Structure regulation of boron-doped calcium hydroxystannate and its enhancement on flame retardancy and mechanical properties of PVC

In this study, a perovskite type calcium hydroxystannate (CaSn[OH](6), CSH) was prepared by a facial coprecipitation method. Then boron was further doped into CaSn(OH)(6) to obtain B@CSH as a new inorganic flame retardant to polyvinyl chloride (PVC). The characterization of chemical composition, morphology, and bonding structure for CSH and B@CSH reveals that the doping of boron can effectively regulate the morphology and particle size of CSH. When applying into PVC, flame retardancy, smoke suppression, and mechanical performance are significantly enhanced by the addition of CSH and B@CSH. Under 5% addition of CSH and B@CSH, the limited oxygen index (LOI) value of PVC composites was increased from 26.6% to 32.9% and 34.0%, respectively. The cone calorimetry tests show that the peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) of PVC composites are all greatly reduced. The PHRR and TSP are reduced by 49.2% and 42.3% with the 5% loading of B@CSH, respectively. Furthermore, the mechanical strength and toughness of PVC are both improved by CSH and B@CSH. The synthesized CSH and B@CSH act as a multi-functional additive for PVC with high efficiency.