PLASTIC painting
There are several ways to paint plastic. One of the most common techniques is spray painting, in which an even layer of paint is applied to the surface of the plastic using an air compressor. Another option is dip painting, in which the plastic is immersed in a vat of paint and then allowed to dry. Finally, electrostatic painting (called cataphoresis) is a technique in which paint is applied with an electrostatic charge to the surface of the plastic, creating a uniform and precise effect.
At Tecna Plast, the system used for painting all components currently in production is the pneumatic system, i.e. the use of air atomisation guns with different nozzle sizes and types depending on the production process.
The paint is pushed by a low-pressure pumping system or pressurised tanks capable of pushing the products with an extremely high flow rate constancy, thus ensuring high homogeneity during dispensing.
The products currently used in painting processes are both solvent-based and water-based, with the customer opting for the latter technology. This technology is much closer to the environment, when customer requirements allows its application.
Applications
The main painting cycles on which we have gained years of experience are those typical of the automotive sector, i.e. both MATT and HIGH GLOSS cycles:
• Single-layer cycles
• Bistrato Cycles
• Three-layer cycles (Primer-Basecoat-Clearcoat)
• Matt Finishes
• Semi-matt finishes
• Semi-gloss finish
• High-Gloss Finishes
• Pastel Effects
• Chrome Effect (in place of Galvanic Chrome Plating)
• Soft Touch Effects
• Anti-scratch effects
Painting cycles
Currently, the paints we apply are both solvent-based and water-based.
​Our aim soon is to be able to apply and guarantee the curing of both mono and dual cure UV-curing products as well.
​Solvent-based paints have long been the most widely used in the automotive industry but have recently been partly replaced by more sustainable products, replacing some chemical components with others more environment-friendly. Solvent-based products consist of a mixture of synthetic resins, pigments, and volatile organic solvents, which evaporate during the thermal curing process. However, due to environmental concerns related to volatile organic solvent emissions, solvent-based paints are becoming less and less popular.
​Water-based paints, on the other hand, are becoming increasingly popular due to their low emission of volatile organic compounds VOC. These paints use water as a solvent instead of volatile organic solvents and consist of a mixture of synthetic resins and less impacting pigments.
Painting plastic: curiosities, challenges and tips
Challenges in plastic coating
Painting plastic offers many advantages, but it presents some significant challenges. One of the main challenges is adhesion of the paint to the nonporous surface of the plastic, which can be difficult. In addition, plastics can undergo deformation due to temperature during the painting process, requiring careful heat management.
​Choosing the right paint is essential to ensure the durability and strength of the paint over time, especially considering exposure to aggressive environmental factors such as sun and weather.
Plastics ideal for painting
Not all plastics are the same when it comes to painting. Some plastics are better suited for this process than others.
​For example, thermoplastic plastics such as ABS, polypropylene (PP) and polycarbonate (PC), polyamides (PA) and polyurethanes (PU) are among the most suitable for painting because they provide good adhesion to the paint and are quite heat resistant.
​On the other hand, thermosetting plastics such as epoxy and melamine are less suitable for painting because of their greater tendency to deform during the painting process. It is therefore important to choose the right plastic for the product you intend to paint in order to ensure a quality result.
Custom finishes after painting
After the plastic is painted, a variety of finishes can be applied to further personalize the product.
​Pad printing, for example, allows logos and text to be printed on the painted surface using a silicone pad.
​Screen printing, on the other hand, involves the application of an adhesive film to the painted surface, which is then followed by color printing using a screen printing process.
​Finally, laser engraving is an engraving technique that allows patterns and designs to be created on the painted surface using a laser beam.
​These finishes can improve the aesthetic appearance of the product and make it more attractive to customers.
