Adsorption properties of vapor-protective fabrics containing activated carbon Original Research Article

Barrier properties of air-permeable protective fabrics incorporating microporous activated carbon are evaluated using simulants of toxic chemical agents, both in dry atmospheres and at high humidity. Performance of an adsorbent fabric is dependent on kinetic factors as well as adsorption capacity, with the overall rate limited by vapor phase mass transfer over a wide range of environmental conditions. For dynamic adsorption, the characteristic sigmoid breakthrough curve of effluent vapor concentration against time is best described using a modified Wheeler equation including an adjustable parameter (a) which compensates for axial dispersion in the fabric. For powdered carbon impregnated in a polyurethane foam fabric, the calculated dynamic adsorption capacity (Ad) is ca 10 percent lower than the equilibrium adsorption capacity (Ae) obtained at the same vapor concentration for each carbon and adsorbent fabric. An additional 10 percent decrease in Ad and Ad for the supported carbon relative to dry powdered carbon is attributed to partial blocking of the pore volume by components of the acrylic binder formulation used in the fabric process. Adequate protection is attained even in the presence of faults (e.g. holes, tears and open seams) provided that the smallest dimension of the fault does not exceed a minimum size determined by the net rate of adsorption. This concept is demonstrated by experiments with fabrics possessing known fault arrays.