The research aim was to analyse the changes in the air permeability, waterproofness, surface, mechanical and thermal properties of the polyamide 6.6 fabric with a polyurethane coating before and after 1, 5, and 10 washes in the same conditions using specialized (V1) and universal (V2) laundry detergent. A new approach based on SEM and DSC techniques and assessment of surface free energy combined with standard methods was proposed to explain the nature of observed changes in waterproof and breathable material after washing treatment. SEM analysis indicated that after 10 washes the porosity of the polyurethane coating increased from 8.94% to 14.56% and 18.75% for V1 and V2, respectively. The air permeability increased from 0.747 mm/s for the reference sample to 0.766 mm/s and 0.774 mm/s after 10 washes for V1 and V2, respectively. The waterproofness of the reference sample of 992 mbar decreased with the increasing number of washes to 246 mbar and 122 mbar for V1 and V2, respectively. After 10 washes the surface free energy (γS) decreased by 18.8% and 24.3% for V1 and V2, respectively. The average tensile strength amounted to 833 N and decreased by 13.5% for V1 and by 20% for V2 after 10 washes. The glass transition temperature of the reference fabric was 47.6°C. After 10 washes it increased by 7.2°C and 8.8°C for V1 and V2, respectively. The temperatures of thermal degradation increased by 24.6°C and 22.2°C and the heat of thermal decomposition decreased by 23.6% and 15.8% after 10 washes for V1 and V2, respectively.
A new approach for the relative surface free energy of cubic material with terrace, step, and kink structures
