Hierarchical nanoporous silica doped with tin as novel multifunctional hybrid material to flexible poly(vinyl chloride) with greatly improved flame retardancy and mechanical properties

Antimony trioxide (Sb₂O₃) is a traditional widely used flame retardant in flexible poly(vinyl chloride) (fPVC). However, more and more serious drawbacks of this flame retardant, such as the underlying toxicity and decreasing reserve in the earth's crust, obligate the development of its substitutes. To address this issue, we synthesized novel mesoporous flame retardant (TOS) by grafting of tin on hierarchical nanoporous silica (HPS) via a facile in-situ synthesis method. Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission gun scanning electron microscope (FEGSEM), transmission electron microscopy (TEM) and N₂ adsorption-desorption measurement were utilized to investigate the composition and structure of the mesoporous material. TOS, HPS, commercial tin oxide (SnO₂) and Sb₂O₃ were added into fPVC composites respectively to carry out comparative study. Results showed limiting oxygen index (LOI) of fPVC composite was significantly increased in presence of TOS, accompanied with UL-94 V-0 rating without dripping. Meanwhile, TOS also enhanced the tensile properties of fPVC composite significantly. All the data illuminated that TOS greatly improved flame retardancy and mechanical property of fPVC as a novel multifunctional hybrid materials.