Chitosan-regulated inorganic oxyacid salt flame retardants: preparation and application in PVC composites

Abstract

A series of chitosan-modified inorganic oxyacid salt flame retardants (IOS-CS) were synthesized and used as flame retardants to improve the fire resistance of poly(vinyl chloride) (PVC) composites while improving the mechanical properties of the materials. The thermal stability of the material was analyzed by TG test; the flame-retardant and smoke suppression properties were evaluated by limiting oxygen index (LOI) and cone calorimeter test, and the mechanical properties were analyzed by tensile test and impact test. The TG results showed that the addition of flame retardant can promote the early cross-linking decomposition of PVC composites, not only advance the decomposition temperature of the material but also promote the formation of char layer and increase the char residual content. LOI and cone calorimeter test results showed that stannate chitosan (Sn-CS) can improve flame retardant and smoke suppression more effectively than other samples. Compared with pure PVC, the addition of Sn-CS increased its LOI from 26.6 to 30.5% and reduced the total heat release value and total smoke release by 18.23% and 52.55%, respectively. At the same time, the addition of the flame retardants had no large deterioration effect on the mechanical properties of the material. The tensile properties of flame-retardant PVC were slightly reduced compared with pure PVC, and the impact resistance was even improved to some extent.