Dielectric polymer‐based composites with high breakdown strengths and thermal conductivities have attracted considerable attention when applied in electronic devices. In this study, a novel poly(m‐phenyleneisophthalamide) (PMIA) dielectric nanocomposite is successfully fabricated by introducing functionalized hexagonal boron nitride nanosheet (fBNNS) fillers. Due to effective functionalization of hexagonal boron nitride nanosheets (BNNSs), fBNNSs fillers are homogeneously dispersed in the PMIA matrix. The breakdown strength and thermal conductivity of PMIA/fBNNSs dielectric nanocomposite are investigated. Research results indicate that the breakdown strength of fBNNSs‐12 reaches 105.6 MV m?1, which is 1.34 times that of pure PMIA. Moreover, owing to high thermal conductivity of fBNNSs, the thermal conductivities of fBNNSs‐12 are observably increased to 8.06 W m?1 K of in‐plane direction and 0.84 W m?1 K of through‐plane direction, respectively. Considering these properties, the manufactured PMIA/fBNNSs dielectric nanocomposites show potential applications in field of electronics. 相似文献
(Sr0.8Pb0.2)TiO3-MgO (50:50 by weight) composites are prepared and their dielectric properties are investigated. The dielectric properties of the samples prepared by using the green samples prepared under different cold pressing conditions are compared. The cylindrical samples prepared by using uniaxial pressing (UP) followed by cold isostatic pressing (CIP) show the higher quality of dielectric properties than the plate samples prepared by using only UP. It is found that the forming pressure before CIP also influences the dielectric constant of the sintered products. Furthermore, the dielectric constant of the rectangular composite samples cut out of the disk samples is direction dependent with respect to the UP direction while the tan δ of the composites is almost independent of the measurement directions. 相似文献
Summary: The melting temperature difference between poly(propylene) (PP) fibre and random poly(propylene‐co‐ethylene) (PPE) was exploited to establish processing conditions for all‐PP composite. Under these conditions, the matrix must be liquid to ensure good wetting and impregnation of fibres, though temperatures must be low enough to avoid melting of fibres. The high chemical compatibility of the two components allowed creation of strong physico‐chemical interactions, favouring strong interfacial adhesion. Static and dynamic mechanical properties and morphology of all‐PP composites were investigated according to method of preparation and compared with the behaviour of hot compacted composites, prepared under different moulding conditions. The composites were compacted with varying pressure and time, and mechanical and thermal properties of the resulting sheets were measured. With increased moulding time, more fibres melted or their original properties deteriorated. Fast cooling or quenching caused imperfect morphology. Moulding pressure played an important role. Morphology of the optimum hot compacted composite was investigated using scanning electron microscopy before and after tensile testing. Tensile fracture surfaces showed a melted phase epitaxially crystallised onto the remaining orientated phase. Compacted composites showed fibre shapes under a thin layer of PPE with all of the gaps between fibres filled by melted PPE matrix.
SEM of compacted all‐PP composite without quenching. 相似文献
