Flame retardant polyvinyl alcohol composite with excellent comprehensive properties prepared using Cu2O/chitosan and phosphorus-based flame retardants

Polyvinyl alcohol (PVA) has good film-forming and barrier properties and can be used as packaging and biomedical materials, etc. However, PVA burns easily and is prone to melt dropping, limiting its wider application. In this study, Cu2O/Cs was prepared by coating chitosan (Cs) on the surface of cuprous oxide (Cu2O), and mixed with ammonium polyphosphate (APP) and phytic acid (PA) to prepare PVA composites. The results showed that the limiting oxygen index (LOI) value of the PVA composite with 8% (by weight) APP and 2% (by weight) Cu2O/Cs as flame retardants was 30.6%, which was 50.7% higher than that of pure PVA. Compared with pure PVA, its composite peak heat release rate (pHRR) was significantly reduced by 81.1%, and its total heat release rate (THR) was also markedly reduced by 67.7%, while its time to ignition (TTI) was increased by 41 s. The main reasons were that the gas generated by APP decomposition during heating reduced the concentration of combustible gas, the generated phosphorus-containing substances promoted the dehydration and carbonization of PVA, and Cu2O and chitosan (Cs) improved the compactness of the carbon layer. In particular, the incorporation of Cu2O/Cs improved the mechanical properties of our PVA composites compared with those containing only APP and PA. In short, the combination of Cu2O/Cs and phosphorus-based flame retardants improved the flame retardant performance of PVA at low additions while taking into account the mechanical properties. This is expected to expand the range of applications of PVA.