Evaluation of calendered activated carbon nonwovens for gas adsorption

Nuclear, biological and chemical (NBC) military protective clothing was found to heat stress to military personnel when worn in the desert climate in the Persian War. Research was begun by Dever, Davis, and Hood [1] in September 1990 to develop a safe but comfortable NBC protective material. Three levels (i.e., 40, 80 and 120 g/m²) of standard and high surface area (HSA) activated carbon on meltblown- spunbond nonwovens before and after thermal point bonding (i.e., calendering) were evaluated. The non-calendered HSA activated carbon (i.e., 80 and 120 g/m²) nonwovens had better gas adsorption properties than did the Army issue protective clothing [2]. Calendering, required to impart sufficient sample strength, created pinholes allowing the chemical warfare gas simulant to pass directly through the samples and melted polymer coated the activated carbon reducing the available carbon adsorption area.

The study described herein evaluates the effect of a central core (i.e., 1, 2 and 3 oz/yd² cotton and 1.8 and 2.6 oz/yd² polypropylene) containing 120 g/m² HSA activated carbon meltblown-spunbond nonwovens. Additional thickness of the core and the non-thermalplastic cotton was expected to eliminate the calendered pinholes. The optimal nonwoven was determined to be the 1.8 oz/yd² PP core calendered at 6 m/min, 250 pli nip pressure, 80°C top calender roll temperature, and a 110°Cbottom calendar roll temperature. The gas adsorption behavior was mathematically modeled. Calculated and experimentally measured adsorption capacities compared favorably, i.e., R² 0.9845. The film coefficient (K) values which predict the shape of the adsorption wave were determined.

Future research will focus on alternative methods of bonding and development of porous polymer supports as an alternative to the activated carbon.