Thermal insulation and fire protection of polyester/cotton fabrics via expandable microsphere-intumescent flame retardant coatings

Integrating thermal insulation and flame retardancy into polyester/cotton (T/C) blend textiles remains a significant challenge for high-performance protective fabrics. In this study, thermo-expandable microspheres (TEM) and an ammonium polyphosphate (APP)-based intumescent flame-retardant (IFR) system were co-deposited onto T/C fabrics via a polyacrylate-based surface coating to form a multifunctional protective layer. The surface morphology, thermal insulation performance, combustion behavior, flame-retardant performance and mode of action of the multifunctional T/C@TEM/APP and T/C@TEM/IFR fabrics were systematically investigated. The coated T/C fabrics exhibited reduced thermal conductivity of 0.07656 and 0.07194 W/m·K, respectively, compared to 0.12980 W/m·K for the uncoated T/C fabric, attributed to the low thermal conductivity of the expanded TEM. The T/C@TEM/APP fabric achieved a high limiting oxygen index of 29.6 %, a reduced damaged length of 10.3 cm, meeting the B1 flammability classification. Further enhancement was observed in T/C@TEM/IFR due to the high flame retardancy efficiency of the APP-based IFR system. TG-IR and char residue analyses revealed that the improved flame resistance of the coated T/C fabrics arose from synergistic effects in both the gas and condensed phases.