EMULSION POLYMERIZATION IN THE PRESENCE OF COLLOIDAL SILICA PARTICLES- APPLICATION TO THE REINFORCEMENT OF POLY(ETHYL ACRYLATE) FILMS

Emulsion polymerization of ethyl acrylate was carried out in the prese nce of different kinds of functionalized and non-functionalized silica particles. 3-(Trimethoxysilyl)propyl methacrylate, 2-hydroxyethyl met hacrylate and 3-(triethoxysilyl)-propanethiol functionalization agents were examined. It is demonstrated that use of the first two coupling agents results latexes able to give films which display remarkable mec hanical properties similar to those of vulcanized elastomers reinforce d with solid particles. A qualitative model is then set up to give acc ount for these properties. It is proposed that a part of the polymer i s covalently bound to silica as tight loops, giving rise to a set of s trong entanglements with the non-grafted polymer during film formation . This model is supported by stress-strain measurements. Some validati on experiments are described using the third grafting agent of the ser ies.