Acoustic and Thermal Properties of Polymer Composites Reinforced with Lignocellulosic Fibers

In this research the Thermogravimetric analysis (TGA) under nitrogen was used to investigate the thermal decomposition processes and sound absorption coefficients was measured using Impedance tube according to ASTM standard E1050 - 10 two microphone method for 2 types of polymer matrix composites. Sample 1 was made of rice straw (RS) reinforced with polypropylene matrix and Sample 2 was made of kenaf fiber reinforced with polypropylene matrix, both composites were fabricated using hot compression moulding technique. The thermal behaviour is of practical interest for conditions associated with temperatures above the atmospheric, as in fire damage, curing or process involving heating procedures. The sound absorption coefficient for a material is the fraction or percentage of incident sound energy that is absorbed by the material. The function of absorptive materials is to transform impinging acoustic energy into heat. The thermal stability of the composites was found to be higher than that of rice straw, kenaf fibers and the polypropylene matrix. The sound absorption coefficients of composites increased as the frequency increased. However, they decreased at the frequency of 1000 Hz and increased again. This decrease and increase was due to the specific characteristic of Lignocellulosic fibers reflecting sound at 1300 Hz but absorbing sound in the middle and high frequency ranges.