Material guide
PVDF, polyvinylidene fluoride
PVDF, polyvinylidene fluoride. A fluoroplastic with top class chemical resistance, but unlike PTFE it is stiff, dimensionally stable and can be welded. That makes PVDF a first choice for tubes, tanks and welded constructions in demanding chemical environments.
What it is
PVDF stands for polyvinylidene fluoride and is one of the fluoroplastics. It shares the family's wide chemical resistance, but where PTFE is soft and creeps, PVDF is stiff, hard and dimensionally stable. It is the combination that makes the material useful: high resistance to acids, solvents and halogens, while it carries load and keeps its shape. PVDF also welds extremely well, which makes it a load bearing material in piping systems and containers for aggressive media. It also withstands a higher continuous temperature than the ordinary engineering plastics. In price the material sits between the engineering plastics and the most expensive high performance plastics. The group is available in different grades, more about that further down.
Properties
Very wide chemical resistance, resists most acids, solvents and halogens
Stiff and dimensionally stable, unlike the soft fluoroplastics
Can be welded, which makes leak tight tube and tank constructions possible
High continuous service temperature compared with engineering plastics
Good wear resistance and mechanical strength
Aging and UV resistant, suits outdoor and process environments
Common applications
PVDF sits in the chemical process industry where the material has to both resist the medium and carry a construction. Typical applications are tubes, fittings and tanks for aggressive liquids, valve and pump components, plus linings and coatings in vessels. The material is common in the semiconductor and surface treatment industries thanks to its purity and chemical resistance, and in laboratories and water treatment. Because it can be welded, it is used where leak tight plastic systems are built up rather than assembled from individual parts. When a customer needs PTFE like chemical resistance but in a load carrying, weldable form, PVDF is often the answer.
Limitations
PVDF is not as chemically all consuming as PTFE. Against strong bases and certain amines and ketones the resistance is poorer, so PTFE or PFA can be a better choice there. Nor is it a high temperature plastic in the class of PEEK, so for really hot environments there are better alternatives. The price sits above the ordinary engineering plastics, which means PVDF is chosen for its chemical resistance and weldability, not for cheap everyday parts. For good mechanics alone without chemical load, an engineering plastic goes a long way.
Our PVDF grades withstand 140 °C in continuous operation and 155 °C for short periods, go down to -20 °C and melt at 171 °C.
Grades and variants
PVDF is supplied in grades adapted to the production method and the requirements. The grades differ in stiffness, impact strength and how easy they are to form and weld.
Base grades
- PVDF homopolymer, the stiffest and most heat resistant form, with the highest chemical resistance. Common in round rod, sheet and tube for machined parts.
- PVDF copolymer, somewhat tougher and more impact resistant, easier to form and weld. A choice where flexibility and crack resistance weigh more heavily than maximum stiffness.
Welding materials
- Welding rod and roll, for joining PVDF constructions and leak tight systems.
The weldability of the material is one of the main points of PVDF, and welding rod is in the range for exactly that. If you need to know which grade suits your medium, get in touch and we will go through the chemical list.
Machining
PVDF is machined with ordinary tools and joined by welding or threading. It is harder and stronger than PTFE, but still sensitive to stress cracking, so avoid running hard and hot in the same operation.
Formats we can supply
PVDF is available as sheets, round rods, tubes and hollow bars, as well as roll and welding rod for welded tube and tank constructions. You see formats and dimensions in the range. Would you like a piece cut to size? Enter the dimensions in VisualCutter and you will see the price straight away.