PVDF (Polyvinylidene fluoride)

PVDF technical characteristics

Polyvinylidene fluoride is typically a semi-crystalline polymer that is approx. 50% amorphous. It has highly regular structure with most of VDF units joined head-to-tail with very less percentage of monomer units joined head-to-head.

It has one of the lowest melting points of the commercial fluoro-thermoplastics, at only 171°C, but has highest heat deflection temperature under load. Temperature range goes from -40°C to +140/150°C.

The high crystallinity and surface tension properties of PVDF provide very low permeation values compared to other fluoropolymers. In fact, PVDF shows low permeabilities to gases and liquids. Though, the permeability of PVDF is influenced by the crystalline degree and the modification of crystalline parts. Moreover polyvinylidene fluoride offers a really low water and moisture absorption.

Polyvinylidene fluoride becomes a great choice between fluoro-polymers also thanks to its great mechanical properties (higher compared, for example, to PTFE) and a lower density (1,78 g/cm3).

Chemical and physical resistance and fire behaviour

Polyvinylidene fluoride offers an outstanding chemical resistance. Parts made of PVDF display great resistance to mineral and organic acids, aliphatic and aromatic hydrocarbons, alcohols and halogenated solvents. Moreover PVDF is considered to have excellent / inert resistance to: strong acids, weak acids, ionic, salt solutions, halogenated compounds, hydrocarbons, oxidants, weak bases.

Polyvinylidene fluoride, similar to other fluoropolymers, exhibits chemical sensitivity, in general, with the following chemical families: strong bases, caustics, esters, ketones. At elevated temperatures, PVDF can be dissolved in organic solvents such as esters and amines, which allows PVDF to be applied as corrosion-resistance coatings on chemical process equipment and architectural panels.

When exposed to flame, PVDF is non-flammable and non-dripped. It is self-extinguishing and UL94 V0 compliant. The LOI is 44%.

It also exhibits good resistance to UV light and radiations.

Electrical properties

Polyvinylidene fluoride performs great electrical insulation. It is primarily used in wire and cables isolation, thanks to its high dielectric constant and dissipation factor.

However, the poor electrical properties allow the production of PVDF films with piezoelectric and pyroelectric behaviour.

There films are prepared from extruded films in B-phase conformation. Both surfaces of the film are metallized and then subjected to high voltage, which leave it permanently polarized.

Such films generate a voltage when stretched or compressed (piezoelectricity) or heated (pyroelectricity) at a temperature close to the melting point. The polymer films also show some ferroelectricity.

Miscellaneous information

PVDF is an inert, a-toxic material and can be certified according FDA and EU 10/2011.

PVDF in few words.

Special properties:

• Low density compared to other fluoropolymers;
• Good mechanical strength compared to other fluoropolymers;
• High permanent operating temperature (140°C);
• Practically no moisture absorption;
• Good dimensional stability;
• High chemical resistance;
• Good resistance to hydrolysis;
• UV resistance;
• Radiation resistance;
• Good electrical insulation;
• High abrasion resistance.

Used in:

• Chemical industry;
• Pumps&Valves;
• Aerospace;
• Semi-conductors;
• Electronic Industry.

Applications:

• Chemical plant engineering;
• Food and pharmaceutical industries;
• Valves;
• Filter plates;
• Fittings.