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 customer can create a resistance which withstands even the harshest environmental conditions.  Additional protection such as surface treatment, painting or cathodic protection is not required. 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. Customers will also find they are able to choose a balanced chemical resistant plastic suitable for a variety of end uses.

The table gives 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.

Allowable pH range at room temperature

Polymer

pH range

 
  Lower Upper
PE, PP 0,5 13,5
POM-C 4 13
POM-H 4 9
PA 6, Pa 66, PA 6 C 4 12
PET, PBT 1 9
PVDF 0,5 13,5
PTFE 0,5 13,5
PPS 0,5 13,5
PEEK 0,5 13,5

*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 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.

Substance categories

PEEK

PPS

PPSU

PEI

PPE

POM-C

PP

PC

Acids - weak + + + + + + + (+)
Acids - strong (+) + (+) (+) (+) (+) -
Alkalis - weak + + + - + + + -
Alkalis - strong + + - - + -
Solvents - alcohol + + + + + + (+)
Solvents - ester + + (+) (+) -
Solvents - ether + + (+) (+) -
Ketone + + - - (+) (+) -
Water - cold + + + + + + + +
Water - hot + + + + + + + (+)

Influence of chemicals

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 usability. 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.

When a change in color occurs during a contact with chemicals, this can indicate a change in the chemical resistance of the plastic.

  • Inorganic acids, bases and salts are used either in their pure form or as mixtures. Basically, thermoplastics are well resistant to weak acids and bases as well as aqueous salt solutions. The concentration and the duration of contact with the plastic play a decisive role here. Detailed information on individual chemicals in our tables.

    Chemical resistance

  • Organic chemicals and the molecular chains of thermoplastics can react with each other. Therefore, alongside actual signs of dissolution (as is the case, for example, with methylene chloride and PVC), swelling can often occur. This swelling (enlargement of the distances between the molecular chains) is a change in volume and shape of a solid under the influence of liquids, vapors 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.

Chemical resistant products

Chemical resistant shapes

For more shapes choose "resistance" in the material selector

Chemical resistant filaments

Chemical resistant composites

More products and processing methods

To complement our products, we offer a comprehensive range of processing methods as well as customised profiles and tubes to meet your individual requirements for your finished part.

For detailed information, please contact us via our contact form.

TESTING

If in doubt, where desired media, chemical concentrations, or temperatures are not listed, or when mixtures are involved, we highly recommend testing on an individual basis to check material behaviour and possible unexpected interactions under realistic application conditions.

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.