PRECIPITATION OF LDPE-EPDM AND LDPE-EVA MIXTURES FROM TERNARY SOLUTIONS

The fast precipitation of mixtures of low-density polyethylene (LDPE) with ethylene-propylene-diene terpolymer (EPDM) and ethylene-vinyl ace tate (EVA) copolymer, from xylene solutions by cooling, leads to fract ionation of the mixtures; LDPE/EPDM mixtures are also fractionated by cooling followed by nonsolvent addition. Studies by density-gradient c entrifugation, IR spectroscopy, optical microscopy and wide-angle X-ra y diffraction showed that the composition and morphology of LDPE/EPDM fractions depend on the precipitation procedures. LDPE crystalline str ucture in each fraction is different, changes with the time and depend s on EPDM content. EVA fractions that co-precipitate are richer in -CH 2-CH2-units. LDPE/EPDM and LDPE/EVA precipitates showed chemical compo sition distribution and morphological characteristics different among themselves. Larger aggregates were observed in the LDPE/EPDM precipita tes. These differences were attributed to differences in the phase dia grams and in the phase separation mechanisms. (C) 1997 Elsevier Scienc e Ltd.