Viscoelastic properties of alkaline treated walnut shell/rice straw fiber/epoxy biocomposite

Abstract

The increasing demand for an eco-friendly environment has led to the recent development of polymer matrix/green plant fiber composites. In this present study, the viscoelastic performance of walnut/rice straw fiber/epoxy biocomposites was examined using a dynamic mechanical analysis (DMA) in three-point bending mode at a constant frequency (1 Hz) and temperature (25 oC to 240 °C). The surface morphology of the developed composites was analyzed using field emission scanning electron microscopy (SEM). The epoxy resin was incorporated with walnut/rice straw fiber in five proportions (2-10 wt%) using the hand lay-up technique. The hybrids of rice straw fiber/walnut shell ash particulates were added in equal ratios. The DMA results showed that epoxy/6wt% walnut/rice straw fiber biocomposite recorded the maximum storage modulus (> 8 × 103 MPa) with low loss modulus and damping factor. This indicates excellent stiffness and high energy storage capacity resulting from excellent interfacial bonding of molecules of epoxy, walnut shell particulates, and rice straw fiber. The epoxy/rice straw fiber biocomposite showed a high rate of molecular mobility, leading to high heat dissipation and damping capacity. The glass transition temperature (Tg) of the developed composites ranges from 70 oC to 130 oC, indicating the working temperature of the materials to be below 70 oC. The tan-δ curves indicate that walnut/rice straw fiber/epoxy biocomposites are heterogeneous materials with separate viscoelastic phases and glass transition temperatures, resulting from the addition of walnut shell particulates and rice straw fiber. These reinforcers are finally noted as critical factors affecting the extent of macromolecular mobility within walnut/rice straw fiber/epoxy biocomposites.