Co-reporter:
Journal of Applied Polymer Science 2017 Volume 134(Issue 11) pp:
Publication Date(Web):2017/03/15
DOI:10.1002/app.44575
ABSTRACTThe homogeneous dispersion and strong interfacial interactions of carbon nanomaterials are vital factors on enhancing the properties of polymer composites. Two-dimensional reduced graphene oxide (rGO) and one-dimensional carbon nanotubes (CNTs) were first grafted by 4,4′-oxydianiline (ODA). The successful grafting of ODA onto the rGO and CNTs were confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The hybrid carbon nanomaterials of the functionalized CNTs and rGO with different ratios were prepared via a solution-mixing method, and their dispersion state was investigated. The hybrid carbon nanomaterials with good stability were introduced to polyimide (PI) via in situ polymerization. The morphology and properties of the polymer composites were studied. The results show that much better mechanical and electrical properties of the composites could be achieved in comparison with those of the neat PI. An improvement of 100.7% on the tensile strength and eight orders for the electrical conductivity were achieved at only a 1.0 wt % hybrid content. A significant enhancement effect was attributed to the homogeneous dispersion of the filler, filler–matrix strong interfacial interactions, and unique structure of the hybrid carbon nanomaterials in the composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44575.
Co-reporter:Yanchao Shi, Guojian Wang
Progress in Organic Coatings 2016 Volume 97() pp:1-9
Publication Date(Web):August 2016
DOI:10.1016/j.porgcoat.2016.02.023
•The novel epoxy/1-oxo-4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane (PEPA) phosphate flame retardant was synthesized by epoxy and PEPA dihydrogen phosphate.•A new method to synthesize the PEPA dihydrogen phosphate was developed with polyphosphoric acid as phosphorylation reagent instead of phosphorus oxychloride.•Incorporation of bisphenol A epoxy resin could enhance the thermal stability, char-forming ability and thermo-oxidation resistance of transparent fire resistant coating efficiently.•Excellent fire protection when the novel flame retardant was applied in the melamine formaldehyde resin system.A series of novel epoxy/PEPA phosphate (EPP) flame retardants were synthesized by 1-oxo-4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane (PEPA), polyphosphoric acid (PPA), and epoxies of bisphenol A epoxy resin E51 (EP) and 1,4-butanediol diglycidyl ether (BDE) with different proportions. The structure of EPP was characterized by 1H nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). Then EPPs as flame retardants were blended with amino resin to prepare the transparent intumescent fire resistant coatings. The fire protection test showed that the best fire protection was obtained when the ratio of EP/BDE was 1/2. The char layers of coatings were investigated by intumescence ratio and scanning electron microscopy (SEM). The intumescence ratio result illustrated that the intumescence ratio of char layers decreased with the increase of EP/BDE ratio. The SEM images demonstrated that incorporation of EP could significantly improve the foam structure of char layers when the ratio of EP/BDE was no more than 1/2. Next, the thermal decomposition behaviors of the coatings were studied by thermogravimetric analysis (TGA) under nitrogen and air. The results demonstrated that incorporation of EP could enhance the thermal stability and residual weight of fire resistant coating as well as the thermo-oxidation resistance of the char layers. Finally, the real-time FTIR proved that the decomposition process of fire resistant coatings included three stages bellow 550 °C, which was consistent with the result in TGA.
Co-reporter:Yanchao Shi, Guojian Wang
Applied Surface Science 2016 Volume 385() pp:453-463
Publication Date(Web):1 November 2016
DOI:10.1016/j.apsusc.2016.05.107
Highlights
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The novel halogen-free flame retardant containing silicon and caged bicyclic phosphate was synthesized.
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A novel transparent intumescent fire resistant coating was developed by the P-Si synergistic flame retardant and melamine formaldehyde resin.
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Excellent fire protection of the transparent intumescent fire resistant coating.
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The P-Si synergistic flame retardant could improve the thermo-oxidation resistance of transparent fire resistant coating.
Co-reporter:Lang Ma;Jinfeng Dai
Journal of Applied Polymer Science 2016 Volume 133( Issue 34) pp:
Publication Date(Web):
DOI:10.1002/app.43820
ABSTRACT
Graphene oxide (GO), as an important precursor of graphene, was functionalized using alkyl-amines with different structure and then reduced to prepare reduced amines grafted graphene oxide (RAGOs) by N2H4 · H2O. The successful chemical amidation reaction between amine groups of alkyl-amines and carboxyl groups of GO was confirmed by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA). Then RAGOs/polyimide nanocomposites were prepared via in situ polymerization and thermal curing process with different loadings of RAGOs. The modification of amine chains lead to homogenous dispersion of RAGOs in the composites and it formed strong interfacial adhesion between RAGOs and the polymer matrix. The mechanical and electrical properties of polyimide (PI) were significantly improved by incorporation of a small amount of RAGOs, the influence of structure of amines grafted on RAGOs on the enhancement effects of composites was discussed. The research results indicated that the proper structure of amine could effectively enhance the properties of composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43820.
Co-reporter:Yanchao Shi
Journal of Coatings Technology and Research 2016 Volume 13( Issue 3) pp:457-468
Publication Date(Web):2016 May
DOI:10.1007/s11998-015-9763-3
Three kinds of novel PEPA-containing polyether flame retardants were synthesized by 1-oxo-4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo [2.2.2] octane (PEPA), phosphorus oxychloride (POCl3), and polyether with different structures (PEG, PPG, and PTMG). Their structures were confirmed by 1H nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The solubility test showed that PEPA modified by polyethylene glycol (PEG) and polypropylene glycol (PPG) had better water solubility than that modified by poly(tetrahydrofuran) (PTMG). The decomposition process of PEPA-containing polyether flame retardants (PCPE) was studied by thermogravimetric analysis (TG) and derivative thermogravimetry. A possible mechanism was proposed to analyze the influence of polyether structure on the thermal degradation process of PCPEs. Afterward, the PEPA-containing polyether flame retardants were mixed with melamine formaldehyde resin to prepare the transparent fire-resistant coatings. The influences of polyether structure on the properties of the coatings were investigated in detail by fire protection test, TG, FTIR, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope. It was found that the fire protection of the coating and foam structure of char layer were significantly improved when the number of carbon atoms in a unit of polyether chain was less. TG results showed that the chain unit of polyether with less carbon atom number could increase the residue weights of the coatings. FTIR and XPS result illustrated that the char layers were mainly composed of aromatic rings and phosphorus oxide, and the antioxidation and char-forming ability of coatings were enhanced effectively with the decrease in the number of carbon atoms in a unit of polyether chain.
Co-reporter:Wei Xu, Guojian Wang, Xiaorui Zheng
Polymer Degradation and Stability 2015 Volume 111() pp:142-150
Publication Date(Web):January 2015
DOI:10.1016/j.polymdegradstab.2014.11.008
Flame retardant rigid PU foams (RPUF) were prepared by using nanostructured zinc oxide (ZnO), Zeolite and montmorillonite (MMT) combined with traditional phosphorus flame retardants as flame retardant systems. Phosphorus flame retardants were ammonium phosphate (APP) and dimethyl methyl phosphonate (DMMP). The former mainly took effect in condensed phase and the latter mainly played role in gas phase. Nanostructured additives (Nanos) were used to reduce flammable gas release rate and to form highly protective char layer. Research results showed that RPUFs showed different combustion performances, when different Nanos added together with APP and DMMP. ZnO and MMT narrowed the heat release peak of RPUFs, but the intensity of the peak did not reduce. Heat release rate (HRR) of RPUF with Zeolite/DMMP/APP flame retardant system was only 91 kW/m2, which was 56% lower than that of pure RUPF and 26% lower than RPUF only with DMMP/APP flame retardant system, while the limiting oxygen index (LOI) of RPUF reached 29.5%. Further study indicated that structure of Nanos and the interaction between Nanos and phosphorus flame retardants was essential to the effect of flame retardant system.
Co-reporter:Wei Xu
Journal of Applied Polymer Science 2015 Volume 132( Issue 30) pp:
Publication Date(Web):
DOI:10.1002/app.42298
ABSTRACT
Two types of polyhydric alcohol/ethanol phosphates (PAEPs) were synthesized by a two-step reaction using phosphorus oxychloride, ethanol, and polyhydric alcohol (glycerol and pentaerythritol). First, phosphorus oxychloride was reacted with ethanol to form a mixture of diethyl chlorophosphate and tri-ethyl phosphate, and then PAEPs were prepared by the reaction between the above mixture and polyhydric alcohol. The chemical structures of PAEPs were characterized by 1H NMR, and the elemental compositions were analyzed by X-ray photoelectron spectroscopy (XPS). The degradation behavior of the PAEPs and their solubility in polyols were studied. The results indicated the PAEPs could be well dissolved in polyols. When PAEPs were used as flame retardant for PU rigid foams at a content of 8 wt %, the char residue of polyurethane foam at 800°C increased from 17.2 to 28% in average, and the peak heat release rate (pHRR) of polyurethane foam decreased significantly from 207 to 133 kW/m2. In addition, PURF with PAEPs showed remarkable intumescent property. The results indicated that PAEPs were effective condensed phase flame retardant with char catalytic and intumescent property. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42298.
Co-reporter:Jinfeng Dai;Lang Ma;Chengken Wu
Journal of Materials Science 2015 Volume 50( Issue 11) pp:3895-3907
Publication Date(Web):2015 June
DOI:10.1007/s10853-015-8934-z
Recent research has highlighted a remarkable growing focus on surface properties and dispersibility of graphene. In this study, we fabricated four types of surface-modified graphene oxide and its derivatives with different C/O ratios by facile chemical methods. The extent of modification, surface energies, and dispersibility of the as-prepared samples were investigated through elemental analysis, X-ray photoelectron spectroscopy, contact angle, inverse gas chromatography, dynamic multiple light scattering method, and atomic force microscope. Results demonstrated that surface energies are affected by functional groups and C/O ratios significantly. The higher the proportion of polar oxygen-containing groups of materials is, the larger the values of polar surface energies and total surface energies are. Dispersibility of graphene oxide and its derivatives depends not only on surface groups and degree of modification of samples, but also on Hansen solubility parameters of solvents. As a result, we proposed a predicted template to screen the ranges of potential graphene solvents. Such a research presented here would facilitate preparation of graphene–polymer composites and development of graphene-based materials.
Co-reporter:Xiaorui Zheng, Guojian Wang, Wei Xu
Polymer Degradation and Stability 2014 Volume 101() pp:32-39
Publication Date(Web):March 2014
DOI:10.1016/j.polymdegradstab.2014.01.015
The improvement of the flame retardancy of rigid polyurethane foam (RPUF) has been attracted much attention, and addition of phosphorus flame retardants and/or nanomaterials is one of good methods. Two systems have been adopted to improve the flame retardancy of RPUF in this work. Firstly, the phosphorus flame retardant system of ammonium polyphosphate (APP) and triphenyl phosphate (TPP) is introduced to promote the char-forming property of RPUF during its combustion. Thermogravimetric analysis (TGA) results show that the thermal stability and the char yield of RPUF have been extremely improved by addition of APP-TPP system. Secondly, organically-modified montmorillonite (OMMT), possessing of its particular nano-layer structure, is incorporated as an additional filler in the APP-TPP/RPUF system to further improve the flame retardancy of RPUF. The CONE combustion tests indicate that 5% OMMT/8% APP-4% TPP/RPUF (ATO-845) exhibit the longest combustion duration time, slowest heat release rate and lowest total smoke production among pure RPUF (ATO-000), 5% OMMT/RPUF (ATO-005), 8% APP-4% TPP/RPUF (ATO-840), and ATO-845 samples. The extraordinary flame retardant performance of ATO-845 is attributed to the synergy effect between OMMT and APP-TPP system in forming a mass of integrated, stable and tight charred layers during the combustion of RPUF.
Co-reporter:Yang Liu;Guo-Jian Wang;Ying-Jie Wu
Colloid and Polymer Science 2014 Volume 292( Issue 1) pp:185-196
Publication Date(Web):2014 January
DOI:10.1007/s00396-013-3066-y
Multi-walled carbon nanotubes (MWCNTs) can self-assemble as cylindrical bundles in some solvents after polystyrene (PS) grafting. In these three-dimensional regular structures, the tubes are oriented and parallel arranged. Every self-assembly structure has an order head and a comparatively loose tail. In order to find out the role that solvent plays, MWCNTs were dispersed in several organic solvents before and after modification. Based on macroscopic stability of suspensions and microscopic state of nanotubes, compatibility between solvents and MWCNTs can be confirmed. According to compatibility difference between tubes and PS, five chosen solvents are divided into three groups: selective solvent, good solvent, and bad solvent. MWCNT-g-PS can self-assemble only in selective solvents. Tetrahydrofuran and benzene are well compatible with PS, but bad with MWCNTs. Driven by the solvent–philic/solvent–phobic interaction, MWCNT-g-PS self-organized regularly as bundles. Because each part of the MWCNT-g-PS is compatible well with 1,2-dichlorobenzene, gathering tendency of the modified tubes have been enervated by their good compatibility and weak amphiphilicity. Grafted or not, nanotubes reveal poor compatibility with methanol and ethanol. Strong incompatibility and limited amphiphilicity make MWCNT-g-PS agglomerate as quickly and irregularly as raw tubes. An adapted hydrophilic/lipophilic balance system is introduced to qualify compatibility and amphiphilicity of MWCNT-g-PS in each solvent. This novel model not only reveals the relationship between solvent and microscopic state of unmodified/modified tubes, but also signifies the decisive role of solvent in self-assembly behaviors of MWCNT-g-PS.
Co-reporter:Jin-Feng Dai;Guo-Jian Wang;Cheng-Ken Wu
Chromatographia 2014 Volume 77( Issue 3-4) pp:299-307
Publication Date(Web):2014 February
DOI:10.1007/s10337-013-2597-1
The surface properties of graphene oxide (GO) and graphene (rGO) have been investigated for the first time using inverse gas chromatography at infinite dilution. The GO and rGO were prepared by classical Hummers method and chemical reduction method, respectively, and their structures were characterized using FT-IR, XDR, XPS, SEM, and TEM. It is found that their dispersive (\( \gamma_{\text{s}}^{\text{D}} \)), polar (\( \gamma_{\text{s}}^{\text{P}} \)), and total (\( \gamma_{\text{s}}^{\text{T}} \)) surface energies were 28.5, 18.0, 46.5 mJ m−2 and 98.3, 6.60, 104.9 mJ m−2 at 313.15 K, respectively. The results indicate that these samples differ in their surface properties, due to their structure (existence of oxygen-containing functional groups, of defects). By referencing the empirical relationship to establishing the donor (KD) and acceptor (KA) interaction parameters of the various samples, the Lewis acid–base character of the surface can be reliably identified. As a result, it is revealed that GO is a Lewis-base material, whereas rGO tends to be amphoteric but is also a Lewis-base material. Evaluation of surface properties of graphene could be used to guide the processing and application in graphene-based nanocomposites in the future.
Co-reporter:Ying Dong;Jiayun Yang
Journal of Coatings Technology and Research 2014 Volume 11( Issue 2) pp:231-237
Publication Date(Web):2014 March
DOI:10.1007/s11998-013-9532-0
The combination of self-crosslinking polyacrylate emulsion and silicone emulsion was used as a binder for the preparation of waterborne intumescent fire-resistive coatings. The influences of silicone emulsion on fire protection and char formation of the coatings were investigated in detail by means of TGA, SEM, energy dispersive spectroscopy analysis, rheological measurement, and fire protection tests. The results showed that using silicone emulsion improved thermal stability and antioxidation ability of the coating and increased the residue weights of the char layer at high temperature. Furthermore, an appropriate amount of silicone emulsion could improve the rheological property of the mixed binders and be conducive to the increase of the intumescent factor of the coatings, thus improving the fire protection of the coating significantly. However, an excess amount of silicone emulsion can lead to uneven dispersion of silicone emulsion in the mixed binder and cause an uneven distribution of cell size of the char layer.
Co-reporter:Ying Dong
Journal of Coatings Technology and Research 2014 Volume 11( Issue 2) pp:265-272
Publication Date(Web):2014 March
DOI:10.1007/s11998-013-9542-y
Nano-sized BN and micron-sized BN were used as fillers in fire-resistive coatings. The experimental results suggested that nano-BN with a multilayer structure could remarkably enhance the fire protection of fire-resistive coatings. Turbiscan data indicated that nano-sized BN had better dispersion stability in waterborne coatings than micron-sized BN. TGA results showed that nano-sized BN could enhance the thermal stability of the coatings, especially under high temperature. FTIR and EDS results exhibited that nano-sized BN was helpful in reducing the oxidation degree and enhancing the antioxidation property of the char layer under high temperature. The morphology observation demonstrated that nano-sized BN could improve the foam structure of the char layer so as to improve the mechanical strength of the char layer. Nano-sized BN was helpful for the even distribution of the cells; thus the efficiency of heat insulation of the char layer was enhanced. These results proved that nano-sized BN was beneficial to the forming and expanding of the intumescent char layer, and could provide better fire protection for the coatings.
Co-reporter:Ying Dong;Qin Su
Journal of Coatings Technology and Research 2014 Volume 11( Issue 2) pp:207-216
Publication Date(Web):2014 March
DOI:10.1007/s11998-013-9549-4
The changes in fire-resistive coatings during the aging process were studied. XPS results proved that the hydrophilic components in fire-resistive coatings migrated from the inside to the outside of the coating in the presence of moisture. This migration behavior changed the compositions and distributions in the coating. The changes of components weakened the intumescent performances of the coating. SEM observations showed that the aging process affected the forming of the foam structure, causing nonuniform distribution of the cells. The thermal stability of the coatings decreased during the aging time. TGA results indicated that the migration behavior also reduced the cooperation between the coating components. XRD spectra showed that less TiP2O7 was produced in the char layer after the aging tests, which would reduce the chemical strength of the char layer and the anti-ablation stability under high temperature. EDS results showed that the anti-oxidation property of the coating was also damaged by the aging test.
Co-reporter:Ying Dong;Qin Su
Journal of Coatings Technology and Research 2014 Volume 11( Issue 5) pp:805-815
Publication Date(Web):2014 September
DOI:10.1007/s11998-013-9538-7
The influence of nano-boron nitride (BN) with a multilayered structure on the anti-aging property of fire-resistive coatings was studied. After accelerated weathering for 20 days, the thermal stabilities and fire protection of the coating without nano-BN were significantly decreased, but the coating modified by nano-BN still maintained excellent intumescent effect and fire protection. The results indicated that nano-BN could improve the anti-aging property of the coatings remarkably. FTIR and XPS characterizations suggested that nano-BN with a multilayered structure could prevent the migration behavior of the hydrophilic fire-retardant additives and keep the fixed ratio of those additives in the coating. TGA results demonstrated that nano-BN could effectively enhance the thermal stabilities of the aged coatings and improve the anti-oxidation property of the char layers formed by the coatings. XRD and EDS results proved that the anti-oxidation of the aged coatings under high temperature could be enhanced effectively after adding nano-BN. SEM observations illustrated that nano-BN addition was beneficial to the improvement of the foam structure of the aged coating.
Co-reporter:Junbo Wang, Guojian Wang
Surface and Coatings Technology 2014 Volume 239() pp:177-184
Publication Date(Web):25 January 2014
DOI:10.1016/j.surfcoat.2013.11.037
•Suitable OMMT could be exfoliated and parallelly distributed in the coating.•Excessive OMMT produced negative effect on the properties of the coating.•OMMT improved fire protection and char layer of the coating by barrier effect.•The thermal property of the coating was enhanced by adding OMMT.•Parallel-arranged OMMT could delay the escape of fire retardant additives.Organic-modified montmorillonite (OMMT) was used as nano-layer filler to improve the fire protection, water and corrosion resistance of waterborne intumescent fire retardant coating. The influence of OMMT on the properties of fire retardant coating and the mechanism of OMMT effect on the coating were investigated in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric (TGA) analysis, Fourier transform infrared spectroscopy (FTIR), fire protection test, water and corrosion resistance test. It was found by XRD that OMMT could be exfoliated and dispersed well in the coating with the addition of 1 wt.%, while excessive OMMT was easy to aggregate and dispersed badly. SEM micrographs and EDS analysis results showed that well-dispersed OMMT nano-layers were parallelly distributed in the coating. The results of fire protection test and the observation results of morphology of char layers indicated that the fire protection of the coating and foam structure of the char layer were remarkably improved by adding suitable content of OMMT. TGA analysis demonstrated that OMMT could enhance the combustion residual weight and thermal stability of the coating. Based on the results of water and corrosion resistance test, the parallel-arranged OMMT could significantly slow down the migration and solvation of fire retardant additives through its barrier effect, thereby improving the water and corrosion resistance of the coating.
Co-reporter:Guojian Wang, Yan Huang, Xiang Hu
Progress in Organic Coatings 2013 Volume 76(Issue 1) pp:188-193
Publication Date(Web):January 2013
DOI:10.1016/j.porgcoat.2012.09.005
A mixture (denoted as PX) of phosphates was prepared by the reaction of phosphoric acid and a kind of bicyclic pentaerythritol phosphate (PEPA, 1-oxo-1-phospha-2,6,7-trioxabicyclo[2.2.2]-4-hydroxymethyl octane). Then PX was successfully copolymerized with PEG200 to achieve a novel phosphorus-containing polymer (denoted as PX-co-PEG). 31P NMR, 1H NMR and FT-IR analysis results showed that there were 38.7 wt.% PEPA phosphates and 61.3 wt.% pentaerythritol biphosphates in the PX mixture. The result of GPC indicated that the molecular formula of PX-co-PEG could be noted as PX2.0PEG3.0. Fire protection test results proved that PX-co-PEG modified amino resin applied on the plywood boards effectively extended the protection time over flame. The decomposition process of fire resistant coating was studied by thermogravimetric analysis and FT-IR which could be divided into three characteristic temperature stages. The solid residue was kept to be 14.6 wt.% at 787 °C.Highlights► Phosphoric acid was used to react with PEPA to synthesize PEPA phosphates (PP). ► PP was copolymerized with PEG200 to achieve oligomer written as PP2.0PEG3.0. ► The degradation of PP-co-PEG could be divided into four stages. ► The degradation of PP-co-PEG modified amino resin could be divided into three stages.
Co-reporter:Guojian Wang, Wei Xu
Polymer Degradation and Stability 2013 Volume 98(Issue 11) pp:2323-2330
Publication Date(Web):November 2013
DOI:10.1016/j.polymdegradstab.2013.08.008
Char-forming property of PU rigid foams, which can be assessed by char residue (%) when PU is burned at certain temperature, was studied by TG and DTG. The results showed that pure PU rigid foam had low char residue of only 17%, while 33% of char residue was achieved when PU rigid foam was modified by adding 8 wt% of 1-oxo-2,6,7-trioxa-1-phosphabicyclo[2,2,2] octane (PEPA), which is a caged bicyclic phosphate. The experiment results of FTIR and XPS showed that the PEPA modified PU rigid foam could be dehydrogenated and dehydrated at temperature between 380 and 450 °C, resulting in the increase of char residue of PU rigid foam. Further study also revealed that the addition of CaCO3 nanoparticles could enhance the char stability when the PEPA modified PU rigid foam was being burned. The mechanism was investigated and it was found that the enhanced char stability could be attributed to the limited permeation of oxygen caused by the formation of calcium phosphate and calcium pyrophosphate by the reaction of PEPA and CaCO3 at high temperature, which were covered on or buried in the char layer.
Co-reporter:Yang Liu;Guo-Jian Wang
Fibers and Polymers 2013 Volume 14( Issue 7) pp:1073-1081
Publication Date(Web):2013 July
DOI:10.1007/s12221-013-1073-8
Polystyrene (PS) grafted multi-walled carbon nanotubes (MWCNTs) were well-organized as bundles by a selfassembly method in tetrahydrofuran (THF). PS was synthesized by atom transfer radical polymerization and grafted to the surface of tubes through covalent bonds. Unmodified tubes agglomerated irregularly and precipitated instantly because of poor compatibility with THF. But soluble PS provides solvent-phobic MWCNTs with suspending stability and dispersibility in the dispersant. Therefore, MWCNT-g-PS has amphiphilic property in this selective solvent and owns ability to self-assemble. Scanning and transmission electron microscope images show that self-assemblies (SAs) are columnar with a tight and ordered head and a loose tail. Their length ranges from 15 to 25 µm while width from 1.5 to 4 µm. In these super structures, tubes are regular organized and parallel arranged. Because MWCNT-g-PS has a huge rigid rod-core and multi-flexible-armed structure in the suspension, a novel micro-phase separation model is proposed to explain this behavior. There are two kinds of micro-phase separation locating on two mutual perpendicular faces on tubes. Solvent-philic/solvent-phobic interaction plays a key role in self-assembly. Moreover, a balance between buoyancy and gravity on SAs decides whether this process is finished or not.
Co-reporter:Xiang Hu;Yan Huang
Journal of Coatings Technology and Research 2013 Volume 10( Issue 5) pp:717-726
Publication Date(Web):2013/09/01
DOI:10.1007/s11998-013-9475-5
A cyclic polyphosphate (CPPA) was synthesized by the reaction of polyphosphoric acid and pentaerythritol. Polyethylene glycol (PEG) was introduced in the structure of CPPA to improve its solubility in water and ethanol and five kinds of reactive type flame retardants (MCPPA) were obtained. 31P NMR, 1H NMR, FTIR, and TGA were used to characterize the composition and structure of CPPA and MCPPAs. The experimental results showed that there were 25% cyclic P–O–C structures in the product and MCPPA had better carbonization ability than CPPA. Five kinds of transparent fire-resistive coatings were prepared by the mixing of amino resin with five kinds of MCPPAs. The results of the fire protection test showed that both the fire-resistive time of coatings and intumescent factor of char layers decreased with the increase of molecular weight of PEG. The results of TGA and EDS showed that the carbonaceous residue of coatings and the antioxidation ability of char layers also decreased regularly with the increase of molecular weight of PEG. The SEM images demonstrated that the coating prepared with low molecular weight of PEG contributed to dense form structure and narrow distribution of cell size. Above all, the transparent fire-resistive coating prepared with PEG 200 had the best fire retardancy and stable thermal behavior.
Co-reporter:Yang Liu;Guo-Jian Wang;Ying-Jie Wu
Colloid and Polymer Science 2013 Volume 291( Issue 11) pp:2619-2630
Publication Date(Web):2013 November
DOI:10.1007/s00396-013-3006-x
Polystyrene (PS) with molecular weight of 2.58 × 104 was grafted to multi-walled carbon nanotubes (MWCNTs) via covalent bonds. The modified tubes can self-assemble as regular bundles in tetrahydrofuran (THF) and benzene while unmodified ones cannot but agglomerate seriously and irregularly in the same solvents. In order to find out the role that polymer plays in self-assembly, a series of PS in different molecular weights were synthesized and grafted on the surface of MWCNTs. THF and benzene are two selective solvents because they are well compatible with PS but bad with tubes. Consequently, grafted MWCNTs show amphiphilicity in them. Solvent-philic/solvent-phobic interaction controls the self-assembly driving force. Small PS offers MWCNTs worse compatibility and poorer amphiphilicity than big PS. With amphiphilicity faded, grafted tubes lose self-assembly ability gradually. Meanwhile, degenerated compatibility cripples tubes’ mobility. Therefore, both number and size of self-assemblies (SAs) decline when molecular weight of grafted PS diminishes. SAs lose their regularity and structural integrativity at the same time. Turbiscan stability index was introduced to quantify the compatibility between dispersate and solvents. Besides, a solvent-philic/solvent-phobic balance system was proposed to calculate compatibility and amphiphilicity of all the modified tubes. This model establishes a connection between compatibility, amphiphilicity, and self-assembly behaviors of modified MWCNTs.
Co-reporter:Cheng-Ken Wu;Guo-Jian Wang;Jin-Feng Dai
Journal of Materials Science 2013 Volume 48( Issue 9) pp:3436-3442
Publication Date(Web):2013 May
DOI:10.1007/s10853-012-7131-6
The facile method to functionalize graphene oxide through surface modification with acetone was studied and improved. The resulting nanomaterials showed variable characteristics as the surface energy could be tailored according to the combination (proportion of H2O to acetone) of mixed solvent under sonication. Stability test and contact angle measurement showed that the treated graphene oxide exhibited different dispersibility and wettability. SEM images of graphene oxide films corroborated the changes in chemical composition of the sheets. FT-IR, XPS, and TGA observation provided direct evidence for chemical composition changes occurred on the surface. The presence of alkyl chain could decrease the surface energy and obviously control the hydrophilicity of the graphene oxide sheets. These results will provide significant guidance for the study of graphene-based bio-materials and nano-composites.
Co-reporter:Guojian Wang, Yilong Wang, Jiayun Yang
Surface and Coatings Technology 2012 206(8–9) pp: 2275-2280
Publication Date(Web):
DOI:10.1016/j.surfcoat.2011.10.003
Co-reporter:Guojian Wang, Jiayun Yang
Surface and Coatings Technology 2012 206(8–9) pp: 2146-2151
Publication Date(Web):
DOI:10.1016/j.surfcoat.2011.09.050
Co-reporter:Guojian Wang, Jiayun Yang
Progress in Organic Coatings 2011 Volume 72(Issue 4) pp:605-611
Publication Date(Web):December 2011
DOI:10.1016/j.porgcoat.2011.07.001
A melamine polyphosphate (MPP)/dipentaerythritol (DPER) mixture was used as fire retardant additives for preparing waterborne intumescent fire resistive coating. The thermal degradation of the MPP/DPER mixture and of the coating was studied by TGA and FTIR. The resulting char of the coating was investigated by XPS, SEM and energy dispersive spectroscopy (EDS). The results showed that the thermal degradation behavior of the MPP/DPER mixture was similar to that of the coating. They decomposed to nonflammable gases, and formed intumescent char layer containing phosphorus oxide at high temperature. The EDS results proved that the resulting char was gradually oxidized with the temperature increase. The SEM micrographs showed that the average cell size of the char layers became bigger and the cell size distribution became wider as the temperature increased from 500 °C to 800 °C, and this non-uniform char layer could damage the fire protection of the coating.Highlights▸ MPP/DPER mixture was used as fire retardant additives for preparing intumescent fire resistive coating. ▸ During the thermal decomposition at high temperature, the coating could release nonflammable gases, and formed intumescent char layer containing phosphorus oxide. ▸ The average cell size of the char layers became bigger and the cell size distribution became wider as the temperature increased from 500 °C to 800 °C, and this non-uniform char layer could damage the fire protection of the coating. ▸ With the temperature increase, the carbon content and nitrogen content of the char layers decreased, and the oxygen content increased, which indicated that the char layers were gradually oxidized at high temperature.
Co-reporter:Guojian Wang, Jiayun Yang
Progress in Organic Coatings 2011 Volume 70(2–3) pp:150-156
Publication Date(Web):February–March 2011
DOI:10.1016/j.porgcoat.2010.10.007
Glass flake (GF) was used as a modifier to improve the fire protection and water resistance of waterborne intumescent fire resistive coating. The influences of GF on the properties of the coatings were investigated in detail by using TGA, XRD, X-ray fluorescence spectrometry (XRF), SEM and fire protection test. The TGA results proved that addition of GF could enhance the anti-oxidation of the char layers and increase the residue weights of the coatings. The XRF results indicated that anti-oxidation of the coatings modified by GF was improved. The SEM images demonstrated that addition of GF could improve the foam structure of the coatings. After immersed in water over 600 h, the results showed that the thermal stability and fire protection of the coating without GF were significant decreased, but the coatings modified by GF could still maintain the excellent intumescent effect and fire protection.
Co-reporter:Xianke Gu, Guojian Wang
Applied Surface Science 2011 Volume 257(Issue 6) pp:1952-1959
Publication Date(Web):1 January 2011
DOI:10.1016/j.apsusc.2010.09.034
Abstract
The scanning force microscope (SFM) was used to investigate morphology of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blend. The effect of solvent and dewetting in surface structure of PEO film was reported. The results manifested that the crystallization of PEO could be suppressed completely in ultrathin region via using chloroform as a solvent, and the branched-like crystallization was recovered after dewetting. Also, the effect of thickness, the ratio of PEO/PAA and dewetting in surface morphology of PEO–PAA blend films were investigated. These results showed that the crystallization was highly dependent on the ratio of PEO/PAA and the thickness of blend film. Furthermore, we assembled the PEO/PAA layer-by-layer film by spin-casting method for the first time, which exhibited highly efficiency. As a complementary tool, we also used lateral force microscopy (LFM) to explore surface information of these films. The result was indicative of interfacial constraints in ultrathin region, and also was supported by the results showing the spin-casting PEO/PAA blends rather than heterogeneous mixture.
Co-reporter:Guojian Wang;Jiayun Yang;Quan Shi
Journal of Coatings Technology and Research 2011 Volume 8( Issue 1) pp:53-60
Publication Date(Web):2011 January
DOI:10.1007/s11998-010-9270-5
Transparent ultrahydrophobic films were synthesized by sol–gel process with organic silicones modified into silica sol and cured under UV irradiation. The effects of hydrolysis temperature, hydrolysis time, molar ratio of organic silicone to silica sol, and surface morphology on the hydrophobicity of the films were discussed in detail using FTIR spectroscopy, scanning electron microscopy (SEM), AFM, optical transmission, and contact angle measurement, respectively. The AFM and SEM images indicated that the surface roughness enhanced the hydrophobicity of the films. The results revealed that methyl-trimethoxysilane (MTMS)-modified silica film prepared at 50°C for 2 h with an MTMS/silica sol molar ratio of 1:10 had a very high contact angle (130°). However, the higher hydrolysis temperature and longer reaction time might have accelerated the self-condensation of silanol and decreased the contact angle of the films.
Co-reporter:Guojian Wang;Jiayun Yang;Yilong Wang;Yuedong Liu
Colloid and Polymer Science 2010 Volume 288( Issue 18) pp:1677-1685
Publication Date(Web):2010 December
DOI:10.1007/s00396-010-2309-4
Block copolymers of poly(tert-butyl methyacrylate) (PtBMA) and polystyrene (PSt) were grafted onto multi-walled carbon nanotubes (MWNTs) by the reaction of azide groups at the copolymer chain end with the surface of MWNTs. After hydrolysis, PtBMA block was transformed to polymethyacrylic acid (PMAA) block, and amphiphilic diblock copolymer-modified MWNTs were finally obtained. The modified MWNTs were characterized by XPS, TGA, FTIR, and Raman, and the results showed that the amphiphilic diblock copolymers were grafted onto MWNTs by the covalent bond. The TEM and SEM observation showed that PMAA-b-PSt copolymer modified MWNTs (S2) formed self-assembly tube bundles with the size up to 20 μm in both ethanol and chloroform. However, PtBMA-b-PSt copolymer modified MWNTs (S1) only formed small-size aggregates or dispersed as single-modified MWNTs. The dispersion stability tests showed that S1 had good dispersion stability in several solvents (water, ethanol, acetone, and chloroform) even after 20 days. Due to the big-size tube bundles formed by self-assemble S2, the dispersion stability of S2 in above all solvents decreased, but it was still much better than that of pristine MWNTs.
Co-reporter:Guojian Wang, Jiayun Yang
Surface and Coatings Technology 2010 204(8) pp: 1186-1192
Publication Date(Web):
DOI:10.1016/j.surfcoat.2009.10.040
Co-reporter:Guojian Wang, Jiayun Yang
Surface and Coatings Technology 2010 204(21–22) pp: 3599-3605
Publication Date(Web):
DOI:10.1016/j.surfcoat.2010.04.029
Co-reporter:Guojian Wang;Yuedong Liu
Macromolecular Chemistry and Physics 2009 Volume 210( Issue 23) pp:2070-2077
Publication Date(Web):
DOI:10.1002/macp.200900315
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