Optimization of atmospheric plasma treatment of LDPE films: influence on adhesive properties and ageing behavior

One of the major disadvantages of low density polyethylene (LDPE) films is their poor adhesive properties. Therefore, LDPE films have been treated with atmospheric pressure air plasma in order to improve their surface properties. So as to simulate the possible conditions in an industrial process, the samples have been treated with two different sample distances (6 and 10mm), and treatment rates between 100 and 1000mms(-1). The different sample distances are the distance of the sample from the plasma source. The variation of the surface properties and adhesion characteristics of the films were investigated for different aging times after plasma exposure (up to 21days) using contact angle measurement, atomic force microscopy, weight loss measurements and shear test. Results show that the treatment increases the polar component (gamma(p)(s)) and these changes improve adhesive properties of the material. After the twenty-first day, the ageing process causes a decrease of wettability and adhesive properties of the LDPE films (up to 60%).