A STUDY ON EFFECT OF CHEMICAL MODIFICATION OF FLAX FIBER ON MECHANICAL, MORPHOLOGICAL, THERMAL AND RHEOLOGICAL PROPERTIES OF FLAX REINFORCED POLYPROPYLENE COMPOSITES

Abstract

Natural fibre reinforced polymer composites (NFPCs) provide the customers with more alternatives in the material market due to their unique advantages such as low density, low cost, high specific strength and stiffness, simple and well-established processing technologies for mass production, such as injection molding and most importantly environmental friendly and sustainability. Poor fibre—matrix interfacial adhesion may, however, negatively affect the physical and mechanical properties of the resulting composites due to the surface incompatibility between hydrophilic natural fibers and non-polar polymers (thermoplastics and thermosets). As the natural fibers bear hydroxyl groups from cellulose and lignin, therefore, they are amenable to modification. A variety of silanes (mostly trialkoxysilanes) have been applied as coupling agents in the NFPCs to promote interfacial adhesion and improve the properties of composites by reducing moisture sensitivity. Furthermore, the poor thermal stability of the fibers limits their use as reinforcers for thermoplastics owing to the high processing temperatures employed during composite production. The aim of this work is to evaluate the moisture absorption and thermal properties of flax fibre as a function of modification of flax fibre by using mercerization and silane treatments. In order to compare the effect of the type of side groups attached three different trimethoxysilanes viz. Vinyl-trimethoxysilane, 3-Amino propyl -trimethoxysilane and Methacrylpropyl-trimethoxysilane were selected. The silane treatment was done on the mercerized fibre alone as it leads to better adsorption of the silane on the fibre surface. The changes introduced by the treatments on the chemical structure of flax fibers have been analyzed by Absorption Transmission Radiation Infrared Spectroscopy (ATR-FTIR) and Micro-FTIR. Thermal behaviour of both mercerized and silane treated flax fibers have been studied by Thermogravimetric Analysis (TGA). The treated fibre has then been used as reinforcement with PP and the mechanical, morphological, thermal and rheological properties of the resultant composites are studied. Further, the effect of addition of a compatibilizer such as PPgMA is evaluated to ascertain the feasibility of prepared NFPCs as potential replacements for talc/glass filled polypropylene composites. Lastly as an . additional exercise, grounded fibers were used to fabricate composites and thus, the effect of aspect ratio was observed on resultant mechanical properties. The observed values were validated by Halpin-Tsai equations within the experimental limit as well.