STUDIES ON NOVEL NATURAL FIBERS AND THEIR REINFORCED EPOXY COMPOSITES

Abstract

Recent economic development and technological growth are inspiring academicians and researchers to look for newer materials which can compete with cutting edge technology and at the same time should be sustainable and safe for environment also. Natural fibers reinforced in different polymer matrices are offering excellent mechanical and thermal properties that is why they are getting more and more attention in this decade as an alternate of synthetic fibers as reinforcement in composites. Traditional lignocellulosic natural fibers like bagasse, wheat straw, jute, sisal, coir, ramie, kenaf, sisal, hemp ,banana, pineapple, flax etc. have been extensively used and exploited as a reinforcement in various polymer matrix because of their biodegradability, easy availability, light weight and outstanding mechanical properties. The major issues that are noticed with these lignocellulosic natural fibers are their hydrophilic tendency and their poor interaction with hydrophobic polymer matrix. Alkylation is the preferred choice for removal of hemicellulose and lignin to improve the compatibility between polymer matrix and these fibers. On account of having excellent properties like high temperature stability and resistance to chemicals and corrosion, epoxy resin is preferred to be used as polymer matrix in a number of reinforced composites. Researchers are looking for various new fibers as reinforcement in polymer matrix and a number of fibers have been tested as reinforcement in epoxy matrix for diverse applications. Alkali treatment is primarily used for the improvement of interaction and compatibility between fiber and matrix. Optimum concentration of alkali for treatment depends upon the nature of these new fibers. Present study is centered on the exploration of two new novel natural fibers/fillers, their extensive characterization and assessment of their suitability as reinforcement in Epoxy matrix The Teff fiber is treated with different concentrations of alkali NaOH (5% and 10%) to improve the properties and the effect has been observed by Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscope (SEM) analysis, X-ray diffraction XRD, Atomic force microscopy(AFM), Mechanical property tester and Thermogravimetric analysis. Flynn-Wall-Ozawa method (FWO), Kissinger-Akahira-Sunose method (KAS iv method) and Friedman method have been used for calculation of activation energy of untreated and treated Teff straw. There is an increase of approximately 31% ( 280 to 368 MPa) in tensile strength and 21% (136 kJ/mol to 164 kJ/mol) in average activation energy in case of 5% alkali treated fiber as compare to untreated one. This treated fiber can be recommended as reinforcement in polymer composites for light weight applications. Epoxy based composites reinforced with African Teff straw (Eragrostis tef) have been fabricated by simple hand lay-up technique with different fiber loading varying form 5% to 25%. The fiber surface is treated with 5% alkali and 10% alkali to improve the interaction between fiber and matrix. The mechanical, morphological, water absorption and thermal characterization of the untreated and treated, both types of composites have been done to analyze the properties and effect of surface treatment on prepared composites. Water diffusion mechanism has also been studied. Increase in tensile strength by 12% as compared to neat epoxy resin was observed in 5% alkali treated Teff straw based epoxy composites. The fibers have been extracted from Saccharum spontaneum plant stem and subjected to various concentrations of alkali that is 3%, 5% and 7% to improve the properties. Untreated and alkali treated fibers have been characterized by Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscope (SEM) analysis, X-ray diffraction XRD, Atomic force microscopy(AFM), Mechanical property tester and Thermogravimetric analysis (TGA/DTG).Flynn-Wall-Ozawa( FWO), Kissinger-Akahira-Sunose (KAS) and Friedman methods were used to observe the activation energy and thermal kinetics of these fibers before and after treatment. The 5% alkali treated fibers exhibit maximum increase in activation energy that is from 145 KJ/mol to 244 KJ/mol as compared to untreated fibers. Similar improvements are observed in tensile strength of fibers (from 280 to 400 MPa), modulus, crystallinity index, surface roughness and thermogravimetric analysis. Filler of different sizes that is 0-500 μm, 500-1000 μm and 1000-1500 μm, have been successfully utilised as a reinforcing material in epoxy matrix. Comparable tensile and flexural strength with neat epoxy for 10% and 15% filler loading and 500-1000μ particle size has been obtained. Flynn-wall-Ozawa method has been applied for calculation of activation energy of pure epoxy sheet and its composites reinforced by Kans grass filler at optimum v loading of 15% and optimum size of 500-100 μm. It was found that pure epoxy sheet has an average activation energy of 192 kJ/mol while reinforcement with 15% loading of Kans grass filler having size of 500-1000 μm increased the activation energy from 192 to 227 kJ/mol