atoms, and restricted the initiation of the dehydrochlorination. A surface treatment for the hydrotalcite with the titanate coupling agent could reduce deterioration of the mechanical and rheological properties of the PVC at low concentration of hydrotalcite. The hydrotalcite also enabled useful application of PVC as a flame retardant as well as a smoke retarder in the light of a LOI value of more than 28.7 and UL 94 V-0 grade at a PVC/hydrotalcite weight ratio of 70/30. Copyright © 2004 Society of Chemical Industry
Co-reporter:Xiaodong Wang;Yongzhi Song;Dezhen Wu;Riguang Jin
Journal of Applied Polymer Science 2004 Volume 92(Issue 4) pp:2714-2723
Publication Date(Web):11 MAR 2004
DOI:10.1002/app.20295
Nanocomposites of poly(vinyl chloride) (PVC) and nano-calcium carbonate (CaCO3) particles were prepared via melt blending, and chlorinated polyethylene (CPE) as an interfacial modifier was also introduced into the nanocomposites through preparing CPE/nano-CaCO3 master batch. The mechanical properties, morphology, and rheology were studied. A moderate toughening effect was observed for PVC/nano-CaCO3 binary nanocomposites. The elongation at break and Young's modulus also increased with increasing the nano-CaCO3 concentration. Transmission electron microscopy (TEM) study demonstrated that the nano-CaCO3 particles were dispersed in a PVC matrix uniformly, and a few nanoparticles agglomeration was found. The toughening effect of the nano-CaCO3 particles on PVC could be attributed to the cavitation of the matrix, which consumed tremendous fracture energy. The notched Izod impact strength achieved a significant improvement by incorporating CPE into the nanocomposites, and obtained the high value of 745 J/m. Morphology investigation indicated that the nano-CaCO3 particles in the PVC matrix was encapsulated with a CPE layer through preparing the CPE/nano-CaCO3 master batch. The evaluation of rheological properties revealed that the introduction of nano-CaCO3 particles into PVC resulted in a remarkable increase in the melt viscosity. However, the viscosity decreased with addition of CPE, especially at high shear rates; thus, the processability of the ternary nanocomposites was improved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2714–2723, 2004
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