Piezoelectric properties and dielectric losses in PVDF–PMMA blends

Abstract

Piezoelectric properties and dielectric losses have been measured in polyvinylidene fluoride (PVDF)/polymethyl methacrylate (PMMA) blends to assess the value of this class of polymers as ultrasonic transducer materials. The electromechanical coupling factor k_t has been found to become vanishingly small in blends having a PMMA content of about 20% by weight. For the same blend composition, the peak of dielectric losses, which at room temperature is located in the low megahertz range, decreases only by 20%. For low PMMA content blends at room temperature, the slow decrease of dielectric losses and the slight frequency shift of the loss peak in the megahertz region are ascribed to the presence of two conjugate amorphous phases. This structure prevents much stronger effects on dielectric losses which could be expected from blending PVDF with a polymer having a high glass transition temperature, such as PMMA. PVDF–PMMA blends, therefore do not represent an attractive class of ultrasonic transducer materials.