Low-melting phosphate glasses as flame-retardant synergists to epoxy: Barrier effects vs flame retardancy

In this research, low-melting phosphate (LMP) glasses (G1, G2, G3) were employed as green flame-retardant synergist additives in epoxy (EP)/ammonium polyphosphate (APP) composite. To investigate their performance additives, comprehensive fire tests and characterizations carried out, including limiting oxygen index test, UL-94 vertical burning cone calorimeter real-time temperature detection, X-ray microtomography, char residue strength analysis. A prominent improvement of properties was observed EP composites containing LMP glasses. EP/9%APP/1%G1 reached V-0 rating test showed a decreased peak heat release rate by around 40% over EP/10%APP the test. It found that mainly physical barrier effect condensed phase flame retardancy. Interestingly, via simulating different combustion temperatures, reveal performance. The mechanism further elucidated as: match between glass phase-transition range contributed to optimized performances. This result provided enlightenment for design application toward improving polymer composites.