Polyurethane coatings – Perfect protection for large vehicles
The physical dimensions of commercial vehicles require often a different coating method and coating system than for automotive OEM coatings. The coatings have to be able to dry at much lower temperatures, sometimes even at room temperature as drying rooms are often too small to deal with the large dimensions of the vehicles to be coated. Nevertheless, the quality of the coating should still be comparable to automotive OEM coatings. Waterbased and solventbased two-component polyurethane coatings can show their strength in this area. Commercial vehicles are subject to extreme conditions. Air plane coatings have to withstand extreme UV- and temperature exposure, coatings on high speed trains have to cope with severe stone damage. Trucks, busses and argricultural vehicles need to withstand harsh environments for a very long time. In addition, the coating process itself should be very short in order to minimize idle time. They should also be in accordance with the ever more stringent VOC legislations in many countries.
New developments in the field of waterborne two-component polyurethane dispersions enable the formulation of low-VOC systems that are well within the VOC limits set by current legislation and offer users maximum freedom in the choice and quantity of co-solvent used. With rapidly drying coating systems based on polyacrylates and in particular with the so-called "internally activated dispersions", production efficiency can be significantly increased, energy costs lowered as a result of lower oven temperatures compared to standard systems and the CO2 balance thereby improved, all without adverse effects on the processing time window.
The property profile of these new waterborne products with respect to gloss, drying and resistance properties is at a comparable level to that of solventborne systems, in some cases even exceeding it.
Requirements that the polyurethane coating raw materials of Bayer MaterialScience fullfill:
outstanding mechanical and chemical resistance
excellent UV-resistance
good elasticity
fast drying at room temperature and elevated temperatures
Compliance to VOC-regulations
The typical coating of commercial vehicles is a two-layer system. However, depending on the application it is possible to use an additional filler or putty. The basecoat / clearcoat built-up also becomes more popular as a replacement for the classical pigmented topcoat. The application in truck driver's cabs is a typical example for this kind of coating system.
In some applications there is a growing trend towards single-layer-coatings (or direct-to-metal, DTM), primarily because of time considerations. These coatings combine the corrosion protection properties of a classic primer with the surface properties of a classic topcoat . Bayhydrol® A polyacrylate dispersions can be used for these waterbased 2K DTM coatings very effectively.
Bayer MaterialScience also offers raw materials for adhesives and sealants in commercial vehicles and in other automotive applications. Have a look here.
Have a look at this additional information on large vehicle coatings:
