State Key Laboratory of Material Processing and Die & Mould Technology, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Nanoscale. 2010 Oct;2(10):2269-74. doi: 10.1039/b9nr00344d. Epub 2010 Aug 21.
Colloidal silica particles were synthesized by the sol-gel process and then modified with 3-methacryloxypropyltrimethoxysilane (γ-MPS) to induce vinyl groups on the surface of the silica particles. By means of in situ emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA), a series of core-shell silica hybrid particles with nanometre poly(MMA-co-BA) shells were fabricated, which were subsequently compounded with isotactic polypropylene (PP) in the molten state. Upon increasing the feed silica : monomer ratio from 1 : 1 to 4 : 1, the poly(MMA-co-BA) shell thickness on the silica core decreased from 50 nm to 10 nm. Owing to the existence of the nanometre poly(MMA-co-BA) shells, the silica hybrid particles were monodispersed in the PP matrix, causing homogeneous debonding at the PP/silica interface, followed by plastic void expansion and matrix shear yielding during impact fracture. These deformation mechanisms greatly toughened the PP-silica composites. A critical shell thickness of poly(MMA-co-BA) was needed to achieve optimal mechanical properties. That is, when the polymer shell thickness was 15 nm, compared to pure PP, the impact toughness of the PP-silica composite was more than doubled with little degradation of tensile strength.
胶态二氧化硅颗粒通过溶胶-凝胶法合成，然后用 3-甲基丙烯酰氧基丙基三甲氧基硅烷（γ-MPS）进行改性，在二氧化硅颗粒表面诱导乙烯基。通过甲基丙烯酸甲酯（MMA）和丙烯酸丁酯（BA）的原位乳液共聚，制备了一系列具有纳米级聚（MMA-co-BA）壳的核壳硅杂化颗粒，随后在熔融状态下与等规聚丙烯（PP）复合。随着进料二氧化硅：单体比从 1：1 增加到 4：1，二氧化硅核上的聚（MMA-co-BA）壳厚度从 50nm 减小到 10nm。由于纳米级聚（MMA-co-BA）壳的存在，硅杂化颗粒在 PP 基体中呈单分散状态，在 PP/硅界面处均匀脱粘，随后在冲击断裂过程中发生塑性空穴扩展和基体剪切屈服。这些变形机制极大地提高了 PP-硅复合材料的韧性。需要一个临界的聚（MMA-co-BA）壳厚度来获得最佳的力学性能。也就是说，当聚合物壳厚度为 15nm 时，与纯 PP 相比，PP-硅复合材料的冲击韧性提高了一倍以上，拉伸强度几乎没有下降。
