A novel hyperbranched phosphorus-boron polymer for transparent, flame-retardant, smoke-suppressive, robust yet tough epoxy resins

The fabrication of fire-safe, robust yet tough polymeric materials represents a challenge for both academia and industry. In this work, a novel hyperbranched polymer (TP) based on trihydroxymethylphosphine oxide and phenylboronic acid for epoxy resin is described. The presence of 2 wt% TP afforded epoxy blend with a high limiting oxygen index of 33.2%, a UL-94 V-0 rating, 36.3% and 13.7% reductions in peak heat release rate and total smoke production, making it superior to previously described counterparts. The high efficiency of TP may be mainly attributed to its promotion of carbonization. Notably, an epoxy thermoset is strengthened and toughened due to the introduction of TP. The presence of 4 wt% of this additive increased the tensile strength, elongation at break, impact strength, and flexural strength by 54.0%, 32.8%, 32.0% and 36.9%, respectively. In addition, the high transparency of the epoxy thermoset is maintained in the presence of TP. Thus, this approach offers an integrated design for the preparation of transparent, fire-safe, strong but tough epoxy thermoset via the introduction of a hyperbranched polymer. It may be expected that this technique will find wide application in different industrial fields.