Space Charge Distribution and Crystalline Structure in Low-Density Polyethylene modified by Metallocene Catalyzed Polyethylene

A small amount of metallocene catalyzed polyethylene (MPE) was blended into low-density polyethylene (LDPE) in this paper. Then the space charge profile in the blends was measured by pulsed electro-acoustic (PEA) method, which showed that the space charges were greatly decreased and field distributions tended to be uniform in LDPE blended with 1 wt% MPE. At the same time the crystalline structures of the blends were studied by differential scanning calorimetry (DSC) method, which showed that LDPE blended with a small amount of MPE could increase crystallization temperature and crystallinity. In addition, the results of wide-angle X-ray diffraction (WAXD) and small-angle light scattering (SALS) experiments showed that the crystalline forms did not change, whereas the sizes of spherulites were smaller in the blends than that of virgin LDPE and had a least value in LDPE blended with 1 wt% MPE. Polyethylene is a typical semicrystalline polymer. Its crystalline structure must affect the distribution of space charge. The decrease of space charge in the blends can probably be attributed to the decrease of spherulites´ size and the form of imperfect spherulite, which lead the trap density to decreasing in boundary regions of spherulites