Flame retardancy of rice husk-filled high-density polyethylene ecocomposites

Rich husk (RH) is a naturally occurring inorganic/organic composite consisting mainly of lignocelluloses and silica. Due to the high silica content in RH, their addition into synthetic polymers may play certain synergistic roles in the flammability of the resulted composites. In this study, the thermal stability and flammability of RH-filled HDPE (HDPE/RH) ecocomposites with different compositions have been evaluated by thermogravimetric analysis and cone calorimetry, respectively. It is observed that the addition of RH has effectively delayed the thermo-oxidation process of the HDPE matrix by about 40 °C, and evident flame retardant effect has also been observed (in comparison to the results obtained from neat HDPE). From analysis carried out on the composition and structure of the combusted residues, it can be inferred that the main mechanisms for the flame retardancy in the HDPE/RH ecocomposite are due to the heat shielding and diffusion barrier effects of the silica-based protective layer which was formed during the heating process.