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     

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     

Rheological behavior and thermal properties of poly(butyl acrylate‐co‐2‐ethylhexyl acrylate)‐grafted vinyl chloride resin

The rheological behavior and thermal properties of a poly(butyl acrylate‐co‐2‐ethylhexyl acrylate) [P(BA‐EHA)]‐grafted vinyl chloride (VC) composite resin [P(BA‐EHA)/poly(vinyl chloride) (PVC)] and its materials were investigated. The rheological behavior, thermal stability, and Vicat softening temperature (VST) of P(BA‐EHA)/PVC were measured with capillary rheometry, thermal analysis, and VST testing, respectively. The effects of the P(BA‐EHA) content and the polymerization temperature of grafted VC on the rheological behavior of the composite resin were examined. The weight loss of the composite resin and its extracted remainder via heating were analyzed. The influence of the content and crosslinking degree of P(BA‐EHA) and the polymerization temperature of the grafted VC on VST of the materials was determined. The results indicated the pseudoplastic‐flow nature of the composite resin. The flow property of the modified PVC resin was improved because of the incorporation of the acrylate polymer. The molecular weight of PVC greatly influenced the flow behavior and VST of the composite resin and its materials. The flowability of the composite resin markedly increased, and the VST of its materials decreased as the polymerization temperature of the grafted VC increased. The initial degradation temperature of the composite resin increased as the P(BA‐EHA) content increased. The VST of the samples was enhanced a little as the content of the crosslinking agent increased in P(BA‐EHA). As expected, the composite resin, with good impact resistance, had better heating stability and flowability than pure PVC, whereas the VST of the material decreased little with increasing P(BA‐EHA) content. Therefore, P(BA‐EHA)/PVC resins prepared by seeded emulsion polymerization have excellent potential for widespread applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 419–426, 2005     

Surface modification of poly(vinyl chloride) for antithrombogenicity study

A process was established to conduct heparinization on the surface of poly(vinyl chloride) for antithrombogenicity utilization. A bifunctional monomer, glycidyl methacrylate (GMA), was grafted onto the surface of PVC by gas‐phase photografting polymerization without degassing first; then heparin was immobilized onto the poly(glycidyl methacrylate) segments. The branch structure of GMA and heparin were characterized by Fourier transfer infrared (FTIR) spectroscopy and electron spectroscopy (ESCA). It was confirmed that the bifunctional monomer GMA and heparin were grafted successfully onto the surface of PVC. The antithrombogenicity of the samples was tested both in vitro and in vivo, respectively. Results indicated that the blood compatibility of those products was improved greatly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1013–1018, 2002     

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.     

Hg(II) removal with polyacrylamide grafted crosslinked poly(vinyl chloride) beads via surface‐initiated controlled/“living” radical polymerization

Polyacrylamide grafted crosslinked poly (vinyl chloride) beads (PAM‐PVC) were prepared by the surface‐initiated controlled/“living” radical polymerization (SI‐CLRP) methodology from the crosslinked poly(vinyl chloride) beads with surface modification with diethyldithiocarbamyl groups under UV irradiation. The macroiniferter, diethyldithiocarbamyl crosslinked poly(vinyl chloride) beads (DEDTC‐PVC) were prepared by the reaction of the surface C? Cl groups with sodium N,N‐diethyl dithiocarbamate. The “grafting from” polymerization exhibited some “living” polymerization characteristics and the percentage of grafting (PG%) increased linearly with polymerizing time and achieved 47.6% after 6 h UV irradiation. The beaded polymer with polyacrylamide surface was also characterized with Fourier transform infrared (FTIR) and scanning electron microscope (SEM). Its adsorption property for Hg(II) ion was also investigated preliminarily. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3385–3390, 2006     

Mechanical properties of poly(vinyl chloride) blends and corresponding graft copolymers

The mechanical properties of the poly (vinyl chloride) (PVC) and poly (glycidyl methacrylate) [poly (GMA)] blend system and the PVC and poly (hydroxyethyl methacrylate) [poly (HEMA)] blend system and their crosslinked films were investigated. At the same time, the mechanical properties for the corresponding graft copolymers such as PVC-g-GMA, PVC-g-HEMA, and their crosslinked films were also investigated in this study. The results showed that the tensile strengths for PVC–poly (GMA) blend systems were higher than those for PVC-g-GMA graft copolymer, and the tensile strengths for PVC-g-HEMA were higher than those for PVC-poly (HEMA) blend systems. However, the mechanical properties for the PVC–poly (GMA) blend system were not affected by the crosslinking of the blend system, but those for PVC-poly (HEMA) and their graft copolymers decreased with an increase of the equivalent ratio ([NCO]/[OH]) of the crosslinker. Finally, the surface hydrophilicity of the PVC-g-HEMA graft copolymer and PVC-poly (HEMA) blends were also assessed through measuring the contact angle. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 307–319, 1998     

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     

Irradiation modification of PVC/ENR blend: effect of TBLS content

The effect of a poly(vinyl chloride) stabilizer, namely, tribasic lead sulfate (TBLS), on the irradiation modification of 50/50 poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, was investigated with a particular attention to inhibition of irradiation-induced crosslinking. The blends were prepared by mixing in a Brabender Plasticoder with the incorporation of 2, 3, and 5 phr (parts per hundred of total resin) TBLS. They were then irradiated using a 3.0 MeV electron accelerator with doses ranging from 0 to 200 kGy. The gradual fall in tensile strength, gel fraction, hardness, and resilience of the irradiated blend with the increase in TBLS content implied the inhibition of crosslinking by the stabilizer. The reduction in crosslink density with the addition of TBLS was further evidenced from the decline in T _gwith a concomitant increase in tan δ maxima with the increase in TBLS content.     

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     

Silane grafting and moisture crosslinking of polypropylene

Peroxide initiated vinylsilane grafting of polypropylene in an intensive mixer, and the subsequent water crosslinking process were studied. Different concentrations of vinyl trimethoxysilane and dicumyl peroxide were used. The materials obtained after mixing in the rheocord were hot pressed at 190°C. The melt viscosity of the obtained sheets, the melting enthalpy and melting temperature (DSC, differential scanning calorimetry), the mechanical properties and the thermal decomposition behavior (TG, thermogravimetric analysis) were studied. No evidence of grafting during the rheocord processing was observed. Nevertheless, for the hot pressed sheets with concentrations higher than 4 phr of vinyl silane an important increase in the melt viscosity was observed. This increase agrees with the change observed in the mechanical properties, which show a maximum for the water crosslinked samples containing 4 phr of vinyl silane. The modulus increases by 39% at 90°C and 33% at 130°C, while the tensile strength rises by ～22% at both temperatures. The silane grafted water crosslinked samples show a more stable thermal behavior than both the silane grafted samples and the unmodified polypropylene.     

Mechanochemical preparation of a novel polymeric photostabilizer for poly(vinyl chloride)

The preparation of a novel polymeric photostabilizer was carried out via the vibromilling of poly(vinyl chloride) (PVC) powder, a reactive light stabilizer (r‐LS), and a peroxide initiator in ball‐containing jars with a planetary ball mill for a certain time. The effects of the initiator content, milling time, and temperature on the grafting ratio were studied with gravimetric analysis and intrinsic viscosity measurements. Fourier transform infrared and ultraviolet–visible spectra were used to investigate the structural development of the mixture of the r‐LS and PVC during vibromilling. The results showed that the r‐LS was grafted onto PVC chains successfully, and the aforementioned factors had a significant effect on the grafting ratio. The optimum preparation conditions were 0.5 wt % initiator, 8 h, and 20°C. A grafting mechanism is proposed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on graft copolymerization of glycidyl methacrylate onto poly(vinyl chloride) and curing behavior of its grafted copolymer

Poly(vinyl chloride) was dehydrochlorinated in an alkali solution and then grafted with glycidyl methacrylate (GMA) using benzol peroxide as the free-radical initator under a nitrogen atmosphere. The efficiency of grafting GMA under the influence of an alkali, GMA concentration, and duration of the grafting reaction, the viscosity properties, and the curing behavior with diamine were investigated. Maximum grafting to the extent of 46.4% was obtained. The optimum curing reaction condition were investigated. © 1995 John Wiley & Sons, Inc.     

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     

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.     

硅烷交联聚氯乙烯的制备和性能

对由悬浮共聚合成的氯乙烯／乙烯基三乙氧基硅烷共聚树脂的水解交联行为和交联聚氯乙烯的性能进行了研究。结果发现，通过聚合过程添加pH调节剂可得到凝胶含量很低的氯乙烯／乙烯基三乙氧基硅烷共聚树脂；该类共聚树脂加工后有一定程度交联发生，凝胶含量随共聚树脂中乙烯基三乙氧基硅烷含量增加而增加；当加工样品在水中浸渍后凝胶含量又有较大幅度提高，说明水解交联的发生；交联后PVC高温力学性能和耐热变形性提高。     

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.     

Crosslinking of poly(vinyl chloride) with bismaleic compound. I. Crosslinking mechanism

Crosslinked poly(vinyl chloride) (PVC) was obtained by using bismaleic compound (BMC). Styrene, as auxiliary crosslinker, can markedly promote the crosslinking course. After having carefully studied the gelling behavior of PVC in crosslinking, and the reactivity of styrene and BMC with PVC, the crosslink mechanism was suggested. The main crosslink reaction is the bridging of bismaleic compound between PVC macroradicals, which were created by thermal degradation of PVC and disproportionation of PVC with initiator radicals and styrene radicals. The first step of crosslink reaction was the BMC grafting on PVC macroradicals. Then styrene copolymerizes with active center bearing on bismaleic compound to propagate graft chain, which make bridging reaction easier to take place. At last, PVC^* reacted with another double bond possessed by grafted BMC to form network structure     

Nondegradative melt functionalization of polypropylene with glycidyl methacrylate

The melt grafting of glycidyl methacrylate (GMA) onto powdered isotactic polypropylene (PP) in a Haake Rheocord RC90 mixer was studied. Grafting degrees were determined by nonaqueous back titration of trichloroacetic acid with sodium hydroxide. The extent of degradation and crosslinking of PP during grafting was indicated by the melt-flow rates (MFR) of the grafted samples. The influences of GMA concentration, initiator type and concentration on grafting degree, reaction efficiency, and degradation were evaluated. A novel method was developed to obtain a high grafting degree with little degradation of PP using acrylamide (AM) as the initiating agent. The grafting process occurred before or during the melting of PP (i.e., solid-state grafting), at which temperature crosslinking is preferred over chain scission. Primary free radicals generated from the rapid decomposition of AM have a higher tendency to attack GMA molecules than PP chains. At the same estimated amount of primary radicals, both grafting degree and grafting efficiency increase with decreasing decomposition temperature of the initiator (for the same decomposition half-life) in the order of AM > benzoyl peroxide (BPO) > 2,5-di(t-butylperoxy)-2,5-dimethyl-3-hexyne (LPO). FunctionalizedPP with the desired grafting degree and little degradation of PP could be obtained by the use of mixed initiators. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1957–1963, 1998