Core-shell DOPO/caramel nano-polymer with desirable UV shielding and flame retardancy for polyamide 6 fabric

The destruction of polyamide 6 (PA6) fabrics due to fire and prolonged UV radiation is an urgent issue that needs to be addressed. Inspired by the adhesion and inclusiveness of the sugar-coated haws, this study developed an adhesive nanoparticle with a core–shell structure (Car@DOPO) by encapsulating DOPO with carbohydrate caramel. The Car@DOPO nanoparticles exhibited excellent UV shielding property on PA6 fabrics, as indicated by a maximum UPF of 41.7, which can be attributed to the π-bonds and dark brown color of caramel shell. Additionally, the coated PA6 fabric demonstrated good flame retardancy, with a flame retardancy index (FRI) of 1.2. The LOI of coated PA6 fabric improved from 22.1% to 30.5%. Moreover, the fire growth rate (FGR) and flame inhibition effect (FIE) decreased by 13.3% and 22.0%, respectively. These improvements can be attributed to the efficient quenching effect of the DOPO core. Notably, the strong adhesion of the caramel shell allowed the Car@DOPO nanoparticles to firmly adhere to the fabric surface, providing coated PA6 fabric with durable flame retardancy. This study demonstrates the successful and sustainable treatment of PA6 fabrics using a carbohydrate nano-polymer.