Surfac Prepration of Plastic Substrate
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Transcript of Surfac Prepration of Plastic Substrate
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Surface Preparation
Bhupendra Singh
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Work of adhesion
The work of adhesion (WA) WA = l (1+cos)
Where l = surface tension of the liquid,
measured in energy units; dynes/cm
= Contact angle of the liquid on the surface
The contact angle of a droplet of liquid on a flatsurface is a function of the energy levels of the
liquid and the solid.
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Contact Angle Diagram
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Various methods are used for the surface
modification such as
Solvent cleaning and etching Mechanical abrasion
Additives
Flame treatment
Corona discharge
Plasma treatment
Ultra violet irradiation
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Solvent cleaning and etching
Most common technique of surface treatment.
Grease and dust comes from various sources such asmold release agent, rust preventives, lubricants, dustetc
Solvents used: Isopropyl alcohol (IPA), Acetone,Methanol, Hexane, Ethyl Acetate, Toluene and otherorganic solvents.
Limitations of Solvent Cleaning Method: Many organic solvents are toxic
Most of the solvents are flammable
Some organic solvents can dissolve the plastic
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Corona discharge The most widely used method for improving the adhesion
properties of the plastic films prior to lamination.
This treatment is used for various polymers such aspolyolefins, polyesters, polyvinylchloride, nylon andothers
A corona discharge system consists of Generator:Amplifies the frequency to higher value of 25-30 kHz.
Transformer:Transformer increases the voltage to the required
voltage in the range of 15000-30000V
Treater
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Corona discharge Treater
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Corona discharge Treater
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Corona discharge Treater
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Corona discharge Treater
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Flame treatment Heat can be applied by means of
Hot air Infra red radiation
Flaming
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Flame treatment Initiation RH R + H R + O2 ROO
ROOH RO
+ OH
Propagation ROO +RH ROOH + R RO +RHROH + R OH
+ RH H2O + R
R + O2 ROO ROOH RO + OH 2 ROOH RO + ROO + H2O
Termination Termination takes place by a) Action of Antioxidant
HA + ROO
ROOH + A
A is inactive
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Flame treatment
Plastic sheeting
Idler roller
Gas / Air mixture manifold
Flame nozzle or bar
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Flame treatment
a) Flame Intensity
b) Air to gas ratio
c) Wall thickness
d) The design of the part
e) The type of flame used and
f) The distance of the burner from the
article for flame treatment
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Flame treatment
Benefits of the flame treatment
Higher treatment levels
Low treatment decay rates
Suitable for various product shapes and
sizes
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Flame treatment
Limitations of the flame treatment
1) Flame treatment is not suitable for mouldedthree dimensional.
2) Sheets having thickness less than 0.6mm are
not suitable for flame treatment.
3) Melting occurs if the flame is too close.
4) Open flame, particularly in or near a paintingoperation is usually forbidden for safety reasons.
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Flame treatment
Applications
1) Flame treatment is most often used to improve
ink adhesion to molded PE and PP surfaces.
2) Flame treatment is also used for acetal, acetal
copolymers and for polyethylene terephthalate.
3) Round containers can be treated on all sides by
rotating the container by dropping it through a ring
burner.
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