Zinc Hydroxystannate Coated by Aluminum Phosphate for Improving Its Compatibility in Flame-retardant Poly(acrylonitrile-co-vinylidene chloride)

Zinc hydroxystannate ([ZnSn(OH)6], ZHS) has been used as an effective halogen-free flame retardant in a wide range of polymeric materials. On the other hand, its poor compatibility with a polymer prevented its dispersion, resulting in aggregation in a polymer matrix. In this study, the surface of zinc hydroxystannate (ZHS) was coated with aluminum phosphate (ALP) to enhance its compatibility in a polymer matrix. The coating condition was controlled by preparing ALP-ZHS composites at different coating temperatures. The prepared ALP-ZHS composites were characterized by SEM. The effects of ZHS-coated ALP on the compatibility between ZHS and the polymer were confirmed by measuring the viscosity and surface properties of the polymer. The ALP-ZHS composite prepared at 80 °C showed improved dispersion and compatibility in the polymer matrix with lower hydrophilicity and viscosity. The effects of ZHS-coated ALP on the thermal and flame retardant properties of PANVDC were analyzed by thermal analysis, limited oxygen index (LOI), vertical burning (UL-94), and microscale combustion calorimetry (MCC) test. The results showed that PANVDC containing ALP-ZHS composites achieved an LOI value of 33.5 % passed the UL-94 V-0 rating and decreased the peak heat release rate significantly.