Chemical resistance is defined as a the degree to which a material resists chemical attack or reaction with a solvent. It is what determines how resistant to chemical corrosion a material is.
To test chemical resistance, a defined surface are of the material is exposed to a set amount and concentration of the chemical for a pre-determined length of time at a specific temperature. After this, the material is removed and examined for signs of corrosion, often down to a microscopic level.
Changes to the material that are observed can include anything from:
In general, thermoplastics have quite a high degree of chemical resistance, hence their usage in many industrial processes. Despite this, some thermoplastics display much higher chemical resistance than others and many are resistant to certain classes of chemicals.
Chemical resistance charts can be used to compare the resistivity of multiple plastic types to a large range of chemicals however it is always important to note under what conditions the resistance has been tested (e.g. temperature, duration).
3D printing filaments with the chemical resistance superpower display high resistivity to many chemicals. They are generally only attacked and corroded by very strong substances like Dimethylformamide or Chlorine.
Printing with chemically resistant materials is beneficial if you think your final product is going to be exposed to harsh solvents, acids or alkalis. Remember that chemical resistance will differ between materials and to some extent between different brands of the same material. Always check the Technical Data Sheet for information on chemical resistance. You can also check for chemical resistance charts for more information and comparison to other materials.