The Water Absorption and Thermal Properties of Green Pterocarpus Angolensis (Mukwa)-Polylactide Composites

Abstract

ABSTRACT The water absorption, chemical resistance, and biological properties are contributing factors to the overall performance of bio-composites, especially for outdoor applications. The functional properties of bio-composites are dependent on the interfacial bonding mechanism, which is controlled by the surface modification and processing parameters of natural fibers. Therefore, this study aims to investigate the potential of enhancing the mukwa/polylactide (mukwa/PLA) interface through an economic and ecological surface modification of recycled mukwa wood fibers via alkali-laccase modification. The fabricated bio-composites intended for making durable farm poles for semi-arid conditions of Southern Africa were characterized via water absorption, chemical resistance, thickness swelling, hardness, and thermal properties. Less thickness swelling and water absorption were found on the alkali-laccase/PLA composites. The less-dense (1.09 g/cm3) alkali-laccase treated composites showed better chemical resistance. Much swelling of the composites was observed on the 40% nitric acid (HNO3), while 60%NaOH shrunk the composites and PLA by <3.5%. The laccase/PLA bio-composite showed a maximum thermal stability of 733 °C. The activation energy (Ea) optimized on the laccase/PLA composite with the highest of 104 kJ mol−1. Maximum crystallinity of 45.8% was achieved on the untreated/PLA composites. The alkali-laccase modification maximized the hardness of composites with 35.45 HV on alkali-laccase/PLA.