Investigation of moisture absorption rate and diffusivity of plant fibre-reinforced composites

This research investigated the moisture absorption rate and diffusivity of plant Fibers-reinforced-composites; using bamboo fiber, raffia and coconut fibers through laboratory experimental investigations. The major limitation of using natural fibers in durable composite applications are their high moisture absorption and poor dimensional stability (swelling); and this swelling of fibers causes micro-cracking and degradation of the composites. In this investigation, the fibers were treated with sodium hydroxide (NaOH) chemical and acetylation to decrease the hydroxyl group in the fibers. Experimental results reveal that the moisture absorption and degree of swelling of the treated bamboo raffia and coconut fiber composites are 25 - 35% lower than those of composites produced with untreated bamboo, raffia and coconut fibers. Experimental results also show that strong intermolecular fiber-matrix bonding decreases the rate of moisture absorption in bio-composites. The diffusivity of the bamboo, raffia and coconut fibers-reinforced-composites for 24hrs at 1000C were experimentally measured to be 4.91, 3.33, and 3.94 mm2/sec respectively. The results showed that when these fiber plant materials are treated with sodium hydroxide (NaON) the diffusivity rate of the fiber reinforced composite material is brought under considerable control and its dimensional stability immensely enhanced though improved strong intermolecular fiber-matrix bonding and the reduction of swelling.