Electret Charge Stability and Thermomechanical Properties of Polypropylene Blends with Ethylene-Methyl Acrylate Copolymer

Electret charge stability has been studied by means of thermally stimulated surface potential decay (TSSPD) for a series of polypropylene homopolymer blends with an ethylene methyl acrylate random copolymer. Charge decay has been investigated in heat-pressed thin films for both positive and negative polarities. It has been found that the electret charge stability was quite sensitive to the copolymer content in the blend ratios investigated. However, above 2 wt% polar copolymer content the charge decay pattern does not substantially change any further. Charge polarity only has a limited effect on the surface potential decay. Flexural modulus has been determined via three-point bending tests at ambient temperature while the evolution of the flexural modulus with temperature has been determined by dynamic mechanical analysis (DMA). Charpy impact tests confirm the increased impact resistance with increasing ethylene copolymer content. Calorimetric measurements have been performed with dynamic scanning calorimetry (DSC) to support the interpretation of charge decay measurements and to assess the sample morphology in pressed thin films.