Smart Breathable Fabric

Smart breathable cotton fabrics were made using a temperature-sensitive copolymer - poly(N-tert-butylacrylamide-ran-acrylamide:: 27: 73). The cotton fabric was coated using an aqueous solution (20 wt%) of the copolymer containing 1,2,3,4-butanetetracarboxylic acid as a cross-linker (50 mol%) and sodium hypophosphite (0.5 wt%) as a catalyst, followed by drying (120°C, 5 min) and curing (200°C, 5 min). The integrity of the cross-linked coatings to the fabric was observed to be excellent. The coatings after integration to the cotton substrate retained temperature-sensitive swelling behavior and showed a transition in the temperature range of 15-40°C. Below 15°C, the coatings swell by 800% while above 40°C they deswell to a swelling percentage of less than 50% (on the basis of dry weight). The transition to swelling was completed in about 20 min while deswelling was quicker in 2-3 min. The response was found to be reversible and stable to repeated cycles of transition. The coated fabrics showed a temperature-responsive water vapor transmission rate (WVTR). The WVTR values of the responsive (copolymer coated) and the nonresponsive (poly(acrylamide) coated) breathable fabric were measured as a percentage (transmission percentage) of control uncoated substrate. The transmission percentage at 20% relative humidity for the copolymer coated fabrics was found to change across the transition temperature (15-45°C) from 58 to 94% compared to the poly(acrylamide)-coated fabrics which changed only from 70 to 94%, showing a clear response to changing environmental temperature.