Synthesis, application, and flame-retardant mechanism of a novel phosphorus-containing plasticizer based on castor oil for polyvinyl chloride

The objective of this study was to synthesize a novel flame-retardant plasticizer (PPC) for PVC using castor oil and to investigate the retardant mechanism of PVC blend plasticized with PPC. The chemical structure of PPC was characterized with FT-IR, 31 P NMR, and 1 H NMR. The melting behavior, thermal property, flame-retardant performance, flame-retardant mechanism, and mechanical property of PVC plasticized with PPC were systematically studied. The results showed that when the PPC content increased from 0 to 20 g in PVC blend, the torque increased from 10.6 to 15.9 N m, and the glass transition temperature increased from 26.5 to 52.6 °C. Leaching tests indicated that PPC had a higher migration resistance than DOP. TG indicated that PPC could improve the thermal stability under 350 °C, and the LOI tests indicated that the LOI value of PVC blends cooperated with PPC increased from 26.6 to 32.4 %. The SEM and flame-retardant performance indicated that PPC was put into effect by promoting PVC carbonization and forming a consolidated and thick flame-retardant coating quickly, which is effective to prohibit the heat flux and air incursion. PPC could improve the flame-retardant performance of PVC blends and keep the mechanical properties unchanged comparing with DOP.