USE OF EVA-CONTAINING MERCAPTO GROUPS IN NATURAL RUBBER-EVA BLENDS .1. MECHANICAL, THERMAL, AND MORPHOLOGICAL PROPERTIES

The effect of ethylene-vinyl acetate (EVA) modified with mercaptoaceti c acid on mechanical, thermal, and morphological properties of blends of natural rubber (NR) and EVA copolymers has been investigated. The i ntroduction of EVASH promotes a crosslinking of natural rubber phase a s indicated by extraction experiments and microscopy analysis. This cr osslinking may be attributed to bonding between sulfhydryl groups alon g the EVASH backbone and double bonds in rubber phase and may be respo nsible for the hardness improvement of most of the studied blends. Bet ter results on hardness and ultimate tensile strength with EVASH addit ion were achieved for NR-EVA (60:40) ratio, probably due to cocontinuo us morphology of this composition. The influence of EVASH on crystalli nity degree of NR-EVA blends was also studied by differential scanning calorimetry. The morphology of the blends was studied through scannin g electronic microscopy. (C) 1995 John Wiley & Sons, Inc.