title: Silica hybrid particles with nanometre polymer shells and their influence on the toughening of polypropylene.
abstract: 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.
authors: 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.
authors: Jing-Zhi
authors: JZ
authors: Zheng
authors: Xing-Ping
authors: XP
authors: Zhou
authors: Xiao-Lin
authors: XL
authors: Xie
authors: Yiu-Wing
authors: YW
authors: Mai
mesh_terms: D003460:Crystallization; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry; D011126:Polypropylenes / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013696:Temperature; D013718:Tensile Strength
chemical_list: D011108:Polymers; D011126:Polypropylenes; D012822:Silicon Dioxide; D012825:Silicon