Butyl Rubber-Nylon Composites with Improved Flame Retardancy & Gas Impermeability

Abstract

Butyl rubber, because of its high packing density and chemical structure is inherently impermeable to air and gases. However, the elastomer is highly flammable owing to its neat carbon-hydrogen backbone structure. The particular rubber is extensively being used as coating materials for nylon, cotton, polyester etc., for development of clothing outfits for service personnel working in hazardous chemical environments . It is, therefore , essential to evolve flame retardant butyl rubber compositions which could make such clothings impermeable to chemical agents having adequate flame retardancy.The present paper describes an attempt towards using various chemical additives viz. brominated phenyl ethers, chlorinated paraffin, various inorganic oxides and halogenated elastomer, either singly or in combinations as potential flame retardants in bromo-butyl rubber compositions. The cements were then prepared by adding toluene to these compositions (20 to 30% solid content). The homogenised cements were then applied on both sides of nylon fabric with varying add -on concentrations in a laboratory coating machine with doctors blade specially designed for this purpose. The coated fabrics were cured at different temperatures in step curing between 70-150°C, tested for impermeability against hazardous warfare agents and found to offer enhanced protection against these chemicals . Standard test methods e.g. (a) exposure of the fabric to direct flame as per BS method 3119 (b) limited oxygen index as per ASTM specification D-2663 were followed in the evaluation of flame retardancy. The fabrics showed no after glow- low after flame (2.5 sec. against 6 sec. specified)and 7.2 cm char length against 12 cm max. permissible value. The hysicomechanical' properties e.g., breaking and tensile strengths were determined . Morphology and rubber fabric adhesion were studied using Scanning Electron Microscopy.