Load bearing characterization of kenaf fiber/poly(vinyl ester) composites reinforced by silanized biomass waste tamarind shell and roasted chickpeas powder

Abstract

The present study explores the enhancement of kenaf fiber-reinforced vinyl ester composites using natural fillers, specifically roasted chickpea powder and silanized tamarind shell biomass powder, to improve mechanical properties, moisture resistance, and interfacial bonding. The uniqueness of this research lies in the combination of surface modified kenaf fiber along with these hybrid fillers, which has not been previously studied. Vinyl ester resin, known for its strong odor and volatile content during curing, is utilized with various additives, such as methyl ethyl ketone peroxide (MEKP), cobalt naphthenate, and DMA, to accelerate the curing process and enhance performance. Roasted chickpeas and tamarind pods are prepared as biofillers by grinding them into fine particles. The biofillers undergo surface modification treatment using 3-APTMS to improve adhesion with the matrix and reinforcement. Composite fabrication is achieved through the hand layup method, followed by ambient and post-curing processes to achieve a stiff structure. The experimental results indicate that the specimen VKC2, containing 3 vol.% silane-treated chickpeas shell filler, exhibits the best mechanical properties with a tensile strength of 155 MPa, flexural strength of 185 MPa, ILSS of 35 MPa, impact energy of 5.8 J, and hardness of 82 Shore-D. These superior values are due to optimal filler dispersion and enhanced interfacial bonding, resulting in efficient load transfer. Specimen VKC3, with 5 vol.% silane-treated chickpeas shell filler, shows the best wear properties with a specific wear rate of 0.015 mm³/Nm and a COF of 0.22, the highest thermal conductivity at 0.53 W/mK, and water absorption of 0.41%. These properties are attributed to the filler creating a dense structure, enhancing wear resistance, forming continuous thermal conduction networks, and moderating moisture uptake. SEM analysis reveals uniform dispersion of fillers, enhancing properties, while agglomeration leads to weaker performance, reinforcing the significance of proper filler content and treatment for optimized composite performance.