Annealing of polyethylene crystals in the hexagonal phase

Abstract

The kinetics of thickening of polyethylene crystals in the hexagonal phase is studied. Distributions of thickness, L, of bands and/or lamellae are obtained by electron microscopy for a specimen annealed at p=6.1 kbar, T=242°C for 30, 300, 3600 and 86400 seconds. The dependence of the average band thickness L ̄ (t) on the annealing time t can be expressed as L ̄ (t)=46· log( t t 0 )+ L ̄ (t 0) [ nm] . Moreover, these distributions can be superposed on each other if we scale L by L ̄ (t) . A model for the thickening process of a lamellae is proposed; coalescence of two bands occurs by disappearance of the boundary with the rate proportional to exp(− αL). The value of α depends on the mobility of defects in the boundary and is discussed in detail.