DYNAMICAL MECHANICAL ANALYSIS OF CONDUCTIVE BR/EPDM/CB BLENDS

摘要

In the present work, Dynamical Mechanical Analysis (DMA) was employed in order to evaluate viscoelastic properties of polybutadiene (BR)/EPDM/Carbon black (CB) blends as a function of the strain amplitude. As expected, storage modulus, G', of conductive samples presented a strong dependence on strain amplitude as described by the Payne effect. This effect appears in compounds at the electrical percolation threshold and is stronger as CB content is rinsed. However, linear viscoelastic region (LVR), a characteristic section of the curve which has had little attention in this type of studies, presented also a great dependence on CB concentration, i.e. LVR is shorter as carbon black content and, hence, the conductivity of samples, increases. Respect to the influence of the elastomeric ratio BR/EPDM, EPDM alone (ratio 0/100), which had the highest viscosity, was the only formulation without a significant G' dependence on strain at 15 % w/w of CB. Also, conductivity was measured before and after the deformation cycle, in such a way that these data were useful as an indication of the structure recovery. As electrical end mechanical hysteresis is related to the state of (CB) distribution these results are envisaged to balance mechanical and electrical stability.