Crack-resistance behavior of polypropylene copolymers

Two heterophasic reactor-grade propylene-ethylene copolymers (RAHEC(R)) wer e diluted with propylene-ethylene random copolymers to obtain materials wit h constant EPR/PE-particle diameter but various interparticle distances. Ac cording to the results of instrumented impact tests, brittle-to-tough trans itions were found at different temperatures. The critical interparticle dis tances shift linearly over the observed range of temperature. Critical inte rparticle distances could be determined not only in the region of predomina ntly unstable crack growth but also in the region of predominantly stable c rack growth. (C) 2001 John Wiley & Sons, Inc.