Improving the fracture toughness and flame retardant properties of epoxy thermosets by phosphaphenanthrene/siloxane cluster-like molecules with multiple reactive groups

摘要

To meet the increasingly stringent requirements for the fire safety and mechanical properties of epoxy thermoset (EP) in advanced manufacturing industry, two kinds of phosphaphenanthrene/siloxane cluster-like molecules with multiple reactive groups (TriDSi and TetraDSi) were synthesized, and then linked into the cross-linked network of epoxy thermoset, separately. The incorporated TriDSi and TetraDSi improved the fracture toughness and flame retardant performance of epoxy thermoset, simultaneously. The impact strength of 6%TriDSi/EP and 6%TetraDSi/EP both increased by more than 120%, compared with that of neat epoxy thermoset. Meanwhile, 6%TriDSi/EP and 6%TetraDSi/EP both passed UL94 V-0 rating with a limited oxygen index of 35.2% and 36.0%, respectively. Moreover, the heat release of burning thermoset was also suppressed significantly by incorporated cluster-like molecules. Through segmer-aggregation toughening effect and group-aggregation flame retardant effect, the cluster-like molecules TriDSi and TetraDSi endowed epoxy thermoset with superior fracture toughness and significantly lowered combustibility. This study provides a promising choice to manufacture advanced epoxy thermoset materials.