Synthesis of Zinc Stannate Microcapsules for Preparation of Flame-Retardant PVC Composites

A multilayer microcapsule [melamine-formaldehyde resin/aluminum hydroxide/zinc stannate] with unique core–shell structure was prepared. Fourier transform infrared, X-ray photoelectron spectroscopy, thermogravimetric analysis, and transmission electron microscope were used to investigate the chemical structure of the microcapsules, fire retardancy, and thermal stability of polyvinyl chloride with these materials as additives were also investigated. Remarkably, addition of certain amount of melamine-formaldehyde/aluminum hydroxide/zinc stannate microcapsules could evidently increase limiting oxygen index values. The smoke density results showed that polyvinyl chloride containing melamine-formaldehyde/aluminum hydroxide/zinc stannate microcapsules produced less smoke than pure polyvinyl chloride. The morphologies of the residues were revealed by scanning electron microscope, ascertained that the formed char layers on the composites were denser than that of the pure polyvinyl chloride and polyvinyl chloride/aluminum hydroxide/zinc stannate microcapsule composites. Furthermore, the mechanical properties of polyvinyl chloride/melamine-formaldehyde/aluminum hydroxide/zinc stannate microcapsule composites were observably improved, highlighting its promising potential in industrial applications.