Two-component paints (also referred to as 2K paints) are paint systems with two components in one paint mix. One component is the paint, and the other is a hardener that reacts chemically with the paint when sprayed.
The result of this two-component system is that the paint dries harder and faster than standard paint because the dedicated hardener undergoes a chemical reaction with the paint, which causes it to harden and dry. This is different to a one-component paint, which dries in the air by solvent evaporation.
And so, the performance difference between a 2K paint and 1K paint is that most 2K paint dries by chemical reaction, while 1K paint dries by air. However, some 2K paints also dry by air, depending on the type of hardener used.
The benefit of a 2K paint is that the paint will have better properties in many cases. It will be harder and therefore more durable than a 1K paint. It will retain colour better and have better overall film integrity, making it last longer.
1-part paints have come a long way, however. Similar to how certain one-part epoxies can outperform two-part epoxies, so too can one-part paints. One-part paints are also easier to work with, making them a better DIY option.
In DIY projects and UPVC spraying, 2K paint is overkill. 1K paint specified for the job will give you as good a finish without any durability concerns.
What is the difference between 1K and 2K paints?
1K paint is paint that contains no added hardener, while 2K paint is paint that has added hardener. The chemical properties of 2K paint mean it dries by chemical reaction, while 1K paint dries naturally in the air.
Another crucial difference is 2K paints tend to be plastic-based coating systems that use acrylic or polyurethane (PU) resins, while 1K paints use pigments and are water-based or solvent-based.
1K paint dries faster and is easier to use, offering excellent durability. 2K paint dries slower and is more difficult to use but is more durable.
Most painters use 1K paint because it is tough enough to get the job done and significantly easier to work. It also dries three to five times faster, so it is touch dry within 30-minutes in most cases, while 2K paint can take 3-4 hours.
2K paint is used in car body shops and specialist applications, while 1K paint is for general use. All aerosol paint cans are 1K, and all standard paints are 1K.
2K paints and UPVC
Although 2K paints have desirable physical characteristics, they are not wholly necessary for UPVC. A high-quality, solvent-based plastic paint will do just fine, and in many cases, it will outperform a 2K paint when professionally applied.
It’s crucial that the paint bonds with the plastic on a molecular level. Plastic paints that simply adhere to the UPVC surface are no good and should be avoided at all costs. The paint needs to bond with the UPVC, so the first layer sticks. Then, subsequent layers will bond with previous paint layers on a molecular level too.
Overall, 2K paint is suitable for UPVC but it is not necessary. You can get a finish just as durable and with half the effort with a quality solvent-based plastic paint. For example, we stamp our work with a 10-year guarantee, and we use 1K paint.
2K paint example products
A reputable product is Technispray Kolorbond K2, a polyurethane paint (PU paint) for coating hard plastics. It includes a separate hardener and is available in over 2,400 colours as standard, making it a good choice for professionals.
At Bespoke UPVC, we always use 1K paint across our projects. The paints we used are manufactured in Europe to ISO standards. We don’t use 2K paint because it takes too long to dry and is not necessary for UPVC spraying projects.