Reaction-induced phase separation towards in situ network in epoxy resins for simultaneously improving thermal conductivity and fire safety

Simultaneously improving the thermal conductivity and fire safety of the polymeric thermal management materials (PTMMs) still remains a challenge. In this work, through reaction-induced phase separation (RIPS), co-continuous networks were in situ formed between polyetherimide (PEI) and epoxy resin (EP) cured with either commercially available 4,4′-diaminodiphenyl sulfone (DDS) or the synthesized bis(4-aminophenyl) phenylphosphonate (BAPP). Boron nitride nanosheets (BNNSs) were selectively localized in the interfacial region between the EP-rich and PEI-rich phases as the thermally conductive fillers ; therefore the thermally conductive networks were constructed. BNNSs and BAPP simultaneously endowed the composites with enhanced thermal conductivity and expected fire safety. In detail, the EP BAPP /PEI/BNNS composite with barely 1 wt% BNNSs showed a thermal conductivity increment over 67%; and both the heat and smoke release were greatly suppressed in cone calorimetry : the peak heat release rate (PHRR) reduced by 58%, total heat release (THR) by 56% and total smoke production (TSP) by 46%, compared with the reference. The successful application of the RIPS method in constructing in situ thermally conductive networks provided promising perspectives for designing versatile PTMMs.