Marwan M. Shamel

Utilizing Malaysian Natural Fibers as Sound Absorber

Previous researchers [1, 2, 3, 4] successfully produced sound absorption panels using agricultural wastes. These panels play important role both in noise absorption and heat insulation preserving the comfort of indoor living spaces. Yang et al. [4] produced rice straw-wood particle composite boards. They found that the sound absorption coefficient of these boards is higher than other wood-based materials in the 500-8000 Hz frequency range. Reason was the low specific gravity of composite boards having high amount of porosity compared to wood-based materials [4]. Another study by Davern [5] aimed at producing airspace layers and examined the influence of porosity on the acoustic properties of materials. He found that the porosity of the perforated plate and the density of the porous material would significantly affect the acoustic impedance and sound absorption coefficient of the panel, in which case, the frequency band near the resonance frequency achieved high acoustic absorption. In addition to Davern’s study, Lee and Chen [6] reported that the acoustic absorption of multi-layer materials is better with a perforated plate backed with airspaces. Other usages of natural fibres are in reduction of sound propagation in automotive interior spaces, or to improve the control of outdoor noise propagation [7, 8]. Recent studies show that researchers are focusing on coir fibre and oil palm fibre in replacing synthetic-based fibres for sound absorption applications simply due to their abundance in tropical countries such as Malaysia.

Cross flow ultrafiltration studies on solutions of pectin with pulsatile flow in-situ cleaning.

A study was conducted to evaluate the cross flow tubular ultrafiltration behavior of aqueous solutions of pectin. The effectiveness of pulsatile flow as a cleaning-in-place (CIP) technique to improve permeate flux was undertaken on the above mentioned solution. This investigation is part of a study to apply membrane filtration in the clarification of tropical fruit juice. The main variables, which were investigated, include the concentration of pectin, pulse frequency and amplitude. It was found that the amount of pectin in the solution significantly affects its ultrafiltration behavior. From the observed profiles, it is evident that the formation of gel layer on the membrane surface is responsible for the leveling of flux at high pressures. The presence of pectin was found to affect the properties of the solution such as viscosity, pH and the size of pectin colloid. Improvements in the permeate flux for pectin solution were obtained by employing pulsatile flow cleaning-in-place technique. Both pulse frequency and amplitude are important parameters that can improve the improvement of in-situ cleaning method. Similar to several findings reported in the literature, pulsatile flow showed significant effectiveness of about 60% higher flux when the ultrafiltration process is operated under laminar condition.

Improvement of Fire Retardant Property of Natural Fiber

Excessive exposure to noise is harmful for human health. Noise-induced hearing loss is one prevalent disorder resulted from above case. One root solution that converts the unnecessary sound waves to dissipated heat energy is acoustic absorption panel. Previous studies had looked upon potential sound-absorbing resources corresponding to natural fiber. However, several characteristics of these biodegradable supplies such as stiffness, anti-fungus and flammability are still yet to be improved. Hence, this research was undertaken to enhance the fire retardant performance of coir fiber for the production of high quality yet low cost acoustic absorption panel. Three types of additives, borax, Di-Ammonium Phosphate (DAP), and urea were investigated to perform chemical treatment for coir fiber. Experimental measurements were executed to validate the results by referring standard of ASTM E6902 (Standard Test Method for Combustible Properties of Treated Wood) by using the Fire-Tube Apparatus. Final results showed that DAP-treated fiber has the lowest percentage loss in mass of 6.67% compared to that of borax and urea-treated fiber with values of 7.60% and 9.48% respectively. This outcome clarified that DAP-treated fiber possesses higher self-extinguishing ability. Further evaluations in term of economic values, degree of hazards against health, flammability as well as reactivity supported that DAP is the best choice since its potency was ahead of the other two chemicals.