Raman spectroscopic study of ultraoriented solid state extruded polyethylene

Raman spectroscopy was used to follow structural changes for polyethylene extruded at 80 and 130 °C by the split billet method. The all-trans chainlength distributions derived from the low frequency Raman longitudinal acoustic mode (LAM) data varied considerably as a function of the draw ratio or processing temperature. Even though the molecular orientation is extremely high for the sample deformed to the highest draw ratio, LAM measurements revealed a broad chainlength distribution, especially for samples prepared at the low temperature. We have interpreted the broad chainlength distribution to arise from conformational defects introduced during mechanical deformation.