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Adhesion in Printing Ink & Coating 2022.pptx

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Adhesion in Printing Ink & Coating 2022.pptx

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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.

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.

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Adhesion in Printing Ink & Coating 2022.pptx

  1. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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

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