Atmospheric plasma and corona treatments are electrical surface treatments used to improve a material’s surface properties for downstream printing, bonding, and adhesion applications. The effects of surface treatments can last hours, weeks, or years depending on the type of material treated, the applied treatment, and the conditions in which the treated material is stored. For best results, secondary processing should be performed shortly after the surface treatment.
At 3DT, we provide customized surface treatment solutions based on each client’s unique application, timing requirements, and processing needs. Here, we’ll discuss the longevity of these treatments, including optimal process windows and decay prevention tips.
Factors Influencing Surface Treatment Longevity
Plasma and corona treated substrates tend to revert to their untreated states over time. The longevity of the surface treatment is influenced by:
- Additives. Additives (plasticizers, pigments, etc.) present in the bulk of the treated material can migrate to the surface over time and reduce surface treatment effectiveness.
- Process contaminants. Process-related impurities such as mold release agents can adhere to the material’s surface and interfere with downstream surface treatments.
- Material density. High-density materials generally maintain their modified surface energy properties longer than low-density materials since their tightly packed polymers slow the migration of subsurface molecules.
- Process window. While several factors influence the shelf life of surface-treated materials, tests with polymer surfaces suggest that the surface activating effects are retained at 28 days post-treatment. 3DT works closely with clients to establish a workable process window that accommodates individual timing and processing requirements while optimizing adhesion results.
Surface treatment longevity also varies according to the type of polymer being treated. Typical surface treatment shelf life on commonly used polymers are listed below.
Process Window Optimization
For optimal results, the time between the surface treatment and secondary printing or bonding operation should be minimized. Roughly 90% of polymers are processed within seconds or hours of being surface-treated. Typical process windows for various substrates are described below.
- Polystyrene labware such as Petri dishes and multi-well plates are typically corona treated, packaged, and shipped to the laboratory, where they are used on an as-need basis. These items must be capable of retaining their modified surface properties for long periods and often have expiration dates exceeding two years.
- Polypropylene syringes are printed directly after corona treatment to ensure optimal ink adhesion.
- EPDM rubber profiles receive adhesives seconds after plasma treatment.
- Blown polymer films are typically corona treated, wound into a roll, and stored until needed. Before the final processing step, the roll is cut into a usable size and bump-treated (retreated with the surface treatment).
- Glass substrates are corona treated to remove contaminants and enhance hydrophilic surface properties for subsequent bonding applications. Treated glass retains its activated surface for days to weeks, allowing manufacturers to perform the required secondary operations within a reasonable timeframe.
Decay Prevention Tips
Key recommendations for preventing surface energy decay after treatment include:
- Optimize storage environment:
- Avoid high temperatures, which promote faster migration of subsurface molecules.
- Maintain low humidity levels
- Protect material from airborne contamination and direct skin contact, both of which can accelerate decay
- Keep material covered: Surface-treated substrates should be properly covered and protected from the surrounding environment using well-fitted, contaminant-free containers and covering.
Long-Lasting Corona and Plasma Treatment Systems from 3DT
Leveraging over 30 years of experience, 3DT creates industry-leading surface treatment equipment for everything from printing and adhesive processes to sensitive cell-culture applications. For custom requests, we work with clients during the application development phase of their projects to establish an individualized surface treatment strategy. With your application, process, and timing needs in mind, we then develop a custom plasma or corona treatment system that ensures optimal timing between the surface treatment and subsequent processing operations.
Designed for seamless integration into existing production lines, our innovative systems include:
- User-friendly operational controls
- Status menu
- Run time log
- Troubleshooting screen
- Fault log
- PLC control (for material handling systems)
In addition to our custom capabilities, we also offer a complete line of standard corona and plasma surface treatment systems capable of handling a range of substrates and geometries.