cold atmospheric plasma technology for surface ... · • dbd plasma jet treatment was superior to...
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Cold atmospheric plasma technology for surface pretreatment and coating
Dirk Vangeneugden & Robby Rego
Surface Treatment - Paper 12.3
Paper 12.3 Dirk Vangeneugden & Robby Rego 2
Contents• Introduction to plasma technology
• Atmospheric plasma or advanced corona technology ?
• From tailored surface activation to in-line coating
• Envisioning future applications in flexible packaging
• Conclusions
Paper 12.3 Dirk Vangeneugden & Robby Rego 3
Introduction to plasma technology
Paper 12.3 Dirk Vangeneugden & Robby Rego 4
What is plasma ?• Next to solid, liquid and gas phase,
plasma is often referred to as the fourth state of matter
• A plasma is a (partially) ionised gas in which ions and electrons are present as well as radicals and molecules in an excited state
• In a “thermal” or “hot” plasma all species have approximately the same (high) temperature
• “Cold” or “non-equilibrium” plasmas have a high electron temperature but a low ion or gas temperature
Paper 12.3 Dirk Vangeneugden & Robby Rego 5
What is plasma ?
Paper 12.3 Dirk Vangeneugden & Robby Rego 6
How to generate a cold plasma ?• Cold plasma discharges can be
generated by stationary and pulsed (DC) or alternating (AC) electrical fields.
• Various electrical power supplies can be used to generate the plasma discharges: (pulsed) DC, DBD (corona), RF, microwave, ICP, …
• Although most applications are at low pressure, intermediate and atmospheric pressure applications are emerging.
Paper 12.3 Dirk Vangeneugden & Robby Rego 7
Plasma assisted surface modificationc c c
Cleaning, etching and sterilisation
Activation
Coating
O2 Plasma
N2 Plasma
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CH4 /Ar
Plasmac
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Plasma
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OH O COOH
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NH2 NO2NH
Paper 12.3 Dirk Vangeneugden & Robby Rego 8
Plasma assisted surface modification
Advantages
• Environmental friendly
• Allows to deposit coatings with unique properties
• Flexible switching between process conditions
• Reliable operation
• Energy efficient
Paper 12.3 Dirk Vangeneugden & Robby Rego 9
Why Atmospheric plasma technology ?Surface activation + coating technology
Cost
Vacuum plasma
Atm. pressure plasma
New
Flame treatment
Corona treatment
Added Value
Paper 12.3 Dirk Vangeneugden & Robby Rego 10
Atmospheric Plasma or Advanced Corona Technology ?
Paper 12.3 Dirk Vangeneugden & Robby Rego 11
Plasma discharges at ambient pressure • Direct current (DC) and pulsed DC discharges
• Hollow cathode discharges
• Dielectric barrier discharges (DBD)
• Radio frequency (RF) discharges
• Microwave (µW) discharges High Voltage
Al2O3
Carrier gasPrecursors
Plasma
Advantages
• Lower investment costs
• In-line processing
Paper 12.3 Dirk Vangeneugden & Robby Rego 12
Corona treatment• Corona treatment is one of the oldest industrial
applications of plasma technology
• It is commonly used for surface activation of plastic foils or textiles before printing, gluing or lamination
• Conventional systems resulted in a non uniform spot-wise surface treatment
• Today, most systems make use of the principle of dielectric barrier discharges which results in more uniform treatment and less degradation
Filamentary discharge
Paper 12.3 Dirk Vangeneugden & Robby Rego 13
Beyond state of the art corona• By controlling the gas atmosphere and electrical
conditions, one can increase the efficiency of the plasma surface treatment significantly
• By adding reactive chemical precursors to the plasma discharge, the surface chemistry can be controlled
• For such surface treatments, the stability in time can be much higher, even up to a level than can be assigned as “permanent”
• The technology opens up possibilities to deposit functional coatings in a continuous system at ambient pressure
Paper 12.3 Dirk Vangeneugden & Robby Rego 14
Direct or indirect plasma treatment ?
PlasmaSpot®
Local treatment of 3D parts
Indirect
PlasmaLine®
Web activation without back treatment
Indirect
PlasmaZone®
Permanent functionalisation and coating
Direct
Paper 12.3 Dirk Vangeneugden & Robby Rego 15
Principle of DBD plasma treatmentInjection of chemicals
Carrier Gas
HVHV
Coated foil
Plasma
Ceramic
• Same principle as industrial corona
• Carrier gasHe – Ar – N2 (– Air)
• Frequency range 250 Hz – 250 kHz
• High voltage range 1 kV – 40 kV
• Dissipated power 0.5 – 10 W/cm2
Paper 12.3 Dirk Vangeneugden & Robby Rego 16
Lab scale atmospheric plasma system
Automation software
Tailor made AFS power supply
Moving HV electrode
Gas flow control
Frame + exhaust
Paper 12.3 Dirk Vangeneugden & Robby Rego 17
Aerosol Assisted DBD Plasma Deposition
Liquid precursor
Purge gas
Aerosol generator
Moving electrode + dielectricum
Fixed electrode + dielectricum
Paper 12.3 Dirk Vangeneugden & Robby Rego 18
Semi-industrial roll-to-roll system
System specifications• Max web width: 600 mm• Line speed: 1 – 200 m/min
Paper 12.3 Dirk Vangeneugden & Robby Rego 19
New development: plasma slit torchSystem properties:• Width: 40 cm• Gas consumption (N2): 300 l/min• Variable power: 1000 – 5000 W• Special electrode design • Unique precursor injection concept
CFD modeling of internal pressure and gas flow
Paper 12.3 Dirk Vangeneugden & Robby Rego 20
From tailored surface activation to in-line coating deposition
Paper 12.3 Dirk Vangeneugden & Robby Rego 21
Current process developments for permanent surface modification• Surface wettability (hydrophylic, hydrophobic,…)• Adhesive coatings (printability,…)• Controlled release coatings • Barrier coatings (O2, H2O, oils, …)• Anti-corrosion coatings• Scratch resistant coatings • Antibacterial coatings• Bio-functional coatings • …
Paper 12.3 Dirk Vangeneugden & Robby Rego 22
Tailored surface activation • Example: activation of plastic
substrates for production of innovative micro arrays
• DBD plasma jet treatment was superior to conventional techniques for surface activation like UV-ozone or wet-chemical acid activation.
Paper 12.3 Dirk Vangeneugden & Robby Rego 23
Surface activation
0
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0 50 100
150
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550
600
650
700
750
time (h)
Surf
ace
ener
gy (d
ynes
)
Surface energy
Dispersive comp
Polar comp
Paper 12.3 Dirk Vangeneugden & Robby Rego 24
Surface activationSurface energy in function of scan speed
50
55
60
65
70
75
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20scan speed (m/min)
Surf
ace
ener
gy (d
ynes
)
Paper 12.3 Dirk Vangeneugden & Robby Rego 25
HMDSO release coatings on PET
0
50
100
150
200
250
300
350
PET
Targ
et
Peel
For
ce (c
N/2
0mm
) Initial
Aged 1wk 60°C
Aged 1 day 60°C as tape complex
Paper 12.3 Dirk Vangeneugden & Robby Rego 26
HMDSO coating deposition speed
0100200300400
500600700
800
0 20 40 60 80
treatment time (sec)
Thic
knes
s (n
m)
passes variationspeed variation
Paper 12.3 Dirk Vangeneugden & Robby Rego 27
Thickness evaluation by interferometry
140nm
Paper 12.3 Dirk Vangeneugden & Robby Rego 28
Thickness evaluation by interferometry
Paper 12.3 Dirk Vangeneugden & Robby Rego 29
Oxygen barrier coatings
S LPLAS LPLAEC projectDevelopment of Nanocomposite Hybrid Barrier Coatings on Plastic Films via an Aerosol Assisted Atmospheric Plasma Process • EC FP5 GROWTH project • Food and electronic packaging applications• Low cost, in-line deposition technology• Start: 01/04/2002 - End: 31/06/2005
Paper 12.3 Dirk Vangeneugden & Robby Rego 30
Oxygen barrier coatings
Precursors AlcoholCatalysts Stabilisors
Solution
Hydrolysis
OEtSiOx
OH
OH
OH
HO
HOOH
EtONano particle
Coating
Al(OC3H7)3Zr(OC3H7)4Ti(OC3H7)4
Si(OC2H5)4
H2N Si(OR)3
Si(OR)3
Si
O
OSi
R
R
OSi
O
O O
MO
OO
(RO)3Si O
O(RO)3Si
OO
Sin
R
Hybrid network formation
Sol-gel synthesis
GellingSol-gel system
Paper 12.3 Dirk Vangeneugden & Robby Rego 31
SEM pictures of plasma depositions
Silicon substrate
350
nm
Coating
Silicon substrate
TetraethoxysilaneTEOS
Methacryloxypropyl-trimethoxysilane
MEMO
Paper 12.3 Dirk Vangeneugden & Robby Rego 32
Sol-gel modification
O SiO
SiOSi
OSi
SiSi
SiSi
CH3
CH3
CH3
H3C
H3C
H3C
H3C
H3C
OO O
O
OO
O
O
O SiO
SiOSi
OSi
SiSi
SiSi
CH3
CH3
CH3
H3C
H3C
H3C
H3C
OO
O
OO
O
CH3 O
O SiO
SiOSi
O
Si
SiSi
SiSi
CH3
CH3
CH3
H3C
H3C
H3C
H3C
OO
O
O
OO
O
CH3
n
Bayresit
SiO
OO
OGLYMO
SiO
O CH3
PTMO
CH3
CH3
OO
OO
O NC
O HSi
O
O
GDMA silane
Si OO
O
O
MEMO
Inorganic cross-linker gives stable films in the plasma process
Paper 12.3 Dirk Vangeneugden & Robby Rego 33
O2-Barrier performance on BOPP
PP58pure
Plasma100 s UV
60 s UV
496
88 101
202
35 5947
1010
50
100
150
200
250
300
350
400
450
500
OTR
[cm
³/m²*
d*ba
r]
Bayresit/Memo50:50 20:80 Bayresit/GDMA
50:50 20:80 Bayresit/Glymo50:50 20:80
Bayresitpure
Film thicknessconventional: 10-30 µmplasma: 0,7-3 µm
Plasma cured
UV cured
Paper 12.3 Dirk Vangeneugden & Robby Rego 34
O2-Barrier performance on Arylite®
Arylitepure
Plasma100 s UV
60 s UV
1000
41 88
19 2110 35
1240
100
200
300
400
500
600
700
800
900
1000
OTR
[cm
³/m²*
d*ba
r]
Bayresit/Memo50:50 20:80 Bayresit/GDMA
50:50 20:80 Bayresit/Glymo50:50 20:80 Bayresit
pure
Plasma cured
UV cured
Film thicknessconventional: 10-30 µmplasma: 0,7-3 µm
Paper 12.3 Dirk Vangeneugden & Robby Rego 35
Chitosan based anti-bacterial coatings• Chitosan is obtained from
chitin, the second most abundant natural biopolymer after cellulose.
• Chitosan is an edible and biodegradable material, which also has antimicrobial activity against different groups of micro-organisms, both bacteria, yeasts and moulds.
012345678
No coating Chitosancoating
E.ColiB. Subtilis
Paper 12.3 Dirk Vangeneugden & Robby Rego 36
Plating experiments on CCA
Paper 12.3 Dirk Vangeneugden & Robby Rego 37
Biofunctional coatings
Bio-engineering by atmospheric plasma treatment
• EC FP6 NEST project • Immobilization of biomolecules in plasmapolymers• Development of low cost, one-step immobilization • Applications: bio-sensors, intelligent packaging, …• Start: 15/05/2004 - End: 14/05/2007
EC project BIOPLASMA
Paper 12.3 Dirk Vangeneugden & Robby Rego 38
Biofunctional plasma coatings• Selection of precursors that polymerize under mild
conditions in order not to destroy biomolecules• Determination of mild plasma conditions that allows
incorporation of biomolecules in plasmapolymers• Optimization of process conditions and type of precursor
for immobilization of biomolecules for specific applications
Paper 12.3 Dirk Vangeneugden & Robby Rego 39
Activity of immobilized enzymes
H2O2
DCFH-DA DCF
β-D-glucose β-D-gluconolactone
Glucose oxidase + O2
485 nm
530 nm
Paper 12.3 Dirk Vangeneugden & Robby Rego 40
Immobilization of BSA-FITCConfocal laser scanning microscopy
0 ng/cm² wet-chemical
~ 100ng/cm² in plasma coating
~ 1µg/cm² in plasma coating
Paper 12.3 Dirk Vangeneugden & Robby Rego 41
EC FP6 Project• Nanocomposite coatings based on inorganic
fullerene-like nanoparticles.• Enhanced reliability and durability of
mechanical components• Consortium: 30 partners (Renault, Rolls-
Royce, Fuchs, Goodrich …)• Start: 01/09/2005 - End: 01/03/2010
Incorporation of nano particles in plasma coatings
Paper 12.3 Dirk Vangeneugden & Robby Rego 42
Envisioning future applications in flexible packaging
Paper 12.3 Dirk Vangeneugden & Robby Rego 43
Improved adhesion In many multi-layered packaging materials delamination is still a topic of concern Tailored atmospheric plasma treatments could improve the adhesion significantly compared to the currently used flame, corona and/or (UV-) ozone treatments On the other hand, the use of chemical primer solutions could be reduced or even completely eliminated
Paper 12.3 Dirk Vangeneugden & Robby Rego 44
Controlled releaseReducing the adhesion properties is also possible by injection of adequate chemical precursors in the plasma discharge. This allows to control the release properties of materials (e.g. unwinding characteristics or peel-seal strength). Controlled release is also an important aspect for peal seals and reclosable packs.
Paper 12.3 Dirk Vangeneugden & Robby Rego 45
Alternative high barrier coatings
The actual barrier performance is still too low: log 2 reduction in oxygen transmission rate was obtained but log 3 to log 5 is often requiredCoating deposition rates (100 – 500 nm/min) are still too low which results in very low line speeds Current estimated costs are at least a factor 100 too high
Paper 12.3 Dirk Vangeneugden & Robby Rego 46
Biofunctional coatings
Chitosan based antimicrobial coatings as a food approved alternative for existing solutions involving migration of active substances (EC regulations)Towards smart and active packaging concepts for enhanced food quality monitoring (consumer driven)
Paper 12.3 Dirk Vangeneugden & Robby Rego 47
Conclusions
Paper 12.3 Dirk Vangeneugden & Robby Rego 48
Conclusions• Atmospheric DBD plasma processes, based upon
the same technology as current state of the art corona technology, offer new possibilities for sustainable dry surface engineering
• By controlling the gas atmosphere and the electrical conditions and by addition of reactive chemicals, one can increase the efficiency of the plasma surface treatment significantly and make the effects permanent
• The technology opens up new possibilities to deposit thin (bio)functional coatings in a continuous system at ambient pressure