Surface melting and lamella rearrangement process in linear low density polyethylene.

The surface melting and lamella rearrangement process that happen in commercially available linear low-density polyethylene (LLDPE) were studied with special emphasis on conformational and crystal structural changes during the process. The thermal melting behavior of the specimens was examined by using differential scanning calorimetry and the occurrence of the surface melting was strongly suggested in low-crystallinity LLDPE (LLDPE-L) in the temperature range of 90−120 °C at the heating rate of 2 °C/min. The structural and conformational disordering process during heating was studied by IR spectroscopy combined with two-dimensional spectral correlation analysis. The formation of conformational defects has been determined to proceed prior to the overall disordering of orthorhombic crystalline structure in all the PE specimens except for LLDPE-L. During the heating process, conformational defects are preferably developed in side chains that are excluded from tightly packed orthorhombic crystal in PEs other...