Chemical Compatibility Guide
Reference guide for Diaphragm Pumps and Piston Pumps
A = Excellent, B = Good, C = Fair to Poor, D = Not recommended, X or Brackets around a rating letter, no data is available, but the ratings are made on the basis of exposure test in similar chemical groups.
Only A Chemical Compatibility Guide
The chemical compatibility listings are intended as a guide only. We assume no liability for the accuracy of their use. The user should test under their own operating conditions to determine the suitability of any compound and material in a particular application.
Thermoplastic Elastomers (TPEs) vs Thermosetting Rubber Diaphragms
ARO is moving toward replacement of traditional thermoset rubber diaphragms with thermoplastic elastomers (TPE). Examples of TPEs include Santoprene®, Nitrile (TPE) and Hytrel®. TPEs are manufactured using a plastic injection molding process where the resin, or diaphragm material, is melted and injected into a mold to produce the diaphragm
Laboratory testing has shown:
Santoprene® outperformed all rubber diaphragms except Buna in the mild abrasive fluids. The Geolast diaphragm had equivalent life to the Buna diaphragms and was superior to the other rubbers compounds. PTFE with the Santoprene® backer exhibited the best flex life of all diaphragms during the test series.
Traditional thermoset includes Buna-N (TS), EPR, Neoprene®, Viton®
Thermosets diaphragms are constructed by sandwiching (laminating) a layer of fabric reinforcement between two sheets of unvulcanized rubber. These are placed in a mold and compressed under heat and pressure to bond and vulcanize the rubber.
|Limitations of the process include:||Results|
|Inclusion of fabric limits design flexibility to achieve optimum diaphragm shape||Lower flex life|
|Incomplete bonding can occur||Delamination|
|Inconsistent quality||Inconsistent life|
|“Wicking” of fabric||Delamination / Leakage|
Thermoplastic Compounds (TPE)
Thermoplastic elastomeric (TPE) diaphragms are manufactured using an injection molding process. The process allows the part to be molded in the shape and configuration required of the diaphragm to provide excellent performance and life. The TPE resins used to manufacture the diaphragms exhibit excellent dimensional and tensile characteristics eliminating the fabric reinforcement.
These materials are manufactured from natural rubber and man made additives to enhance resistance to various fluids. Diaphragms are manufactured using a compression molding process. A nylon fabric mesh is molded in the diaphragm to add strength to the compound.
PTFE is the most chemically inert man-made compound known. New diaphragm design and material processing have significantly improved flex life, which is now equivalent to or exceeding rubber compounds. A backer diaphragm is used to provide additional support.
* Not Available in all models
**Maximum temperature limits are based on mechanical stress only. Certain chemicals can significantly reduce the maximum safe operating temperature.
Halogenated Solvents Explosion Hazard
Pump models containing aluminum wetted parts cannot be used with 111.-Trichloroethylene, Methylene Chloride, or other Halogenated Hydrocarbon solvents that react and explode. Although manufacturers of those solvents typically add inhibitors to prevent a reaction, there is no assurance that they will prevent a reaction under all conditions. Special caution should be exercised when handling reclaimed or used solvents since the inhibitors are often degraded. Only Stainless Steel, Acetal, or PVDF pumps should be used for these materials. Other examples of Halogenated Hydrocarbon Solvents (H.H.C.) include, but are not limited to, the following: Trichloroethane, Methyl Chloride, Carbon Tetrachloride, and Chloroform Dichlorethylene.
Wet End Material Chemical Compatibility Guide
Polypropylene – A general purpose low cost material having broad chemical resistance for use in a wide variety of chemical applications.
Kynar (PVDF) – A high performance fluorpolymer resin with excellent chemical resistance properties. Used for pumping aggressive chemicals at elevated temperature. Material also has excellent mechanical properties.
Groundable Acetal – An excellent material for use in solvent transfer applications. The material incorporates metallic fibers in the resin to render the material conductive to eliminate static charge build up and potential static discharge.