Crosslinking Modification Of Poly(Vinyl Chloride) Resin

Chemical crosslinking is an effective way for poly(vinyl chloride) (PVC) to improve the heat resistance, the dimensional stability at high temperature and the elasticity of soft product. Concerning the serious PVC degradation in the peroxide or radiation crosslinking process, and the poor processing property of crosslinked PVC resin synthesized by free-radical crosslinking copolymerization, the silane crosslinking of PVC was adapted in this thesis. The effects of preparation methods, silane concentration, processing and hydrolytic conditions on the structure of PVC, and finally the prospects of the application of crosslinking PVC are presented in this paper.R-glycidoxypropyltrimethoxysilane (KH560) has been firstly used to introduce cross-linking 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 cross-linking. FTIR spectra showed that grafting and cross-linking 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(phr/phr) ratio of BaSt2/ZnSt2 and 1:1 molar ratio of NaHSO3/KH560, while the premature cross-linking was avoided. Thermal properties had been studied. The reasults showed that the Vicat softening temperature of cross-linked PVC could be improved about 10℃when 5 phr epoxylsilane was added, and thermal degradation could be delayed with increasing in gel content.Moreover, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792) has been used as crosslinking agent in the grafting and hydrolytic crosslinking reactions of plastic PVC. It was found that the crosslinking efficiency of silane was higher. the premature cross-linking was decrease with the increase of plasticizer, when the 80phr plasticizer and 5phr KH792 were added, the gel content can reach 80%-90%. The compression set and the tensile strength are decreased obviously after crosslinking, however, the hardness of crosslinking PVC changes slowly.