Cryogenic dielectric and mechanical properties of nanowire-Al ₂O₃ filled PBT/GF composites

The cryogenic dielectric and mechanical properties of nanowire-Al ₂O₃ filled PBT/GF (glass fiber) composites are investigated by combing macro-performances testing and microstructures analysis. Compared with PBT/GF composites, the PBT/GF/Al₂O₃ ternary systems present improved tensile strength as well as impact strength. The fracture surface shows a typical toughened characteristic under SEM observation, which may be explained by the "crack bridging" toughening mechanism. At the same time, POM study indicates diminished spherulitic texture for the three phase composites, which is due to nucleating effect of the nanoparticles. DSC and WAXD analysis suggest that nanowire-Al₂O₃ can hinder the crystal growth and lower the degree of crystallinity. Cryogenic dielectric spectra of the composites showed a broad y loss process shifting to low temperature region with the increasing content of Al₂O ₃, which suggested that the existence of the nanowire might facilitate the molecular motions of PBT matrix and improved the low temperature toughness. Suitable amount of Al₂O₃ can also be helpful to reduce the micro-defects, which may contribute to the higher electrical strength of the systems.