Analysis of the Effect of Ca(OH)₂ Treatment on the Hardness and Microstructure of Areca Palm Frond Fiber Biocomposites

Abstract

This study aimed to analyze the effect of calcium hydroxide (Ca(OH)₂) treatment on the hardness and microstructure of areca leaf sheath fiber biocomposites reinforced with polyester resin. The fibers were treated with Ca(OH)₂ solutions at concentrations of 0%, 5%, and 10%, followed by composite fabrication using the hand lay-up method with a composition of 25% fiber and 75% polyester resin. Material characterization was conducted through Shore hardness testing according to ASTM D2240, metallographic observation, and digital image analysis using ImageJ software. The results demonstrated that increasing Ca(OH)₂ concentration significantly improved the hardness of the biocomposites from 74.24 SHA for untreated specimens to 96.64 SHA and 99.86 SHA for 5% and 10% treatments, respectively. Microstructural analysis revealed more uniform fiber distribution, stronger fiber–matrix interfacial bonding, and reduced porosity after alkali treatment. The 10% Ca(OH)₂ treatment produced the most homogeneous microstructure and the most stable mechanical performance. These findings indicate that Ca(OH)₂ alkali treatment effectively enhances the mechanical and microstructural characteristics of areca leaf sheath fiber biocomposites for sustainable engineering material applications.