Phosphorus-containing tung oil-based siloxane toughened phenolic foam with good mechanical properties, fire performance and low thermal conductivity

Abstract

Phenolic foam (PF) is widely used as exterior-wall insulation material but has poor mechanical properties and high friability. To improve the robustness of PF without sacrificing its inherent advantages, a novel reactive tung oil-based toughener that contains P and Si is synthesized and embedded into the rigid molecular structure of PF as long, flexible chains to fabricate biomass-based PFs (TDKPFs). The introduction of these long, flexible chains effectively improved the compressive and bending strengths, which were almost 180% and 198% that of pure PF, respectively. The TDKPFs had a lower thermal conductivity of 0.0316 W/(m·K), suggesting superior thermal insulation. Notably, these TDKPFs solved the reduction in flame resistance that is caused by the introduction of alkyl long chains and had a high limiting oxygen index of 41.7%. Cone calorimetry tests indicated that the peak heat-release rate of the TDKPFs was reduced by 15.6%. In particular, the total smoke release of the TDKPFs was 7.29 m2/m2, a reduction of 75.8% over pure PF (30.2 m2/m2), indicating superior smoke-suppression. The mechanism analysis revealed that a compact hybrid barrier with rich polyphosphate and silica formed, inhibiting the transfer of heat, O2, and mass during combustion. Thus, TDKPFs have great potential as insulation materials.