A Study on the Curing Characteristics, Tensile, Fatigue, and Morphological Properties of Alkali-Treated Palm Kernel Shell-Filled Natural Rubber Composites

Abstract

Effects of alkali treatment of palm kernel shells (PKS) were investigated relative to curing characteristics, tensile properties, and fatigue of PKS- filled natural rubber (NR) composites. The PKS powder was subjected to alkali treatment using 5% sodium hydroxide. The treated PKS was incorporated into the NR composites during compounding, with the concentrations of the composites ranging from 5 to 20 phr. The properties of treated PKS-filled NR composites were compared with those of untreated PKS-filled NR composites. The cure times, scorch times, and maximum torque values were all lower for alkali-treated PKS/NR composites compared with those of untreated PKS/NR composites. Tensile strength and elongation at break were higher for treated PKS composites, while the moduli (M100 and M300) were lower than those of untreated PKS/NR composites. The fatigue tests for treated PKS/NR composites also showed higher fatigue values than the untreated PKS/NR composites. Scanning electron microscopy revealed that the higher tensile strength, elongation at break, and fatigue values of treated PKS/NR composites were due to the removal of hemicellulose and lignin in PKS fillers. This removal increased in the surface roughness of the filler and led to improved rubber-filler adhesion.