EFFECT OF THE CORE SHELL LATEX PARTICLE INTERPHASE ON THE MECHANICAL-BEHAVIOR OF RUBBER-TOUGHENED POLY(METHYL METHACRYLATE)/

Two- and three-layer composite latex particles were used to prepare ru bber-toughened poly(methyl methacrylate) (RT-PMMA). The interfacial th icknesses of the multilayered particles were varied by using different emulsion polymerization synthesis techniques. The resulting interphas es were previously characterized by C-13 nuclear magnetic resonance te chniques. The poly(divinyl benzene)/poly(butyl acrylate) (PDVB/PBA) in terphase thickness was found to be in the range of 5-7 nm. It was also found that the PBA/PMMA. interphase thickness could be varied from 5 to 7 nm (batch addition of MMA) to 15 to 17 nm (interphase compatibili zed with PMMA macromonomer). The interphase thickness was expected to play an important role in the mechanical behavior of PMMA. The effect of the interphase of two- and three-layer particles on the tensile and fracture behavior of PMMA composites was evaluated. The fracture surf aces were examined by scanning electron microscopy. The two-layer PBA/ PMMA particles with a thicker interphase (15-17 nm) exhibited higher K -IC values with the PMMA composites compared with PBA/PMMA particles w ith a thinner interphase (5-7 nm). The three-layer particles were foun d to be more effective in toughening PMMA compared with the two-layer particles. The differences in toughening behavior are speculated to ar ise from the morphological effects caused by a thicker interphase, whi ch in turn results in better coverage by the PMMA shell and a more uni form distribution of the toughening particles in the PMMA matrix. (C) 1997 John Wiley & Sons, Inc.