Influence of initial polymer concentration in solution and weight‐average molecular weight on the drawing behavior of polyethylenes

Abstract

AbstractThe influence of initial polymer concentration in solution (c), weight‐average molecular weight (Mω), and drawing temperature on the solid‐state drawing behavior of linear polyethylenes was investigated. Optimum conditions, with respect to maximum attainable draw ratio, are observed in isothermal drawing experiments. Moreover, it is shown that high maximum attainable draw ratios can also be obtained upon multistage drawing of UHMW‐PE (ultrahigh‐molecular‐weight polyethylene, Mω > 106 g/mol) gel films cast from concentrated solutions. The high maximum attainable draw ratio in combination with the high molecular weight (Mω > 106 g/mol) and polymer concentration (c = 10% w/v) is of particular interest because it results in tapes or fibers with a high Young's modulus (100 GPa) and tensile strength (2.5–3.5 GPa). It is also shown that the maximum attainable draw ratio of polyethylenes scales with the Bueche parameter (c · Mω) to the −0.5 power. This experimental observation indicates that intermolecular interactions not only dominate the rheological properties of polyethylene melts and concentrated solutions, but also strongly influence the solid‐state drawing behavior of linear polyethylenes.