Author: Ahmad Bilal

Publisher:

Published: 2015

Total Pages: 215

ISBN-13:

Environmental awareness and depletion of wood resources worldwide has directed researchers to alternative fibre recourses. The use of agricultural by-products such as rice husk (RH), rice straw, wheat straw and cotton stalks, etc., which are produced in billions of tonnes annually around the world, can provide an alternative to wood based products. Recently, the use of agricultural by-products in the manufacturing of lignocellulosic thermoplastic composites (LTCs) has emerged as a promising field of interest. These agricultural by-products are cheap and abundant, and hence it could be worthwhile using them. This research focused on exploring the potential of RH in the manufacture of thermoplastic composites. RH was used as reinforcing phase; polyethylene (PE) as a thermoplastic polymer matrix; and maleic anhydride polyethylene (MAPE) as a compatibiliser to manufacture thermoplastic composites using the injection moulding process. Three different forms of RH, namely raw rice husk (RRH), ground rice husk (GRH) and expanded rice husk (ERH), were used for a preliminary investigation of the mechanical and physical properties of RH/PE composites. The overall performance of RRH composites was better than the GRH and ERH composites. The results led to the selection of RRH for further research. The mechanical properties of RH, including elastic modulus and hardness, were investigated by nanoindentation, as the traditional methods for investigating the mechanical properties of long fibres could not be applied due to short fibre size of RH. These properties were investigated at the cross-section, outer surface, and inner surface of RH. The best results were obtained at the cross-section of RH, with minimum variation. Existing theoretical models available for predicting the mechanical properties of short fibre reinforced composites (SFRC) were applied to predict the elastic modulus of RH/PE composites, which was best predicted by the Neilson modified Halpin-Tsai model. A statistical design of experiments based on experiments with mixtures (EWM) was used to statistically analyse the mechanical, flammability, and physical properties of RH/PE composites. Response trace plots were used to analyse the effects of each constituent material (RH, MAPE, and PE) used in the manufacturing of composites. The effect of relative proportions of these constituent materials was also studied using contour plots. The incorporation of RH in the composites improved the mechanical properties, excepting Charpy impact strength. The fire retardancy also improved with RH incorporation. On the other hand, the physical properties deteriorated slightly with an increase in RH content. MAPE also played a significant role in determining the strength of the composites. The flammability properties were not much influenced by MAPE incorporation. The physical properties, including water absorption and the corresponding thickness swelling, were also influenced by MAPE incorporation. The optimal formulation of the constituent materials for overall "best" mechanical, flammability and physical properties was determined using multiple response optimisation. The mechanical, flammability, and physical properties of the composites manufactured with the optimised formulation closely matched the values predicted by the statistical models.