Novel heat durable electromechanical film: Processing for electromechanical and electret applications

Eetta Saarimäki, Mika Paajanen, Ann-Mari Savijärvi, Hannu Minkkinen, M. Wegener, O. Voronina, R. Schulze, W. Wirges, R. Gerhard-Multhaupt

    Research output: Contribution to journalArticleScientificpeer-review

    72 Citations (Scopus)


    New ferroelectrets were developed on the basis of foams from cyclo-olefin polymers and copolymers. The results obtained on the cyclo-olefin polymer foam demonstrate a significant improvement of the service temperature for ferroelectret transducer materials. Suitable compounding and preparation led to cyclo-olefin ferroelectrets with an electromechanical activity of around 15 pC/N, which is thermally stable at least up to 110degC. The properties in sensor and actuator applications are strongly dependent on the processing parameters related to film-making, sensor and actuator preparation, gas content and electric charging. The processing window for the film stretching was very narrow compared to the earlier developed polypropylene ferroelectrets. The film porosity, softness and thus the electromechanical activity are adjusted by gas-diffusion expansion. The activity of the electromechanically operating sensors and actuators was increased by stacking several layers of cellular cyclo-olefin film. For applications such as flat loudspeakers, the foamed films are tuned by tensioning them on a support frame. Correct tensioning was essential also for reducing the distortion levels.
    Original languageEnglish
    Pages (from-to)963-972
    Number of pages10
    JournalIEEE Transactions on Dielectrics and Electrical Insulation
    Issue number5
    Publication statusPublished - 2006
    MoE publication typeA1 Journal article-refereed


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