Novel heat durable electromechanical films: cellular film making from cyclic olefin polymers

A cellular electromechanical film has been developed from both, cyclo-olefin polymer (COP) and cyclo-olefin copolymer (COC). Cyclic olefins are thermally more durable than polypropylene (PP), which is the basis for the existing electromechanical film. This paper concentrates on studying cellular film making of the electromechanical film from cyclo-olefin compounds and a mineral filler. Due to the stiffness of the COP and COC as well as challenging film processing, the high temperature grade of cyclo-olefins were blended with a lower temperature polymer in different ratios in order to increase the film for inability in solid state processing. The effect of a blended polymer and its ratio in the manufactured compounds was studied from the cast films by a dynamical mechanical thermal analysis (DMTA). The blends were extruded in to a form of a cast film and drawn biaxially using a laboratory scale stretcher or sequentially on a small pilot line in MD and consequently using an Instron extensometer in TD. One COP based blend manufactured was drawn in TD on a small pilot line stenter to demonstrate film making on a film line similar to commercial film making units. Voided structure of the biaxially drawn films was improved by a gas diffusion expansion treatment and evaluated from scanning electron microscope (SEM) micrographs. Film samples were electrostatically charged and metallized and consequently, the level of the electromechanical sensitivity was measured from these blend based films by a dynamical method. It was shown that a cellular electromechanical film with an electromechanical coefficient around 10-15 pC/N durable at high temperatures of around 80-110°C, can be manufactured from the COP and the COC based blends.