MICROSTRUCTURAL CHANGES INDUCED IN LINEAR POLYETHYLENE BY PLASTIC-DEFORMATION (ROLLING)

Mechanical spectrometry and differential scanning calorimetry analysis completed by wide-angle X-ray diffraction and density measurements were performed on linear polyethylene in order to characterize the influence of a plastic deformation (rolling) on the microstructure. Thus, rolling performed at room temperature results in the breaking of the thicker lamellae. The changes in the microstructure in polyethylene induced by rolling are in agreement with those suggested by other authors. A phenomenological model, applied to the alpha' relaxations exhibited by polyethylene, allows quantitative analysis of the microstructural changes due to plastic deformation. Thus, rolling induces an increase in the interactions between phases through an increase in the number of tie molecules connecting the broken crystallites. Moreover, rolling results in an increase of crystallographic defect concentration within the crystalline phase and this plastic deformation induces phase transformation from orthorhombic to monoclinic lattice, which is preferentially developed for thicker lamellae.