Boron nitride filled immiscible blends of polyethylene and ethylene-vinyl acetate copolymer: Morphology and dielectric properties

Morphological structure of polyethylene/ethylene-vinyl acetate copolymer (PE/EVA) blends was investigated by selective solvent extraction of EVA. A blend with co-continuous structure was obtained when the mass ratio of PE/EVA was 1/1. Boron nitride (BN) was filled in the co-continuous PE/EVA blend. The morphology of PE/EVA/BN was observed by scanning electron microscope (SEM). As a result, BN was found to be selectively located in PE phase. A new co-continuous structure formed between EVA phase and PE/BN phase. The dielectric properties and tensile properties of PE/EVA/BN composites were evaluated. Comparison was made between the properties of PE/BN, EVA/BN and PE/EVA/BN composites at the same BN loading level of 30 wt%. The volume resistivity and dielectric loss tangent of PE/EVA/BN composites are similar with EVA/BN, while the dielectric constant is similar with PE/BN. Even though the elongation at break of PE/EVA/BN composites was improved significantly when compared with PE/BN, the tensile strength was obviously impaired, which could be ascribed to the large interface in the co-continuous structure.