ABSTRACT:The flame-retardant and smoke-suppressant properties of inorganic tin compounds such as zinc hydroxystannate (ZHS) and zinc stannate (ZS) were investigated in a comparison with alumina trihydrate, magnesium hydroxide, and Sb 2 O 3 through the limiting oxygen index test and smoke density test. The flame-retardant mechanisms were studied through the char yield test, SEM, quantitative analysis, thermogravimetry and differential thermal analysis. The thermal degradation in air of flexible PVC treated with the above compounds was studied by thermal analysis from ambient temperature to 800°C. The results showed that tin compounds such as ZHS and ZS could be used as a highly effective flame retardant for flexible PVC, and it appears that the tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid.

ZnO/MgO, ZnO/CaO, and ZnO/CaO/ MgO can form solid solutions. The solid solution for we as flame retardant (SSFR) was obtained by annealing at 1023 K for 4.5 h in a muffle furnace. Flexible poly (vinyl chloride) (PVC) filled with SSFR and Sb 2 O 3 was investigated by differential thermal analysis thermogravimetry. Limiting oxygen index (LOI), mechanical properties, and electrical properties were studied. The surface of the char formed after combusting of the PVC compounds was observed through scanning electron microscopy and the effect of the surface area to the LOI was also studied. The data suggested that a small amount of SSFR and Sb 2 O 3 have good synergy and can greatly increase the LOI and the char yield, and that the thermal degradation temperature and the activation energy decreased. It can be concluded that the mechanism of SSFR is a condensed-phase mechanism. Moreover, one can conclude that the surface area can enhance the LOI. All the results showed that SSFR is effective and safe as a flame retardant in flexible PVC.

The thermal degradation in air of hemp fabric treated with various compounds containing nitrogen, phosphorus, halogens, and boron, in combinations of two compounds, has been studied by differential thermal analysis and thermogravimetry from ambient temperature to 600 C. The kinetic parameters were obtained using the equation of Broido. The values of activation energies for the oxidative decomposition of samples were found to be in the range 52-102 KJmol 1. Hemp fabric treated with flame retardants showed a high limiting oxygen index and char yield which indicated that the flame retardance of treated hemp was improved. Effect of the different elements on degradation behaviors has been proposed.

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.