| | Category | CH | P03 | Wettability Reversion in Plastics Treated with Glow Discharge |
| | Plasmas |
| | Abstract | Corona discharge treatments are widely used to promote wettability and |
| | adhesion in industrial processes for lamination of composite materials, as |
| | well as application of paints, adhesives, and inks. However, the effects |
| | of the treatment are not permanent. General industrial practice dictates |
| | that treated plastic materials be subsequently processed within 4 hours of |
| | treatment. In this project, I investigated the effect of corona discharge |
| | treatment on various plastics at increasing post-treatment durations to |
| | quantify the change in wettability over post-treatment time. |
| | To determine how the effectiveness changes with time, I conducted |
| | several experiments involving the measurement of contact angles of water |
| | droplets on the surfaces of six plastic materials treated by corona |
| | discharge plasma. These contact angles reflect the surface energies—a |
| | measure of wettability—of the plastics, which are changed during corona |
| | discharge treatment. Samples of widely used plastics, such as |
| | polyethylene, polypropylene, polystyrene, polyvinylchloride, polyethylene |
| | terephthalate, and polymethyl methacrylate, were selected. These plastic |
| | samples were mounted on microscope slides and treated with a corona |
| | discharge plasma for one minute. At various times after treatment, water |
| | droplets were placed on the plastic surfaces. Image analysis of pictures |
| | taken with a digital camera was used to determine the contact angles of |
| | the water droplets. My study showed that the effect of increased |
| | wettability of plastic surfaces by corona discharge treatment was not |
| | completely irreversible. This reflects the partial reversion of the plastic |
| | surface back to the untreated state. |
| | The measured contact angles of all plastics slowly increased as a function |
| | of elapsed time from two minutes to five days. This experiment showed |
| | that, for most plastics tested, the contact angle recovered to around 50% |
| | of the value for the untreated contact angle within 15 minutes. After four |
| | hours, the contact angle recovered to around 65% of the value for the |
| | untreated contact angle. After 5 days, the contact angle recovered to |
| | around 75% of the value for the untreated contact angle. Thus, |
| | processes which require high wettability after treatment of the materials |
| | should take place within 15 minutes after corona discharge treatment. |
| | However, if processes do not require such high wettability, several days |
| | can elapse before the subsequent processes must take place. These |
| | results have useful applications in reducing process costs and maximizing |
| | process output in fields such the automotive, aerospace, and medical |
| | industries. |
| | Bibliography | Ono, Shigeru, Shinriki Teii, and Shinako Takayama. Surface Treatment of |
| | Plastic Film by Using an Atmospheric Pressure Corona Torch. HAKONE 8. |
| | The 8th International Symposium on High Pressure Low Temperature |
| | Plasma Chemistry. 20 Jan. 2009 |
| | <http://www.ut.ee/hakone8/papers/T7/Ono(TP).pdf>.The Plastics |
| | Network. Corona Treatment: Why is it Necessary? The Plastics Network. |
| | 20 Jan. 2009 <http://plasticsnetwork.files.wordpress.com/2007/12/corona- |
| | treatment.pdf>. |