Certain materials are better suited to cleanrooms than others, as the extent to which particles are released, for example through friction, varies from material to material. However, outgassing behavior, chemical, biological and microbial properties and cleanability are also important when selecting the right cleanroom material. The following article looks at which cleanroom-compatible materials are available, how they are tested and what standardization exists in this regard.

Materials used in the cleanroom

The following materials in particular are used in the cleanroom:

  • Metals
  • silicate materials
  • Plastics

Stainless steel is the most commonly used metal in cleanrooms. A basic distinction is made between different types of stainless steel. Austenitic stainless steels are used in cleanrooms, such as those with the material number 1.4301 or 1.4404. Stainless steel is used, for example, to manufacture cleanroom furniture.

Silicate materials include, in particular, glass, which is often used in cleanrooms to separate rooms, usually in the form of toughened safety glass (ESG).

When it comes to plastics, thermosets are used in the cleanroom, for example. Thermosetting plastics include epoxy resins, for example. In cleanrooms, floor coverings in particular are made of these plastics. However, plastics are also used in dispenser systems for consumables in the cleanroom; or in cleaning trolleys, for example.

Unsuitable for cleanrooms is the use of wood, for example for furniture, or the use of cardboard boxes. This is because wood and cardboard give off a lot of particles when used in certain ways.

Test methods for cleanroom materials

The Fraunhofer Institute for Manufacturing Engineering and Automation (Fraunhofer IPA) has developed standardized test methods to enable a comparable selection of materials for cleanroom construction and operation. These test methods for analyzing and validating cleanroom materials were developed as part of the CSM industry association, which was founded in 2003 by Fraunhofer IPA together with industrial partners from the cleanroom sector. CSM stands for “cleanroom suitable materials”.

The test methods were developed for the following points relevant to cleanrooms:

  • Particle emission
  • Outgassing
  • Chemical resistance
  • Biological resistance
  • Microbicidal properties
  • Cleanability

The particle emission of materials in the cleanroom, which is caused, for example, by rolling friction and sliding friction of rollers on a cleanroom floor or by static friction when walking with shoes on this floor, is tested by the Material-Inspec test bench developed by Fraunhofer IPA.

In terms of outgassing, the emission of volatile organic compounds (VOCs) from the materials to be tested is examined. VOCs are airborne organic contaminants.

When testing chemical resistance, the respective material is examined with regard to its reaction to the following chemicals, which can be found in cleaning agents and disinfectants:

  • Formalin
  • Hydrogen peroxide
  • Peracetic acid
  • Isopropanol
  • Caustic soda
  • Ammonia
  • Sulphuric acid
  • Hydrochloric acid
  • Phosphoric acid
  • Sodium hypochlorite

Biological resistance testing examines whether the material in question is inert to molds and bacteria and whether microorganisms can metabolize the material.

When testing the microbicidal properties of a particular material, it is examined whether the surface of the material is able to kill bacteria and fungi.

The cleanability test checks how effective wipe cleaning is on the material to be tested. Three damp wiping processes are carried out and then any residual soiling is examined.

Standardization of cleanroom material testing

As far as the standardization of cleanroom materials is concerned, the guideline VDI 2083 Sheet 17 is particularly relevant, which bears the German title “Reinraumtechnik – Reinheitstauglichkeit von Werkstoffen”. The English title is “Cleanroom technology – Compatibility of materials with the required cleanliness”.

The publisher of the guideline VDI 2083 Sheet 17 is the VDI Society for Construction and Building Technology (VDI-GBG). VDI stands for Association of German Engineers. Experts from the fields of architecture, construction, technical building services and facility management, including architects and engineers, work together in the VDI-GBG.

Specifically, the guideline VDI 2083 Sheet 17 deals with the contamination of materials and the cleanability of surfaces, among other things. The guideline also contains the definition of the cleanliness suitability and cleanroom suitability of materials, together with the procedures used to determine the cleanroom suitability of certain materials.

Furthermore, the directive offers the possibility of classification, as it can be used to determine a material index (ISOm class), which can be used to compare the different materials with regard to their possible particle release under tribological load.

Material questions answered by abovo

The question is not only which materials are suitable for the cleanroom, but also which material is best suited for the specific application in the cleanroom.

The abovo team will be happy to advise you at any time on which materials are best suited for your cleanroom applications. Simply contact us by e-mail or telephone without obligation.