端羟基聚二甲基硅氧烷制备的改进

以八甲基环四硅氧烷为单体,四甲基四乙烯基环四硅氧烷为改性单体,羟基硅油为封端剂和相对分子质量调节剂,四甲基氢氧化铵为催化剂,在羟基硅油质量分数小于0.13%,催化剂质量分数为0.004%～0.007%时,采用共聚法制备了相对分子质量大于45×104,收率大于90%的端羟基聚二甲基硅氧烷。结果表明,随羟基硅油质量分数的增加,试样的相对分子质量和收率都呈下降的趋势;随四甲基氢氧化铵质量分数的增大,试样相对分子质量减小而收率逐渐增加并趋向平稳。

Improvement of preparation of hydroxyl-terminated polydimethylsiloxane

An improved method for preparing hy-droxyl -terminated polydimethylsiloxane was de-scribed.This product was prepared w ith octamethyl-cyclotetrasiloxane and tetramethyltetravinylcyclote-trasiloxane as monomers,a low visco sity hydroxyl -terminated silicone oil as an end -bl ocking agent and tetramethylammonium hydroxide as catalyst.The influences of hydroxyl -terminated silicone oil and catalyst on relative molecular mass and yield were studied.The results showed that with the in-crease of mass fraction of hydroxyl -terminated sili-cone oil,the relative molecular mass and yield of theproduct decreased.However,the inf luence of mass fraction of catalyst on these two asp ects was differ-ent,that is,relative molecular mass decreased with the increase of mass fraction of cata lyst,while yield of product increased and approached to a certain value.