Adhesion is one of the essential properties in printing Ink and coatings industry that ensures the coating (or ink film) remains adhered to the surface for long especially under aggressive conditions.

1. By: Ir. Sugeng Endarsiwi, ST, MBA
(Certified Professional Engineer / PII)
Factor Influencing The
Adhesion of A Cured Film
Theory of Adhesion
https://coatings.specialchem.com/coatings-properties/adhesion

2. Adhesion in Printing
Ink & Coatings
• What is Adhesion of Coatings?
• Theories of Adhesion
• Adhesion Bond Failure
• Factors Influencing Adhesion
• Methods to Achieve Good Adhesion
• Test Methods to Evaluate Adhesion

3. • Adhesion of a coating refers to the strong bond between the coating
and substrate of a substance.
Adhesion is one of the essential properties in printing Ink and coatings
industry that ensures the coating (or Ink film) remains adhered to the
surface for long especially under aggressive conditions. The nature of
adhesion has a direct relation with the durability and quality of a coating.

4. The important requirement for most coatings and inks is that they form a
strong bond and adhere strongly to the substrate for long after the curing
and film formation* is complete.
The bond strength between coating and substrate is dependent on the two
properties of a material that include:
Adhesion – the bonding strength of an adhesive to the substrate surface
Cohesion – the strength of a bond between adhesive particles
* Film formation plays a key role in adhesion. Upon curing, several factors, such as shrinkage and pressure
impact film formation.
The key elements governing adhesion of coatings and inks
to the substrate include:
• Substrate-coating interface
• Composition of coatings and inks
• Film formation (must be such that the interface
becomes as strong as possible)

5. Theories of Adhesion
Many theories explain the mechanism of adhesion. The main theories based on which adhesion occur are:
Adsorption Theory –
A force of attraction between surface molecules and adherend at their interfaces i.e. intermolecular forces.
Chemisorption Theory –
An extension of adsorption theory in which adhesion occurs when chemical bonds are formed across the interface.
Mechanical Interlocking –
Molecule interlocking around irregularities on the surfaces/substrate.
Electrostatics (electronic) Theory –
Electrons are transferred from one surface to the other to build up dissimilar charges, exerting a force of attraction.
Diffusion Theory –
The adhesion of polymeric materials to the inter-penetration of chains at the interface.
NOTE: No single theory explains adhesion in a general and comprehensive way. Some theories are applicable for certain substrates and applications while
other theories differ based on different circumstances.

6. Theories of Adhesion
Many theories explain the mechanism of adhesion. The main theories based on which adhesion occur are:
Adsorption Theory –
A force of attraction between surface molecules and adherend at their interfaces i.e. intermolecular forces.
According to the adsorption theory, the two materials adhere to each
other due to attractive forces between the molecules of the materials.
The surface forces developed are designated as secondary or van der
Waals force. For these forces to develop, the paint molecules must make
intimate molecular contact with the substrate surface.
In addition, acid-base interactions and hydrogen bonds may also
contribute to intrinsic adhesion forces.
To obtain good adsorption, it is important to establish continuous contact between the paint film and the adherend so that Van der Waals force or the acid-base interaction or
both take place. This can be achieved by a phenomenon known as ’Wetting’.
Complete, spontaneous wetting occurs when Contact angle = 0°, or the material spreads uniformly over a substrate to form a thin layer. Wetting is favored when:
The substrate's surface tension, better known as the critical surface energy, C, is high
The surface tension of the wetting liquid is low

7. Theories of Adhesion
Many theories explain the mechanism of adhesion. The main theories based on which adhesion occur are:
Chemisorption Theory –
An extension of adsorption theory in which adhesion occurs when chemical bonds are formed across the interface.
The chemisorption theory is based on the chemical bonding
mechanism explaining that the primary chemical bonds may form
across the interface. The chemical bonds are strong contributions to
the intrinsic adhesion significantly.
Adhesion promoters work according to chemisorption theory. Adhesion
promoters are functionalized on one end to react with the substrate
and on the other end to react with coating.

8. Theories of Adhesion
Many theories explain the mechanism of adhesion. The main theories based on which adhesion occur are:
Mechanical Interlocking –
Molecule interlocking around irregularities on the surfaces/substrate.
According to the mechanical theory of adhesion, to function properly to achieve
optimum adhesion, the paint film must:
Penetrate cavities on the surface
Displace trapped air at the interface
Lock-on mechanically to the substrate
One way that surface roughness aids in adhesion is by increasing the total contact area between the paint and the adherend. Thus, the mechanical theory generally teaches that the
roughening of surfaces is beneficial as it:
Gives "teeth" to the substrate (mechanical interlocking), and
Increases the total effective area over which the forces of adhesion can develop.
Roughening is only effective if the coating wets the surface well.
Get the clues to improve the adhesion of your inks, lacquers, and others on metal substrates by better characterizing surfaces with a smart combination of AES, SIMS and XPS.

9. Theories of Adhesion
Many theories explain the mechanism of adhesion. The main theories based on which adhesion occur are:
Electrostatics (electronic) Theory –
Electrons are transferred from one surface to the other to build up dissimilar charges, exerting a force of attraction.
The electrostatic theory states that the electrostatic forces are formed
at the coating-adherend interface. The electrostatic forces account for
resistance to separation. The theory found that electrical discharges
take place when a coating is peeled from a substrate.
Electrostatic adhesion is regarded as a dominant factor in biological cell
adhesion and particle adhesion.

10. Theories of Adhesion
Many theories explain the mechanism of adhesion. The main theories based on which adhesion occur are:
Diffusion Theory –
The adhesion of polymeric materials to the inter-penetration of chains at the interface.
The fundamental concept of the diffusion theory proposes that adhesion occurs
through the inter-diffusion of molecules in the coating and adherend. The
diffusion theory is primarily applicable when both the coating and adherend are
polymeric having compatible long-chain molecules that are capable of
movement. Solvent cementing or heat welding of thermoplastics is a result of
diffusion of molecules.
Note: The electrostatic and diffusion theories of adhesion are generally not regarded as highly as the other theories in general bonding practice. However, there are certain
applications where these are very important and help explain why bonds form.

11. With strong adhesion, the
coating can prevent damage on
the surface. One notable
example is the use of coatings
in corrosion protection.
However, after prolonged
exposure to external factors,
such as water, humidity and UV
exposure, the coating adhesion
can be affected adversely. Also,
an improper selection of
coatings for a surface,
incompatibility of coating with
surface and inadequate surface
preparation can lead to
adhesion failures in coatings.
Adhesion Failure in Coatings
Adhesion Science: Principles & Practice by Steven Abbott

12. Methods to Achieve Good Adhesion
The following factors have predominant importance to improve adhesion:
• Wetting of the surface
• Surface treatment
• Structure of the materials to be bonded
Also, a variety of additives impact physical/mechanical properties which in turn can improve or worsen coating adhesion as listed here.

13. Factors Influencing Adhesion
There are several factors that lead to adhesion failure between paint film/coating and substrate as listed below.
• Poor substrate cleaning when soils that are not completely removed from the substrate prevent the coating from
bonding to the substrate surface.
• Surface profile, such as smooth surfaces that do not hold coatings well.
• Inappropriate wetting of coating on the substrate affecting surface bond and proper adhesion.
• Insufficient crosslinking or uncured coating/ over-curing of coatings leading to poor adhesion of the coating to the
substrate surface.
• External environmental factors such as water, humidity, UV exposure, etc.
These factors can lead to several surface defects and hence, adhesion failure. Some common surface defects are:
Blistering – Occurs when a coated object is immersed in water. Blisters are dome-shaped defects that appear on the
surface. Blistering is caused by water-soluble materials within or under the coating, rapid drying of coatings or chemical
exposure.
Peeling – Reduction in bond strength of the paint film due to contamination or incompatibility of coats.
Flaking – Causes the paint to become separated from the substrate.
Undercutting – Involves the corrosion buildup under coating.

14. https://www.linkedin.com/in/sugeng-endarsiwi-mba/
Author:
Sugeng Endarsiwi was born in Purworejo, Midst Java but when grow up live in
Banten west java. 18 years working at overseas as Printing Ink Manufacturer.
Vietnam for 13 years, and Malaysia for 4 years. During working overseas, He
also has project to completed to Sri Lanka, Philippine, Thailand and Singapore.
Graduated from Trisakti Printing Academy, Jakarta (ATGT), and Bachelor of Art
as Industrial Engineering from UMB, Jakarta. An Executive MBA graduated from
Jesselton University college, Malaysia.
• Certified Engineer at PII (The Indonesia Engineer Institution), 2022
• Chartered Management Association (CMA, HK SAR), 2022
Currently live in Tangerang, Indonesia after relocate from Malaysia since 2021.
Email address: endarsiwi.sugeng@gmail.com