Effect of stretching on electrical properties of LDPE/MgO nanocomposites

This paper researched the effect of stretching on electrical properties of LDPE/MgO. Pulsed electro-acoustic (PEA) method, dielectric analyzer and high resistance meter were used to research the DC breakdown, space charge behavior, permittivity, loss tangent and volume resistivity of neat LDPE and LDPE/MgO nanocomposites with concentration of 1, 3 and 5 wt% with and without elongation ratio of 1.1. Results indicate that the DC breakdown strengths of neat LDPE and nanocomposites decrease after stretching. The heterocharges near electrodes in neat LDPE change to homocharges after stretching and a large amount of positive and negative charges accumulated in samples with concentration of 3 wt% and 5 wt%. Meanwhile, homocharges near cathode electrode in nanocomposite with concentration of 1 wt% decrease a little and a small amount of positive charges were observed in the samples after stretching. Furthermore, there are different increases in amplitudes of permittivity in all samples after stretching as well as the loss tangents especially in the frequency domain from 10
^-1
-10
²
Hz. The results of volume resistivity show that comparing with the nanocomposite with concentration of 1 wt% whose volume resistivity decrease after stretching, larger volume resistivity is observed in neat LDPE and nanocomposites with concentration of 3 wt% and 5 wt%. As we know, the electrical properties of polymer based nanocomposites is dominated by interface between nanoparticles and polymer matrix. After stretching, the area of interface may increase, which may increase the amount and depth of charge traps. Additionally, the free volume may increase and the force stressed on polar molecular may decrease, leading to the change of electrical properties of nanocomposites.