Evaluating the performance of the outer layer of extreme heat protective clothing using different woven structures

This study examines the interplay of weave patterns, picks per inch (PPI) and key performance metrics including heat protective performance (HPP), air permeability, thermal resistance and water vapor transmission rate (WVTR). Three weave structures (twill, sateen and honeycomb) using Nomex-IIIA yarn were tested. Heat flux of 80 ± 2 kW/m² was applied, combining flame and radiative heat. The honeycomb weave exhibited superior heat protection compared to twill and sateen. HPP increased by approximately 24% with the PPI rising from 40 to 64. Air permeability and thermal conductivity decreased by roughly 50% and 38%, respectively, with increasing PPI. Sateen and twill showed similar trends. WVTR increased with PPI up to 52, then declined. Overall, higher PPI enhanced HPP for all weave structures, with the honeycomb structure showing the best performance. Thermal conductivity and air permeability decreased as PPI increased due to the greater compactness in these three fabrics.