surfac prepration of plastic substrate

8/14/2019 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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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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thanks

surfac prepration of plastic substrate

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