Synergistic flame retardancy, thermal stability and reinforcing effects of silk fibroin/cobalt phytate on rigid polyurethane foam composites
Abstract Rigid polyurethane foam (RPUF) is utilized extensively in many different sectors because of its special benefits. Nevertheless, this also emphasizes how crucial its flame-retardant qualities are. In this paper, a simple and green coprecipitation method was used to prepare cobalt phytate (PA-Co) flame retardant, which was then introduced into silk fibroin (SF)-based RPUF. The successful preparation of PA-Co was confirmed by Fourier transform infrared spectroscopy (FTIR) testing. In addition, thermogravimetric analysis (TG), cone calorimeter test and compression test were employed to systematically analyze the thermal stability, flame retardancy, smoke suppression performance and mechanical properties of RPUF composites. TG results indicated that RPUF-4 composite (containing 5 wt% SF and 6 wt% PA-Co) exhibited the highest decomposition temperature at 50 % mass loss (T50 %), maximum mass loss rate temperature (TMax) and apparent activation energy (E) under three heating rates, thus demonstrating the optimal thermal stability. Specifically, the peak heat release rate (PHRR) and total heat release (THR) of RPUF-4 composite were 55.04 % and 36.08 % lower than those of RPUF-0 (containing 0 wt% SF and 0 wt% PA-Co), respectively. Furthermore, its total smoke release (TSR) and peak smoke production rate (PSPR) decreased by 54.17 % and 60.98 % in comparison with RPUF-0. In addition, the mechanical properties and thermal insulation performance of RPUF-4 composite were superior to those of previously reported PA-Co modified SF-based RPUF. This work realizes synergistic enhancement of flame retardancy, smoke suppression and mechanical properties via component synergy and interface regulation, providing a valuable reference for designing high-performance RPUF composites.