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

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 biocomposites intended for making durable farm poles for semi-arid conditions of Southern Africa were characterised 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/cm 3 ) 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 biocomposite showed a maximum thermal stability of 733 ˚C. The activation energy (Ea) optimised 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 maximised the hardness of composites with 35.45 HV on alkali-laccase/PLA.

A comprehensive study on the effect of hybridization and stacking sequence in fabricating cotton-blended jute and pineapple leaf fibre biocomposites

“…It was observed that, for 4P5J – 1, the hybridization of pineapple increased the moisture absorption significantly (an increase of 22.5% compared to JFRP) after 21 days. This could be attributed to a combination of factors, including the presence of more hydroxyl groups in the jute-cotton fibre ply (which can form hydrogen bonds with water molecules, leading to water retention [ 85 ]), which was on the outside of the composite, and poor interfacial adhesion between the alternating jute/PALF plies and the matrix, facilitating enhanced moisture absorption through capillary effect and microcracking [ 86 ]. The presence of voids observed in the SEM micrograph of 4P5J-1 may also contribute to water retention.…”

“…On the other hand, for all the other composites, hybridization effectively reduced moisture absorption to approximately 16.70%, 14.84%, and 29.50% for 4P5J – 2, 4P5J – 3, and 4P5J – 4, respectively, when compared to the moisture absorption of 12.44 wt% JFRP after 21 days. The significant reduction in moisture absorption may be attributed to a lower presence of hydroxyl groups on the composite surface [ 85 ] as well as improved surface adhesion when stacking the same type of plies together.…”

Impact of Water Absorption on Tensile Strength: A Comparative Study of Jute Fiber Composites with Various Fiber Content

“…When the percentage of jute fiber in the material rises to 10% and then 15%, the strength drop becomes more obvious. Hydrolysis, caused by absorbed water, weakened the fibers and reduced their mechanical characteristics, lowering the composite's strength [37][38].…”