Abstract: | High thermal conductivity fillers of boron nitride (BN) and vapor‐grown carbon fiber (VGCF) were used alone or incorporate to prepare polypropylene (PP) composites. The effects of filler content, particle size and shape, and single vs. hybrid BN/VGCF fillers were investigated with respect to the thermal conductivity of the PP composites. The thermal conductivity of PP/BN composites depended upon the content and particle size of the BN. Increased content and length of VGCF had the effect of increasing the thermal conductivity of the PP composites. Hybrid fillers were created with a mixture of medium‐sized BN and long‐length VGCF; hybrid BN/VGCF fillers enhanced the thermal conductivity of PP composites with a lower total content compared with PP composites containing only medium‐sized BN particles. POLYM. COMPOS., 37:936–942, 2016. © 2014 Society of Plastics Engineers |