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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

    cc

    cc

    cc

    cc

    CH4 /Ar

    Plasmac

    cc

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    c

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    cc

    cc

    cc

    c c c

    Plasma

    cc

    cc

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    cc

    OH O COOH

    cc

    cc

    cc

    cc

    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 (W) 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 ?

    PlasmaSpotLocal treatment of 3D parts

    Indirect

    PlasmaLineWeb activation without back treatment

    Indirect

    PlasmaZonePermanent 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

    10

    20

    30

    40

    50

    60

    70

    80

    0 50 100

    150

    200

    250

    300

    350

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    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 60C

    Aged 1 day 60C 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

    TetraethoxysilaneTE

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