polymerization mechanism in adhesive

1. CHAPTER 2
POLYMERIZATION
MECHANISM
By Nur Isfarina binti Ismail

2. DEFINITION
 POLYMER: are macromolecular (large molecule)
which are long chain made up of combination of
many repeating units.
 MONUMER: small molecules that will be
polymerization to become polymer.
 HOMOPOLYMER: a polymer that derived from
polymerization of a single monomer.
 COPOLYMER: a polymer derived from
polymerization of more than one monomer.

3. MECHANISM OF ADHESION
• CHEMICAL BONDING
- primary bond: ionic, covalent, metallic bond.
- secondary bond: hydrogen bond, Van der
Waals bond.
• PHYSICAL BONDING
Mechanical interlocking
2. Diffusion theory
3. Adsorption theory
4. Electrostatic
1.

4. CHEMICAL BONDING
 Mechanism chemical bonds may across the
interface.
 Strong and significant contribution to the
adhesion in some across.
 Can be derived into 2 type:
1. Primary bond: ionic, covalent and metallic.
2. Secondary bond: hydrogen, Van der Waals

5. PHYSICAL BONDING
1.
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MECHANICAL INTERLOCKING
When surface are held together with adhesive
and the adhesive penetrate through the cavities
or porous.
Anchored the substrate and adhesive while
solidification.
The weakest part can be the strength of adhesive
when it bonded.
Rough surface increase area of physical contact.

6. 2.
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DIFFUSION THEORY
Based on solubility of one material to another.
The adhesive can diffuse into adherent surface if
it content adherent solvent with interlocking of
molecules.
One end of the molecules diffuses into the other
material.
Strong enhanced by heat and pressure.

7. 3.
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ADSORPTION THEORY
Bonding process of intermolecular attraction
between adhesive and adherent at interface.
The surface form are Van der Waals force.
The adhesive should have lower surface tension
than adherent to wet solid surface.
The adhesive applied to adherent spread
spontaneously when joined is formed.

8. ELECTROSTATIC
• The difference in electronegativity of adhering
material.
• Adhesive force attribute to the transfer of
electrons to form electrical charge at joint.
• Usually used in coating industry.
4.

9. MECHANISM FAILURE IN BONDED
JOINT
 Predominant mechanism of failure in adhesive
bonded are adhesive, adhesive-cohesive and
cohesive failure.
 It is cause by stress, fatigue, temperature and
etc.

10. CRITERIA OF GOOD ADHESIVE
BOND
 Adhesive must be soluble in adherent.
 Adhesive spontaneously wet the surface.
 Adhesive with right viscosity to the right adherent.
 The surface has microscopic roughness.
 Surface treatment

11. WETTING OF THE SURFACE
 The adhesive must wet the surface and applied in
liquid form.
 The viscosity of adhesive is critical to wetting, low
viscosity make more easy to wet to the surface.