Structure-property relationships of metallocene linear low density polyethylene (LLDPE)

摘要

In this study, the structure-property relationships of metallocene linear low density polyethylene (m-LLDPE) are investigated. Particularly, the influence of the branch content (BC), composition distribution, and comonomer type on the thermal and mechanical properties of m-LLDPEs was studied. The mechanical properties were studied by means of stress/strain experiments. The increase in BC of m-LLDPEs lowered the crystallinity and the modulus. The ultimate mechanical properties of m-LLDPEs were weakly dependent on BC. The comonomer type had no significant effects on the mechanical properties of m-LLDPEs. The Ziegler-Natta LLDPEs (ZN-LLDPEs) were also studied for comparison purposes. However, ZN-LLDPEs showed higher small strain properties but lower ultimate properties than m-LLDPEs of similar Mw, branch type, and BC. In addition, the influence of strain rate on the mechanical properties of m-LLDPEs was examined. For low BC m-LLDPEs, there exists a very narrow strain rate window within which a maximum in modulus and ultimate properties was observed. The strain rate had no influence on the mechanical properties of the highly branched m-LLDPEs. (Abstract shortened by UMI.).