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Corona and Plasma Technology
Scanmaster Seminar
Anno 2016
Why Surface Treatment ?
Improved Adhesion Improved Wettability Surface Cleaning
Overview Surface TreatmentSurface Treatment Technologies
Cleaning Solvent based cleaning liquidsWaterbased cleaning liquides
Mechanical Surface Treatment Sand blastingBrushingBlasting
Chemical Surface Treatment Chemical PicklingReactive gasses
Thermal Surface Treatment Gas Flame Treatment
Electrical Surface Treatment Corona Discharge-Free air Discharge-DBD (Dielectric Barrier Discharge)-Nozzle Plasma-Arc corona
Low pressure Plasma-with non polymerized gasses-with polymerized gasses
Coating MetalisingNon Metalic coating -Anorganic coating-Organic coating-Painting with colour-Primer
High energy sources/beam Electron beamLaserUV
The SurfaceOuter surface layers play an important role to surface properties
”uncleanness” like dust, dirt oil etc. >1µm
Adsorption layers, such as gasses and moist 1-10nm
Reactive layers, like oxides,
additives, release agents etc. 1-10nm
Adhesion point – surface
Modified polymer structure
Non modified polymer
material.
The Surface
Bild: Dipl.-Ing. (FH) Simone Fischer
Substrate surface
Roughness &Gloss
CorrosionOptical propertiesDiffusion
OxidationCorrosion Passivierung
1st atomic layerAdhesion WettabilityKatalyseBioverträglichkeitMikrorauheit
Reaction on the Surface
Surface treatment
Bild: Dipl.-Ing. (FH) Simone Fischer
- Radicals created by the plasma discharge breaks the polymer bonds on the surface.
- Oxygen containing groups will be introduced into the polymer surface
� Increased wettability on the polymer surface
Surface Energy ExamplesSurface Energy – Polymers Necessary surface energy for
successful bond with :
PTFE < 20 mN/m UV based inks 48-56 mN/m
Silicone < 20 mN/m Water based inks 50-56 mN/m
PP 30 mN/m Coatings 46-52 mN/m
PE 32 mN/m UV based adhesives
44-50 mN/m
PS 34 mN/m Water based adhesives
48-56 mN/m
PC 34 mN/m
ABS 34 mN/m
XLPE 32 mN/m
PUR 34 mN/m
Wettability Surface Pre-Treatment effect on the wettability of Polymer surfaces
Impro
ved a
dhesio
n
Increased surface pre-treatmentBild: Dipl.-Ing. (FH) Simone Fischer
Polymer surface
Surface Energy
Contact Angle:
� The wettability can be measure using contact angle
meters
� Both Polar and Non Polar measurements are
possible
� The contact angle is measure as the tangent line
from the ”coroner of the water droplet”
Surface EnergyNorms for measuring surface energy
� The measured value is referred to as mN/m or
dyne/cm
� If the dispensed liquid pulls together and forms
droplets (within 2-3 seconds) the value is not
achieved
� This type of surface measurement is based on ISO
8296. Method for determining surface energy on PE
film.
Surface Energy
Low Surface Energy Liquid does NOT wet the surface
High Surface EnergyLiquid does wet the surface
Surface EnergyMeasuring the cleaning effect on Stainless steel
Surface Energy - Conclusion
NOTE!
� A high Dyne level (mN/m) does not automatically mean
that good adhesion is guaranteed
� Test inks can be used, with background in adhesion tests,
to verify treatment levels
� Test inks can ”detect” dirty areas on the material.
� Adhesion tests is always recommended
Over Treatment
Treatment time
Over Treatment
Surface Energy
Adhesion
Shelf Life of Surface Treatment
Shelf Life
Pulling force MPa
Shelf Life of Surface Treatment
The shelf life of treated surfaces is very different and varies
from minutes to years. Most materials is in the range ”weeks”
Factors:
� Material
� Surface treatment method
� Plasma vs. Gas flame treatment
� Level of additives
� Age of polymer on time of treatment
� Air humidity
� Temperature
� Etc.
Corona vs. Plasma Treatment
What is the difference between Corona and Plasma Treatment ?
Everything is a Plasma and for instance Corona is just a part of a Plasma !
Plasma Treatment
Corona – Low frequency
DBD – Dielectric Barrier Discharge
Corona – High frequency
Jet System –
Atmospheric Plasma
Gas flame treatment
Vacuum System