Keywords: Natural fibre polymer composites; sodium bicarbonate; cell morphology; mechanical properties

Abstract

Foaming composites reduce transportation costs and fuel usage by achieving weight reduction through the introduction of foaming gas. This study investigates the impact of extrusion temperature profiles and sodium bicarbonate (NaHCO3) foaming agent loading (2 and 4%) on the density, morphological foam structure, and mechanical properties solid and foamed poly (lactic acid) (PLA) biocomposites reinforced with kenaf fibre. The biocomposites were prepared via melt-blending method. Two extrusion temperature profiles, set at 165-170-175-160 ºC (higher temperatures, HT) and 155-160-165- 150 ºC (lower temperatures, LT). Results indicate that, with an increase in NaHCO3 loadings, a gradual decrease in density was observed, with LT extrusion showing a higher density reduction (up to 8%) compared to HT. Field emission scanning electron microscope observations revealed a more consistent foam cell size structure for LT-extruded samples. However, the tensile properties of the foamed biocomposites deteriorated, with approximately 23% decrease in tensile strength and 26-29% in elongation at break. In conclusion, a lower extrusion processing temperature (LT) was found to be optimal for producing uniform porous biocomposite foams with lower density and higher mechanical strength.