PRIMARY AND SECONDARY PYROELECTRICITY IN HIGHLY ORIENTED POLYVINYLIDENE FLUORIDE

Measurements of the pyroelectric response in both free and constrained conditions are presented for low-draw ratio, high-draw ratio and voided from I polyvinylidene fluoride sheets. The results are used together with related data for the piezoelectric response and for the thermal expansion behavior to estimate the primary and secondary components of the total macroscopic pyroelectricity. For the high-draw ratio and voided sheets the primary response was approximately 90% of the total pyroelectricity compared with 40% for the low-draw ratio nonvoided sheet. It is proposed that the role of reversible temperature-dependent crystallinity is more pronounced in the high-draw samples. Previous NMR studies provide support for this conclusion.