Differences between PVDF and PFA: a guide to selection in centrifugal pumps

Corrosion of pump components and fluid leakage into the environment these are just some of the most serious problems process pumps could encounter incorrectly designed and with unsuitable materials. In the chemical sector, pharmaceutical and in processes where aggressive substances are handled, the Centrifugal pumps they must be made of materials capable of maintaining their characteristics even in the presence of acids, solvents, high temperatures, or particularly corrosive compounds.

Among the plastic materials most commonly used for the production of components in contact with this type of fluid, we find the PVDF (polyvinylidene fluoride) and the PFA (perfluoroalkoxy), two fluorinated polymers that offer different characteristics and are used in various manufacturing sectors. The choice between these materials depends on the chemical composition of the handled liquid, the operating temperature, the general process conditions, and the level of protection required by the production chain over time.

Knowing the differences between PVDF and PFA makes it possible to identify the most suitable configuration for your company's needs, avoiding issues related to material compatibility and ensuring greater operational continuity of the system after installation.

PVDF and PFA: two plastic materials for advanced industrial applications

Plastic materials are currently a fundamental technology in the construction of pumps designed for handling chemical fluids. Compared to traditional metallic materials, in fact, certain families of polymers offer greater resistance to specific aggressive substances, reducing the risk of deterioration of the parts in contact with the liquid.

PVDF and PFA both belong to the fluoropolymer family, but they exhibit different properties. This distinction influences their use within industrial plants:

• The PVDF It is often chosen when it is necessary to combine good chemical resistance with high mechanical characteristics and a lower investment compared to other fluorinated materials. Its widespread use concerns numerous applications where fluids present a medium level of aggressiveness or where the process does not reach particularly extreme conditions.
• The PFA, on the other hand, represents a solution intended for situations where chemical compatibility is sought: thanks to its molecular structure, it offers superior resistance to many corrosive substances and maintains its characteristics even in the presence of high temperatures.

PVDF pumps: features, advantages and applications

The Centrifugal pumps made with PVDF components, they offer good resistance to many chemical substances and represent a frequent choice in systems where they are handled acids, bases or chemical solutions with moderate characteristics.

One of the main strengths of PVDF concerns chemical resistance, as it maintains good stability in contact with many substances used in industrial processes, allowing for the handling of fluids that could be aggressive to other materials.

Another important element is mechanical strength. Compared to other polymers intended for industrial applications, PVDF in fact features a more robust structure, a characteristic that makes it suitable even in the presence of mechanical stress or prolonged operating conditions.

The material also offers good abrasion resistance, an important aspect when the handled fluid contains particles or elements that can contribute to the wear of the pump's internal surfaces.

Moreover, from an economic standpoint, PVDF generally has a lower cost than PFA. For this reason, it is frequently chosen when the application allows for a good level of reliability without resorting to materials with characteristics superior to the actual needs of the system.

The limitations of PVDF and situations in which to evaluate PFA in centrifugal pumps

Although PVDF is a widely used material in chemical applications, presents some limitations that must be considered when choosing the pump.

• The resistance to strongly oxidizing solvents and certain concentrated acids is lower compared to PFA: in the presence of particularly aggressive substances, this difference can influence the lifespan of the component and the stability of performance over time.
• Another element to evaluate concerns the maximum operating temperature: PVDF can operate over a wide temperature range, but exhibits lower values compared to PFA. When the process involves high temperatures combined with corrosive fluids, PFA can offer greater guarantees.

This does not mean that PVDF is a limited choice, but only that it is not 100% suitable for extreme chemical applications. It is still extremely compatible with a wide variety of pharmaceutical sectors and industrial ones. What is most important, when speaking of materials, is the correct initial evaluation, which makes it possible to avoid oversizing and to identify the material most consistent with the process.

For this reason, in the selection of Centrifugal pumps, the comparison between PVDF and PFA must start from the analysis of the handled substance and the actual operating conditions.

PFA pumps: enhanced protection for highly aggressive fluids

The PFA it is used in systems where the chemical aggression level of the fluid requires higher protection than PVDF: This material features a structure that guarantees high chemical inertia, allowing for work with substances that can compromise other plastic materials.

• One of the main advantages of PFA is its greater chemical resistance compared to PVDF. The material maintains good stability even with strongly oxidizing acids and particularly aggressive solvents, conditions that are frequent in specialized industrial sectors.
• The low permeability represents a further distinctive element: PFA restricts the passage of molecules through its structure, an important characteristic in processes where fluid purity and system protection play a significant role.
• Operating temperature is also a key factor. PFA retains its properties at higher temperatures than PVDF, thereby expanding the range of applications for pumps used in thermally demanding processes.

Due to these characteristics, the Centrifugal pumps with PFA components find a place above all in sectors where the fluid presents high corrosiveness or where process continuity depends on maximum compatibility between material and handled substance.

Factors to consider when choosing between PVDF and PFA in centrifugal pumps

As we have seen, PVDF and PFA have different characteristics; consequently, it cannot be said that one is a better solution than the other. Instead, the right choice exists based on the relationship between technical requirements, fluid characteristics, and system configuration.

The first element to analyze is, of course, the chemical nature of the fluid. Acids, bases, solvents, and oxidizing agents can behave very differently when they come into contact with plastics. Consequently, a preliminary compatibility test allows you to identify the most suitable material.

We've discussed the operating temperature, Another aspect concerns security and operational continuity of the system: A pump made of the right material reduces the risk of premature wear and helps keep the production process stable.

Of course, the budget is another factor to consider. PFA does indeed offer superior performance in terms of chemical compatibility, but it is more expensive than PVDF and other materials such as PP and ETFE. The choice must therefore take into account the actual operating conditions.

Finally, we must also consider the pump technology. The material must be evaluated in conjunction with the chosen configuration—for example, systems with magnetic drive or pumps equipped with mechanical seal—because the combination of technology and materials affects the overall performance of the equipment.

Typical PVDF applications: when it represents the most suitable solution

PVDF is used in numerous industrial sectors thanks to its ability to handle a wide range of fluids while maintaining a good balance between chemical resistance, durability, and operating costs.

• One of the main areas is industrial water treatment, where pumps are used to transfer and meter chemicals employed in purification and control processes. In these applications, PVDF must ensure good compatibility with various substances while maintaining stability even during prolonged operating cycles.
• PVDF is also used in systems dedicated to acid and base dosing. Its resistance to many chemical solutions makes it possible to create reliable systems for managing reagents used in production processes.
• Another sector involves standard chemical plants:  In these cases, PVDF is often chosen because it provides good performance without requiring materials with properties that exceed the application's needs.
• Materials such as PVDF are also used for handling moderately corrosive fluids. In these applications, the Centrifugal pumps With PVDF components, they offer a suitable solution for companies seeking reliability, durability, and a balanced return on investment.

Typical PFA applications: from fine chemistry to the most corrosive fluids

The PFA is used in applications where the fluid composition, temperature, or process conditions require superior protection. Its high chemical resistance makes it particularly suitable for industrial environments where highly corrosive substances are handled.

• One of the main sectors is fine chemicals, characterized by the handling of compounds with high levels of purity and specific formulations. In these processes, the material of the parts in contact with the fluid plays an important role in preserving the quality of the handled substance.
• PFA is also used with highly corrosive acids, including hydrochloric acid (for which we have the STN range in CDR) and sulfuric acid concentrated (which is why the CDR catalog includes the DTN-L pump). These substances can damage various materials and require solutions capable of maintaining stability over time.
• The pharmaceutical industry also uses systems made from fluorinated materials such as PFA, especially when high standards of purity, chemical resistance, and contamination control are required.
• Another area of application involves systems that use aggressive solvents and processes characterized by high temperatures In these scenarios, the PFA offers features that allow the Centrifugal pumps to work with complex fluids while providing greater protection for internal surfaces.

The choice of PFA is therefore recommended when the process involves particularly harsh conditions and when chemical compatibility is a critical factor in the pump's design.

PVDF or PFA: choosing the right material to enhance the reliability of centrifugal pumps

A comparison of PVDF and PFA shows how two seemingly similar materials can meet different industrial needs. PVDF it represents a suitable solution for numerous chemical applications where acid and base resistance, good mechanical strength, and a balanced performance-to-investment ratio are important. For this reason, it is used in water treatment plants, dosing systems, and chemical processes involving moderately aggressive fluids.

The PFA instead, it finds its use in the most demanding conditions, thanks to greater chemical resistance, better compatibility with aggressive solvents and strongly oxidizing acids, as well as the ability to work at higher temperatures. It is a frequent choice in the sectors of Fine chemicals, pharmaceutical and in applications where process continuity depends on the maximum protection of the wetted materials.

The selection between PVDF and PFA must therefore start from the analysis of the liquid characteristics, operating parameters, and the pump's construction technology. CDR Pompe, with vast experience in the design and sale of process pumps, supports companies and engineers in choosing the Centrifugal pumps most suitable, offering customized solutions, technical consulting, and dedicated support to ensure reliability and performance over time.

Contact us to learn more about all our services and to discover the pump with magnetic drive and mechanical seal that best suits your company's needs.

Frequently Asked Questions

What are the main differences between PVDF and PFA in centrifugal pumps for chemical fluids?

PFA has greater chemical inertia, low permeability, and maintains higher temperatures; PVDF offers a good balance between chemical resistance, mechanical strength, and lower cost. Both are fluoropolymers. PVDF is suitable for moderately aggressive fluids, PFA for solvents, oxidizing acids, and harsh processes.

Can PVDF pumps handle acids and bases without corrosion problems?

Yes, PVDF pumps are widely used with acids, bases, and moderately aggressive chemical solutions. However, compatibility depends on concentration, temperature, and process conditions. With highly oxidizing solvents or some concentrated acids, the resistance of PVDF is lower than that of PFA, so it is necessary to test the fluid.

When is it advisable to choose a centrifugal pump made of PFA instead of PVDF?

It is advisable to choose PFA when the fluid is highly corrosive, the temperature is high or maximum purity is required. Typical examples are hydrochloric acid, concentrated sulfuric acid, aggressive solvents, fine chemicals and the pharmaceutical industry. In these conditions PFA provides better protection for the internal surfaces and ensures process continuity.

Does PFA cost more than PVDF and is it worth the investment in process pumps?

Yes, PFA has a higher cost compared to PVDF, PP and ETFE, but offers superior performance in chemical and temperature compatibility. The investment is justified when working conditions are severe. With moderately aggressive fluids, PVDF avoids oversized components and guarantees reliability at a more cost-effective price.

Which factors should be considered when choosing between PVDF and PFA in a pump with magnetic drive or without a shaft mechanical seal?

The chemical nature of the fluid, operating temperature, safety and continuity of the system, budget and pump technology are all factors to be considered. The material must be considered in conjunction with the configuration, whether it is one-piece magnetic drive or not mechanical seal, because the combination affects the overall behavior. First, it is necessary to verify the chemical compatibility with the liquid.

Why is it important to check the chemical compatibility before installing a centrifugal pump?

The verification prevents unsuitable material from causing damage to internal parts, reduced performance, more maintenance, and the dispersion of fluids in the environment. It is necessary to analyze the composition, concentration, temperature, and operating conditions of the fluid. It is crucial in sectors chemical pharmaceutical and applications where process continuity is critical.