With plasma, components can be tempered with various coats. This is done by supplying gaseous and liquid starting substances. The raw materials, mostly short-chain monomers, crosslink in the plasma to form long-chain polymers. The selection of raw materials determines the coat characteristics:
Hydrophobic (water repellent) | Hydrophilic (water attracting / wetting) | Scratch protection, corrosion protection | Carbon coats | Barrier / Diffusion barrier | PTFE-like| Anti-friction coats / Nonstick coats | Adhesion promoter / Primer | Water / steam barrier | Metallisation | Nano-silver
Benefits of plasma coating
- Extremely thin coats in the nm range are possible
- Constant processes suitable for series production possible due to complete automation
- Wide range of variants are possible
- No temperature increase
- No solvents
- Excellent penetration into crevices and holes
- Suitable for piece goods and bulk material
Coating with plasma polymerisation
For coating with low-pressure plasma, gaseous or liquid monomers are introduced which polymerise under the influence of the plasma. The coating thicknesses achieved with plasma polymerization are in the range of one micrometre. The adhesion of the coatings on the surface is very good.
For coating with the Plasmajet process (atmospheric plasma), the gaseous monomers are introduced directly into the plasma jet by means of a carrier gas. Thus, the plasma focusses the monomer on the surface and polymerises it. The layer thickness is several hundred nanometres.
This process technology is much more complex than for activating and degreasing.
It is used for example to produce barrier coats in fuel tanks, scratch-resistant coats on headlights and CDs, PTFE-like coatings, hydrophobic coats, etc.
There are three coating processes that have established themselves on an industrial scale:
Hydrophobic coats ► Monomer: e.g. hexamethyldisiloxane (HMDSO)
PTFE-like coats ► Monomer: fluorinated process gases – also refer to epilamisation
Hydrophilic coats ► Monomer: vinyl acetate, hexamethyldisiloxane mixed with oxygen in a given ratio (significantly more HMDSO than O2)
Carbon polymer
Fluorine
Plasma
Tetrafluormethane CF4
FAQ Frequently Asked Questions
What effects can be achieved by coating metals using plasma polymerisation?
Coating metals using plasma polymerisation allows for various effects, e.g. activation lasting from one to several weeks, and the application of both decorative and functional coatings. A sputtering system is generally particularly well suited for use with metals.
Can plastics be coated using plasma polymerisation?
Plastics can generally be coated quite easily using plasma polymerisation. The Process Development department at Diener electronic will be happy to advise you on whether your specific requirements can be met.
For example, CDs and DVDs can be coated with a scratch-resistant layer without compromising their quality.
PTFE-like coatings can be applied to improve the lubricity of the treated items. Furthermore, it is possible to attach specific functional groups to the plastic surface (e.g. amino groups for bioanalytical applications).
Can glass and ceramics be coated using plasma polymerisation?
The only difficulty in coating glass and ceramics lies in preparing the surface appropriately (see the chapter on Activation and Etching). Once this difficulty has been overcome, there are no further obstacles to the wide range of applications for coatings. The specific adhesion strength of the coating must be tested on a case-by-case basis. In the event of ‘incompatibility’ between the coating and the substrate material, intermediate layers may need to be applied to act as adhesion promoters.
What types of coatings can be produced using low-pressure plasma, and which monomers are used for this?
Low-pressure plasma is primarily suitable for producing hydrophobic/hydrophilic, adhesive and anti-friction coatings.
Silicon- and carbon-containing substances are used as monomers. These include, for example, various acrylates and common silicon-containing monomers of the HMDSO type.
Which monomers must not be used?
Due to their highly toxic nature, halogen-containing gases and monomers (F₂, Cl₂, Br₂, I) must not be used with atmospheric plasma!
What coating thicknesses can be achieved using low-pressure plasma, and how can these be measured?
Depending on the coating, different coating thicknesses can be achieved; these depend on various factors, such as the geometry of the workpieces, the intended application, the flexibility and stability of the coating, and much more. Our Process Engineering department will be happy to demonstrate solutions for this.
Can powder be coated?
Yes, it is possible to coat powders using a specialised process. Diener electronic’s specialised systems for powders and bulk materials are designed for this purpose.
Can textiles be coated?
Diener electronic’s specialised roll-to-roll low-pressure coating system can be used to coat textiles. However, the processing time is not suitable for high-speed production. Textile coatings are generally neither washable nor abrasion-resistant.
