Thermal conductivity of sorghum and sorghum-thermoplastic composite panels

Thermal conductivity of a material is a key parameter to simulate heat transfer during manufacturing of a composite under heat and pressure. This study investigated the thermal conductivity of composite panels hot-pressed with varying proportions of sweet sorghum and high-density polyethylene (HDPE). Thermal conductivity of the composites was tested under steady-state conditions. The effects of temperature (12.5-62.5°C), density (0.7-1.0g/cm³) and HDPE (0-40%) content on thermal conductivity of the composite products were investigated. Thermal conductivity increases in a linear manner with temperature and density, and in a nonlinear manner with HDPE content. An empirical equation for describing the thermal conductivity of sweet sorghum and HDPE composite panels was fitted, and has a good agreement with testing data. Compared with other empirical equations for predicting the thermal conductivity of wood, the experimental values in this study consistently had lower values, indicting a significant difference in thermal conductivity of composites manufactured with agro-based natural fibers compared to wood fibers. Additionally, predicted thermal conductivity values are limited by those estimated by the parallel and series models for two phase composites.