CORE-SHELL PARTICLES DESIGNED FOR TOUGHENING EPOXY-RESINS - I - PREPARATION AND CHARACTERIZATION OF CORE-SHELL PARTICLES

A two-stage, multistep soapless emulsion polymerization was employed t o prepare various sizes of reactive core-shell particles ( CSPs) with butyl acrylate (BA) as the core and methyl methacrylate (MMA) copolyme rizing with various concentrations of glycidyl methacrylate (GMA) as t he shell. Ethylene glycol dimethacrylate (EGDMA) was used to crosslink : either the core or shell. The number of epoxy groups in a particle o f the prepared CSP measured by chemical titration was close to the cal culated value based on the assumption that the added GMA participated in the entire polymerization unless it was higher than 29 mol So. Simi lar results were also found for their solid-state C-13-NMR spectroscop y. The MMA/GMA copolymerized and EGDMA-crosslinked shell of the CSP ha d a maximum glass transition temperature (T-g) of 140 degrees C, which was decreased with the content of GMA at a rate of - 1 degrees C/mol %. However, the shell without crosslinking had a maximum T-g of 127 de grees C, which decreased at a rate of -0.83 degrees C/mol %. The T-g o f the interphasial region between the core and shell was 65 degrees C, which was invariant with the design variables. The T-g of the BA core was -43 degrees C, but it could be increased to -35 degrees C by cros slinking with EGDMA. The T-g values of the core and shell were also in variant with the size of the CSP. (C) 1998 John Wiley & Sons, Inc.