Powder Coating Pigments
In previous issues of Boyatürk magazine, we focused on the pigments used in paints, their color indices and their properties. Also in earlier issues, we discussed the industrial pigments manufactured by Sudarshan and their properties.
Assoc. Prof. Gürses Öner - Regional Director Turkey and North Africa - Sudarshan Chemical Industries Ltd.
Powder Coatings and Pigments
In previous issues of Boyatürk Magazine, we have discussed pigments used in paints, their colour indices and properties.
In previous issues, we also described industrial pigments produced by Sudarshan and their properties.
In this article, we will focus on Sudarshan pigments that can be used in powder coatings, which have emerged as a symbiosis of the paint and plastics industries, and the properties to be considered when selecting these pigments.
When discussing industrial paint pigments, we will exclude white and black pigments and special effect pigments, which we did not cover in our previous discussion.
We find it useful to reiterate a point we made in our previous article. In the product catalogues of various major companies, there are many pigment recommendations within the same colour groups. Sometimes colourists, depending on their mood at the time, or when achieving any colour, resort to using more than 2 pigments to create that colour.
However, the ideal approach when creating any colour is generally to use 2 different pigments alongside black and white pigments.
The limitation of the number of pigments used is possible because the colour is produced in its most vivid state when the number of pigments is kept to a minimum. As the number of pigments used increases, the colour becomes duller and more matte.
For this reason, pigment manufacturers not only produce as many pigments as possible to facilitate the work of colourists, but also modify the production properties of these pigments to produce them with different characteristics.
For example, a yellow colour can range across a wide spectrum from greenish yellow to orangish yellow. The same applies to red colour. Therefore, in catalogues for yellow and red colours, many alternative pigment options appear.
We do not see as many differences for green, blue and violet pigments. By modifying the crystal sizes of pigments, they increase colour intensity while affecting transparency or opacity as well as attempting to modify environmental durability. On the other hand, while yellow and red pigments exist in different chemical structures at different cost levels, green, blue and violet pigments are generally found in high-quality characteristics, so we do not see their types oriented towards different costs.
Powder coatings are fundamentally classified as an industrial paint, but since they are not produced in liquid form and are produced using an extruder, they need to be addressed separately.
Moreover, since powder coatings are exposed to high temperatures both during their production and application, the pigments must have high heat resistance.
Like industrial paints, powder coatings are paints applied in facilities on various vehicles, equipment, machines and commercial vehicles. We can classify powder coatings according to the resin types used, as shown in Table 1.
Table 1. Powder Coating Systems
Epoxy Systems
Epoxy/Polyester Systems
Polyester/PT910 Systems
Polyester/Primid Systems
Polyester/TGIC Systems
Polyurethane Systems
Acrylic Systems
Yellow Powder Coating Pigments
Sudarshan has 6 different yellow pigments in the yellow colour group for powder coating applications. Three of these can be classified as economical and the other three as high-performance yellows.
Economical yellows are pigments in the azo pigment group that are either not suitable or have limited suitability for outdoor conditions. The economical yellow that is relatively suitable for outdoor conditions is Sudafast Yellow 132K pigment.
A yellow pigment tending towards a medium red, 132K has a colour index of PY191. Despite its high properties, it is advisable to pre-test 132K's performance in polyester systems, whether TGIC-containing or not. 132K is not recommended for polyurethane systems. Due to patent restrictions, this pigment is the only PY191 pigment that can be sold in Europe. The other two economical yellow pigments are Sudacolor Yellow 162K and 165, with colour indices of PY17 and PY13 respectively.
Both pigments are disazo pigments. Among the Sudarshan yellow pigments mentioned, Sudaperm Yellow 2906, a PY154 pigment, has limited properties in terms of heat resistance and its use is recommended up to 160°C.
Sudafast Yellow 132K, a PY191 pigment, is one of the pigments with the highest heat resistance and can be used at temperatures up to 300°C.
Sudaperm Yellow 2903, a PY151 pigment, is a high-performance pigment in the greenest shade of yellow and, while suitable for almost all systems, it is beneficial to test it in the manufacturer's own formulation in epoxy systems.
Similarly, Sudaperm Yellow 2935, another high-performance pigment, is a red-toned yellow pigment with a colour index of PY139. The heat resistance of all other yellows is defined as 200°C.
Of these 6 yellow pigments, all except 162K and 165 have compliance with the European Food Contact Compliance Standard AP(89)1 and RoHS compliance; additionally, 132K pigment has FDA compliance.
Table 2 summarises the key properties of Sudarshan yellow pigments
Table 2. Yellow Powder Coating Pigments
Sudarshan Red Powder Coating Pigments
Sudarshan recommends 4 pigments in the red colour group for powder coating applications. One of these is economical and the other 3 are high-performance pigments. The economical red is a ruby pigment, Sudacolor Red 635, and is classified with a colour index of PR 57:1.
This pigment is definitely recommended for economical interior applications and also has limited light fastness over extended periods. The other high-durability pigments, Sudaperm Red 2953K and 2957K, are DPP pigments.
2953K has a colour index of PR264 and is a blue-toned exterior medium ruby pigment, 2957K is a semi-transparent yellow-toned PR254 pigment. The fourth pigment is a Naphthol red pigment, a yellowish red, Sudaperm Red 2963K, and is defined with a colour index of PR170.
All of these reds have thermal values above 200°C. Each pigment has compliance with the European Food Contact Compliance Standard AP(89)1 and RoHS. Table 3 shows the properties of these pigments.
Table 3. Sudarshan Red Powder Coating Pigments
Sudarshan Orange Powder Coating Pigments
Three different orange pigments are available, two of which are high-performance and one economical orange pigment. The economical type is Sudacolor Orange 203K, a disazo pigment classified as PO13.
The high-performance orange pigments are Sudaperm Orange 2915 and 2917, and both pigments are benzimidazolone pigments. Of these, 2915 is a PO36 and 2917 is a PO64 pigment.
All three pigments have heat resistance above 160°C, and the resistance of pigment 2917 is at the 300°C level. Both high-performance pigments have European Food Contact Compliance Standard AP(89)1 compliance and RoHS compliance, while pigment 2917 also has American FDA compliance. Table 4 shows the properties of Sudarshan orange pigments.
Table 4. Sudarshan Orange Pigments
Sudarshan Blue, Green and Other Powder Coating Pigments
Sudarshan has one pigment each in PB15:1 and PB15:3 colour indices and one in PG7 colour index that are widely used in powder coating applications as in plastic applications.
These are Sudafast Blue 2764, a PB15:1 pigment, Sudafast Blue 2789, a PB15:3 pigment, and Sudafast Green 2730K, a PG7 pigment. All three pigments are phthalocyanine pigments. The heat resistance of all three pigments is 280°C for 2764 and 300°C for the other two, and their outdoor durability and light fastness are also at the highest levels.
All three phthalocyanine pigments have European Food Contact Compliance Standard AP(89)1, American FDA compliance and RoHS compliance. Table 5 shows the properties of Sudarshan's phthalocyanine pigments.
Sudarshan has also recommended two separate pigments in quinacridone chemistry for red and violet pigments for powder coating applications. Both of these high-performance pigments are Sudaperm Pink 2992 and Sudaperm Red Violet 2995 pigments.
2992 has a colour index of PR122 and 2995 has a colour index of PV19. The heat resistance of 2992 is quite high at 300 degrees while the heat resistance of 2995 is at the 200 degree standard. Both pigments have high outdoor durability and light fastness.
Sudarshan has also introduced the Sudaperm Violet 2943K pigment with colour index PV23 to the industry during this period. 2943K pigment is a transparent violet with heat resistance above 220°C and has high outdoor durability and light fastness.
Table 5. Sudarshan Phthalocyanine and Quinacridone Pigments
Conclusion
Sudarshan recommends 19 different pigments across the entire colour spectrum from red to yellow, yellow to green, and then to blue and purple colour ranges for powder coating applications, providing solutions to demands in every sector.
Beyond these recommendations, they are used without any problems by all, from the largest leaders in the industry to the smallest players. All of these pigments also comply with international standards.
Although pigments in other colour indices used in the plastics industry exist and have potential for use in powder coatings, they are not mentioned here because testing has not yet been completed in this field.
For example, PR48:2, PR48:3, PR53:1, PY62, PY83, PY110 are a few examples of these.
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