ABSTRACT:Since the large fire at the Brown Ferry cable plant which occurred at noon on March 22, 1975 in Alabama, attention has been given to the use of flame retardant cable in buildings to meet fire safety requirements. Flame retardants are used in wire and cable applications to prevent the conversion of an electric spark into fire and subsequently to prevent the spread of fire throughout a structure along the wiring. There are many substances used as flame retardants in wires and cables. In Egypt, Multi-Purpose Reactor insulation and jacket cables have been constructed from a flame retardant substance, poly(vinylchloride) (PVC). In the present work, elemental and X-ray fluorescence analyses have been performed to determine the composition of PVC in the jacket cable samples. In addition, the conductivity (), permittivity (Ј), and dielectric loss (Љ) as well as positron annihilation lifetime (PAL) are measured in the temperature range 30 to 140°C. It is found that the amount of chlorine in the flame-retardant PVC (FRPVC) jacket cable is significantly higher (5%) than the conventional PVC jacket cable. Inverse relationships between and free volume size and fractions (V, f) through the temperature range are obtained. However, a distinct positive relationship between and I 2 above 100°C is found. The results of PAL and electrical measurements indicate that FRPVC has good electrical insulation properties below 100°C.

Flame-retardant polyvinylchloride (FRPVC), typically used in cable insulation and jacketing construction for multi-purpose reactor (MPR) at Atomic Energy Authority of Egypt, as well as carbon-black FRPVC (CB-FRPVC) and nonflame-retardant PVC and CB-PVC materials produced by Egyptian Electrical Cable Company (EECC), have been irradiated up to 160 KGy, at room temperature with a 60 Co gamma source. Free-volumes and thermal stability of irradiated and nonirradiated PVC samples have been examined using positron annihilation Lifetime Spectroscopy (PALS) and thermogravimetric analysis (TGA). In addition, the mechanical properties: tensile strength and elongation at break were examined. Considerable presence of flameretardant and carbon black additives in CB-FRPVC sample led to both quenching and inhibition of Ps formation. The mechanical and thermal characterization showed that irradiation of PVC samples up to 80 KGy effectively induced cross-linking to maxima. Higher doses then after results in degradation and thus a decrease in mechanical strength.

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