Chemical Compatibility Guide
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This chemical compatibility guide is intended to serve only as a starting point to determine which flexible tubing material is most appropriate for your specific application. The data presented here should not be used as a substitute for thorough product testing in the environmental and operating conditions to which it will be exposed. Operating conditions to be considered include the pressure variation and temperature range that the tubing is exposed to, and whether the tubing will be permanently bent or cyclically flexed. Environmental conditions to be considered include whether the tubing is exposed to UV (sunlight) or excessive humidity. .
Chemical Resistance Basics
The ability of a polymer to withstand a specific fluid can be summarized into four broad categories:
| A | Excellent | Little to no effect over the entire service life |
| B | Good | Some degradation. Tubing may need to be replaced every few weeks/months |
| C | Fair | Use with caution. May work well in limited/controlled applications |
| D | Poor | Do not use at all |
There are three primary mechanisms of polymer degradation that have an influence on the ratings above:
Chemical Reaction
- Certain fluids will cause a change in the chemical structure of the polymer through the formation or breaking of bonds, resulting in a loss of physical properties and possibly the generation of toxic byproducts.
Swelling
- If a chemical is able to dissolve the polymer or be absorbed into the polymer matrix, swelling occurs. As the polymer swells, the distance between the polymer chains increases, causing the tube to soften and expand. If the tube is pressurized, the possibility of failure will increase.
Plasticizer Extraction
- Plasticizers are oily, low volatility additives used mainly in PVC to give it flexibility by allowing the polymer chains to slip past one another. Generally, when a tube has a higher plasticizer content, it will be more flexible and have a lower durometer.
- Since plasticizers are not chemically bound to the polymer, they can be removed by solvent extraction. This usually happens in combination with swelling. When the polymer swells, the plasticizers can more freely move around and may eventually leave the polymer matrix altogether. This process will cause the tubing to crack and become brittle over time.
- Since volatility is dependent on temperature, high temperatures can cause plasticizers to evaporate from the plastic in what is known as outgassing. *Note: High temperatures will also accelerate the rate at which chemical reactions, swelling, and extraction occur.
In a given class of polymers, there are hundreds, if not thousands, of commercially available formulations that impart specific advantages onto that resin, including causing it to be more or less resistant to certain types of chemicals. For example, in the case of thermoplastic polyurethanes (TPUs), polyether-based TPUs can more easily stand up to hydrolysis and microbial attack in wet environments, but are not suitable for use with oils and grease. Polyester-based TPUs typically function well with oil and grease but should not be used if they will be in frequent or continuous contact with water. Furthermore, even two ether-based TPUs having similar mechanical properties are not guaranteed to function in exactly the same manner in a particular set of conditions.
Disclaimer: The information in this guide is taken from outside sources that we believe to be accurate. However, Grayline does not warrant that the information in this guide is accurate or complete or that any material is suitable for any purpose. Grayline tubing products are sold upon condition that purchasers shall make their own assessment of suitability of specific tubing products for their particular application or use. Purchasers assume all risks and liability for the use of these products, including use in accordance with the seller’s recommendations.
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