Charge distribution in polyethylene/ethylene vinylacetate laminates and blends

The formation of space charge in polyethylene/ethylene vinylacetate copolymer (PE/EVA) laminates was investigated using a pulsed electroacoustic (PEA) method. The formation of heterocharge was observed in PE while positive charge (holes) was distributed over the EVA specimen. In the laminates, however, a large amount of charge accumulates at the interface between PE and EVA, resulting in an increase of the electric field in the PE layer. When the thickness of the EVA layer is smaller than that of the PE layer, negative charge dominates in the PE layer due to enhanced charge injection caused by the increased electric field in the PE layers. When these polymers are blended, the amount of heterocharge in the PE/EVA blends varies inversely with the vinylacetate content by the enhancement of homocharge trapping at PE/EVA interfaces and/or by the enhancement of charge injection via an increased electric field in the PE component.