Study of dielectric spectra of ldpe/zeolite nanoscale and micronscale composites

Type NaY zeolite powder with nanoscale and micronscale were doped in low-density polyethylene(LDPE). The zeolite particles with nanoscale and also with micronscale were uniformly distributed in LDPE shown in SEM images. The dielectric spectra of LDPE/zeolite composites and pure LDPE are tested by broadband dielectric spectrometer at two different temperatures, 293K and 353K. The study found that composites´ dielectric constant generally decline, which is relative with the zeolite porous structure. At the same time, the dielectric constant of LDPE/zeolite nanoscale composite was smaller than the dielectric constant of LDPE/zeolite micronscale composite at the same doping concentration, which attributed to the enormous specific surface area of nanoscale zeolite that increased the interface area and the amount of gaps between LDPE and zeolite nanoparticles. The law of the dielectric loss showed that there were loss curve peaks in the middle frequency range both with the LDPE/zeolite naoscale and micronscale composites. In accordance with the Maxwell-Wagner (M-W) theory, the loss peak position calculated from M-W equation was consistent with the experimental curve which means the loss peak applied to the interfacial polarization. There were also some differences of dielectric losses between LDPE/zeolite nanoscale and microscale composites, the loss curve peak of nanoscale composite was much lower than the curve peak of micronscale composite. It can be explained that the nanoscale particles of zeolite were combined more closely with LDPE substrate than the microscale particles which reduced the interfacial polarization. When the temperature rose up to 353K, the dielectric constant of LDPE/zeolite nanoscale and micronscale composites decreased concurrently. At the same time, the loss curve peak moved to the high frequency direction which was also conformed to the M-W theory using Arrhenius equation calculations.