Influence of Alkali And Microwave Treatments of Fiber on The Water Absorption And The Mechanical Properties of Coir Fiber/Polyester Composites

In this study, coir fibers were surface treated with alkali and microwave treatments. The effect of alkali and microwave treatments of coir fibers as reinforcement of coir fiber/polyester composite on water absorption and mechanical properties (tensile, flexural and impact strength) was reported. Treatments were divided into two types: microwave treatment of coir fibers for 10 minutes (M10) and 20 minutes (M20) without alkali treatment; and alkali treatment of coir fibers with soaking during 24 hours in 5w/v% NaOH solution, followed by heating in the oven for 2 hours (2N) and also followed by microwave treatment during 10 minutes (NM10) and 20 minutes (NM20). Coir fiber then was pressed like mat which was used as reinforcement of polyester composite. Hand lay-up technique with compression molding was used to fabricate composite. The water absorption and mechanical properties like tensile strength, tensile modulus, flexural strength and impact strength were studied. Fracture of tensile testing was evaluated by Scanning Electronic Microscopy (SEM). The results obtained showed that alkali and combination of alkali and microwave treatment improved significantly the water absorption of the composite. For mechanical properties of the composite, alkali and microwave treatments of coir fiber tend to increase tensile strength, tensile modulus, flexural strength and impact strength. However, for both M10 and NM20 treatments, the flexural strength of composite decrease due to the poor adhesion between fiber and matrix in the composite. Then, SEM characterizations show treated fiber improved the adhesion fiber-matrix in the composites.