Natural rubber with low heat generation was prepared by the inclusion of boron carbide (B4C). Tensile testing, scanning electron microscopy (SEM), dynamic mechanical analysis, and thermal constant analysis were performed. The results show that a slight deterioration of tensile strength only occurred at a high volume content (>20 vol %). The thermal conductivity increased for the formation of well-maintained B4C thermal conductive pathways. SEM images and theoretical analysis demonstrated that the specific area of B4C was small and the interfacial activity was low. Infrared thermal images taken by the infrared camera proved the low heat generation of the composites, which originated from the high thermal conductivity and the weak interface. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2050-2055, 2010