【作者】 陆世浚；

【导师】 单国荣；

【作者基本信息】 浙江大学 ， 化学工程， 2005， 硕士

【摘要】 本文通过四甲基四乙烯基环四硅氧烷(Vi-D4) 与八甲基环四硅氧烷(D4) 共聚,将双键引入聚硅氧烷线型分子,以过硫酸钾(KPS)引发双键交联得到一定交联度的硅橡胶乳胶粒子。以此为种子乳液进一步反应,使甲基三甲氧基硅烷(MTMS)在种子乳胶粒表面反应形成硅树脂壳层,得到硅树脂包覆硅橡胶的核-壳乳胶粒子。将得到的硅橡胶改性环氧树脂,研究了硅橡胶粒子和核-壳粒子改性环氧树脂的机械性能。以十二烷基苯磺酸钠为乳化剂、硫酸为催化剂,进行D4与Vi-D4阳离子开环共聚,得到了聚硅氧烷乳液。比较了超声预乳化和机械搅拌预乳化对预乳液粒径分布、聚合反应动力学及乳液粒径分布的影响,发现超声预乳化聚合中同时存在小液滴成核和胶束成核;用超声预乳化得到的乳液稳定,最终转化率较高。研究了单体比例、聚合温度、催化剂浓度和乳化剂浓度对聚合动力学及乳液粒径分布的影响。通过色谱分析计算得到D4与Vi-D4共聚的竞聚率分别为rD4=1. 3572;rVi-D4=0. 3583,并对共聚物组成随转化率的变化进行了预测。研究了预聚物中Vi-D4配比、温度及KPS加入方式对硅氧烷预聚物交联及乳液粒径分布的影响。Vi-D4配比增加,温度升高都使硅橡胶的凝胶分率增加;60℃时乳液粒径分布较宽,而90℃时乳液平均粒径较大。KPS与H2SO4同时加入使凝胶分率下降。研究了工艺条件对核-壳粒子形成的影响,中性条件和弱酸弱碱条件下MTMS凝胶反应较为缓和,乳液稳定。MTMS质量分率较大时乳胶粒之间容易聚并。采用单体预溶胀法得到的乳液平均粒径与预测值的差别比半连续滴加法大。透射电镜观察证实了核-壳结构的形成。橡胶改性环氧树脂的机械性能表明,改性环氧树脂的弯曲模量、弯曲强度和断裂伸长基本上低于纯环氧树脂,并随橡胶粒子质量分率的增加而减小;两种改性环氧树脂的冲击强度都大于纯环氧树脂,并在橡胶粒子质量分率10%的时候出现峰值;改性环氧树脂的机械性能随硅橡胶的凝胶分率增大而增强。电镜图片表明,纯环氧树脂断裂面呈现明显的脆性断裂,而改性环氧树脂为韧性断裂。核-壳型粒子在环氧树脂中的分散性能比硅硅橡胶粒子好,质量分率较高的时候尤为明显。更多还原

【Abstract】 Double bonds were introduced into the polysiloxane chain by the copolymerization of octamethylcyclotetrasiloxane（D4） and tetravinyltetramethylcycoltetrasiloxane（Vi-D4）. When these double bonds were initiated by potassium persulfate（KPS）, silicone particles with certain degree of cross linking were gained. To be a second monomer, methyltrimethoxysilane（MTMS） came into being a shell which enwrap the silicone particle. The mechanical property of epoxy resin modified with silicone particles and core-shell particles was also studied.The polysiloxane emulsion of D₄ and Vi-D4 was prepared using sodium dodecyl benzene sulfonate as an emulsifier and sulfuric acid as a catalyst. The effect of ultrasonic and string emulsification method on the monomer drops diameter, copolymerization and latex particles diameter were compared. It was found that two kinds of nucleation mechanism, monomer drop nucleation and micelle nucleation, existed in the copolymerization emulsified by ultrasonic method. Compared with stirring emulsification, by ultrasonic method the stability of latex emulsified was stronger, and the conversion was higher. The effects of the monomer ratio, temperature, catalyst and emulsifier concentration on the conversation and latex particles diameter were also studied. The reactivity ratios of D4 andVi-D4 were calculate with analyzing by chromatogram（ rD₄ = 1.3572; rVi-D₄ = 0.3583）. The trend of copolymer composition changing with conversion was predicted.The effect of the Vi-D4 fraction in pre-polymer, reaction temperature, and the feeding mode of initiator on crosslink of polysiloxane were studied. The gel fraction of silicone rubber increases with the increasing of Vi-D4 ration and temperature. The gel fraction of silicone will decrease if KPS feeds with H2SO4.The effect of the technics on forming of core-shell particles was studied. We found that the sol-gel reaction of MTMS is more peaceable in neutrality or weakly acidic and alkalinity. When the fraction of MTMS is large, the emulsion particles will accumulate easily. Thedifference of mean particles between prediction value and core-shell particles prepared by the method of pre-swelling is bigger than by the method of semi-continuous method.The mechanical properties of modified epoxy resin show that the flexural modulus, flexural strength and elongation at break is lower than that of pure epoxy resin, and it decreases with the increasing of rubber fraction. The impact strength of both modified epoxy resin is better than the pure epoxy resin, and it would appear peak value when silicone rubber fraction arrive 10%. The mechanical properties of modified epoxy resin increase with the enhancing of gel fraction. It show that the fracture surface of pure epoxy resin appears brittle fracture, but the modified epoxy resin appears gliding fracture. The dispersibility in epoxy resin of core-shell particles is better than that of silicone particles, and it would become more remarkable when the rubber fraction increases.更多还原