Experiment
In this application note, the water contact angles on differently treated polymer films were determined with an OCA 25. According to the requirements of the ASTM D5946, the width and length of sample film are at least around 25 mm and 300 mm, respectively. As environmental conditions will influence the measured value to a certain extent, the tests are conducted at a temperature of 23 ± 2 °C and a relative humidity of 50 ± 10%. The handling of polymer films is prone to build-up of static charges, which potentially leads to inaccurate contact angle measurements. To avoid this, an air ioniser is used to keep the samples free of static build-up before and during the measurements.
As mentioned above, both plasma-treatments and corona-treatments can be applied to treat polymer surfaces. In this application, the sample film was plasma-treated immediately before the measurements using the handheld piezobrush® PZ3 (with the Module Standard
), developed by relyon plasma GmbH. The test areas were treated for 3 s, 5 s, 10 s, 20 s and 30 s, respectively.
To ensure the purity of the distilled water and cleanness of the syringe, a preliminary test was carried out. In it, the surface tension of the water used for the later measurements was verified tree times using the pendant drop method. The measurements yielded a surface tension of 72.28 ± 0.32 mN/m, which is in good agreement with literature values [2].