NATURAL FIBER REINFORCED FUNCTIONALIZED ACRYLONITRILE BUTADIENE STYRENE COMPOSITES

Abstract

Natural fibres (NF) are drawing interest as reinforcing fibres for polymer matrix composites, in place of synthetic and inorganic fibres, because of being biodegradable, renewable and low cost and also because of their wide availability, low density, eco-friendly nature and acceptable mechanical properties. Polymer composites reinforced with natural fibres offer benefits including, lightweight, good physical, thermal and mechanical properties, and cost-effective and eco-friendly nature. Therefore, these composites are being increasingly used in the automotive and building construction components and other systems. However, natural fiber (NF) are polar and hydrophilic and polymers are nonpolar and hydrophobic. This creates a poor interfacial adhesion in their composites, and the following three processes and combinations of these processes are being used to improve this adhesion: (i) Fiber treatment process (ii) Compatibilizer process (iii) Palsule process (iv) A combined fibre treatment and compatibilizer process and (v) A combined fibre treatment and Palsule process. Composites reported by Palsule process have been processed upto 150oC. This study aims to extend Palsule process to composites requiring higher processing temperatures, retaining, thermal stability of thermally sensitive natural fibers. In this study, chemically functionalized acrylonitrile butadiene styrene has been selected as a matrix and the following two composites have been developed by Palsule process, one using an original natural fiber and the other using a post-consumer fiber, that is eco-friendlier, as its use eliminates the use of fresh natural fiber: I. Bamboo fiber (BBF) reinforced chemically functionalized acrylonitrile butadiene styrene (CF ABS) composites: the (BBF/CF-ABS) composites. II. Post-consumer wood fiber (PCWF) reinforced chemically functionalized acrylonitrile butadiene styrene (CF-ABS) composites: the (PCWF/CF-ABS) composites. The first recycling of CF-ABS matrix based above two composites, has been performed and the recycled composites, the R-(BBF/CF-ABS) composites and the R-(PCWF/CF-ABS) composites have been developed. Three compositions, the 10/90, 20/80 and 30/70, of each of the BBF/CF-ABS and PCWF/CF-ABS composites have been processed by twin screw extrusion and their samples (as per the ASTM standards) have been developed by injection molding. Processing has been performed at relatively higher temperature, that is required for CF-ABS; taking into consideration relatively low thermal stability of natural fibers. Mechanical properties, except tensile elongation and impact strength, of 10/90, 20/80 and 30/70 BBF/CF-ABS composites and 10/90, 20/80 and 30/70 PCWF/CF-ABS composites are higher than those of the CF-ABS matrix and with the amounts of reinforcing BBF or PCWF increasing in the composites, these properties also increase. The measured tensile modulus and strength of the composites, correlates with predictions of Halpin-Tsai, Hirsch and Nielsen models and Palsule equation. The formation of these two composites, is due to fibre/matrix bonding in them, and their SEM micrographs exhibit this good adhesion between reinforcing fibers (BBF and PCWF) and CF-ABS matrix in both, the BBF/CF-ABS composites and PCWF/CF-ABS composites. FTIR analysis establishes that this fibre/matrix adhesion has resulted from the esterification between maleic anhydride of CF-ABS and –OH of ligno-cellulose of natural fibres, (BBF or PCWF) and also hydrogen bonding between their functional groups. Thermal analysis indicates intermediate thermal stability of the BBF/CF-ABS composites and PCWF/CF-ABS composites in-between those of the reinforcing fibers (BBF and PCWF) and their CF-ABS matrix. The BBF/CF-ABS composites show thermal stability upto aprox. 275oC and the PCWF/CF-ABS composites show thermal stability upto aprox 300oC. Water absorption study indicates that the amount of absorbed water and the resulting thickness swelling of the BBF/CF-ABS composites and also the PCWF/CF-ABS composites increases with increasing BBF or PCWF content in them. The water absorbed wet, W-(BBF/CF-ABS) and the wet, W-(PCWF/CF-ABS) composites show lower tensile properties than the respective dry composites; but show higher tensile properties than the dry CF-ABS matrix. Comparative study shows that the 30/70 BBF/CF-ABS composite by Palsule process has higher mechanical properties than the same composite by any other process and thus indicate the techno-economic advantages of Palsule process.BBF/CF-ABS composites have properties required for some automobile applications and their full potential for these applications is subject to evaluation of its design, machinability and other parameters, that has been recommended as future work. This study also recycles the above reported two composites and evaluates the following two resulting recycled composites. The first recycling of bamboo fiber (BBF) reinforced chemically functionalized acrylonitrile butadiene styrene (CF-ABS) composites (BBF/CF-ABS) composites and the first recycling of post-consumer wood fiber (PCWF) reinforced chemically functionalized acrylonitrile butadiene styrene (CF-ABS) composites (PCEF/CF-ABS) composite has been performed to examine the status of fibre/matrix adhesion in the resultant recycled composites. III Structure and mechanical and thermal properties of the resulting R-(BBF/CF-ABS) composites have been established. IV Structure and mechanical and thermal properties of the resulting R-(PCWF/CF-ABS) composites have also been established. The FE-SEM and FTIR results establish that the reinforcement/matrix bond is retained in the recycled composites. The result indicates that all the R-(BBF/CF-ABS) recycled composites have higher tensile properties, flexural properties and impact properties than the respective R-(PCWF/CF-ABS) recycled composites but higher original CF-ABS and R-(CF-ABS) and lower the respective original composites. The R-(10/90 BBF/CF-ABS), R-(20/80 BBF/CF-ABS) and R-(30/70 BBF/CF-ABS) recycled composites have higher thermal stability than the respective R-(10/90PCWF/CF-ABS), R-(20/80 PCWF/CF-ABS) and R-(30/70 PCWF/CF-ABS) recycled composites but higher original CF-ABS and R-(CF-ABS) and lower the respective original composites. The recycling of the original BBF/CF-ABS composites and original PCWF/CF-ABS composites has several potential advantages and the obtained recycled composites the R-(BBF/CF-ABS) and R-(PCWF/CF-ABS) composites have few potential applications. All these composites are eco-friendly and the recycled composites are even more eco-friendly and sustainable.