Bismuth trioxide replaced diantimony trioxide to obtain polyvinyl chloride leather with high flame retardancy and low flame propagation rate

Diantimony trioxide (Sb2O3) has been widely used in polyvinyl chloride leather (PVCL, PVC powder: plasticizer = 50 phr: 50 phr). However, the EU and the IARC have included it in the list of restricted substances. In response to these restrictions on Sb2O3, this work developed a high flame retardant PVCL with reduced or no Sb2O3 content by introducing bismuth trioxide (Bi2O3). The results showed that the horizontal burning rate of 1Bi2O3/ 3Sb2O3/PVCL decreased by 51.2% compared to that of 4Sb2O3/PVCL. When the addition amount of Bi2O3 reached 6 phr, the horizontal burning rate of 6Bi2O3/PVCL decreased by 20.5% compared to that of 4Sb2O3/ PVCL, which can achieve complete replacement of Sb2O3. The improved flame retardancy can be primarily attributed to the flame retardant effect of Bi2O3 in PVCL foam layer. During combustion, Bi2O3 facilitated crosslinking and charring in the PVCL foam layer matrix, contributing to condensed phase flame retardancy. Additionally, it promoted the decomposition of the PVCL foam layer matrix, generating more HCl (g), thereby enhancing gas phase flame retardancy. This study has developed a high flame retardant PVCL through a simple method, which was expected to meet the application needs of the automotive interior materials.