The optimum coating condition by response surface methodology for maximizing vapor-permeable water resistance and minimizing frictional sound of combat uniform fabric

The objectives of this study are to investigate how the variables of the water-repellent coating condition, concentration of polyurethane (PU) and curing temperature, set up by response surface methodology, affect vapor-permeable water resistance and fabric frictional sound. Also it aims to analyze the relationship between tensile properties and the sound pressure level (SPL) of the fabric and, finally, to suggest the optimum coating condition for minimizing the fabric frictional sound and maximizing the vapor-permeable water resistance. It was observed that the higher PU concentration increased the water resistance and SPL, but decreased WVT (water vapor transmission). It was shown that higher curing temperature, the other variable of the coating condition, increased the water resistance and SPL but decreased WVT. The relationship between tensile properties and SPL was analyzed and it was found that tensile stress at break (R²= .716) and toughness (R²= .717) were highly related to SPL; however, tensile strain at break (R²= .508) was not. Finally, the optimum coating condition for minimizing fabric frictional sound and maximizing vapor-permeable water resistance was obtained at the PU concentration of 60% and the curing temperature of 149.7℃, and the predicted SPL and WVT were 72.27 dB and 8478.85 g/m² 24 h, respectively. The coefficients of determination (R²) were 0.82 and 0.85, respectively, which indicate that the model fit was highly significant (p < 0.05).