Fabrication and Evaluation of Specialty Nonwoven Materials

The present work is to develop multifunctional materials with high performance on chemical absorption, adsorption and on acoustic absorption and insulation using natural fiber nonwovens via carbonization and activation. Evaluation of these textile materials includes tensile strength, thermogravimetric analysis, sound absorption and transmission loss, scanning electronic microscopy and surface properties. Carbonization of cotton nonwoven was carried out in a high temperature oven with nitrogen between 300 °C and 500 °C. The physical activation was undertaken using CO2. The N2 adsorpton isotherm curves of the cotton nonwoven showed the presence of micropores and macropores. High BET surface area and average pore diameters close to micropores were obtained. The comparison between the N2 and CO2 adsorption showed that BET surface area for N2 adsorption is much smaller than that for CO2 adsorption and median pore width for the N2 adsorption is greater than that for CO2 adsorption due to the activated diffusion effects. Intensive research has been done with an emphasis on how to optimize the method of carbonizing and activating cotton nonwoven. Activated carbon fiber (ACF) made from rayon fabrics showed slightly higher surface area than cotton ACF. The increase of carbonization and activation temperature leads to produce high adsorptive capacity and microporosity. Longer heating time also contributed to high surface area, but widened microporosity and developed mesopores. Surface area of 879.05 m2/g and BJH average diameter of 27.67 Å were achieved when rayon was carbonized and activated at 800 °C for 4 hours. Surface area of cotton ACF was as high as 982.10 m2/g. Chemical activation method was also investigated by impregnation of cotton fabric with ZnCl2, which increased final ACF yield, surface area and developed micropores. A nonwoven composite of ACF with cotton nonwoven as a base layer was developed. The study concluded that the ACF composite exhibited a greater ability to absorb normal incidence sound waves than the composites with either glassfiber or cotton fiber. The analysis of sound transmission loss revealed that the three composites still obeyed the mass law of transmission loss. The ACF composite exhibited great sound absorption and sound insulation properties