Polarization effects in uncharged laminates

It has been suggested that polymer laminates in which a charge has accumulated at the interface of two polymers will exhibit piezoelectric properties. It has also been suggested that a composite which consists of a polymer matrix and dispersed inorganic ferroelectric particles exhibits piezoelectricity after poling. The author proposed a technique of multielement electret preparation that is based on these two concepts. A partially oriented polyethylene terephthalate (PET) film and a composite of polymethyl methacrylate (PMMA) and powdered BaTiO₃ ceramics are used. The technique does not require conventional poling by an external electric field procedure. It is shown that the best polarization effects can be obtained in the uncharged PET-PMMA/BaTiO₃-PET laminate and its separated films. This laminate can have interesting piezoelectric properties due to its heterogeneity and the charges embedded at the interface between the PET and PMMA/BaTiO₃ films