CORE SHELL POLY (DIMETHYLSILOXANA)--VINYL ESTER MICROSPHERE AS IMPACT MODIFIER FOR VINYL ESTER THERMOSETS

Abstract

We report a two-step method for preparation of core shell elastomeric microspheres (CSR) using suspension polymerisation process and demonstrate its potential which proves it as an effective impact modifier for thermosetting vinyl ester resin. The first step involves suspension addition curing of siloxane macromonomer with platinum based hydrosilylation catalyst. The result of reaction parameters on the particle size distribution was decided and the elastomeric microspheres were eventually coated to prepare core-shell (PDMS-vinyl ester) microspheres. Vinyl ester composites were prepared by varying the amounts of microspheres (1-7 % w/w) and consequences of coating on the mechanical properties, that is quasi-static as well as dynamic properties were evaluated. The mechanical properties were found to improve at low loadings (≤ 3 % w/w), and the presence of an vinyl ester coating on the PDMS in the CSR led to improved dispersion, which was evident from its improved mechanical properties. The izod impact strength increased by 132 % on introduction of core shell PDMS – vinyl ester (3% w/w). Morphological studies revealed that the roughness of the fractured surface increased due to introduction of microspheres. In contrast to the PDMS containing composites, where the microspheres were removed entirely due to impact loading, the fractured surface of CSR containing composites revealed the presence of broken microspheres, which is a direct evidence of improved adhesion between elastomeric phase and the vinyl ester matrix.