Guide
Chemical resistance of plastics: reading the resistance list
How resistant is a plastic to a chemical? Semadeni's resistance list rates 26 plastics against individual substances at 20, 40 and 60 °C. This guide explains the classes a, b and c, shows values for common media and says where the list reaches its limits.
How do I read a chemical resistance list for plastics?
Semadeni's resistance list rates each plastic against an individual substance at a given concentration and temperature as a (very good resistance), b (limited resistance) or c (not resistant). The ratings apply to pure substances; mixtures, mechanical stress and the actual application can deviate and must be tested by the user.
Open the full resistance list (PDF in German, 35 pages)
The three resistance classes
a = very good resistance: no or only slight damage after exposure for more than 30 days.
b = limited resistance: with longer exposure, depending on the plastic, damage can occur, such as hairline cracks, loss of mechanical strength or discolouration.
c = not resistant: can lead to destruction of the plastic, deformation and the like.
What shifts the rating
- Temperature: The list gives values for 20, 40 and 60 °C. Caustic soda solution 50 %, for example, is rated a for PE-HD at 20 °C, b at 40 °C and c at 60 °C.
- Concentration: Many substances appear in the list at several concentrations. Nitric acid at 20 °C is rated a for PP at 10 %, b at 50 % and c at 65 %.
- Mechanical stress: Parts under stress can lose strength with certain media (stress cracking), even though they resist the medium alone and would withstand the stress alone. This applies especially to welded parts.
- Mixtures: All ratings refer to pure substances. With mixtures of substances, resistance can differ considerably from the list.
Extract from the resistance list, 20 °C
Open the full resistance list (PDF in German, 35 pages)
a = very good resistance · b = limited resistance · c = not resistant. Values for 20 °C from Semadeni's resistance list; the list also gives 40 and 60 °C and covers 17 further plastics. The ratings apply to pure substances and are recommendations without guarantee; users must carry out their own tests for the intended use.
How to use the list
- Find substance and concentration: The list is sorted alphabetically by substance (German names). If a substance appears at several concentrations, use the row that matches your concentration or lies above it.
- Read the operating temperature: Read the row for the actual operating temperature, not only 20 °C. Where there is no letter at 40 or 60 °C, the list gives no value.
- Compare materials: The columns show 26 plastics side by side, from ABS to silicone. The abbreviations follow ISO 1043 and are written out at the start of the list.
- Test the application yourself: The list is a pre-selection. For mixtures, welded or stressed parts and safety-relevant applications, your own test under operating conditions is required.
Limits of the list
All information in the resistance list is based on data and documents from the raw-material manufacturers or on many years of practical experience. It consists of recommendations without guarantee and does not release the user from carrying out their own tests for the intended use. No legal claim can be derived from it.
The full list as a PDF
The table above is an extract. The complete resistance list and technical information (PDF, 35 pages, in German) rates 26 plastics against several hundred individual substances at 20, 40 and 60 °C. It also contains the designations of the plastics according to ISO 1043, general and mechanical data, behaviour under temperature, notes on sterilisation and on cleaning and care.
Where PTFE and PVDF stand
In the extract, PTFE and PVDF are the plastics with the most a ratings. PTFE is rated a for every substance shown, including nitric acid 65 % and sulphuric acid 98 %. PVDF is not resistant to acetone and has limited resistance to nitric acid 65 %. PMMA, PC and PS are not resistant or have limited resistance to solvents such as acetone and toluene.
