Strain-induced crystallization of swollen,crosslinked polyethylene

The kinetics of strain-induced crystallization of swollen polyethylene networks have been measured using dynamometry coupled with optical birefringence. Fibers were prepared by gel-spinning ultrahigh-molecular-weight polyethylene followed by crosslinking in dicumyl peroxide and swelling in xylene. Retractive force on crystallization was monitored at various temperatures and draw ratios. Fiber visualization was achieved using optical illumination coupled with video recording and digital analysis of the in situ transformation. Avrami plots of the transformation data showed good linear fits for low draw ratios in the range α < 1.2 and moderate undercoolings (60 < T_c < 70°C). Time exponents of unity were found, indicating a one-dimensional, heterogeneous growth mechanism whose temperature dependence could be described by a formalism similar to that recently used for flow-induced growth.