Fast neutrons effect on the dielectric properties of poly (vinyl alcohol)/hydroxypropyl cellulose blends

Thin transparent films of poly (vinyl alcohol)/hydroxypropyl cellulose (PVA/HPC) (100/0, 96/4, 92/8, 88/12, 84/16 and 0/100 wt/wt%) blends were prepared by using solution-cast technique. In the present study, the temperature-dependent (in the range 295-390 K) dielectric dispersion was used to probe the molecular mobility of the amorphous phase of the blend systems near the glass transition temperature (Tg). The dielectric properties on certain chosen blends (100/0, 92/8 and 88/12 wt/wt%) before and after irradiation with different fast neutron fluencies within the range from 105 to 108 n/cm2 were investigated. The results noticed that all the samples face to changes in the values of the dielectric permittivity (ε'), dielectric loss tangent (tan δ) and a.c. electrical conductivity (σac). The data also indicated that the measurable changes in the glass transition temperature (Tg) may be due to the fact that the position of Tg is strongly dependent on the molecular weight, purity and water content of the sample. These changes may be attributed to degradation process and/or to cross-linking process either by the presence of HPC with different concentrations or by irradiation with different fast neutron fluencies or both of them. This suggests that, the observed dispersion and the correlated barrier hopping mechanism depend on composition and temperature of blend matrix.