Wettability is due to two factors: nanostructured and functionalized. Both can be achieved by plasma treatment of the polymer surface. In this paper, we examined surface kinetics in detail at different processing rates. We systematically measured wettability as a function of plasma particle dose, which provided a good insight into the kinetics of etching and functionalization.
COBISS.SI-ID: 33006119
Nanostructured protective coatings on aluminised polymer substrates were deposited by a plasma enhanced chemical vapour deposition (PECVD) technique in an industrial-size plasma reactor with a volume of 5 m3. Plasma was sustained in a capacitively coupled radiofrequency (RF) discharge powered by an RF generator operating at 40 kHz and having an adjustable output power up to 8 kW. Polymer samples with an average roughness of approximately 5 nm as determined by atomic force microscopy were mounted into the plasma reactor and subjected to plasma. The combination of various techniques for plasma and surface characterisation adopted in this work provided insight into the mechanisms involved both in the gas phase and on the surfaces of materials facing plasma upon nanostructuring and functionalization.
COBISS.SI-ID: 32269863
A kinetic model describing the interaction of gaseous plasma with model polymers is presented. Both surface nanostructuring and functionalization were studied as a function of the irradiation with VUV photons only, neutral radicals only and a combination of these reactants with charged particles. The separation of each reactant enabled the distinction between different effects. Polymers exposed to VUV only showed a hydrophobic surface with small roughness. On the contrary, when exposed to all reactants, etching was observed and we related the nanostructuring to oxygen neutral active species and formed a rough surface. The abundant polar groups and a rough surface significantly increased the polymer hydrophilicity.
COBISS.SI-ID: 31983655
An innovative technique for measuring the surface loss coefficients was developed. The loss of H and O atoms on the surface of three technologically important polymers was measured systematically at different densities of atoms in the vicinity of the polymer samples. The loss was predominantly by heterogeneous surface recombination of H and O atoms to parent molecules. The recombination coefficient for hydrogen atoms did not depend on the density (and thus flux) of atoms onto the polymer surface, but it depended on the type of polymer. The largest coefficient of approximately 0.0023 was determined for PET and the lowest of 0.0008 for PTFE (Teflon).
COBISS.SI-ID: 31436839
The functionalization kinetics upon exposure of polymer to the late afterglow of oxygen plasma was investigated. The experimental setup allowed for negligible influence of UV radiation or charged particles from gaseous plasma. The results clearly indicated preferential formation of functional groups with a low binding energy shift. The measurable formation of carboxyl or ester groups was observed only at fluences higher than approximately 2×1022 m-2. Despite the overlapping of high binding energy shift peaks with the shake-up peak, it was possible to conclude that the pheny ring was etched preferentially leading to nanostructuring of the originally smooth polymer surface. The results experimentally confirmed the theoretical predictions elaborated previously by Kushner’s group.
COBISS.SI-ID: 31702823