The influence of drawing temperature on mechanical properties and organization of melt spun polyethylene solid-state drawn in the pseudo-affine regime

摘要

Mechanical properties of high density polyethylene (HDPE) solid-state drawn with fixed draw ratio at different temperatures in a fiber/tape spin line were investigated.All drawing experiments were performed in the pseudo-affine regime,i.e.no effective relaxation of the molecules occurs during drawing.For such conditions,the Young's modulus is uniquely determined by the applied draw ratio.The general appearance of the stress-strain behavior of drawn HDPE,and in particular its yield strength,however,is strongly influenced by the stretching temperature applied.For a fixed draw ratio,a significant drop in yield stress can be observed with decreasing drawing temperature.Characterization of structure and organization of the solid-state drawn HDPE was performed using various analytical techniques,such as wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC).It is proposed that solid-state drawing at temperatures above the alpha-relaxation temperature results in relative large crystals so that corresponding tapes show a high yield point.Drawing at low temperatures below the alpha-relaxation temperature of PE,however,causes formation of small or imperfect crystals that can be destructed at low stress (low yield point),which is a preferable start situation for a second solid-state drawing step in a multiple drawing process.