Flame retardation of polypropylene: Effect of silane treated antimony compounds

Flame retardation of polypropylene was accomplished by blending with antimony compounds (Sb 2 O 3 and SbPO 4 ) in conjunction with polyvinyl chloride (PVC) or ferric oxide. The compatibility and dispersion of antimony compounds in the polymer matrix was enhanced by using silane coupling agents, viz., vinyltriethoxysilane (A‐151) and γ‐aminopropyltriethoxysilane (A‐1100). Rheological properties of filled polypropylene were studied in the temperature range 180 to 220°C at shear rates of 29.5 to 119.5 sec −1 . An increase in the melt viscosity was found in the filled polypropylene as compared to virgin polymer. Silanation of antimony compounds also influenced the melt rheology of flame retardant polypropylene. Incorporation of 6 phr Sb 2 O 3 and 19 phr PVC raised the oxygen index of polypropylene to 22.9 and this sample was found to be self extinguishing in 65 s with a burning rate of 0.06 mm/s as compared to 1.1 mm/s for unfilled polypropylene. Though silanation of antimony compounds slightly reduced the oxygen index of flame retardant polypropylene, yield strain and flexural rigidity of injection molded samples was improved over unsilanated flame retardant polymer.