| Abstract: | CONCLUSION. Oxygen plasma treatment changes the topography of PP film from a spherulitic to a nodular structure. The size of the nodules increases with the treatment time. The two power levels compared (100 and 60 W), affected the surface topography similarly creating in the same length of time nodules of nearly equal sizes. The longer the treatment time, the easier it was to image the PP surfaces without contamination of AFM tips. This phenomenon might be related to changes in the chemical composition making the surface layer more rigid in the course of time and hence easier to monitor with AFM. Considerable increase in the surface free energy of PP and birch is observed due to the oxygen plasma. This change takes place at very short treatment times. Thus, the preconditions for improvement of adhesion should already exist at the low treatment time levels. Treatment of lignocellulosics for 5 min or more with HMDSO plasma changes the surface of the material highly hydrophobic. The polymer layer formed is extremely thin and follows closely the features of the substrate. The hydrophobic pre-treatment of wood surface with HMDSO plasma polymer was not beneficial for adhesion between wood and polypropylene film. Although the HMDSO plasma treatment can not be used as a pre-treatment and as an adhesion promotor between PP and lignocellulosics, it may have some prospects as a water barrier in applications in which the material is not exposed to abrasion. |
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