Oxygen Cold Plasma Treatment to Improve Hydrophilicity of HDPE Pellets

We demonstrated the environmentally friendly method, Cold Plasma treatment with oxygen plasma gas, in order to introduce the polar groups into non-polar polymer. HDPE pellets were treated with cold plasma under the mixture of plasma gas and air at atmospheric pressure. After that, the treated samples were immediately subjected into the twin-screw extruder. Plasma treatment time, 30 seconds, 1 and 2 minutes, was studied. From the contact angle measurement, all treated samples showed lower contact angle value than the neat HDPE from 96.83 degrees to 80.84 degrees - 84.53 degrees suggesting that the hydrophilicity of all treated samples were improved. The polar part of surface free energy (gamma(p)(s)) of all treated samples increased from the neat HDPE from almost zero to 13.34 -21.88 mN/m. ATR-FTIR results confirmed the increasing of gamma(p)(s) value. It was due to the new oxygenated functional groups which were introduced into the non-polar polymer. Lastly, from SEM images, the roughness of cross-sectional area increased after plasma treatment which attributed to the incompatible between the polar component and the non-polar component.