Preparation and chemical reactions of rigid cross‐linked poly(vinyl chloride) foams modified by epoxy compounds

A novel method to prepare semi‐interpenetrating polymer network rigid cross‐linked poly(vinyl chloride) (c‐PVC) foams with improved shear toughness in the absence of anhydride components is reported. The cross‐linked network structure in the c‐PVC foams was composed of polyurea network modified by epoxy structure. The cellular morphology was characterized by scanning electron microscopy. Tensile, compressive, and shear properties of the foams were studied. The obtained c‐PVC foams showed high shear properties compared with the comparative samples with the same density and cellular morphology. Possible reactions during the preparation of c‐PVC foams were studied by means of Fourier transform infrared spectrometry and nuclear magnetic resonance measurements through the model experiments. The results showed that allophanate structure resulting from the reaction between isocyanate compounds and epoxy compounds formed in the molding step, which was included into the final cross‐linked network in the cross‐linking step. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40567.     

Modification of tung oil–based polyurethane foam by anhydrides and inorganic content through esterification process

In this study, we have reported the synthesis of modified polyol from tung oil. The synthesis involves three steps: first, conversion of tung oil to hydroxylated tung oil by hydroxylation; second, alcoholysis with triethanolamine; and finally, the esterification of polyester polyol when reacted with phthalic anhydride (PA) or maleic anhydride (MA). Boric acid is also introduced into the polyol by chemical modification, which enhances the thermal properties of polyurethane foam (PUF). PUF is formulated by the reaction between polyol and isocyanate. A systematic comparison of flame retardancy and mechanical and thermal properties of modified PUF has been examined. The structural properties of modified polyol were characterized by Fourier transform infrared spectroscopy, proton NMR spectroscopy, and gel permeation chromatography, while the thermal and mechanical properties of the formulated PUF were studied by scanning electron microscopy, limiting oxygen index, differential scanning calorimetry, Izod impact, and flexural and compression strength. Thus PUF prepared from modified polyol with a proper distribution of soft and hard segments possesses better mechanical and thermal properties. The PA‐modified foams show better properties compared to unmodified and MA‐modified foams due to the aromaticity and crosslinking behavior of PA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45786.     

Structure–property relationships of lightly chemical crosslinked poly(vinyl chloride) thermoplastic elastomer

Chemical crosslinked poly(vinyl chloride) (C‐PVC) was synthesized by vinyl chloride suspension polymerization in the presence of diallyl phthalate (DAP) and plasticized to prepare poly(vinyl chloride) (PVC) thermoplastic elastomer (TPE) materials. The chemical crosslinking and physical crosslinking structure in chemical crosslinked PVC‐TPE were investigated. It showed that the gel fraction and the crosslinking density of gel increased as the feed concentration of DAP increased. C‐PVC prepared by VC/DAP copolymerization was lightly crosslinked as compared with irradiation crosslinked PVC. Physical entanglements would greatly influence the crosslinking density of gel when the gel fraction was high. Chemical crosslinking had little influence on the recrystallization behavior of PVC. A structure model of chemical crosslinked PVC‐TPE was proposed, in which chemical networks acted with physical networks cooperatively. It also showed that chemical crosslinking and physical crosslinking influenced the processability and mechanical properties of chemical crosslinked PVC‐TPE cooperatively. Although the processability of PVC‐TPE deteriorated with chemical crosslinking, the dimension stability and elasticity of PVC‐TPE were improved as the permanent chemical networks were introduced. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 868–874, 2000     

Characterization of crystalline structure and free volume of polyamide 6/nitrile rubber elastomer thermoplastic vulcanizates: Effect of the processing additives

Blends of polyamide 6 and nitrile rubber (PA6/NBR) dynamically vulcanized may generate innovative products for special purposes where both high temperature and chemical resistance are key factors. In this investigation, we show that the crystalline nature of the PA6 can be controlled in terms of its morphological aspects (degree of crystallinity, crystal size, and structure) as a consequence of the presence of NBR and processing additives. Our results indicate that this crystalline control is dependent on the plasticization caused by the processing additives. Furthermore, imide‐like linkage formation was favored in the presence of ethylene‐co‐vinyl acetate (EVA)‐g‐maleic anhydride, resulting in changes in the molecular mobility of the PA6 matrix, crystallization parameters, and viscoelastic properties when compared to the others EVA additives. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45576.     

Synthesis and characterization of melt‐processable polyimides derived from 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene

A series of molecular‐weight‐controlled imide resins end‐capped with phenylethynyl groups were prepared through the polycondensation of a mixture of 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene and 1,3‐bis(4‐aminophenoxy)benzene with 4,4′‐oxydiphthalic anhydride in the presence of 4‐phenylethynylphthalic anhydride as an end‐capping agent. The effects of the resin chemical structures and molecular weights on their melt processability and thermal properties were systematically investigated. The experimental results demonstrated that the molecular‐weight‐controlled imide resins exhibited not only meltability and melt stability but also low melt viscosity and high fluidability at temperatures lower than 280°C. The molecular‐weight‐controlled imide resins could be thermally cured at 371°C to yield thermoset polyimides by polymer chain extension and crosslinking. The neat thermoset polyimides showed excellent thermal stability, with an initial thermal decomposition temperature of more than 500°C and high glass‐transition temperatures greater than 290°C, and good mechanical properties, with flexural strengths in the range of 140.1–163.6 MPa, flexural moduli of 3.0–3.6 GPa, tensile strengths of 60.7–93.8 MPa, and elongations at break as high as 14.7%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Poly(acrylic acid)–poly(vinyl alcohol) semi- and interpenetrating polymer network pervaporation membranes

A series of poly(acrylic acid) (PAA)–poly(vinyl alcoho) (PVA) semiinterpenetrating (SIPN) and interpenetrating (IPN) polymer network membranes were prepared by crosslinking PVA alone or by crosslinking both PVA and PAA. Glutaraldeyde and ethylene glycol were used as crosslinking agents for the PVA and PAA networks, respectively. The presence of PAA increases the permeability of the membranes while the presence of PVA improves their mechanical and film-forming properties. The mechanical properties of the membranes were investigated via tensile testing. These hydrophilic membranes are permselective to water from ethanol–water mixture and to ethanol from ethanol–benzene mixtures. The IPN membranes were employed for the former mixtures and the SPIN membranes for the latter, because the IPN ones provided too low permeation rates. The permeation rates and seperation factors were determined as functions of the IPN or SIPN composition, feed composition, and temperature. For the azeotropic ethanol–water mixture (95 wt % ethanol), the separation factor and permeation rate at 50°C of the PAA-PVA IPN membrane, containing 50 wt % PAA, were 50 and 260 g/m²h, respectively. For the ethanol–benzene mixture, the PAA–PVA SIPN membranes had separation factors between 1.4 and 1200 and permeation rates between 6 and 550 g/m²h, respectively, depending on the feed composition and temperature. © 1996 John Wiley & Sons, Inc.     

Bifunctional silane (TESPD) effects on improved mechanical properties of silica containing nitrile‐butadiene rubber/poly(vinyl chloride) compound

Organo bifunctional silane (TESPD) is added into silica containing NBR/PVC blend and its effects are investigated with respect to the vulcanization property, the processability, and the physical property. The addition of the TESPD into silica filled NBR/PVC compound increases the degree of crosslinking by formation of a strong three‐dimensional network structure between silica surface and rubber matrix via coupling reaction, which results in improved mechanical properties. It also improves the processability of the compound compared to the Control compound. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The simultaneous addition of styrene maleic anhydride copolymer and multiwall carbon nanotubes during melt‐mixing on the morphology of binary blends of polyamide6 and acrylonitrile butadiene styrene copolymer

The effect of simultaneous addition of multiwall carbon nanotubes (MWNTs) and a reactive compatibilizer (styrene maleic anhydride copolymer, SMA) during melt‐mixing on the phase morphology of 80/20 (wt/wt) PA6/ABS blend has been investigated. Morphological analysis through scanning and transmission electron microscopic analysis revealed finer morphology of the blends in presence of SMA + MWNTs. Fourier transform infrared spectroscopic analysis indicated the formation of imide bonds during melt‐mixing. Non‐isothermal crystallization studies exhibited the presence of a majority faction of MWNTs in the PA6 phase of 80/20 (wt/wt) PA6/ABS blend in presence of SMA + MWNTs. Rheological analysis, dynamic mechanical thermal analysis, and thermogravimetric analysis have demonstrated the compatibilization action of simultaneous addition of a reactive compatibilizer (SMA copolymer) and MWNTs in PA6/ABS blends. An attempt has been made to investigate the role of simultaneous addition of SMA copolymer and MWNTs on the morphology of 80/20 (wt/wt) PA6/ABS blend through various characterization techniques. POLYM. ENG. SCI., 55:457–465, 2015. © 2014 Society of Plastics Engineers     

Effect of compatibilizer and silane coupling agent on physical properties of ethylene vinyl acetate copolymer/ethylene‐1‐butene copolymer/clay nanocomposite foams

In this study an attempt was made to obtain lower density of ethylene‐vinyl acetate copolymer (EVA)/ethylene‐1‐butene copolymer (EtBC) foams without sacrificing mechanical properties. For this purpose EVA/EtBC/clay nanocomposite foams were prepared. To investigate the effect of compatibilizer and silane coupling agent on the physical properties of the EVA/EtBC/clay foams, maleic anhydride‐grafted EtBC (EtBC‐g‐MAH) and the most commonly used silane coupling agent in rubbers, bis(3‐triethoxysilylpropyl) tetrasulfide (Si‐69) were used in the preparation of EVA/EtBC/clay nanocomposite foams. The formation of EVA/EtBC/clay nanocomposite foams was supported by X‐ray diffraction results. And, using a compatibilzer and silane coupling agent, lower density of EVA/EtBC/clay nanocomposite foams were obtained without sacrificing mechanical properties except compression set. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3259–3265, 2006     

Compatibilized blends of PVC/PA12 and PVC/PP containing poly(lauryl lactam‐block‐caprolactone)

Specially designed block copolymers have played a role as compatibilizing agents in the system of immiscible polymer blends. We applied lauryl lactam (LA)–caprolactone (CL) block copolymer [P(LA‐b‐CL)] as a compatibilizing agent for immiscible poly(vinyl chloride) (PVC) blends with various polymers. These blends possess high thermal performance and toughness. We investigated the effect of P(LA‐b‐CL) as a compatibilizing agent for immiscible PVC blends with poly(ω‐lauryl lactam) [polyamide 12 (PA12)]. We also described the invention of a new compatibilizing agent system involving P(LA‐b‐CL) for PVC/polypropylene (PP) blends. The mechanical and thermal properties of (1) PVC/PA12 blend compatibilized with P(LA‐b‐CL) and (2) PVC/PP blend compatibilized with P(LA‐b‐CL)/PA12/maleic anhydride–modified PP were both enhanced. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1983‐1992, 2004     

Effects of compatibilizer type and rubber‐wood sawdust content on the mechanical,morphological, and thermal properties of PVC/LDPE blend

This article aimed to investigate the mechanical, morphological and thermal properties of PVC/LDPE blend with and without the addition of compatibilizers. The effects of LDPE content, compatibilizer type and rubber‐wood sawdust loading on the properties of the blend were evaluated. The experimental results suggested that as the LDPE content was increased the mechanical properties of PVC‐LDPE blend progressively decreased due to poor interfacial adhesion. The continuity and compatibility between PVC and LDPE phases could be improved through three different types of compatibilizers which included chlorinated polyethylene (CPE) poly(methyl‐methacrylate‐co‐butyl acrylate) (PA20) and poly(ethylene‐co‐methacrylate) (Elvaloy). The PA20 was found to be the most suitable compatibilizer for the blend. A radical transfer reaction was proposed in this work to explain the structure and thermal changes of the PVC in PVC‐LDPE blend. The decomposition temperature of PVC in the blend decreased with the loading of the PA20 and the wood sawdust. As the sawdust content was increased the tensile and flexural moduli increased with considerable decreased in the tensile, flexural and impact strength, a slight improvement being achieved if the PA20 was incorporated in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 598–606, 2006     

PVC modification through polymerization of a monomer absorbed in porous suspension‐type PVC particles

In‐situ polymerization is the polymerization of one monomer in the presence of another polymer. It can be performed by sequential emulsion polymerization, or by reactions in the melt, in the solid phase, or in solution. The current report describes two methods to obtain poly(vinyl chloride) (PVC) modification through polymerization of a monomer absorbed in commercial porous suspension‐type PVC particles. The generated modified PVC products differ significantly in their structure and properties. The first approach includes absorption of a monomer/peroxide solution within porous suspension‐type PVC particles, followed by polymerization/crosslinking in the solid state at 80°C in an aqueous stabilizer‐free dispersion. The monomer/crosslinker pairs selected are styrene/DVB (divinyl benzene), methylmethacrylate/EGDMA (ethylene glycol dimethacrylate), butyl acrylate/EGDMA, and ethylhexyl acrylate/EGDMA. The influence of composition and nature of the polymerizing/crosslinking constituents on the modified PVC particle structure was studied by microscopy methods, porosity measurements, and dynamic mechanical behavior (DMTA). The level of molecular grafting between PVC and the modifying polymer was determined by solvent extraction experiments. This work shows that the different monomers used represent distinct courses of monomer transport through the PVC particles. The characteristics of the modified PVC particle indicate that the polymerization/crosslinking process occurs in both the PVC bulk, i.e., within the walls constituting a particle, and in the PVC pores. No indication of chemical intermolecular interaction within the modified PVC particles was found. In the second approach, a solution of monomer, initiator, and a crosslinking agent is absorbed in commercial suspension‐type porous PVC particles, thus forming a dry blend. This dry blend is subsequently reactively polymerized in a twin‐screw extruder at an elevated temperature, 180°C, in the molten state. The properties of the reactively extruded PVC/PMMA blends are compared with those of physical blends at similar compositions. Owing to the high polymerization temperature, short‐chain polymers are formed in the reactive polymerization process. Reactively extruded PVC/PMMA blends are transparent, form single‐phase morphology, have a single T_g, and show mechanical properties comparable with those of the neat PVC. The resulting reactively extruded PVC/PMMA blends have high compatibility. J. Vinyl Addit. Technol. 10:109–120, 2004. © 2004 Society of Plastics Engineers.     

Effect of crosslinking on mechanical and viscoelastic properties of semiinterpenetrating polymer networks composed of poly(vinyl chloride) and isocyanate crosslinked networks

Semiinterpenetrating polymer networks (SIPNs) of PVC/isocyanate/poly‐triol were prepared by premixing small (150 μm dia.) porous (30% voids) unplasticized PVC particles, 10% by weight of isocyanate, and a triol at different OH/NCO mol ratios. Three types of isocyanates (methylene bis‐phenyl diisocyanate (MDI), oligomeric MDI isocyanates (PAPI), and toluene diisocyanate (TDI) prepolymer/polytriol) were used. Two‐roll milling was followed by hot‐press curing. The tensile, flexural, and impact strengths increased when small amounts of crosslinked isocyanate networks were created in PVC. The isocyanate/polyol hydroxyl stoichiometry was varied, and the effects of crosslinking on the tensile, impact, and flexural strengths of PVC/isocyanate/triol SIPNs were examined. The strength increments were greater when the OH/NCO mole ratio went from 0 to 0.25, than when it went from 0.25 to 1.0. In many cases, increasing OH/NCO mol ratio from 0.5 to 1.0 decreased tensile, impact, and flexural strengths. Both PAPI and MDI (30% NCO content) gave bigger improvements in the these mechanical strengths than the TDI (only 9.7% NCO). These SIPN blends exhibited lower tan δ peak temperatures and a single distinct loss modulus, E″, peak values at lower temperatures than those of PVC that had been exposed to the same processing temperatures. Substantial amounts of isocyanate networks exist in SIPN phases according to DMTA studies. The OH/NCO ratio did not generally correlate with the decreases in the glass transition temperatures in these three sets of blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1402–1411, 2000     

Study on morphology of compatibilized poly (vinyl chloride)/ultrafine polyamide‐6 blends by styrene–maleic anhydride

Ultrafine polyamide‐6 (UPA6) with a size of 4–8 μm was prepared via jet‐milling. Blends of poly (vinyl chloride) (PVC) and UPA6 using a reactive copolymer styrene–maleic anhydride (SMA‐18%) were prepared. The change in morphology and structure of the blends were studied using differential scanning calorimetry, scanning electron microscopy, and X‐ray diffraction. The blend behavior was also determined experimentally using dynamic mechanical analysis. Contrasted to the original PA6, the crystallinity of the UPA6 decreased, the size of its crystallites were reduced, and its melting point decreased to 175°C. In all blends, PVC formed the continuous matrix phase. SMA is miscible with PVC and tends to be dissolved in the PVC phase during the earlier stages of blending. The dissolved SMA has the opportunity to react with PA6 at the interface to form the desirable SMA‐g‐PA6 copolymer. This in situ formed SMA‐g‐PA6 graft copolymer tends to anchor along the interface to reduce the interfacial tension and results in finer phase domains. Cocrystallity existed in PVC/(UPA6/SMA) at a ratio of 82/(18/5). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 850–854, 2005     

Novel acetylene‐terminated polyisoimides with excellent processability and properties comparison with corresponding polyimides

Two novel acetylene‐terminated isoimide oligomers and their corresponding imide oligomers have been synthesized by using trifluoroacetic anhydride or acetic anhydride as dehydrating agent, respectively. Their main structure was confirmed by Fourier transform infrared spectroscopy (FTIR). The isoimide oligomers were amorphous and showed excellent solublility in many common solvents, such as acetone and tetrahydeofuran, whereas the imide oligomers cannot dissolve in them. Differential scanning calorimetry and rheometer were used to study crosslinking behavior and processability of these oligomers. The isoimide oligomers exhibited considerably wider processing window and lower viscosity compared with imide ones. As expected, the isoimide form could be converted to imide form through thermal treatment, which could be demonstrated by FTIR. After the oligomers were cured, the polyisoimides showed similar properties compared with corresponding polyimides. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of some PVC‐grafted maleic anhydrides (PVC‐g‐MAs) on the morphology,and the mechanical and thermal properties of (alfa fiber)‐reinforced PVC composites

This work studied the poly(vinyl chloride) (PVC) chemically modified with maleic anhydride (MA) through reactions in solution, using benzoyl peroxide as an initiator. Quantities of the grafted MA were determined by the titration of carboxylic acid groups derived from the anhydride functions. Estimation of the grafted MA level was also performed by using IR absorbance ratio. Increases in reaction time led to higher levels of grafted MA. The effects of three different PVCs grafted with maleic anhydride (PVC‐g‐MAs) types on the morphological, mechanical, and thermal properties of PVC/alfa (fiber) composites were examined. The interfacial properties between fiber and PVC were improved after the addition of PVC‐g‐MA, as was evident from SEM morphology study. Enhancements of the mechanical properties and thermal stability of the PVC‐g‐MA‐treated composites were strongly dependent on the amount of MA grafts. J. VINYL ADDIT. TECHNOL., 19:225–232, 2013. © 2013 Society of Plastics Engineers     

Die polymeranaloge Bildung von Imidgruppen in Methacrylsäure/Methacrylnitril-Copolymeren

Polymers with glutarimide-units have been prepared by an intramolecular cyclisation by heating of methacrylonitrile-methacrylic-acid-copolymers. The progress of the reaction has been determined by measuring the IR-spectra, the modulus in torsion and the increase of heat resistance. The formation of glutaric anhydride groups in addition to imide groups could be avoided by addition of urea before heating. The mechanical properties of the imid containing polymers as sheets, films and foams have been measured.     

Mechanical Properties of Silicone Rubber Enhanced Microcellular EPDM Foams Based on Supercritical CO2 Foaming Technology

Microcellular ethylene-propylene-diene monomer (EPDM) foams derived from miniaturizing the cellular structure can improve mechanical properties of traditional EPDM foams. It is a current challenge that microcellular EPDM foams prepared by supercritical CO₂ foaming technology cannot undergo the post-crosslinking process due to the disappearance of cellular structure, which strongly restricts the development of the mechanical properties of EPDM foams. Hence, a scalable and blending route by selecting the silicone rubber (SR) with different crosslinking temperature compared to EPDM is developed to improve mechanical properties of EPDM foams. During the pre-crosslinking process of EPDM, SR forms a complete crosslinking network, which can make up for the strength of EPDM without the post-crosslinking. Meanwhile, the silica can reduce the domain size of SR and enhance the compatibility between EPDM and SR. As expected, the addition of SR improves the storage modulus, viscosity and matrix strength of EPDM, which shows enhanced mechanical properties of EPDM foams. When the foam density is basically the same, the tensile strength and compressive strength of SR/EPDM foam are increased by 461% and 283% respectively compared with that of EPDM foam. Finally, the maximum tensile strength and compressive strength (40% strain) of SR/EPDM foam achieves 3.58 MPa and 0.59 MPa, respectively.     

Highly reinforcing and thermal stabilizing effect of imide structure on polyurethane foam

In order to improve the heat‐resistant property of polyurethane foams, a series of polyurethane‐imide foams (PUIFs) with different contents of the imide group were fabricated via the prepolymer foaming method. It was found that the PUIFs showed a closed cellular structure with almost circular cell shapes. With increasing content of imide groups, the cell wall thickness and apparent density of the foams gradually increased, and the cell size showed a trend of first increasing and then decreasing. All foams exhibited a multistage deformation response when subjected to compressive loading, and the compressive strength and modulus of the PUIFs were significantly improved by incorporation of the imide group, increasing by roughly 5500% and 6400% for the PUIF with 34.25 wt% imide groups, indicating the remarkable reinforcing effect of the imide group on the PUIF. TGA and dynamic mechanical analysis showed that with increase of the imide group content the thermal degradation temperatures, the char yield and the degradation activation energy for the PUIFs sharply increased, while the storage modulus (G′) and T_g were obviously improved, reaching 575 MPa and 283 °C respectively, much higher than that of most reported PU foams, indicating the remarkable enhancement of the thermal mechanical stability of the PUIF. The heat insulation of the PUI system was also enhanced by the incorporation of imide groups. Such PUIFs showed potential applications for use in high temperature environments. © 2018 Society of Chemical Industry     

接枝率对PVC/PA6-g-SMA共混物结构与性能的影响

采用熔融共混方法制备了聚氯乙烯（PVC）与不同接枝率苯乙烯-马来酸酐共聚物(SMA）接枝改性聚酰胺6（PA6-g-SMA）的共混物,研究了PA6-g-SMA接枝率对PVC/PA6-g-SMA共混物力学性能及凝聚态结构的影响。结果表明,接枝率越高,PA6-g-SMA与PVC的相容性越好,在PVC基体中能以更小的相畴均匀分散,对PVC的增韧增强作用越明显;当PA6-g-SMA的接枝率为5.12 %,添加量为15 ％（质量分数,下同）时,共混物的冲击强度为64.7 kJ/m2,拉伸强度为55 MPa。