Polyvinylidene fluoride

Production Methods

PVDF, the addition polymer of 1,1,difluoroethene, is prepared by high-pressure free-radical polymerization in aqueous systems. It has applications in electric and electronic devices, as weather-resistant binders for exterior architectural finishes, and in a number of areas of the chemicalprocessing industry. The lack of additives and thus the exceedingly low contamination levels make the polymer useful in ultrapure water systems, for example, where high purity is necessary for construction materials.

Definition

ChEBI: A polymer composed of repeating 1,1-difluoroethyl units.

General Description

Poly(vinylidene fluoride) PVDF is a semi crystalline non-centrosymmetric polymer which exhibits piezo-, pyro- and ferroelectric properties. It is a linear polymer that shows permanent electric dipoles perpendicular to the direction of the molecular chain. These dipoles result from the difference in electronegativity between the atoms of hydrogen and fluorine with respect to carbon. Depending on the processing conditions, PVDF exhibits several different crystalline phases (α,β,γ,δ). The β phase of PVDF is the phase that exhibits the best ferroelectric and piezoelectric properties.

Industrial uses

The fluorohydrocarbons are of two kinds: polyvinylidenefluoride (PVF2) and polyvinyl fluoride(PVF). Although similar to the other fluoroplastics,they have somewhat lower heatresistance and considerably higher tensile andcompressive strength.PVF2, the toughest of the fluoroplastic resins,is available as pellets for extrusion andmolding and as powders and dispersions forcorrosion-resistant coatings. This high-molecular-weight homopolymer has excellent resistanceto stress fatigue, abrasion, and to coldflow. Although insulating properties and chemicalinertness of PVDF are not as good as thoseof the fully fluorinated polymers, PTFE andFEP, the balance of properties available inPVDF qualifies this resin for many engineeringapplications. It can be used over the temperaturerange from –73 to 149°C and has excellentresistance to abrasion.