Automotive coatings are developing towards environmental protection while also enhancing the appearance and decorative effect of the entire vehicle. Products with various environmental protection certifications are now preferred. The limitation of VOCs has become a key indicator for automotive coatings, and by using water-based coatings, VOC emissions from the entire vehicle can be reduced by more than half. Water-based PU coatings are getting more and more popular.
Applications of PU coatings
Automobile parts and interior and exterior decorative components are diverse, and the performance requirements for coatings vary accordingly. For example:
- Acrylic polyurethane (PU) coatings are used for bumpers;
- Polyurethane (PU) primer is used for fenders, side guards, and under bumper guards;
- Polyurethane (PU) coatings are used for wheel covers, spoilers, and door handles;
- 2K polyurethane (PU) coatings are used for automobile interiors
Polyurethane coatings for car body
Primer
The vast majority of automotive primers use cathodic electrophoretic paints. Cathodic electrophoresis PU coatings can be prepared using closed-type polyurethane (PU), polyester resin, epoxy resin, etc.
Nowadays, as the industry shifts towards waterborne solutions, the transition to a waterborne primer can significantly reduce VOC emissions. The 3C1B process, which uses a waterborne primer, was first implemented in 2010, employing two-component urethane as a clear coat to meet appearance requirements. On the other hand, a solvent-based, two-component polyurethane mid-coat primer is used in the 3C1B process to enhance the system’s resistance to stone strikes. Basecoats have also begun to transition to waterborne formulations. The use of two-component polyurethane clearcoats in the waterborne 3C1B process has become the standard in many automotive process plans.
Polyurethane (PU) electrophoretic coatings fall into three main categories: waterborne polyurethane (PU) resin electrophoretic paints, polyurethane (PU) modified waterborne resin electrophoretic paints, and waterborne closed polyisocyanate. Among these, waterborne closed polyisocyanate is most commonly used as a crosslinking agent in various electrophoretic paints.
Medium coating paint
Polyurethane (PU) paint, including various modified polyurethane paints, has a wide range of varieties and applications. Waterborne polyurethane (PU) paint, in particular, performs very well in meeting environmental requirements, especially in terms of flexibility and impact resistance, which are superior to those of solvent-based coatings. The anti-stoning and cold resistance properties of polyurethane (PU) paint are key development directions for automotive coatings.
Refinish paint
Waterborne two-component polyurethane coatings for automotive refinish paints typically contain additives such as leveling agents, defoamers, catalysts, light stabilizers, thickeners, and organic co-solvents, which are added to the hydroxyl-containing components. After mixing with the polyisocyanate component, the viscosity is adjusted with water, and the coatings are then applied using the spray method.
How to obtain high quality automotive water-based PU coatings?
By selecting the right UV absorbers, light stabilizers, and antioxidants to add to PU waterborne paints, the long-term weathering resistance of the paint can be significantly improved. This helps maintain the gloss of the coating while preventing surface cracking and spotting. Additionally, it also prevents the peeling of the automotive paint surface, providing better protection.
