Corona treating is an efficient and cost-effective way of raising the wettability, bonding-properties, and surface tension of polypropylene products. Corona treatment can effectively improve bonding on a wide range of materials that show poor or no adhesion to media such as printing inks, paints, coating, and adhesives. Because of corona treatment’s flexible nature, it can even successfully treat tough-to-bond polymeric and elastomeric materials.
Unfortunately, corona treating is not without minor drawbacks. When treating polypropylene with low-frequency corona, small marks may be visible on the surface of the product after treating, which are referred to as “fish-marks.” These marks tend to appear more visible on glossy material than on matte materials. The reason they appear is due to the frequency at which the material is treated. Low-frequency corona treaters operate at a line frequency of 50 or 60 Hertz. This means it’s a common issue that ALL low-frequency corona treaters are subject to leave possible “fish-marks” on polypropylene.
Fortunately, this problem can be mitigated in a number of ways, such as increasing the distance between treating heads and material being treated. Or increasing the line speed can be helpful in finding the “sweet spot,” where the necessary treatment is obtained with minimal spots appearing on the surface. Furthermore, the marks can be minimized when covered by printing, labeling, or applying adhesives.
Finally, this problem can be avoided all together by using high-frequency corona treatment, if the process and geometry of the product permit. High-frequency systems require more product integration and handling and are typically more expensive due to their sophisticated design and components. With high-frequency corona treating, all adverse effects that come with low-frequency treating on polypropylene, such as fish marks, are avoided.
Another option for improving surface energy and adhesion is plasma treatment. Plasma treatment is highly suitable for three-dimensional plastic parts and rubber parts and can be a viable, albeit pricier solution. Plasma treatment is also widely used on metal, ceramic and glass surfaces.
3DT offers all systems mentioned above; from the low-frequency, cost-efficient yet effective MultiDyne to high-frequency systems, including PolyDyne Pro, FlexiDyne Pro and UltraDyne. As well as the flexible, powerful PlasmaDyne Pro.
All systems are offered as standard systems for numerous applications or customized for a specific application. Contact our expert sales team regarding your adhesion challenges!