Improving properties of modified acrylic sheet via addition of graft natural rubber

The mechanical properties of a modified acrylic sheet prepared by bulk copolymerization of methyl methacrylate (MMA) and styrene (ST) were improved by the addition of a small amount of graft natural rubber (GNR). The graft copolymerization of MMA and ST onto natural rubber latex was carried out by emulsion polymerization using potassium persulfate as an initiator. The properties of the modified acrylic sheet containing GNR with 22.5 wt.% graft copolymer were investigated as a function of GNR content. The results indicated that the impact resistance, tensile strength and elongation at break of the modified acrylic sheet increased with the increase in the amount of GNR in the range of 0.5-4 parts. From the stress-strain behavior, the characteristic of the modified acrylic sheet shifted from brittle to ductile when the amount of GNR was increased. The scanning electron micrographs of the modified acrylic sheets show the relatively smooth fracture surface with relatively few small cracks. This implies that the GNR can be used as an impact modifier for acrylic plastics. (C) 2007 Elsevier B.V. All rights reserved.