Effect of Moisture on the Thermal Protective Performance of Heat-Resistant Fabrics

Abstract

The effect of fabric moisture on thermal insulation properties of twelve heat resistant fabrics made with polybenzimidazole (PBI), aromatic polyamide (aramid) and blends of PBI with aramid or with flame retardant rayon fibers is investigated in several high intensity radiant and convective heat exposures. Three fabric preparations were evaluated: oven dry samples, samples condi tioned in a standard atmosphere (65% R.H., 21 ° C) and samples soaked with liquid water. This research shows that moisture enhances the thermal in sulation of all single layer protective fabrics evaluated against 2.0 cal/cm2 ·sec mixed convective exposure and against 0.48 cal/cm2 · sec radiant energy expo sure. Moisture hurts the thermal protective performance (TPP) of the same fabrics in high intensity radiant tests (i.e., 2.0 cal/cm2 · sec, 100% radiant heat). The mechanisms by which moisture acts to change the TPP of a fabric is discussed in light of fabric heating rates.