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Matting Agents for Coatings and Inks

In many coating applications, there is a preference in the market for matte finishes. Different methods and matting agents exist for indoor and outdoor coatings.

Get detailed information about the various types of matting agents used in coatings and inks and how to disperse a matting agent. Find out more about various methods to achieve a matted paint surface, what are the main factors which influence matt effect and quick overview of popular applications.

What is Matting Effect


Matting Agents for CoatingsIn our everyday life, we encounter many matt surfaces: at home, automobile finishes, on the way to work, or at night in restaurants. In our homes, most of the furniture has a matt appearance and when wood panels cover the sealing in a restaurant; they are more or less matt.

The choice between gloss or matt is not only influenced by factors relating to fashion and appearance; but practical issues influence our decision too, such as:

  • Clean-ability
  • Surface sensitivity, and
  • Haptic qualities

Economic efficiency is another important consideration when choosing between a glossy or matted surface. For example, in some coated applications, scratches, craters and impurities on the substrate are not easy to recognize after applying matted coatings, whereas this is not the case with glossy surfaces.

Now, find out more about matting effect. How to achieve a matted surface? And, what are main factors which influence matt effect? Let’s discuss them in detail…

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Like color, both matting and gloss are subjective impressions that are identified by our senses. Light is reflected from an even surface into our eyes and we categorize it according to its gloss. Strictly speaking, only part of the light falling upon a surface is directly reflected, the rest passes into the paint film and is internally scattered and absorbed by pigments and the substrate. (Dark yellow)

Light Reflection
The intensity of reflection depends on the degree of surface-smoothness


Mirrors, for example, are recognized as high gloss surfaces as they reflect light with high clarity. In contrast, when micro-rough paint films scatter light, only a reduced amount of light is reflected. In this instance, a yellow matt covering appears.

The conditions to obtain a perfectly matted effect are to scatter the incoming light. This means diffracting the directed light that illuminates the substrate. Otherwise, a substrate that would perfectly transmit the light would produce a gloss aspect.

Differents types of matting
Different types of matting
Matt effect
Matt Effect


The micro-roughness of the paint film surface is the reason why the light is scattered in a way that results in a matted surface.


How to Achieve a Matted Paint Surface?


Pumice flour has been used in the past to brush the dry paint film surface in one direction. The small scratches attained during this process created the fine, noble looking matted surface.

Nowadays, there is a wide range of objects produced with matted surfaces. Although some are complicated in construction, they are quickly manufactured. Additives based on silicas, waxes, organic materials and even fillers are added to the paint, to form a micro-rough surface after the drying process.

Matted Coating Formation
Matted Coating Formation


After applying a solvent-based paint:

  • The solvent immediately starts to evaporate
  • The viscosity increases, and
  • The print hardens up until the final dry, hard and elastic paint film

The evaporation of solvents causes the matting additives to be distributed throughout the whole film, making the paint film thinner.

This shrinkage is the main reason for creating a micro rough surface, or,
in other words, a matted paint film

The pictures explain why paints with high VOC content are easier to matt as systems with high solid contents. We can state: the higher the resin solid content of paints, the more difficult it is to produce matted surfaces. UV or EB systems show nearly no shrinkage, this is the reason why such systems are so difficult to matt.

Microtom cut of a paint film with matting agent
Microtom cut of a paint film with matting agent


Main Types of Matting Agents



Silica Matting Agent


In the broad field of obtainable silicas for matting there are two groups which differ in terms of their production process.

  • One is the hydro-thermal process, which produces silicas with a relatively soft morphology
  • By using the silica-gel process products can be obtained which have a harder morphology

Both processes can produce standard silica and after treated products. After treatment means that the silica surface can be partially modified with organic (waxes) or inorganic materials.

Compared to silica-gel matting agents, modified silica possesses a different particle size, particle size distribution, in the pore volume. Hydrothermal matting agents are different in particle size and distribution. We can also find untreated and treated materials.

Currently there is only one product popular for specific application, which is produced according to pyrogenic process, and shows a very high matting efficiency, especially in water-based systems.

Features of Silica Matting Agents


  • Silicas have a relatively high efficiency in terms of matting power
  • When used in higher concentration, an increase in viscosity could be observed
  • During storage they tend to build up sediment, this is particularly the case with untreated silicas. To avoid this tendency combinations of silicas and wax or pyrogenic silicas are used
  • It is possible to adjust the matting degree under angle of 45°, 60° and 85°
  • The coatings containing silica matting agents are recoat-able. All of them are 'stir-in' products

Synthetic Aluminum silicates are applied in emulsion paints primarily as a high-quality extender to partly replace the titanium dioxide. However, they may also be used to impart an evenly balanced matting effect into the dried emulsion paint. In long oil Alkyd systems, they work as a matting agent, but must be dispersed with pigment and fillers. Matting silicas are used in all-coating systems, though not in powder coatings.

Waxes as Matting Agent


In paints, coatings and inks, waxes based on Polyethylene, Polypropylene, Carnauba, and Amide are mostly used. Waxes products based on Polytetrafluorethylene (PTFE) are also used as matting agents.

In contrast to silicas, waxes modify the surface properties of a paint film by floating to the top of the surface. This phenomenon affects the following properties:

  • Degree of matt / gloss
  • Slip and mar resistance
  • Anti-blocking and abrasion properties
  • Anti-settling and surface tension

Most of the products are delivered as micronized products, which are available in a wide range of concentrates that are based on wax emulsions. Dispersions differ according to particle size and particle size distribution.

» View All Wax Grades Suitable for Use as Matting Agent 

Fillers as Matting Agents


Although the appearance of paints changes through the addition of previously mentioned matting additives, the performance is not affected. By using specific fillers, we clearly increase the Pigment-Volume-Concentration of paint involving with all the side effects it implies. That's the reason why this method of matting is limited for only pigmented, economical lower classes paint systems.

The fillers with preferential narrow particle size distribution must disperse together with the pigments. To adjust a required gloss degree, it is praxis to adjust it by using stir in Silica at the end of the paint production process.

Organic Materials as Matting Agents - With modern grinding techniques it is possible to grind plastic material based mainly upon Poly methyl urea resin. Such products have a low influence on viscosity, they show temperature stability up to 200°C, they have good solvent resistivity, and they are easy to disperse.


How to Disperse a Matting Agent?


While staying on the topic of matting agents they can be divided into two groups:

  • Stir in products, and
  • Products that must be dispersed together with pigments and fillers

About the second group, handing is not difficult. It is a matter of dispersing a sufficient quantity of the agent in combination with pigments and fillers using the right equipment (high speed dissolver, pearl mill, etc.).

The dispersion of stir in matting agents based on silicas, waxes or organic products can be done in three different ways:

Via Concentrates (Masterbatch)


There are positive and negative aspects related to masterbatch production.

  • Positive: Very easy handling of the concentrates, and also, that they can be incorporated using stirrers at a low agitation speed
  • Negatives:
    • Firstly, the matting agent content of the concentrates are usually not high, and
    • Secondly, the stability of the matting-pastes can be reduced during storage due to evaporation of the solvents from the concentrate surface. This causes a build-up of semi-dry lumps, which are difficult to disperse in the final paint.
    • Finally, if the paste contains resin it cannot be used universally.

Directly During the Production Process of Paints, or


Incorporation during the production process of the paints is a common method way of adding matting agents. Fluffy products should be incorporated in a low viscosity binder solution, via a stirrer or dissolver.

Most matting agents are designed for an easy dispersion process. For example, dispersing with a pearl mill will result in a greater reduction of the particle size, which leads to a higher level of gloss, and therefore higher dosing of matting agents are necessary to adjust the required matt degree.

At the End of the Paint Production Process to Adjust the Matt Degree According the User’s Request


To adjust the final matt degree through the incorporation of matting agents, it requires stir in products which can be easily dispersed using a simple stirrer. It is necessary, however, to ensure that there is enough space in the vessel so that the matting agent can be poured on the top and the vessel can be closed in order to avoid dust.

Periphery speed m/sec

Periphery Speed of Matting Agent

Peripheri Speed m/s


Controlling the Quality of Matting Agents Dispersion


When we use fillers as matting agents it is advisable to measure Grindometer or Hegmann value in order to receive information about the dispersing degree. Second, we can control the gloss degree at an angle of 60°.

For the other above-mentioned product groups, the main parameter should be the control of gloss behavior. However, to get an extensive understanding about the matt degree of the paint it is necessary to take measurements at angles of 60° and 85°. Sometimes here Grindometer values can be determined, too.

As long as there is no rule that is comparable with common paint systems, it is to accept. Values higher than 25 microns are usual e.g. by using silica-matting agents. If we reduce this Grindometer value, we will also reduce the matt effect and increase the gloss. Viscosity and transparency (for clear, sensitive applications) should be compared to a standard.


Parameters Influencing the Matt Effect


Users will usually test more than one quality of matting agent. They will evaluate products, different in chemical composition, production and concentration, and recognize during incorporation, differences in dispersing properties.

Matting Agent Concentration


Graphs below demonstrate the influence of the average particle size and concentration of a matting agent on the gloss effect.

Gloss Parameter
Gloss Parameter
Wax Parameter
Wax Parameter

The following rules apply:

  • The higher the matting agent dosing in a coating, the stronger the matting effect.
  • The matting power of matting additives depends on their chemical, morphological, and physical properties.

Matting Agent Properties


  • Matting agents with smaller average particle size do not give a quality matting effect, but they produce smooth paint films
  • In contrast, products with larger particle sizes are stronger in matting efficiency but the paint film surface is not so smooth. Matting agents with large particles show a tendency to build up separation and sedimentation in clear paint systems during storing time

Untreated silicas and fillers, in particular, need to be combined with anti-settling agent or fine particle size waxes to avoid these phenomena. Fine particle size waxes and easy to disperse hydrophobic pyrogenic silicas are recommendable, as they have a similar refractive index to these additives.

Matting Agents and Transparency


The equal refractive index of silica, wax and organic matting to resin systems which are commonly used in paints are one reason for their popularity. Substrates like wood, foils, and leather (natural & artificial) must be coated with transparent coating systems.

It is of prime importance to select an application that has little influence on transparency, and to choose a resin and matting agent which have similar 'refractometers', as this also improves the transparency of the system. The amount of matting agent added to the paint film also impacts upon transparency.

More efficient matting agents require lower dosing levels and
therefore provide better transparency
 

Paint System


Factors which typically impact upon the paint system are:

  • The binder system
  • The method of applying the paint
  • The film layer thickness, and
  • Drying conditions

The images below demonstrate the difference in matting effect in different paint systems with 10% matting agent base on Silica and the influence of different application processes on the matting effect

Difference in Matting Effect 

Sometimes paints are dried under different conditions, e.g. during week forced before weekend just air-drying. Different matt degree is the result. One can increase the same gloss effect by applying several layers of the same paint film. The graphics below demonstrate these effects.

Drying Conditions Resulting in Gloss and Matt Effect 

Popular Applications of Matting Agents


Applications of Matting agents

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