Plasma treatment is a common process for treating various materials prior to coating, printing or gluing. One of the main purposes of the plasma treatment is to improve the wettability of the material as good wettability is required in all the aforementioned processes. As more products rely on plastics, from medical devices to automobile bumpers, this concept has grown more important since plastics generally exhibit poor wettability for many liquids. This is due to the low surface free energy of many plastics. Plasma treatment offers a safe, effective and environmentally friendly technique to enhance wettability —even for complex geometries—without the use of harmful chemicals or high temperatures.
Why evaluate plasma treatment with contact angle measurements?
When a surface undergoes plasma treatment, it is exposed to ionized gases in a vacuum chamber. This bombardment triggers chemical reactions at the material’s surface, increasing its surface energy and, consequently, its wettability. But how do you know if your plasma treatment was effective?
Contact angle measurement is the go-to method for this evaluation. The contact angle—a simple measurement of the angle formed where a liquid droplet meets a solid surface—is highly sensitive to changes at the surface monolayer. A lower water contact angle after treatment indicates improved wettability, which is essential for strong adhesion and uniform coatings.
Learn more:
What is contact angle?
Why is contact angle important?
How to optimize plasma treatment using contact angle measurements?
Several parameters affect the outcome of plasma treatment, including:
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Gas type
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Process pressure
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Plasma power
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Treatment time
Optimizing these parameters is critical for achieving the desired surface properties. Contact angle measurements provide a fast, quantitative, and non-destructive way to monitor and fine-tune your process. A water contact angle alone will give indication of the effectiveness of the plasma treatment as low water contact angle indicates better wettability of the surface.
To further analyze the effect of plasma treatment, surface free energy of the surface can be calculated by performing contact angle measurements with two or more probe liquids.
Case example: Polypropylene plasma treatment
In practice, optimizing plasma treatment time is often done by monitoring the water contact angle at different intervals. To read how optimum plasma treatment time of polypropylene can be evaluated, please download the case study through the link below.
