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Coating Plasma Innovation

Atmospheric Plasma treatment, effect on the plasma chemistry on adhesion

Nicolas Vandencasteele

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Plasma

Applications

Adhesion improvement

Conclusion

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Plasma4th state of matter: ionized gas

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Cold atmospheric plasma

Energetic electrons chemistry

Cold:Tgas < 100 °CTions,neutrals < 100 °C Telectrons ≈ 10 000 °C

Atmospheric:Plasma gas is at atmospheric pressure Open reactor, high density of particles

Hot:Tgas ≈ Tions,neutrals ≈ Telectrons

104<T<108 °C

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Corona

High Voltage

Ambient airFilamentary discharge

• Used for activation or cleaning• Flat substrate• Most of the time need to be used

inline with other process• Gas used: none (ambient air)

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Plasma DBD

High Voltage

Controlled atmosphereHomogeneous discharge

• Used for activation or cleaning and deposition

• Flat substrate• Used online or offline• Gas used:N2, (Ar, He)

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Plasma vs Corona

Controlled chemistry Stable treatment

Surface energy measurements on BOPP film

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Plasma vs CoronaMicroscopy (AFM) image of BOPP film1 µm x 1 µm images (Tapping)

Identical discharge power

Es = 38 mN/mEs ≤ 30 mN/m Es = 60 mN/m

Untreated Plasma

DBD Corona

Controlled chemistry, homogenous discharge no surface damage

Process

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Plasma gas + dopant

Dopant:ppm of reactive gases mixed with plasma gas (only safe gas green top bottles)

APPLICATIONS

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Applications: Cleaning

Cleaned sample

CO2↗, H2O ↗ …

Contaminated surface

Plasma

Surface contamination

Removal of surface contamination without substrate degradation

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Applications: Grafting

C

O

C

O

C

O

C

O

H

CC

O

C

OO

C

O

C

O

H

C CC CC C

O

Amine Amide Imide

N

C

H H

C2O

C

NH

C

O

C

ON

C

H

C

Gas: N2 + dopants

Surface functionalization

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Applications: Grafting

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Amine Amide Imide

Qua

ntity

(a.u

.)

Grafting of nitrogen containing groups

Standard

Advanced 1

Advanced 2

Atom

ic %

(XP

S)

Dopant 2

Tunable surface functionalization

Dopant 1

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Applications:CoatingSpecific molecules (precursor ) are added to the plasma gas. Those molecules are activated ( ) by the plasma and react with the sample surface to form a thin film.

SiOx film (hydrophilic)HMDSO precursor

Coating nature dependend on precursor AND plasma chemistry

SiCyOx film (hydrophobic)

ADHESION IMPROVEMENT

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ECTFE – Surface energy increase

Very limited ageing after 3 weeks

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ECTFE – Adhesion increase

Different plasma chemistries

0

10

20

30

40

50

60

70

0

50

100

150

200

250

Untreated Corona Plasma 1 Plasma 2 Plasma 3

Surf

ace

ener

gy [m

N/m

]

Peel

For

ce [N

/m]

ECTFE laminate (Araldite 2028)

Peel Force Surface Energy

Surface energy is not the main factor improving adhesion

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ECTFE – Adhesion increase

Chemistry, not SE, is the main factor improving adhesion

0

2

4

6

8

10

12

0

50

100

150

200

250

Untreated Corona Plasma 1 Plasma 2 Plasma 3

at. %

N

Peel

For

ce [N

/m]

ECTFE laminate (Araldite 2028)

Peel Force %N grafted

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PET – Adhesion increase

Adhesion not always directly related to surface energy

0

10

20

30

40

50

60

0

100

200

300

400

500

600

700

800

900

1000

Untreated Corona Plasma a Plasma b Plasma c

Surf

ace

Enrg

y [m

N/m

]

Peel

For

ce [N

/m]

PET thermoset adhesive

Peel force Surface Energy

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PET – Adhesion increase

Chemistry, not SE, is the main factor improving adhesion

00.511.522.533.54

0

100

200

300

400

500

600

700

800

900

1000

Untreated Corona Plasma a Plasma b Plasma c

At. %

Nitr

ogen

Peel

For

ce [N

/m]

PET thermoset adhesive

Peel force Surface Composition

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Adhesion increase

Acrylic PETUntreated vs Corona 15%Untreated vs Plasma Up to 85%

Corona vs Plasma 35%

Thermoset PETUntreated vs Corona 200%Untreated vs Plasma Up to 2300%

Corona vs Plasma 800%

Araldite 2028 ECTFEUntreated vs Corona 1000%Untreated vs Plasma Up to 4870%

Corona vs Plasma 350%

Results depend on adhesive and plasma chemistries

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Conclusion

• Plasma treatment enables stable modification of surface energy

• Plasma allows to tailor the surface modifications to specific adhesive and substrate combination

• Level of adhesion can be controlled over a large range

• Plasma treatment can be applied to almost any materials (PEEK, Fluorinated polymers, PI, metals, paper…)