Excellent impact strength of ethylene-methyl acrylate copolymer toughened polycarbonate

The intrinsic notch sensitivity of polycarbonate (PC) demands improvement in the notched impact strength for a variety of applications. Blends of PC/ethylene-methyl acrylate (EMA) copolymer of different compositions were prepared by melt blending using a co-rotating twin-screw extruder. The notched izod impact strength of PC/EMA blends showed a positive blending effect and increased 381% with incorporation of a very little amount of EMA (5%) with a marginal decrease in the tensile strength of PC. Tensile data was also analyzed by using predictive theories. Incorporation of EMA decreases the glass transition temperature of PC and facilitates its processing. Scanning electron micrographs of cryogenically fractured samples after etching were used to study the phase structure. A two phase morphology was seen with a fine dispersion of rubber granules in the PC matrix. On the other hand, the impact fractured surface of PC/EMA blends indicated debonding of EMA particles, leaving hemispherical bumps, indicating inadequate interfacial adhesion between PC and EMA.