Fabrication of zirconium phenylphosphonate/epoxy composites with simultaneously enhanced mechanical strength, anti-flammability and smoke suppression

A two-dimensional layered zirconium phosphonate (ZrPP) was synthesized from phenylphosphonic acid, and its structure was well characterized. ZrPP exhibited a larger lamellar spacing distance (1.474 nm) than zirconium phosphate (ZrP) (0.743 nm) so that ZrPP can be better dispersed within the epoxy matrix. The 3 wt% ZrPP-EP composite showed excellent flame retardancy in terms of lower total heat release and total smoke production that was decreased by 11.2% and 17.5%, respectively. Moreover, ZrPP can promote the formation of a dense and compact char layer, resulting in a higher char yield of 8.5% and 21.9% under air and nitrogen atmosphere, respectively, in the TGA test. which can be served as a physical barrier to isolate oxygen, protect the internal matrix, and suppress smoke release during combustion. Furthermore, the tensile and impact strength of 3 wt% ZrPP-EP composite was 45.6% and 63.8% higher than that of unmodified EP, respectively, which was also superior over 3 wt% ZrP-EP composite.