Study of the electrical properties of flame retardant poly(vinylchloride) using positron annihilation lifetime spectroscopy



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 (σ), permittivity (ϵ′), and dielectric loss (ϵ″) 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 σ and free volume size and fractions (V, f) through the temperature range are obtained. However, a distinct positive relationship between σ and I2 above 100°C is found. The results of PAL and electrical measurements indicate that FRPVC has good electrical insulation properties below 100°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 638–644, 2005