Experimental Study On Mechanical Properties Of Conducting Films

Most of the materials and devices that have led to the information revolution are in the form of thin films deposited on rigid substrate. Too frequently, however, we think of these materials solely in terms of their electronic or optical properties, preparation and electrochemical polymerization process. We need to remind ourselves that other, nonelectronic properties of these materials can be equally important. For example, certain mechanical properties and fatigue failure mechanism related to their applications.In this paper, the mechanical behaviors of the polythiophene(Pth) and ploypyrrole(PPy) films are experimentally investigated using an electronic speckle pattern interferometry (ESPI) method and an equipment with a sensitive mechanical sensor. Furthermore, we have done some tension test on PPy films by means of AGS-10KNG. Several tensile stress-strain curves of these conducting films of different thickness were drawn. The experimental results showed that these conducting polymer films have good mechanical characterizations. We also found significant effects of thickness on the strength and Young's modulus of the conducting polymer films. High strength and stiffness can be achieved only in polymer films thinner than a critical thickness.The relationship between the microstructure and mechanical behaviors of conducting PPy films was described based on SEM techniques at the first time. As shown in SEM micrographs and with the mechanical characteristics, the river patterns and cap-shaped aggregation structure formed by capillarity or island microstructure formed by three-dimensional nucleation mean excellent mechanical properties (tensile strength and toughness).Various attempts have been made to study the effect of electrochemical polymerization processes including temperature, electrolyte composition and the deposited location on the strength and brittle-tough properties. By the mechanical measurement and testing, we found, compared with the mixed electrolyte composition of Isopropyl alcohol (IPA) +5% Boron trifluoride diethyl etherate (BFEE)+5% Polyethylene glycol (PEG), the better mechanical properties of conducting PPy films were given by the mixed electrolyte compositon of IPA+5%BFEE+5%DEG. The mechanical properties of theconducting PPy films have significant differences. In order to improve the mechanical properties of PPy films, an optimal condition of electrochemical synthesis of conducting PPy films has been recommended. Finally, it is particularly necessary to know their fatigue fracture behaviors of these films. In this paper, a new fatigue testing method was developed by which fatigue failure on the surface deposited by electrochemical synthesis on the base of the 304 stainless steel plate cyclic tension-tension loading. The fatigue tests were investigated by the fatigue tester with SEM. The experimental results showed that the fatigue microcrack propagation and the fatigue embattlement process can be expressed by an experimental approach. Additionally, the fatigue failure types of the thin film on the substrate can mainly represent the microcrack initiation and propagation, fragment and decohesion observed microscopically.