Effect of small additions of carbon nanotubes on the electrical conductivity of polyurethane elastomer

Effect of low concentrations of carbon nanotubes on electric dipole relaxation in a polyurethane elastomer

“…Some part of the polymer volume was assumed to acquire an altered structure characterized by lower mobility of polymer chains. This assumption is consistent with the decrease in σ dc of PU after the introduction of SWNTs recorded in [1].…”

“…The introduc tion of SWNTs was found to increase the glass transition temperature T g of the polymer. However, this contra dicts the estimates of T g [1], which suggested a decrease in T g after the introduction of SWNTs in the given range of concentrations. In [1], T g was estimated from the D and T 0 parameters in (1) in an assumption that [8] (2)…”

“…For cross linked polyurethane elastomer (PU), the effect of small (0.002-0.008 wt %) additions of single walled carbon nanotubes (SWNTs) on its direct current conductivity (which is independent of the electric field frequency σ dc ) was reported to correlate with the effect of these additions on its mechanical properties [1]. Both characteristics changed nonmonotonically with the addition concentration.…”

“…The dependence of the "strength parame ter" D calculated from the temperature dependence σ dc (T) was also maximum at these concentrations. The σ dc (T) dependence was found [1] to obey the empirical Vogel-Fulcher-Tammann (VFT) law [3][4][5]: (1) where σ dc0 and T 0 are the fitting parameters. The so called Vogel temperature T 0 is often interpreted as the "statistical freezing" temperature of electric dipoles or a transition into the dipole glass state [6,7].…”

“…The inconsistency between the results was attributed in [1] to the differences in the frequency ranges char acteristic of the elastic and thermomechanical (TM) methods. For homogeneous media, however, the differ ence cannot be radical because the TM method is low frequency and direct current conductivity is indepen dent of the field frequency.…”