CORRELATION BETWEEN MICROSTRUCTURE AND PHYSICAL-PROPERTIES IN STYRENEETHYLENE COPOLYMERS

The structural organization and the physical properties of a new copol ymer styrene-ethylene have been analyzed. The composition was 80% of e thylene units, corresponding to 52% in weight, with a distribution of styrene units in the chain implying the absence of styrene-styrene seq uences. The length of the polyethylene chains, limited by the insertio n of the phenyl group, is not sufficient to allow good crystallization , and in fact the copolymer shows a very low crystallinity, of the ord er of 5-10%, and a broad melting range, with a peak centered at 120 de grees C. The small crystalline domains are segregated into an amorphou s matrix, producing a thermoplastic elastomer. The mechanical properti es at large deformation were analyzed at different temperatures. The c opolymer shows good elastic properties, in terms of deformation revers ibility as well as of energy dissipation in the hysteresis cycles. Als o the stress level and the elastic recovery are very good, if compared with others thermoplastic elastomers. (C) 1995 John Wiley & Sons, Inc .