Chemical resistant plastics

Chemical compatibility, chemical resistance and corrosion resistance are among the greatest advantages of plastics in comparision to metals. By choosing the right polymer family, the user can put himself in the position of being able to withstand even the harshest environmental conditions without the need for additional protection such as surface treatment, painting or cathodic protection. In our product portfolio you will find specific acid resistant plastic materials, polymers resistant to strongly alkaline media, including hot water and steam, as well as solvent resistant plastics. Users will also find they are able to choose a balanced chemical resistant plastic suitable for a variety of end uses.

The following tables give an indication of pH limits and substance categories to be used as a general guide to plastic chemical resistance, and to indicate where different product families may be used, under room temperature conditions with no mechanical load.
*Glass fibre reinforced grades show a sightly lower resistance to strong alkalis compared to unfilled grades.
**PVDF reacts sensitively to contact with hot alkalis by causing stress cracks when exposed to mechanical stress. The exposure limits are pH 12 and 40° C, neither one of which may be exceeded.

The term chemical resistance is generally used to describe the resistance of a material to the effects of chemicals. 

In most cases, inadequate chemical resistance shows itself by swelling or softening of the material, which can result in loss of mechanical properties and overall serviceability. The molecules of the medium diffuse into the space between the polymer chains and push them apart. Since most diffusion processes are temperature dependent, the chemical resistance specifications should always be considered in light of the temperature specified by the test conditions. Users should be especially cautious when using amorphous thermoplastic polymers in the presence of chemicals which can lead to stress crack formation and part failure. Microcracks can form, which can eventually grow into large crack networks under the influence of mechanical stress.

  • Neither water nor inorganic substances dissolved in water such as acids, alkalis and salts will attack thermoplastics to any major extent. Exceptions to this are alkalis in certain concentrations and at certain temperatures in the presense of PVDF, which will initiate the formation of stress cracks, and oxidizing media, which can cause stress cracks in PP and PE. Colour changes that might appear in contact with chemicals can indicate a change in a plastic's chemical resistance
  • The effect of organic media on thermoplastics is different from that of inorganic ones.   Organic chemicals and the molecular chains of thermoplastics can interact with one another.   This means that in addition to real signs of dissolution (for example in the case of methylene chloride and PVC), very often swelling may occur. Swelling (enlargement of the distances between the molecular chains) is a change in the volume and shape of a solid body under the influence of liquids, vapours or gases.
     Polymer chains also can become enveloped by some particular solvents.   In this context, it should be pointed out that swelling causes stresses due to changes in length however, most swelling of this type can be eliminated later by drying. 
  • In the case of mixtures of chemicals, it is generally not possible to reliably predict whether the thermoplastic will be subject to chemical attack, because in many cases unknown secondary effects occur. As an example, if concentrated hydrochloric acid is mixed with nitric acid in a ratio of 3:1, aqua regia forms, one of the most aggressive media in existence.   In such a case only PVDF can be used long term and only at 20°C, despite the fact that many thermoplastics are chemically resistant to each of these components individually.

The most important criteria for testing chemical compatibility are temperature, chemical concentration, exposure period, and mechanical load. The following table lists the resistance of various materials to different chemicals, with standard tests performed under standard atmospheric conditions 23 °C/50% r.h. in accordance with DIN 50014.

This information is provided to the best of our current knowledge and is designed to provide data about our products and their applications. It is thus not intended to provide any legally binding assurance or guarantee of the chemical resistance of our products or their suitability for a specific application. Any existing industrial property rights must be observed.

If you wish to verify the resistance of our materials to common sanitary or sterilisation methods used in the food, medical or pharmaceutical sector, click here:
If in doubt, where desired media, chemical concentrations, or temperatures are not listed, or when mixtures are involved, we hightly recommend testing on an individual basis to check material behaviour and possible unexpected interactions under realistic application conditions.