Plasma for PUR in-mold coating
Many manufacturers prefer surface pre-treatment with atmospheric pressure plasma to increase adhesion of plastics. At the K 2025 trade fair, Plasmatreat GmbH, the global market leader for atmospheric plasma technology, and the research institute Neue Materialien Bayreuth (NMB) GmbH presented a new field of application: Openair-Plasma technology is used to modify the surfaces of injection-molded components before applying PUR coating systems. This method improves quality, minimizes rejects, simplifies process steps, and reduces environmental impact. Plasma technology has a number of advantages over alternative methods such as flame treatment.
Polyurethane (PUR) coating systems are already widely used in the automotive sector for manufacturing exterior parts, such as hoods and front bumpers. These coatings protect plastic components from environmental influences, absorb forces, and exhibit self-healing properties in the event of mechanical damage. However, the trend of manufacturing components from inexpensive mono-materials, such as polypropylene (PP), to reduce costs and improve recyclability creates new challenges. PP is a non-polar material to which paint coatings cannot adhere well or last long. Therefore, pre-treatment is essential for PP. Conventional pretreatment methods, such as flame treatment or the use of chemical adhesion promoters, increase adhesion strength; however, they also have significant disadvantages. These include high heat input, which can damage the component; the need for additional occupational safety and environmental measures; and interrupted processes due to handling and drying times. Plasma technology, an alternative pretreatment method, eliminates these disadvantages solely through its technological features.
PUR In-Mold Coating - fully automated, fast, in-line process
This new approach, developed by plasma specialist Plasmatreat GmbH and research institute Neue Materialien Bayreuth (NMB) GmbH, demonstrates the potential for an efficient, effective, and environmentally friendly future PUR In-Mold Coating process. Plastic components are manufactured and treated with a specially developed wide plasma nozzle immediately after the injection molding process. The robot-guided nozzle precisely and at high speed performs large-area pretreatment of the plastic components with Openair plasma. Then, the components are flooded with the PUR coating in the same system. Plasmatreat developed the Plasma Control Unit (PCU) to monitor the plasma treatment. This control unit continuously monitors all parameters of the plasma process with integrated quality assurance modules to ensure functionality and reproducibility. This manufacturing process combines injection molding, plasma pretreatment, and PUR coating into a fully automated, in-line process, avoiding additional logistics, cleaning, and waiting times.
Efficient PUR Coating with plasma: New perspectives for industry
This new plasma application offers numerous advantages over other surface pretreatment methods. Openair-Plasma pretreatment increases the surface energy of non-polar plastics, such as polypropylene (PP), enabling permanent and reliable adhesion of the PUR coating. The reliable plasma process ensures consistent results and reproducible quality, even with complex component geometries. Unlike the conventional flame treatment process, the component is exposed to significantly less heat, preventing damage. Using plasma also allows for a reduction in the material thickness of the plastic component, leading to cost savings. Additionally, the process is highly flexible. Plasma pretreatment can be carried out over large areas or selectively. The wide plasma nozzle quickly adapts to high processing speeds. Another advantage is environmental protection: the process does not require chemical solvents or release VOC emissions. Since components can be processed directly, without drying times or additional cleaning steps, PUR In-Mold Coating achieves short cycle times and high production volumes.
The collaboration between NMB and Plasmatreat stems from specific requests from the automotive industry. Our solution demonstrates how resource conservation, efficiency, and the highest product quality can be combined. With plasma in the PUR In-Mold Coating process, we are opening up completely new perspectives for the automotive industry and other sectors, such as the household appliance industry," says Lukas Buske, CEO at Plasmatreat GmbH.
