Improvement of the flame retardance of epoxy resin composites reinforced with cyclodextrin phosphate melamine salt

Epoxy resin is widely applied in civil aircraft, automobile and electronics products because of its good processing, adhesion, and mechanical properties, but its application is limited due to its easy combustion. Therefore, it is worthwhile to carry out flame-retardant treatment for epoxy resin. In this study, a new bio-based three-source integrated intumescent flame-retardant cyclodextrin phosphate melamine salt (CDPM) was synthesized from beta-cyclodextrin, phosphoric acid, and melamine, and it was employed as an additive flame retardant to fabricate CDPM/epoxy resin (CDPM/EP) composites. Thermogravimetric analysis results manifested that CDPM slightly improved the thermal stability of CDPM/EP composites. The CDPM/EP composite containing 10 wt.% CDPM acquired a limiting oxygen index of 32.9% and passed UL94 V-0 rating. Moreover, the peak heat release rate, total heat release, and total smoke production, were respectively decreased by 46.4%, 55.5%, and 61.8% in contrast with neat epoxy resin. These results demonstrated that CDPM/EP could exert excellent flame retardance and smoke suppression performance. Scanning electron microscope and Raman results confirmed that CDPM facilitated the formation of residual char. Moreover, thermogravimetric/infrared results showed that CDPM/EP produced plenty of phosphorus-containing free radicals and nonflammable NH3 during pyrolysis process, which played a good flame retardance effect in gas phase. This study provides a new approach for the design and development of low-cost intumescent bio-based flame retardant for epoxy resin.