Beschichten durch Plasmapolymerisation
Haftungsprobleme
Hydrophile Oberflächen
Hydrophobe Oberflächen

Coating by plasma polymerization with a low-frequency, or high-frequency generator

Coating by plasma polymerization with microwave plasma

1. How does coating by plasma polymerization work?

For coating with low-pressure plasma, monomers are introduced (either gaseous or liquid), which then polymerize 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.

The process is much more complex than for activating and degreasing.

For example, barrier coatings can be produced in fuel tanks, scratch-resistant coatings on headlights and CDs, PTFE-like coatings, hydrophobic coatings, etc.

There are three coating methods which have become established on a large scale:

Hydrophobic coatingsMonomers: e.g. hexamethyldisiloxane (HMDSO)
PTFE-like coatingsMonomer: fluorine-containing process gases - see also epilamization
Hydrophilic coatingsMonomers: Vinyl acetate, hexamethyldisiloxane defined mixed with oxygen (significantly more HMDSO than O2)
ApplicationGroupMaterialType of gasPressure [mbar]Performance [%]Time [Min]
Coating processMetalAluminiumHMDSO + O20.1 - 0.550 - 1001 - 60
Stainless steelHMDSO + O20.1 - 0.350 - 1001 - 60
PlasticPlasticHMDSO + O20.1 - 0.550 - 1001 - 60
PlasticC4F80.1 - 0.550 - 1001 - 60
GlassGlassC4F80.1 - 0.550 - 10030 - 120
Special process
Special process1. Activation5 minutes O2
2. Coating process5 minutes HMDSO
3. "Etching"12 seconds O2
4. Coating process5 minutes HMDSO
5. "Etching"12 seconds O2
6. Coating process5 minutes HMDSO

2. What effects does the coating of metals by means of plasma polymerization permit?

The coating of metals by plasma polymerization allows various effects such as one to several weeks sustained activation and functional coatings in addition to the application of decorative coatings.

A sputter system is generally suitable, especially for metals.

GroupMaterialType of gasPressure [mbar]Performance [%]Time [Min]
MetalAluminiumHMDSO + O20.1 - 0.550 - 1001 - 60
Stainless steelHMDSO + O20.1 - 0.350 - 1001 - 60

(The process parameters including performance and time must be adjusted to take account of the equipment specification (generator type and strength, electrode assembly) as well as the material properties of the workpiece).

Mix the gases as follows for a durable hydrophilic coating with HMDSO: HMDSO : O2 = 1:4

Mix the gases as follows for a durable hydrophobic coating with HMDSO: HMDSO : O2 = 4:1

3. Can plastics be coated by plasma polymerization?

Plastics can generally be coated by plasma polymerization in an uncomplicated way.

So CDs and DVDs, for example, can be given a scratch-resistant coating without their quality suffering.

PTFE-like coatings can be applied to increase the low-friction characteristics of the treated products. Furthermore, it is therefore possible to attach functional groups to the plastic surface (e.g. amino groups for bio-analytical applications).

GroupMaterialType of gasPressure [mbar]Performance [%]Time [Min]
PlasticPlasticHMDSO + O20.1 - 0.550 - 1001 - 60
PlasticC4F80.1 - 0.550 - 1001 - 60

(The process parameters including performance and time must be adjusted to take account of the equipment specification (generator type and strength, electrode assembly) as well as the material properties of the workpiece).

The polymerization can also be carried out in several stages:

Example:

1.Activation5 minutes O2
2.Coating process5 minutes HMDSO
3."Etching"12 seconds O2
4.Coating process5 minutes HMDSO
5. "Etching"12 seconds O2
6.Coating process5 minutes HMDSO

 

Then possible curing of the coating with a few seconds of oxygen plasma. In this step however, the coating becomes hydrophilic!

4. Can glass and ceramics be coated by plasma polymerization?

The only difficulty when coating glass and ceramics is to prepare the surface accordingly (see Activation and Etching). Once this difficulty has been overcome, there is nothing to prevent applying a variety of coatings. The respective adhesion of the coating must be checked in each case. If "incompatibility" occurs between the coating and substrate material, intermediate layers may possibly have to be applied as a bonding agent. An example of a successful hydrophobic and oleophobic coating is shown in the image.

GroupMaterialType of gasPressure [mbar]Performance [%]Time [Min]
GlassGlassC4F80.1 - 0.550 - 10030 - 120

(The process parameters including performance and time must be adjusted to take account of the equipment specification (generator type and strength, electrode assembly) as well as the material properties of the workpiece).

5. Can textiles be coated by plasma polymerization?

Textiles can be very well coated in plasma. The difficulty remains in achieving long-term stability of the coatings against surfactants. Hydrophobic coatings can be achieved by the application of fluorine-containing gases/monomers.

6. Which applications are possible?

For more information, see "Applications".