Zinc Hydroxystannate- or Zinc Stannate-coated Calcium Carbonate as Flame Retardant for Semirigid Poly(vinyl chloride)

Abstract

The flame retardant and smoke suppressant properties of semirigid PVC treated with CaCO3, zinc hydroxystannate, zinc stannate, zinc hydroxystannate-coated calcium carbonate, and zinc stannate-coated calcium carbonate have been studied through the limiting oxygen index, anaerobic char yield, and smoke density rating (SDR) methods. The thermal degradation in air of the treated semirigid PVC is studied by thermogravimetry (TG) and differential thermal analysis (DTA) from ambient temperature to 1073 K. The morphologies of the additives and the unaerobic char formation are studied through SEM. The mechanical property is also studied. The results show that the semirigid PVC treated with zinc hydroxystannate-coated calcium carbonate or zinc stannate-coated calcium carbonate has a higher limiting oxygen index and anaerobic char yield, lower SDR and starting decomposition temperature, a more compact structure of char formation and reduced tensile strength and elongation, and improved impact strength than the semirigid PVC without flame retardant.

Hydrothermal synthesis and characterization of single-crystalline zinc hydroxystannate microcubes

“…The major applications for ZHS and ZS have been in halogen-containing polymers, such as rigid and flexible poly(vinyl chloride) [3][4][5][6][7], polyester resins [8][9][10], chlorosulfonated polyethylene [11] and alkyd resinbased paints [12]. In addition to the low toxicity, ZHS and ZS have the key advantage over many other flameretardants for its outstanding smoke-suppressant properties.…”

Zinc Stannates as Alternative Synergists in Selected Flame Retardant Systems

“…A more recent publication [20] shows that ZHS-coated (at about 10 wt%) CaCO3 and ZScoated CaCO3 as treatment for semi-rigid PVC promotes a significant improvement in LOI from a value of 28.5 vol% for a PVC/plasticiser/CaCO3 only formulation to as high as 36.5 vol% for both ZS-or ZHS-coated modifications. These results are plotted in Figure 4 from the published data [20] and because the addition of up to 3 wt% alone of either ZHS or ZS (equivalent to the approximate respective contents in the coated samples) generates maximum LOI values of 32.5 and 33.5 vol% respectively, the stannate-coated samples show synergistic effects. The anaerobic char yields increased from 21.9 wt% to above 50 wt% for the highest concentration (30phr) ZS-coated CaCO3 variant with the claim that the increased char compactness in which tin and zinc play an important part, is the cause of the increased flame retardancy.…”

Study of the thermal decomposition of flame-retarded unsaturated polyester resins by thermogravimetric analysis and Py-GC/MS

“…Zinc and tin containing compounds such as zinc stannate (ZS), zinc borate (ZB) and zinc hydroxystannate (ZHS) have been shown to exhibit very low toxicity, are compatible with a variety of flameretardants while acting as smoke suppressants for various polymer systems [13][14][15][16][17][18][19]. Synergistic effects are envisaged when these smoke suppressants are combined with conventional flameretardants and/or nanoclays.…”