PP / PVDF
PP is the economical option, resistant to most acids and alkalis. PVDF offers broader resistance and high temperature performance.
Technical Guide
Material Compatibility
Guide
Chemical resistance guide for PP, PVDF, aluminum, SS316L body and PTFE, EPDM, NBR, FKM, Santoprene diaphragm.
Material Selection
Right Material =
Long Pump Life
Incompatible pump casing and diaphragm materials are the cause of swelling, cracking, corrosion and premature failure. The chemical composition, concentration and operating temperature of the fluid should be considered together in material selection - a compatible material at room temperature may become incompatible at high temperature.
It is not only the casing that comes into contact with the fluid: the diaphragm, seal, O-ring and valve ball can also be of different materials. The life of the pump is determined by the weakest component, so each wetted part must be verified individually. The summary and elastomer table below is a starting point - for specific fluids refer to the full chemical compatibility table.
- PP (Polypropylene): acid, alkali, salt solution compatible; aromatic solvent incompatible
- PVDF: broad chemical resistance including strong acids, halogenated solvents
- Aluminum: neutral fluids; acid, alkali and brine incompatible
- SS316L: mild chemicals, food; HCl and chloride environment incompatible
- PTFE diaphragm: widest chemical resistance, -200°C to +260°C
- The weakest wet component determines pump life - verify them all
Material Summary
Body and Diaphragm
Material Comparison
Alüminyum / SS316L
Aluminum for mechanical strength; suitable in neutral fluids. SS316L hygienic option for food and light chemicals.
PTFE Diyafram
Widest chemical compatibility. Preferred in strong acids, bases and solvents. Price is higher than others.
EPDM / NBR Diyafram
EPDM is compatible with hot water and steam, for food applications. NBR is suitable for hydrocarbon and oil transfer.
Aperture Selection
Elastomer / Diaphragm
Selection Guide
| Diaphragm | Most Suitable | What to Avoid | Max. Temperature |
|---|---|---|---|
| PTFE | Acids, bases, solvents, ketones - almost all chemicals | - (not flexible; need support diaphragm) | ~+200°C |
| Santoprene (TPE) | Acids and bases (NaOH, sulfuric, HCl); general purpose, FDA option | Oil and hydrocarbons | ~+135°C |
| EPDM | Water, steam, dilute acid/base, alcohol, polar solvent | Oil, fuel, hydrocarbon | ~+150°C |
| NBR (Buna-N) | Petroleum, oil, fuel, gasoline, motor oil | Strong acid, ketone, ozone | ~+100°C |
| FKM (Viton) | Hydrocarbon, oil, fuel, aromatic; many acids; high temperature | Ketone (acetone, MEK), hot water/steam | ~+200°C |
| Neoprene (CR) | Water, seawater, dilute chemicals; economic general purpose | Strong oxidizer, aromatic solvent | ~+120°C |
Material Questions
Material Selection
Questions
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For most acids, PVDF is the safest casing choice. PP may be adequate in low and medium concentration acids; in strong base (caustic) environments PP is safer than PVDF. For special cases such as hydrofluoric acid (HF), the chemical compatibility table should be consulted.
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For clean, neutral water (pH 6-8), an aluminum housing is suitable. Salt water, acidic or alkaline water will quickly damage aluminum; SS316L or plastic (PP/PVDF) housing is recommended for salty and chloride environments.
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They all come into contact with the fluid, so the casing, diaphragm, seal, O-ring and valve ball must all be individually matched. The life of the pump is determined by the weakest component in contact with the fluid - even if the casing is durable, a mismatched diaphragm will lead to premature failure.
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PTFE withstands almost all chemicals (acid, base, solvent, ketone) and is the widest choice. Santoprene is strong in acids and bases (NaOH, sulfuric, HCl); EPDM is good in water, steam and dilute acid/base but not in oil and hydrocarbon. NBR (Buna-N) for petroleum, oil and fuel; FKM (Viton) is suitable for hydrocarbon and high temperature but not for ketones (acetone, MEK).
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In non-chemical or mild chemical applications EPDM is economical and sufficient. In aggressive chemical, high temperature or ATEX applications, the additional cost of PTFE is more than offset by long life and safety.
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As the temperature increases, the chemical resistance of the material decreases: the chemical penetrates faster into the polymer, swelling and softening increase. A material that is compatible at room temperature (20-25°C) may become incompatible at high temperature. In practice, if the operating temperature is above 20°C, it is necessary to interpret the compatibility grade one grade lower and not exceed the maximum temperature limit of elastomers (e.g. NBR ~100°C, PTFE ~+200°C).
Information Center
Related Guides
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ReviewChemical Compatibility Chart
Check the chemical resistance of the pump casing and diaphragm material as A/B/C/D from the table.