- Thermoactivated hardener enables efficient coating of plastic add-on parts
- Parts can be finished with clearcoat at just 80°C
- Possibility of coating plastic, composite & metal automotive parts together
Although many bodywork parts are still made from sheet steel, plastics are increasingly used for add-on automotive parts. To ensure that the coated plastic parts look just as good as the coated metal, they are coated in exactly the same way, but at a lower temperature. Bayer MaterialScience has now developed a new technology for coating plastic parts on automobiles at low temperatures. Bumpers, mirror housings, spoilers, tailgates and roof modules can be finished with their outer clearcoat at an energy- and cost-efficient temperature of just 80 °C. In the medium term, this technology will offer the possibility of coating plastic, composite and metal automotive parts together for the first time.
The drawbacks of conventional coating technology
When using conventional, uncatalyzed coating technology, plastic parts generally need several days to dry completely after being coated with two-component polyurethane coatings. This leads to delays in further processing and requires special measures for storing the coated parts.
For some time, catalysts have therefore been used for curing. However, their use means that crosslinking begins immediately upon application. As a result, the coating cannot flow freely and does not achieve an optimal appearance. All previous attempts to satisfy the need for rapid curing without compromising on appearance have failed.
First film formation, then curing
A thermolatent hardener is the core of this technology that makes it possible to separate film formation and curing. The coating initially flows smoothly on the substrate and forms an even film. Only when the temperature rises is the hardener present in the coating activated by a special latent catalyst. This ensures the coating dries rapidly on the plastic substrate. No significant changes to the coating formulation are required. Thermolatent two-component PU systems can therefore be used for coating plastic add-on parts in series production. Even in cases where the faster drying is not such an advantage, the new development still enables the parts to be processed with greater ease and speed after baking.
Initial samples will be available to development partners starting the first quarter of 2015, with market launch to follow.