Flame retardant and dielectric properties of glass fibre reinforced nylon-66 filled with red phosphorous

Incorporation of red phosphorous into glass fibre reinforced nylon-66 composites not only confers good fire retardancy but also retains good dielectric properties, that makes them suitable for application as electrical insulation components. The limiting oxygen index (LOI) and Underwriter's Laboratory Bulletin 94 (UL-94) flame retardancy rating of the red phosphorous filled nylon-66 composites increase consistently with their red phosphorous contents. However, the arc resistance and dielectric strength were found to decrease as the phosphorous contents increased. On the other hand, the presence of glass fibre not only improves the flame-retardant properties but also plays an important role in improving the dielectric strength of the composites. However, the arc resistance reduces significantly with the glass fibre loading. To understand these interesting phenomena, thermogravimetric analysis, limiting nitrous oxide (N2O) index, smoke emission properties and gas temperature analysis of the burning polymer during combustion were investigated. Possible mechanisms are discussed.