DAMAGE ZONE IN PVC AND PVC MBS BLENDS .1. THE EFFECT OF RUBBER CONTENT AND TEMPERATURE/

The damage zone development in poly(vinyl chloride) (PVC) and its tran sparent blends with methyl methacrylate-butadiene-styrene (MBS) core/s hell rubber was studied as a function of temperature and rubber conten t in a triaxial stress state under slow tensile loading. Failure at th e semicircular notch occurred by shear yielding followed by stress whi tening. In unmodified PVC, the shear yielded plastic zone size was not affected by temperature in the range between -40 and 40 degrees C. In the blends, the plastic zone preceding stress whitening increased in size with temperature and rubber content, shifting the stress-whitened zone further away from the notch root. Below 0 degrees C, stress whit ening initiated at the notch root and the stress-whitened zones had a crescent shape similar to those of PVC/CPE blends studied previously. In unmodified PVC, stress whitening initiated from the growth of preex isting microvoids at the tip of the shear yielded zone containing two families of curving slip lines emanating from the notch root. In contr ast, stress whitening in the blends was more intense and was initiated by the cavitation of the rubber particles. (C) 1997 John Wiley & Sons , Inc.