Electrical And Thermal Properties Of Gamma-Irradiated Nitrile Rubber/Rice Husk Ash Composites

The effects of both the rice husk ash (RHA) loading and fumed silica (FS) loading on the structure, thermal stability, and electrical properties of acrylonitrile-butadiene rubber (NBR) composites were studied. The filler loading were chosen to be 5 and 20 phr for RHA and 5 and 30 phr for silica. Also, the effect of the gamma-irradiation dose (25 kGy) on these parameters was investigated. The structure and thermal stability were studied with X-ray diffraction and thermogravimetric analysis techniques. Furthermore, some electrical parameters, such as the direct-current electrical conductivity (sigma(dc)), activation energy (E-a), dielectric constant (epsilon'), and dielectric loss (epsilon ''), were determined. The incorporation of both RHA and FS resulted in improved thermal stability after gamma irradiation at 25 kGy. The loading of FS on NBR was shown to decrease sigma(dc), epsilon', and epsilon '' and increase E-a. On the other hand, the loading of RHA showed the opposite trend. Finally, gamma irradiation of NBR composites filled with both fillers decreased the values of sigma(dc), epsilon', and epsilon '' for all the samples, which followed the trend for the unirradiated composites. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1495-1502, 2010