Thermal and dielectric properties of the aluminum particle reinforced linear low‐density polyethylene composites

The possibility of obtaining relatively high thermal conductivity and dielectric constant but low dielectric loss polymeric composites by incorporating the core‐shell‐structured aluminum (Al) particles in a linear low‐density polyethylene (LLDPE) by melt mixing and hot pressing was demonstrated in this study. The morphology, thermal and dielectric properties of the composites were characterized using X‐ray diffractions, thermal analysis, scanning electron microscope, and dielectric analyzer. The Al particle decreases the degree of crystallinity and has no appreciable influence on the melting temperature of LLDPE. The thermal conductivity, dielectric constant and loss factor of the composites increase with an increase in Al content at all the frequencies (1 ～ 10⁶ Hz). The thermal conductivity and dielectric constant of the 70 wt% flaky Al particles filled LLDPE are 1.63 W/mK and 50, much higher than those of the spherical Al reinforced one. Moreover, the surface treatment of Al particles with γ‐Aminopropyltriethoxysilane silane coupler improves the thermal conductivity. The dielectric loss factors of the composites still remain at relatively low levels in the measured frequency range. Further, the dielectric permittivity frequency independence in the measured frequency range was observed due to the nanoscale‐Al‐oxide insulating shell of Al. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers