Water absorption in alkaline-treated coir pith – For use as reinforcement material in polymer matrix composites

Abstract

Green composites, made of sustainable materials and manufacturing, have been attractive owing to their low cost, renewability, and biodegradability. Coir pith is one of the agrowaste based products available in huge quantities in tropical countries and has superior properties compared to many other natural agrowaste based materials. Due to its sponginess, fluffiness, high porosity, high water absorption, and retention capacity, coir pith poses a significant challenge in its use as a reinforcement material due to interfacial adhesion issues with the polymer matrix phase in composite making. This interfacial adhesion is associated with the high-water absorption capacity of coir. Chemical treatment of natural fibers is one of the methods that have been applied to alter the morphology and chemistry of fibers. In the current study, coir pith was treated using 2% sodium hydroxide (NaOH) concentration for 20, 40, and 60 min, washed, and oven dried for 72 h. The dried samples were used for the water absorption studies by immersing the samples in distilled water for 2 h and measuring the weight changes every 15 min. The results show that treated coir pith absorbs more water than raw untreated coir pith, and detailed observation of the surface of coir pith after treatment indicates increased surface roughness compared to the surface of a raw particle.