Silicone Rubber Foam With Flame‐Retardancy and Reversible Actuation

ABSTRACT Silicone rubber foams are widely used for thermal insulation in structures due to their flexibility and thermal stability. However, they are prone to interfacial debonding from the substrate structures, and eventual insulation failure under thermal cycling. In addition, their inherent flammability poses serious fire safety concerns. To address these issues, a silicone rubber/ammonium polyphosphate foam (TW‐FRP5) with excellent flame retardancy and reversible actuation was developed using a hybrid chemical and physical foaming method. Opposite to most polymeric materials, TW‐FRP5 showed maximum contraction upon heating of 0.23% and an elongation upon cooling of 1.73% from −40°C to 60°C, which was repeatable as temperature cycles. This reversible actuation mitigates thermally induced interfacial failure in foam insulation layers. It also achieved a limiting oxygen index of 34% and a UL‐94 V0 rating. The flame‐retardant mechanism was further revealed. The possible competition between silicon–oxygen framework erosion and dilution and cooling due to ammonium polyphosphate decomposition on the flame retardancy was discussed. This study lays a theoretical and practical foundation for the design of high‐performance thermal insulation materials in building and other structure applications.