Abstract

An article comprising vinylidene fluoride polymer which has been rendered piezoelectric by stretching the article to a final draw ratio of less than about 6:1 and polarizing and has an equivalent activity A* of at least 6, where A* is given bywhere d3h is the hydrostatic coefficient of the stretched and polarized vinylidene fluoride polymer after heating at 120° C. for 1 hr, in units of pC/N; do is the density of the unstretched and unpolarized polymer, in units of g/cc; and d is the density of the stretched and polarized polymer before heating at 120° C. for 1 hr, in units of g/cc, said article having an aggregate dimensional change of less than 15% upon heating at 120° C. for 1 hr, as measured by the sum of the absolute dimensional changes along three orthogonal coordinate axes, one of which is a principal direction of stretching. Vinylidene fluoride polymer with these characteristcs is prepared by stretching, conditioning, and polarizing, or, alternatively, stretching, polarizing, and conditioning.