Effect of compression pressure on mechanical and electrical properties of polyaniline pellets

While conductivity and other electrical properties are key parameters in the design of polymer electronics, equally important mechanical properties of conducting polymers have rarely been reported. The influence of preparation conditions of polyaniline pellets on mechanical and electrical properties was therefore studied. Conductivity of polyaniline is commonly measured using pellets prepared by the compression of powder. It is shown that a pressure of at least 300 MPa is needed to obtain a reliable value of conductivity. At lower pressures, the samples have lower apparent conductivity, density, Young modulus, and hardness. Above the compression limit of 300 MPa, these parameters become constant, except for the density. The same behavior was observed both for conducting polyaniline hydrochloride and for the non-conducting polyaniline base. The puzzling observation that density of the pellets decreased as the compression pressure increased is discussed considering the relaxation processes.