In situ phase separation of novel phosphorus-containing polyester in epoxy resins towards simultaneously improved thermal conductivity and fire safety

Polymeric thermal management materials (PTMMs) attained with expected thermally conductive performance and flame retardancy are still urgently being required. Herein, a novel phosphorus-containing polyester named poly(bis(1,1’-biphenoxyl)hexyl 5-(diphenylphosphoryl-amino)isophthalate) (PBHPI) was synthesized and incorporated into the epoxy resin (EP). After curing with 4,4’-diaminodiphenyl sulfone (DDS), in situ networks were obtained via reaction-induced phase separation (RIPS) between PBHPI and EP DDS , which induced the preferable distribution of boron nitride nanosheets (BNNSs) at the interface between the PBHPI-rich and EP-rich phases; therefore the photon transmission pathways were constructed. Due to the flame inhibition activity of PBHPI and the physical barrier effect of BNNSs , EP DDS /PBHPI/BNNSs composites exhibited expected fire safety performance of heat insulation and smoke suppression in cone calorimetry: the peak heat release rate (PHRR) reduced by 60%, total heat release (THR) by 40% and total smoke production (TSP) by 41%, compared with EP DDS . In addition, the incorporation of barely 1 wt% BNNSs improved the thermal conductivity of the composites. This work combining the molecular design of the novel phosphorus-containing polyester and the RIPS methods to construct in situ networks provided a feasible solution and unique insight into the design of PTMMs in a facile and convenient way.