Polyvinylidenefluoride - PVDF
General Description : A semi-crystalline, semi-opaque and white engineering thermoplastic that is melt processable and very expensive. It has good temperature and general chemical resistance (though neither are as good as PTFE's) and good abrasion and radiation resistance. It is somewhat stiffer and stronger than most (melt-processable) fluoropolymers but has high dielectric losses. It has a highly dipolar molecule so that, if the correct morphology is achieved, valuable piezo- and pyro-electric properties result. The desired form is known as the ß phase or Form I, in which the predominantly "head to tail" polymer chains have an all-trans extended planar zig-zag form with the dipoles of adjacent chains parallel to one another. This is formed from the more common Alpha phase (Form II) by mechanical deformation followed by electrical polarisation at very high electrical fields. In practice, both uniaxial and biaxial mechanical orientations are used which, after poling, give a different balance of piezo-/pyro-electric properties. Applications of PVDF include pipes and fittings, bearings, linings and vessels (all especially for the chemical processing industry), wire insulation and piezo-electric devices.