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

• Novel mesoporous hybrid material (TOS) was synthesized via facile in-situ method.
• TOS was incorporated into flexible PVC composite to enhance its properties.
• Flammability of TOS based flexible PVC composite was decreased significantly.
• Mechanical properties of TOS based flexible PVC composite were improved greatly.
• This hybrid material has potential to totally replace antimony compounds in PVC.

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.

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