A novel fiber-reinforced polyethylene composite with added silicon nitride particles for enhanced thermal conductivity

A novel thermally conductive plastic composite was prepared from a mixture of silicon nitride (Si3N4) filler particles and an ultrahigh molecular weight polyethylene–linear low density polyethylene blend. The effects of Si3N4 particle sizes, concentration, and dispersion on the thermal conductivity and relevant dielectric properties were investigated. With proper fabrication the Si3N4 particles could form a continuously connected dispersion that acted as the dominant thermally conductive pathway through the plastic matrix. By adding 0–20% Si3N4 filler particles, the composite thermal conductivity was increased from 0.2 to ∼1.0 W m−1 K−1. Also, the composite thermal conductivity was further enhanced to 1.8 W m−1 K−1 by decreasing the Si3N4 particle sizes from 35, 3 and 0.2 μm, and using coupling agent, for the composites with higher filler content. Alumina short fibers were then added to improve the overall composite toughness and strength. Optimum thermal, dielectric and mechanical properties were obtained for a fiber-reinforced polyethylene composite with 20% total alumina–Si3N4 (0.2 μm size) filler particles.