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A highly cross‐linked poly (cyclotriphosphazene‐resveratrol) microsphere (PRV) was synthesized by using hexachlorocyclotriphosphazene (HCCP) and bio‐based resveratrol (REV) as raw materials, and the obtained PRV microspheres were applied to improve the flame retardancy and mechanical property of epoxy resin (EP). The TGA results showed that the PRV microsphere is an excellent charring agent and the char yield is as high as 62% at 800°C. The incorporation of PRV makes the initial degradation earlier yet significantly increases the char residue of EP composites. Moreover, the introduction of PRV microspheres into EP greatly promoted the flame retardancy performance. Under 3% of addition of PRV microspheres, the peak heat release rate (PHRR) and total heat release (THR) were decreased by 58.3% and 29.6%, respectively, the limited oxygen index (LOI) value was increased to 29.7% from 25.3% of pure EP. In addition, because of the uniform distribution in EP matrix and the enhancing effect of PRV microspheres, the mechanical properties including tensile modulus of EP composites were strengthened. PRV microspheres in this paper provide a possibility to synthesize a dual functional filler, which acts as both flame retardant and strengthening agent.

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.

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