新型加成型硅橡胶的合成及某些性质

SYNTHESIS AND PROPERTIES OF NOVEL SILICON RUBBER VULCANIZED BY HYDROSILYLATION

在硫酸盐存在下,有机硅环体(Me_2SiO)_4,(MeViSiO)_4,(HMeSiO)_(3～6)和(Me_3Si)_2O[或(Me_2ViSi)_2O]在80～90℃聚合,合成了7种聚(甲基乙烯基-甲基氩)硅氧烷,并在铂-醇配位化合物催化下,经由分子间和分子内硅氢化反应硫化为硅橡胶。此工艺过程的特点是硫化速度慢,温度高,安全操作时间长;在[Si—H]/[Si—Vi]<1(mol比)时,可硫化为含乙烯基侧基的硅橡胶。气体渗透性(标准状态下)测试表明,P_(O_2)=54×10^(-16)m^2/(Pa·s),α_(o_2-N_2)=2.4。

Seven kinds of poly (methylvinyl-methylhydrogen) siloxanes were synthesized by polymering the cyclic silo-xane monomers (Me2SiO)4, (MeViSiO)4, (MeHSiO)3-6 and the dimer (Me3SiO) 2O[or (Me2ViSiO)2O] in the presence of sulfate catalyst (Table). The reaction formula is as follows :R= Me or Vi . The polymerization could be performed favorably at 80-90°C by using about 2.5% (mass)catalyst . The molecular weights, the contens of Si - H and Si-Vi groups and their ratios were controlled by the amounts of the cyclics and the dimers.These polysiloxanes with two different reactive groups, Si-H and Si-Vi, can be vulcanized in the presence of the catalysts of Pt-alcohol complexes. Compared with the conventional two- pack vulcanization system by hydro-silylation, this one-pack vulcanization system has the char-acteristics of slower vulcanization rate and higher vulcanization temperature .The vulcanization temperature changes from 20°C to 140°C according to the structures of the polysiloxanes. Moreover,elastic films can be formed when the[Si- H] /[Si-Vi] values are below 1 .With the decrease of [Si-H]/[Si-Vi] value , the vulcanization temperature increases . They can also be vulcanized conveniently when both their molecular weights and [Si-Vi] contents are relatively low .For the polysiloxane with vinyl endgroups , the vulcanization is achieved at room temperature , but the time for its vulcanization is much longer than that for the conventional system .The described vulcanization characteristics are supposed due to the intermolecular and intramolecular hydrosilylation simultaneously occurring during the vulcanization . The vinyl endgroup has relatively low steric hindrance , which makes it possible for the polysiloxane to vulcanized slowly at room temperature .The silicone rubber membranes were obtained by the Pt-alcohol complex catalyzed hydrosilylation of the polysiloxanes in hexane and their permeability coefficients for some gases were determined by the volumetric method . The experimental results indicated that this novel silicone rubber has the excellent gas permeability and fair selectivity .