THE EFFECT OF MIXING ON THE PROPERTIES OF POLYETHYLENE BLENDS

A linear low-density polyethylene (LLDPE) with hexyl branches has been blended with high-density polyethylene (HDPE) and a comparison has be en made of the effects of three methods of blending on the quality of the blends produced. A twin-screw extruder, roll mills and solution pr ecipitation have been compared for their effectiveness in producing a uniform blend. Compositional variations have been measured by Fourier- transform infra-red spectroscopy, crystallization and melting characte ristics have been studied using differential scanning calorimetry, and the morphology has been examined by wide-angle X-ray scattering and s canning electron microscopy. In general, it is concluded that in the m elt the two grades of PE are compatible and co-crystallize on quenchin g. The most uniform product is produced by the twin-screw extruder, si nce the blends have higher melting points, crystallinity, yield stress and elongation at break. The solution-blended product crystallizes at a lower temperature than the others, consistent with a reduction in h eterogeneous nucleation.