Zinc hydroxystannate microencapsulated to improve its safety and application to flame-retardant, smoke-suppressed polyvinyl chloride composites

Abstract

The aluminum hydroxide (ATH)/zinc hydroxystannate (ZHS) microcapsule and melamine-formaldehyde resin (MF)/aluminum hydroxide (ATH)/zinc hydroxystannate (ZHS) microcapsule as halogen-free flame retardants were designed and employed in poly(vinyl chloride) (PVC) composites, a series of PVC/ATH/ZHS microcapsule and PVC/MF/ATH/ZHS microcapsule composites were obtained, intumesces and acts as a thermal insulator, providing active fire protection to the composite structure. The flame retardancy and mechanical properties of the composites were investigated by means of horizontal burning, vertical burning, limiting oxygen index, cone calorimetry, smoke density, thermogravimetric and mechanical instrument experiments. The results showed that the MF/ATH/ZHS microcapsule was dispersed well in the PVC matrix, which its tensile strength, elongation at break, flame retardancy and smoke density were better than that of PVC/ATH/ZHS microcapsule. The introduction of 6.15% of ATH/ZHS microcapsule and MF/ATH/ZHS microcapsule to the PVC matrix could make the LOI value of PVC composites increased by 28%, and can also slow the heat release and mass loss upon combustion. Meanwhile, the charring ability of composites was enhanced considerably, the horizontal burning rating and vertical burning rating reached HB, V-0 respectively, while MF/ATH/ZHS microcapsule could also improve the self-extinguish and resistance of melt drip properties of the composites at the low loading in PVC matrix.