An experimental investigation of electromechanical responses in a polyurethane elastomer

Abstract

The electromechanical response of a polyurethane elastomer was investigated at room temperature and in the temperature range near its glass transition. It was found that the Maxwell stress contribution to the strain response can be significant at temperatures higher than the glass transition temperature. In addition, the material exhibits a very high electrostrictive coefficient Q, about two orders of magnitude higher than that of polyvinylidene fluoride. It was also found that in a polymeric material, the chain segment motions can be divided into those related to the polarization response and those related to the mechanical response and the overlap between the two yields the electromechanical response of the material. In general, the activation energies for different types of motion can be different, resulting in different relaxation times in the dielectric, the elastic compliance, and the electrostrictive data, as observed in the polyurethane elastomer investigated. The experimental results indicate that at the temperatures investigated, the activation energy for the mechanical related segment motions is higher than that of nonmechanical related segment motions.

The transverse strain response of electroactive polymer actuators

“…On the other hand, the electrostrictive effect is due to the coupling between the polarization and the mechanical response in a material. The transverse electrostrictive strain response, S e , due to the applied field, again for small strains, is [6]:…”

“…It follows that the total induced strain due to both effects is proportional to the square of the electric field. As noted earlier [6], separating the contributions of the different mechanisms requires knowledge of other material parameters such as the elastic compliance, the dielectric constant and the electrostrictive coefficient of the polymer films.…”

Measurement of Error in Electrostriction Based Dielectrics

“…Zhang et al [6] use non-tensor form of stresses (T) and strains (S) for experimental determination of induced strains in the case of Polyurethane elastomers (DOW 2103-80AE) and the relative change in thickness of the dielectric slab of a parallel plate capacitor is considered as…”

“…The expression (27) is valid if the direction of electric field z E is making an angle θ with respect to the normal to the surface of sample (Figure 5), then the expression [3] for the stress tensor in triclinic case would be ( ) For experimental study [6] [17], a parallel plate capacitor with dielectric film/slab has been considered due to its simple symmetrical geometry. However, due to electrostrictive deformation, the permittivity of different regions is different so the solution to the field or potential must be different although having the same general form of solution (to the Laplace equation).…”

Electroactive Thermoplastic Dielectric Elastomers as a New Generation Polymer Actuators

“…This strong true electrostriction effect might be attributed to the dielectric mismatched periodic nanostructures. The interfaces between nanodomains result in the development of an inhomogeneous electric field across the film thickness (Guiffard et al, 2006;Kim et al, 2011;Li & Rao, 2002;Shankar et al, 1997;Su et al, 1997aSu et al, , 1997bZhang, et al, 1997). The nonuniform field distribution can enhance the strain response because coupling between the strain and electric field in a dielectric elastomer is described by a quadratic relationship, delineated by eq.…”