聚硅氧烷改性苯丙乳液──Ⅰ共混改性

聚合物乳液的共混改性可以得到一些独特的性能，改性的效果取决于共混聚合物的相容性及其形态结构，也取决于共混乳液的稳定性。本文研究了聚硅氧烷改性苯丙乳液的稳定性，聚硅氧烷改性橡胶膜的形态结构、两相间相容性，及其对改性橡胶膜力学性能的影响。ＥＳＣＡ和ＳＥＭ结果表明改性橡胶膜中存在明显的相分离，聚硅氧烷在膜的表面富集；通过接枝共聚使苯丙乳液粒子中含有部分聚硅氧烷，或聚硅氧烷乳液粒子中含有部分苯丙共聚物，两者都能降低两相间的界面张力，改善两相间的相容性，从而明显提高改性橡胶膜的力学强度，但只有当聚硅氧烷分子链与苯丙分子链通过接枝和机械缠结，才能明显抑制有机硅分子链向膜的表面迁移。     

Preparation and characterization of ceramic composites derived from rice husk ash and polysiloxane

Ceramic matrix composites (CMCs) were prepared from a polysiloxane network filled with rice husk ash (RHA), a reactive filler. CMCs were obtained by pyrolysis at 1000 and 1600 °C of green bodies prepared from a mixture of polysiloxane network and RHA at a weight ratio of 4:1, respectively. The RHA and the CMCs were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), in addition to density and mechanical measurements. The CMCs were obtained without macroscopic defects, and their initial observed porosity was reduced by polymeric infiltrations cycles of the polymeric precursor, which improved their flexural strength and modulus up to 100%.     

紫外光固化环氧聚硅氧烷树脂的制备与性能

以1,2-环氧-9-癸烯和双侧氢封端的聚二甲基硅氧烷为反应物,在卡斯特催化剂〔铂(0)-1,3-二乙烯-1,1,3,3-四甲基二硅氧烷〕的催化下发生硅氢加成反应,成功制备了环氧基聚硅氧烷预聚物,并使用阳离子型光引发剂对其进行紫外光固化,制得紫外光固化环氧聚硅氧烷树脂。对合成双端环氧基聚硅氧烷预聚物的反应条件进行优化。利用FTIR和1HNMR对所合成预聚物的结构进行了结构表征,采用热失重分析、差示扫描量热法、接触角、耐碱性、耐醇性、凝胶率、邵氏A硬度和断裂面微观形貌对固化膜的性能和形貌进行了测试。结果表明：在反应温度为75 ℃、催化剂有效成分添加量为0.009‰（以双端含氢聚硅氧烷和1,2-环氧-9-癸烯的质量和为基准,下同）条件下,8 h时反应程度达93.95%;当使用光引发剂BL9380用量为3%（以预聚体质量为基准,下同）、固化时间为20 s时,制得的树脂表面活性能为18.4~18.8 mN/m,耐碱性、耐醇性良好,凝胶率为93.9%,邵氏A硬度为37,空气气氛下两个最大分解速率分别为437.6和511.3 ℃,780 ℃下质量残余率为13.9%,固化膜的综合性能最好。     

Influence of pyrolysis temperature on fracture response in SiOC based composites reinforced by basalt woven fabric

The fracture resistance of ceramic based composites reinforced by various ceramic fibres can be dramatically enhanced when an efficient fracture mechanism takes place during the crack propagation. Presented work shows an effect of the pyrolysis temperature of the composite matrix on the fracture behaviour of the composite. The matrix is formed from the polysiloxane resin precursor and the reinforcement is a basalt woven fabric. The temperature range under investigation was from 600 °C, where the onset of fracture properties were observed up to 800 °C. Above this temperature basalt fibres suffer by rapid degradation of the microstructure. The optimum stage of the polysiloxane resin transformation maximizing the fracture resistance of the composite was identified. The fractographic analysis of the fracture surfaces revealed the differences in the acting fracture mechanism.