The Role of Temperature in the Entanglement Kinetics of a Polymer Melt

Abstract

Large-amplitude oscillatory shear (LAOS) experiments were conducted at different temperatures on a molten low-density polyethylene standard, designated IUPAC LDPE X. Jeyaseelan et al. (1993) have successfully employed a simplification of transient network theory to describe the LAOS behavior of this polymer melt, at 150°C. The transient network is described by two kinetic rate constants, one for the formation of entanglements due to Brownian motion (k 1 ), and another for the destruction of entanglements (k 2 ) due to the imposed deformation. Upon comparison of the predictions of this transient network theory with the measured LAOS behavior of this polymer, we find that the kinetic rate constants k 1 and k 2 are invariant in the range of temperatures examined (150 to 190°C). The temperature dependence of departures from linear viscoelasticity is fully accounted for in the equilibrium entanglement kinetics.