The other night, my roommate and I discovered an unfortunate truth about our kitchen calendar.
Every time we attempted to write on the smooth surface, ink from the pen or marker would bead up on top and smear. For us, this led to a valiant ten-minute attempt. However, when your product relies on the printability of your material, this phenomenon can become an urgent issue.
At Strouse, we use corona surface treatment to treat certain flexible materials for increased wettability and printability. During product creation, this is often a necessary first step before any cutting or slitting processes.
As we go through corona surface treatments, you’ll begin to understand the difference between corona and plasma processes, the materials involved, and whether it makes sense to seek corona treatments for your project.
What is Corona Surface Treatment?
All materials have an inherent surface energy ranging from high to low. Plastics, cloth, and paper products typically have lower surface energy than other materials, making it challenging to bond inks, adhesives, and other coatings to a product.
Corona surface treatment, also known as “air plasma,” is a modification that changes the surface energy of materials to create a better bond for inks, adhesives, or other coatings.
Originally, corona treatment was invented as a crude way to print on plastic, but it has since evolved into a far more efficient and controllable process. Converters apply voltage to atmospheric air and cover material in ionized gases full of active molecules, raising the surface energy.
Films and paper products can be corona treated to raise their surface energy and allow other materials to bond strongly to the product’s surface.
The electrical discharge creates a plasma field – a mix of electrons and ions that bombard the surface, removing surface contaminants and reacting with the surface to form hydrophilic functional groups that promote the formation of chemical bonds between the surface material and inks or adhesives.
THE DIFFERENCE BETWEEN PLASMA AND CORONA SURFACE TREATMENT
Plasma and corona treatments are similar yet slightly different surface energy-altering processes.
Corona surface treatments are often referred to interchangeably with plasma systems but differ slightly in usage and cost.
Like the corona treatment process, atmospheric plasma is essentially made by energizing the air and directing it over the material to increase the surface energy. Yet, compared to corona treatments, atmospheric plasma affects smaller surface areas with higher energy levels.
Corona treatments affect larger areas and can treat inside of parts or 3-dimensional parts, while atmospheric plasma is applied in spots, limiting its surface area. On the other hand, plasma treatments don’t produce ozone gas (a natural result of corona treatments).
Lastly, although the effects of plasma treatment might last longer, it typically requires a higher initial investment in equipment and operational costs. Due to the price, plasma treatments are reserved for substrates with incredibly complex structures.
Which Materials Undergo Corona Surface Treatment?
To hold adhesive or ink, a surface must have a certain level of “wettability” allowing substances to spread. Poor wettability results in smearing or slipping due to the substrate’s inability to form a cohesive bond.
Because some materials are naturally less absorbent, they require additional preparation before printing or lamination. Corona surface treatment is ideal for plastic, foil, film, and other non-absorbent substrates.
These are the materials with which converters commonly use corona surface treatment for:1. Flexible Materials
- Paperboard stocks
- Metalized surfaces
- PVC (Polyvinyl chloride)
- PET (Polyethylene terephthalate)
- HDPE (High-density polyethylene)
Corona treatment activates the surface of polymers, textiles, or other flexible materials depending on their surface geometry.
Carefully planning your material selection is crucial to ensure a cohesive final product. If you’re unsure whether to corona treat your materials for your application, you can have your design evaluated by a flexible material converter:
Should I Corona Treat My Materials?
While there are many benefits to corona-treating your materials, the drawbacks may make you wish to reconsider.
One limitation of corona treatment is that the treatment will not last forever.
Converters must test the inherent surface energy (dyne level) before printing or laminating adhesive onto the material. When dyne levels are low, the material is more challenging to process.
As the corona treatment wears away over time, the material may need to be re-treated before it can be transformed into another product.
Rather than choosing a material that needs to be corona treated to hold ink or adhesive, it might be worthwhile to try to find a material that suits your product but naturally holds substances without needing an additional process.
Still searching for that perfect material? Try seeking advice from Strouse based on your product: