Ideal Filler Properties in Paint Formulations

Ideal Filler Properties in Paint Formulations 1. What is a Filler? According to DIN 55943, EN 971-1 and ISO 3262 Part 1, a filler is a substance consisting of particles that are practically insoluble in the application medium and is used to increase volume or improve technical properties and/or affect optical properties.

2. Why are Fillers Used in Paint?

Fillers are used in paint formulations for the following purposes: • To reduce costs, • To extend (dilute) primary pigments as extenders and diluents, • To improve or modify many functional properties of powder coatings. Most fillers are inorganic and generally in a completely oxidized state. They are heat-resistant, resistant to ultraviolet (UV) degradation and chemical effects, and do not interact with the binder system.

3. Filler Minerals

3.1. Calcium Carbonate Calcium carbonate is the most commonly used white filler in paints due to its low cost, high brightness for TiO2 extension, high purity, low abrasiveness and resistance to weather conditions. PCC and ultra-fine wet ground grades contribute to rheology and stability and provide good coverage and gloss retention. 3.2. Barite Paints and primers represent the largest use for filler-grade barite (barium sulfate). Micronized barite at high brightness is used as an extender to provide the weight that customers associate with quality and because of low binder demand for high loadings. 3.3. Kaolin The primary use of kaolin in coatings is as a TiO2 extender. Partially calcined grades generally provide the best elongation, durability and coverage. Water-washed and delaminated clays are used in water-based coatings to control gloss, film integrity, durability, scrub resistance, coating power, suspension capability, flow and leveling. 3.4. Talc The primary use of talc in paint is for gloss control. It also contributes to TiO2 extension, suspension stability, leveling, chemical resistance, film integrity and weather resistance. 3.5. Wollastonite Wollastonite is used as an extender pigment in coatings to provide resistance to sheen and early rusting. Its needle-like structure provides film durability and superior scrub resistance. Fine-ground and micronized grades provide smooth flow, water resistance, improved wet adhesion and good gloss in epoxy powder coatings. 3.6. Diatomite Diatomite is used to roughen the paint film to provide leveling and improved intercoat adhesion. It also increases film toughness and durability and helps control vapor permeability for less swelling and peeling. 3.7. Titanium Dioxide Titanium dioxide (TiO2) is the most important white pigment used in the paint industry. It is widely used because it effectively scatters visible light, thus imparting whiteness, brightness and opacity when incorporated into a paint formulation. Titanium dioxide is commercially available in two crystal structures: anatase and rutile. Rutile TiO2 pigments are preferred over anatase pigments because they scatter light more effectively, are more stable and are more durable. Titanium dioxide pigments do not dissolve in the paint formulations in which they are dispersed; accordingly, their performance properties, such as chemical, photochemical and physical properties, are in principle determined by the particle size of the pigment and the chemical composition of its surface. 3.8. Graphite Natural graphite can be used in steel structure maintenance coatings because of its flake structure and good coverage ratio. Its good conductivity and black color make it suitable for use in electronic and computer electrical protective coatings. This coating can contain up to 75% graphite. Another area of use is antistatic floor coatings. It can be used in heat-resistant coatings, primers, sealant coatings and water-resistant coatings. Due to its good light fastness, it can be used as an effect (visual effect) pigment in automotive paints.

4. Ideal Filler Properties

The properties of an ideal filler are: • Inert (inactive); * Does not interact with the binder system, * Lightness and non-fading, * Resistant to solvents, acids, alkalis and chemicals, * Heat-resistant, * Insoluble in water. • Fixed properties such as composition, particle size and low specific gravity, • Non-toxic and safe, • Non-abrasive, • Low cost. Other important filler properties that affect the smoothness, texture and gloss of paint are: • Particle shape, • Oil absorption rate, • Specific gravity. Particle shape affects the gloss, smoothness, texture and transparency of the paint. Oil absorption has a significant effect on the flow and smoothness of the paint. Specific gravity affects the coverage and application cost of the paint. [caption id="attachment_138829" align="aligncenter"] Table 1. Oil absorption rates of non-metallic fillers commonly used in paints[/caption] On the other hand, the particle size of a mineral can be expressed in various ways depending on the method by which it is measured. Common methods used to measure particle size are: • Hegman fineness, • Sieving, • Sedimentation and • Laser scattering methods. [caption id="attachment_138830" align="aligncenter"] Table 2. Filler particle size measurement methods[/caption] [caption id="attachment_138831" align="aligncenter"] Table 3. Properties provided by some fillers to paint[/caption]

5. Conclusion

A large number of natural minerals are used in paint formulations due to both their functional effect of filling volume and extending pigments and their impact on cost reduction. The contributions these minerals make to paint, such as adhesion, barrier properties, coverage, gloss, resistance to chemical effects and corrosion, are important. Furthermore, the particle shape, particle size, particle size distribution, density and oil absorption capacity of these minerals emerge as filler properties that must be considered in application. References 1.DIN 55943, Colouring Materials-Terms and Definitions, 19 p., 2001. 2.Douglas S. Richart, Using functional fillers in coating-powder formulation, Powder Coating, February 1998. 3.EN 971-1, Paint and Varnishes-Terms and Definitions for Coating Materials- Part 1: General Terms, 33 p., 1996. 4.ISO 3362-1, Extenders-Specifications and Methods of Test-Part 1: Introduction and General Test Methods, 6 p., 2020. 5.RT Vanderbilt Company, Inc., An Introduction to Mineral Fillers for Paints & Coatings. 6.VINCENTZ, Detlef Gysau, Filler for Paints, 3rd Revised Edition European Coating Library. 7.https://www.tipure.cn/-/media/files/tipure/legacy/titanium-dioxide-for-coatings.pdf?rev=70975dd1245f4082841a13ef41058282 (18.10.2021) 8.https://www.european-coatings.com › Buecher (21.02.2022) https://coatings.specialchem.com/selection-guide/fillers-selection-for-paints-coatings (21.02.2022) 9.https://www.alpapowder.com (21.02.2022) Prof. Dr. Öner Yusuf Toraman Niğde Ömer Halisdemir Üniversitesi Mining Engineering Department