Simulations of effective permittivity and polarization properties of polyethylene nanodielectrics

Many papers reported that the effective permittivity of nanodielectrics decreased slightly by incorporating of small amount of nanoparticles, and increased at high nanoparticle loadings. The reduction of permittivity was close related to the molecular chains movements, chemical and physical interactions and polarization effects in interfacial region. This paper simulated the effective permittivity and polarization properties of LDPE/Al₂O₃ nanodielectrics based on the revised interphase power law (IPL) model. The results indicated that the IPL model is well fit to the experimental results of reduced permittivity in LDPE/Al₂O₃ nanocomposites at low loadings (<;1 wt%) by considering the large “interface thickness” (nano-size effects). In this situation, the role of interface becomes conspicuous. The improved IPL model takes into consideration of changed nanoparticle shape and orientation (β=1) as well as the reduction of interface thickness or its permittivity for high loading samples. It is capable of fitting to the experimental results at high loadings. The interface thickness significantly decreases with increasing nanoparticle fraction, especially at low loadings. That is caused by the reduction of nano effect through interaction of nanoparticles. There is a transition process from low to high nanoparticle loadings. During the transition process, the interface thickness decrease and its permittivity increase, leading to a slight increase of real permittivity. The transition is also benefit to other dielectric properties in nanocomposites.