Preparation of crosslinked and thermostable paste poly(vinyl chloride)

The grafting of a mercaptoalkyltrialkoxysilane onto an activated poly(vinyl chloride) (PVC) paste resin with subsequent hydrolytic crosslinking has been studied. The resins were prepared by copolymerization of vinyl chloride monomer and glycidylmethacrylate (GMA). The grafting of a mercaptosilane was carried out during gelation of the plastisol. In this step the formation of a chemical network was avoided. By steaming at 120°C for 30 min the grafted samples crosslinked. The gel yield increased with increasing fraction of GMA and up to a given level with the fraction of the mercaptosilane. When using a resin of PVC homopolymer no crosslinking occurred. The silane grafted and crosslinked samples were found to have satisfactory thermal stability. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:849–853, 1998     

Crosslinked PVC polymerization: Study on process dependencies

A systematic study of how different processes and crosslinking agents affect the crosslinked polymerization of poly(vinyl chloride) (PVC) to be used for plastisol application was carried out. Two processes, microsuspension (MS) and seeded polymerization (SP), and two crosslinking agents, diallyl phthalate (DAP) and 1,3‐butanediol dimethacrylate (BDMA), were considered. Variations in degree of polymerization and gel content as functions of conversion, as well as the amount of crosslinking agent, was experimentally investigated for both processes and the results were precisely analyzed. We found that the microsuspension process is much better for crosslinked polymerization of PVC to be used for plastisol application; the seeded polymerization process was restricted by the transfer of crosslinking agents to the polymerization sites. Diallyl phthalate was proven to be a good crosslinking agent as generally known until now. Consequently, to perform crosslinked PVC polymerization in industry, the type of process should be taken into account and proper materials and steps should be set up. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1947–1954, 2002     

Self‐crosslinking and cocrosslinking with nitrile rubber of poly(vinyl chloride) with pendent N,N‐diethyldithiocarbamate group

In order to realize the self‐crosslinking and cocrosslinking of poly(vinyl chloride) (PVC) with nitrile‐butadiene rubber (NBR), PVC with pendent N,N‐diethyldithiocarbamate groups (PVC‐SR) was prepared from the reaction of PVC with sodium SR in butanone. The PVC‐SR was self‐crosslinked and the PVC‐SR/NBR blend was cocrosslinked under heating at 170°C. The effect of the degree of functionality of PVC‐SR on the torque, gel content, glass‐transition temperature, and tensile properties was investigated. The results showed that the crosslinking reaction did not occur for PVC, NBR, or the PVC/NBR blend. Introducing the SR groups into PVC caused the crosslinking reaction to occur and the high gel contents of the crosslinked samples were obtained in 15 min. The degree of crosslinking increased with the degree of functionality of PVC‐SR. The mechanism of the crosslinking reaction was discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 634–638, 2001     

Phase dispersion–crosslinking synergism in binary blends of poly(vinyl chloride) with low‐density polyethylene: Entrapping phenomenon in PVC/LDPE/DCP blend

The co‐crosslinked products and the entrapping phenomenon that may exist in a poly(vinyl chloride)/low density polyethylene/dicumyl peroxide (PVC/LDPE/DCP) blend were investigated. The results of selective extraction show that unextracted PVC was due to not being co‐crosslinked with LDPE but being entrapped by the networks formed by the LDPE phase. SBR, as a solid‐phase dispersant, can promote the perfection of networks of the LDPE phase when it is added to the PVC/LDPE blends together with DCP, which leads to more PVC unextracted and improvement of the mechanical properties of PVC/LDPE blends. Meanwhile, the improvement of the tensile properties is dependent mainly on the properties of the LDPE networks. Finally, the mechanism of phase dispersion–crosslinking synergism is presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1296–1303, 2003     

Structure and properties of poly(vinyl chloride)‐triallyl cyanurate plastisols

Triallyl cyanurate (TAC) has been used as a reactive plasticizer to promote the high‐temperature creep resistance of poly(vinyl chloride) (PVC) plastisols. The resultant crosslinked structure is characterized using gel content and swell ratio measurements as well as Fourier transform infrared spectroscopy. The crosslinking reaction was initiated using peroxide. The effect on the network structure of using a free radical scavenger in the formulation has also been studied. The gel yield and crosslink density in the gel increase with increasing TAC concentration in the plastisol, while the grafted PVC fraction and the residual unsaturation of TAC behave in the opposite way. Introduction of TAC into the plastisol promotes creep resistance at high temperatures, and the logarithmic creep rate was found to decrease linearly with increasing crosslink density.     

Influences of diallyl phthalate as chain extender on the properties of high molecular weight poly(vinyl chloride) resin

A higher porosity with better thermostability is desirable for poly(vinyl chloride) (PVC) resin. In this study, high molecular weight PVC resins are prepared by vinyl chloride monomer (VCM)‐diallyl phthalate (DAP) suspension copolymerization in a 20‐L reactor at 50 °C using DAP as chain extender. SEM, BET, and analyses of plasticizer absorption results show the high molecular weight poly(vinyl chloride) (HPVC) by DAP‐VCM copolymerization is loose and porous. With increasing DAP content when the mass ratio of DAP/VCM (ω) is below the gel point, the porosity and the degree of polymerization increase. Nevertheless, the bulk density and particle size decrease. When more than the gel point, these relationships are reversed. Thermogravimetric analysis revealed that the HPVC had better thermostability than that of commercial PVC, and its thermostability increases with increasing ω before it reaches the gel point. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45093.     

化学微交联聚氯乙烯的结构和性能

通过氯乙烯/邻苯二甲酸二烯丙酯(VC/DAP)悬浮共聚,合成了含部分凝胶结构的化学微交联PVC树脂,对微交联PVC的玻璃化转变行为、加工性能、消光性能、加热-形变行为和力学性能进行了研究。当DAP用量在0.25%mol以下时,PVC的玻璃化温度变动不大。凝胶含量的增加将导致交联PVC_d~T的光泽度下降,消光性能提高;塑化时间和加工扭矩均增加,加工性能急剧变差;加热变形值下降,最高使用温度提高。凝胶对PVC拉伸性能的影响较为复杂,但压缩永久变形则随凝胶含量的增加而下降,材料的弹性性能逐渐提高。     

Epoxylsilane crosslinking of rigid poly(vinyl chloride)

Crosslinking is an effective way to improve the qualities of poly(vinyl chloride). A crosslinking system consisting of R‐glycidoxypropyltrimethoxysilane (KH560) has been first used to introduce crosslinking into rigid poly(vinyl chloride). Different thermal stabilizers (organotin, Ca/Zn stearate, and Ba/Zn stearate) as well as sodium bisulfite additive were tried to promote the grafting of epoxyl group and enhance the degree of crosslinking. FTIR spectra showed that grafting and crosslinking of KH560 with poly(vinyl chloride) could take place, and a gel content of 40% could be obtained when more than 10 phr epoxylsilanes were used in the condition of 2 : 1 (parts by weight) ratio of BaSt₂/ZnSt₂ and 1 : 1M ratio of NaHSO₃/KH560, while the premature crosslinking was avoided. Thermal properties had been studied. The results showed that the Vicat softening temperature of crosslinked PVC could be improved about 10°C when 5 phr epoxylsilane was added, and thermal degradation could be delayed with increase in gel content. Therefore, epoxylsilane‐crosslinked PVC will have the potential for extensive applications © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Crosslinking of rigid poly(vinyl chloride) with epoxysilane

Crosslinking is an effective way to improve the properties of poly(vinyl chloride). A crosslinking agent consisting of R‐glycidoxypropyltrimethoxysilane (KH560) has been used for the first time in order to introduce crosslinking into rigid poly(vinyl chloride). Different thermal stabilizers (organotin, Ca/Zn stearate, and Ba/Zn stearate) as well as sodium bisulfite were tried in order to promote grafting of the epoxy group and enhance the degree of crosslinking. Fourier transform infrared (FTIR) spectra showed that grafting and crosslinking of KH560 with poly(vinyl chloride) could take place, and that a gel content of 40% could be obtained when more than 10 phr of epoxysilane was used with a 2:1 (weight) ratio of BaSt₂/ZnSt₂ and a 1:1 molar ratio of NaHSO₃/KH560, while premature crosslinking was avoided. The Vicat softening temperature of crosslinked PVC could be increased by about 10°C when 5 phr of epoxysilane was added, and thermal degradation could be delayed with increasing gel content. Therefore, epoxysilane‐crosslinked PVC has the potential for extensive applications. J. VINYL ADDIT. TECHNOL., 13:103–109, 2007. © 2007 Society of Plastics Engineers.     

Radiation crosslinking of poly(vinyl chloride) with trimethylolpropanetrimethacrylate. IV. Effect of diundecyl phthalate: Dependence of physical properties on composition

Blends of poly(vinyl chloride) (PVC) with polyfunctional monomers may be crosslinked by ionizing radiation. The physical properties of PVC blended with trimethylolpropanetrimethacrylate (TMPTMA) and diundecyl phthalate (DUP) were studied. The TMPTMA monomer crosslinked the blend by homopolymerization and/or grafting to PVC. The plasticizer, DUP, was chemically inert under irradiation but, by plasticizing the macromolecules and diluting the monomer, changed the kinetics extensively. Characteristics of the glass transitions and the tensile mechanical properties have been correlated with blend composition and radiation dose. Before irradiation, poly(vinyl chloride) was plasticized by both DUP and TMPTMA monomer. The increase in glass transition temperature and mechanical strength following irradiation to 5 Mrad was correlated with the TMPTMA content of the blend. Both the molecular structure of the network and the DUP content of the blend were factors in determining the physical properties of the final crosslinked blend. The molecular structure was determined by the kinetics of the crosslinking reactions, which in turn were determined by the blend composition. A molecular interpretation consistent with the physical properties, chemical kinetics, and mechanism of the crosslinking system has been presented.     

PVC接枝改性及交联改性方法研究进展

综述了近年来聚氯乙烯（PVC）接枝改性和交联改性方法的研究进展;其中,接枝改性方法包括在PVC链的C原子上接枝含C、N、S元素基团等及其他亲核取代方法;交联改性方法包括过氧化物交联、三嗪化合物交联、双烯化合物交联、硅烷交联及其他化学交联方法等;最后,对PVC化学改性的发展前景进行了展望。     

Modification of the mechanical and thermal properties of PVC by semi IPN formation with poly(butyl acrylate)

Semi1 and semi2 interpenetrating polymer networks of poly(vinyl chloride) PVC and in situ formed poly(butyl acrylate) (PBA) have been synthesized and characterized using diallyl phthalate (DAP) and ethylene glycol dimethacrylate (EGDM) as the crosslinkers of PVC and PBA, respectively. These two types of IPNs have been compared with respect to their mechanical and thermal properties. The semi1 IPNs displayed a decrease in their mechanical parameters and the physical properties as well, while in contrast, the semi2 IPNs exhibited a marginal increase in the corresponding values when compared to the crosslinked PVC in the case of semi1 IPN and linear PVC in case of semi2 IPN. The representative samples of semi1 and semi2 IPNs revealed a two‐stage‐degradation typical of PVC while confirming the increased stability of the samples with higher onset temperature of degradation. The softening characteristics as detected by thermomechanical analysis are in conformity with their mechanicals. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and thermal properties of blends of low‐density polyethylene and ethylene vinyl acetate crosslinked by both dicumyl peroxide and ionizing radiation for wire and cable applications

Formulations of chemically crosslinked and radiation‐crosslinked low‐density polyethylene (LDPE) containing an intumescent flame retardant such as ammonium polyphosphate were prepared. The influence of blending LDPE with a poly(ethylene vinyl acetate) copolymer (EVA) and the effects of various coadditives, including polyethylene grafted with maleic anhydride (PEgMA), vinyl silane with boric acid, and talc, on the mechanical and thermal properties were investigated. Chemical crosslinking by dicumyl peroxide and crosslinking by ionizing radiation from an electron‐beam accelerator were both used and compared. Improved mechanical properties were observed by the partial replacement of LDPE with EVA. Similar mechanical or thermal properties were observed with coadditives such as PEgMA and vinyl silane with boric acid. The addition of a small amount of talc improved the tensile strength of the formulations. All crosslinked formulations showed good thermal stability on the basis of the retention of mechanical properties after thermal aging for 168 h at 135°C and a hot‐set test. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Transesterification and crosslinking of poly(vinyl chloride‐co‐vinyl acetate) copolymers in the melt

A new method to obtain hydroxylated poly(vinyl chloride) (PVC‐OH) and its crosslinking in the melt are studied. Starting from a vinyl chloride‐co‐vinyl acetate copolymer, a transesterification reaction in the presence of an alcohol during the processing of plasticized polymer is investigated as a function of the processing temperature and alcohol nature (1‐butanol or 1‐octanol). Reaction evolution is followed by ¹H‐NMR and IR spectroscopies. The best results are obtained for 1‐octanol, and they show the absence of secondary reactions and the progressive appearance of OH groups in the polymer as acetate groups disappear. On the other hand, crosslinking of the thus‐obtained PVC‐OH with hexamethylene diisocyanate (HMDI) during the processing is also studied. The gel content and the mechanical properties at 140°C are studied as a function of three crosslinking variables: number of OH groups present in the polymer, concentration of HMDI added to the polymer, and time of crosslinking. The results show that by optimizing those parameters it is possible to obtain gel contents up to 100% and an increase of 600% in the Young's modulus and 1300% in the ultimate tensile strength with respect to the plasticized PVC. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 621–630, 1999     

Effect of electron‐beam irradiation on poly(vinyl chloride)/epoxidized natural rubber blend: dynamic mechanical analysis

The irradiation‐induced crosslinking in 50/50 poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend was investigated by means of dynamic mechanical analysis. The influence of trimethylolpropane triacrylate on the irradiation‐induced crosslinking of PVC/ENR blends was also studied. The enhancement in storage modulus and T_g with irradiation dose indicated the formation of irradiation‐induced crosslinks. This is further supported by the decrease in tan δ_max and loss modulus peak. The compatibility of the blend was found to be improved upon irradiation. The Fox model was used to provide a further insight into the irradiation‐induced compatibility in the blend. Scanning electron microscopy studies on the cryofracture surface morphology of the blends as well as the homopolymer have been undertaken in order to gain more evidence on the irradiation‐induced crosslinking. © 2001 Society of Chemical Industry     

Irradiation Crosslinking of PVC/ENR Blend: A Comparative Study with the Respective Homopolymers

Electron beam initiated crosslinking on a 50/50 poly(vinyl chloride)/epoxidized natural rubber blend was studied in the absence and presence of 3 phr trimethylolpropane triacrylate (TMPTA). Comparative studies were made on PVC and ENR homopolymers. The samples were irradiated by using a 3.0 MeV electron beam machine at doses ranging from 20 to 200 kGy in air and room temperature. The changes in tensile strength, gel fraction and tan δ curves of the samples were investigated. The enhancement in tensile strength, gel fraction, glass transition temperature together with a concomitant decline tan δ peak revealed that under the irradiation conditions employed, the PVC/ENR blend crosslinked by electron beam irradiation. Addition of 3 phr TMPTA found to be effective in increasing the degree of crosslinking. Similar observations were also noted for the homopolymers PVC and ENR, implying that both PVC and ENR in the blend undergo crosslinking to a certain extent.     

Networks of photocrosslinked poly(meth)acrylates in linear poly(vinyl chloride)

Five different multifunctional acrylic monomers (trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol pentaacrylate) were photopolymerized alone or in a matrix of linear poly(vinyl chloride) (PVC) with 2,2‐dimethyl‐2‐hydroxyacetophenone as a photoinitiator. The course of photopolymerization was estimated with Fourier transform infrared spectroscopy. The amount of insoluble gel formed during photopolymerization was determined gravimetrically. The crosslinked polymerization of pure monomers was much faster than that in the presence of PVC. However, the efficiency of the reaction was higher when it was carried out in a PVC blend because of the higher mobility of the propagating macroradicals. The influence of the monomer structure and functionality on the polymerization course was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3725–3734, 2002     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry     

Hierarchical structure and properties of rigid PVC foam crosslinked by the reaction between anhydride and diisocyanate

Rigid crosslinked poly(vinyl chloride) (c‐PVC) foams by forming semi‐interpenetrating network (SIPN) structure via the reaction of phthalic anhydride (PA) and diisocyanate were prepared. The influence of PA on hierarchical structure and mechanical properties of c‐PVC foam was studied. The Fourier transform infrared spectrometer results showed that the presence of PA resulted in the formation of imide structure in the SIPN of obtained c‐PVC foams, which introduced a structural defect of SIPN. Thus, the residue (gel) from tetrahydrofuran extraction of the foams decreased with the increase of PA content. Dynamic thermal analysis showed the presence of three aggregation state structures in the c‐PVC foams, depending on the loading of PA. The addition of PA in the formulations affected cellular structure and mechanical properties of the obtained foams. Furthermore, the influence of chemical environment of anhydride compounds on the formation of imide structure in the crosslinking network of c‐PVC foams was discussed. A strategy for reducing defect of crosslinking network and improving mechanical properties was put forward. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46141.     

Aminosilane grafting of plasticized poly(vinyl chloride) I. Extent and rate of crosslinking

The grafting of poly(vinyl chloride) (PVC) by reactive aminosilane compounds, which make them moisture-curable, has been investigated. Plasticized poly-(vinyl chloride) has been successfully grafted with aminosilane during extrusion. The grafted polymer was crosslinked in the presence of moisture. Although the hydrolysis and condensation of the crosslinking agent is very rapid, the speed of the reaction is controlled by the rather slow diffusion of water in the plasticized PVC. This water diffusion speed follows Fick's Law and is strongly dependent on temperature. To achieve a high crosslinking speed, the extruded PVC has to be placed in warm water or in a steam heated vessel. The effects of catalyst concentration, moisture concentration, and immersion time and temperature on the rate and degree of crosslinking were investigated. Since the formulation used contained a tin stabilizer, the addition of a tin catalyst to the immersion water had little effect. Crosslinking did occur in samples stored at room temperature due to the presence of moisture, but the reaction rate was increased substantially if the sample was immersed in water. Reaction rate was very temperature dependent and followed an Arrhenius relationship. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2111–2119, 1997