Crystallization and phase separation of high-density polyethylene in the presence of comb-like polymer, poly(octadecyl acrylate)

The influence of poly(octadecyl acrylate) (PODA), which is a comb-like polymer with ethylenic side chains, on the crystallization and morphological behavior of high-density polyethylene (HDPE) in a binary blend was investigated. The studied parameters were the cooling rate, degree of crystallinity, spherulite size, and unit cell dimension of HDPE, and they were evaluated by optical microscopy, small angle light scattering, differencial scanning calorimetry, and wide angle X-ray diffraction. Scanning electron microscopy was also used for investigation of the cross-section and the external surface of HDPE/PODA blend films. Although the melt state studies proved these components to be immiscible, the presence of PODA was shown to influence the crystallization phenomena of HDPE. The spherulite size of HDPE increased from 11.6 (HDPE/PODA 100:0) to 16.5 mu m in the presence of 30 wt% of PODA in blend when the samples were quenched. Similarly, the spherulite size of HDPE changed from 17.5 to 38.6 mu m due to the presence of PODA in the slowly cooled samples. Ringed spherulite forms due to the twisting of the lamellae were observed in the slowly cooled (HDPE/PODA 70:30) sample. (C) 1997 Elsevier Science Ltd.