We present chain structure, phase morphology, and toughness relationships in thermoplastic polymers and polymer/rubber blends. In neat polymers, molecular aspects of craze/yield behavior are controlled by two chain parameters: entanglement density v, and characteristic ratio C,. The crazing stress is proportional to ye1/', and the yield stress is proportional to C,. The dispersed rubber toughens a polymer/rubber blend mainly by promoting energy dissipation of the matrix. The toughening efficiency correlates with the rubber phase morphology and the chain structure of the matrix. , MID-JULY 1990, Yo/. 30, No. 13 Polymer T, OC dyne/cm* g/cc Me mmole/cc C, iPAR 250 1.98 x lo7 1.128 2480 0.491 3.4 itPAR 260 2.
753
POLYMER ENGINEERING AND SCIENCE