Effect of the electron radiation generated by a high-voltage linear accelerator on the wettability, contact angle and surface free energy (SFE) of a biaxially oriented polypropylene (BOPP) film was studied. Radiation doses of 25, 50, 100, 250, and 500kGy were used. Water, glycerol, formamide, diiodomethane, and α-bromonaphthalene were applied as measuring liquids. The calculations of SFE were made with the methods of Owens–Wendt and van Oss–Chaudhury–Good, using the results of measurements of the contact angle with various sets of the measuring liquids. Wettability tests were also performed. It was found that the contact angle decreased with the rising radiation dose for all the measuring liquids and the shapes of these dependences were similar to one another. However, significant quantitative differences were observed. The largest changes in the contact angle were detected in the dose range of up to 100kGy. The SFE values when measured with different methods and various measuring liquids differed generally in the whole range of the applied doses. Therefore, the surface free energy cannot be accepted as an absolute measure of the thermodynamic state of the surface layer of a radiation-modified BOPP film. Its values can be compared with one another only when they were determined with the same method and same measuring or standard liquids.

The choice of plasma gas can determine the interaction between material and plasma and therefore the applications of the treated materials. Nitrogen plasma can integrate functional groups such as primary amines and carbon dioxide plasma can incorporate carboxylic groups on the surface of polymers. For specific adhesion such as bio-adhesion, polar groups must be attached to the surface to enhance bio-film formation but the acidic or basic character also controls the adhesion mechanism.

Nitrogen and carbon dioxide plasmas are chosen to treat the surface of polystyrene and to show the effects of different functionalizations, i.e. attachment of acid or basic groups and degradation are compared in the present work.

Nitrogen-containing plasma induces mainly weak degradation at a rate of ∼0.13 µg cm⁻²s⁻¹. The roughness of the treated surface remains mostly unchanged. Functionalization leads to amino group attachment at a concentration of 1.2 sites nm⁻². We found that carbon dioxide plasma treatment shows more drastic degradation with a rate three times higher than that of nitrogen plasma and can create more functional groups (4.5 sites nm⁻²) at mild plasma treatment. However, the roughness of the surface is altered. In both cases the aromatic groups are degraded through the plasma treatment (again this is more evident with the CO₂ plasma) and the induced functionalization was shown to be quick (the upper monolayer of polystyrene film can be functionalized rapidly). Copyright © 2005 John Wiley & Sons, Ltd.
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/abs/10.1002/sia.2029

After the atmospheric pressure plasma treatment of polypropylene (PP) film surface, we measured the contact angle of the surface by using polar solvent (water) and nonpolar solvent (diiodomethane). We also calculated the surface free energy of PP film by using the measured values of contact angles. And then we analyzed the change of the contact angle and surface free energy with respect to the conditions of atmospheric pressure plasma treatment. Upon each condition of atmospheric pressure plasma treatment, the contact angle and surface free energy showed optimum value or leveled off. Through AFM analysis, we also observed the change of surface morphology and roughness before and after plasma treatment. The surface roughness of PP film showed the highest value when the plasma treatment time was 90 s. Finally, we analyzed the change of chemical compositions on the PP film surface through XPS. As the result of analysis, we observed that polar functional groups, such as –CO, –C=O, and –COO were introduced on the PP film surface after atmospheric pressure plasma treatment.

A Nylon-6,6 film has been treated using an atmospheric pressure air dielectric barrier discharge (DBD). The resultant surface modifications were studied using X-ray photoelectron spectroscopy (XPS), contact angle measurement and secondary ion mass spectrometry (SIMS). The surface oxidation arising in the DBD discharge was found to arise in two stages: in the first stage, the creation of the carbon sites singly bonded to oxygen is dominant, the second stage leads to further conversion of such lightly oxidised carbons to those more heavily oxidised. The marked increase found in the hydrophilicity of the surface post-treatment is in the main believed to be associated with the earlier outcome. Partial recovery of the surface contact angle values is found for the treated samples following extended storage in ambient air. The final contact angle obtained for the treated samples was ∼50°, still reduced significantly from that of 83.5° for the untreated material.

Interfacial interactions underpin phenomena ranging from adhesion to surface wetting. Here, we describe a simple, rapid, and robust approach to modifying solid surfaces, based on an ultrathin cross-linkable film of a random copolymer, which does not rely on specific surface chemistries. Specifically, thin films of benzocyclobutene-functionalized random copolymers of styrene and methyl methacrylate were spin coated or transferred, then thermally cross-linked on a wide variety of metal, metal oxide, semiconductor, and polymeric surfaces, producing a coating with a controlled thickness and well-defined surface energy. The process described can be easily implemented and adapted to other systems.

Atmospheric pressure N₂ cold plasmas are generated with a torch-type generator using 60-Hz AC power. High flow rate N₂ gas is injected into the plasma generator and high voltage of about 2 kV is introduced into the power electrode through transformer. Discharge characteristics of N₂ cold plasma, such as current–voltage profile, gas temperature and radial species in plasma, are measured. As one possible application, the N₂ cold plasma is used to modify the surface of polymer, especially polypropylene, for adhesion improvement. Power dissipation in discharge has the maximum value at optimal power electrode position, z=3 mm, which lead to the generation of more energetic electrons capable of creating N₂* and N₂⁺ excited states in plasmas effectively. These excited species can induce high population of oxygen and nitrogen atoms on polymer surface through creation of polymer excited states. Maximum bonding strength about 10.5 MPa is obtained at optimal power electrode position.

Effects of the electron radiation generated by a high-voltage linear accelerator on wettability and surface free energy (SFE) of low-density polyethylene (PE-LD) film were studied. Radiation doses of 25, 50, 100, 250, and500 kGy were used. Water, glycerol, formamide, diiodomethane, and α-bromonaphthalene were applied as measuring liquids for contact angle measurements. The calculations of SFE were made by Owens-Wendt and van Oss-Chaudhury-Good methods, using the results of measurements of contact angle with various systems of the measuring liquids. Wettability tests were also performed. It was found that the contact angle decreased with the rising radiation dose for all the measuring liquids and the shapes of these dependences were similar. However, significant quantitative differences were observed. The largest changes in the contact angle were detected for the dose range of up to 50 kGy. SFE values when measured by different methods and various measuring liquids differed generally in the whole range of the doses applied. Therefore, the surface free energy cannot be accepted as an absolute measure of the thermodynamic state of the surface layer of radiation-modified PE-LD film. Its values can be compared with one another only when they were determined using the same method and the same measuring or standard liquids.

In this work, the effect of atmospheric-pressure plasma treatments on surface properties of polyimide film are investigated in terms of X-ray photoelectron spectroscopy (XPS), contact angles, and atomic force microscopy (AFM). The adhesion characteristics of the film are also studied in the peel strengths of polyimide/copper film. As experimental results, the polyimide surfaces treated by plasma lead to an increase of oxygen-containing functional groups or the polar component of the surface free energy, resulting in improving the adhesion characteristics of the polyimide/copper foil. Also, the roughness of the film surfaces, confirmed by AFM observation, is largely increased. These results can be explained by the fact that the atmospheric-pressure plasma treatment of polyimide surface yields several oxygen complexes in hydrophobic surfaces, which can play an important role in increasing the surface polarity, wettability, and the adhesion characteristics of the polyimide/copper system.

In this paper, continuing previous work, we report on the installation and the testing of an experimental dielectric barrier discharge (DBD) reactor run in a controlled atmospheric pressure gaseous environment other than air. Here, the effects of a N₂-DBD treatment on the surface of a test polymer material (UHMW polyethylene) are examined, reported, discussed and compared to results obtained previously following air-DBD treatment. Surface analysis and characterization were performed using x-ray photoelectron spectroscopy, contact angle measurement and scanning electron microscopy before and following the DBD processing described. The discharge parameters used were correlated with the changes in the surface characteristics found following DBD treatments of various durations in a nitrogen atmosphere. The work focuses on the control of the gaseous environment supporting the discharge and on the possibility of overcoming the potentially dominant effect of reactive oxygen-related species, derived from any residual air present. The results obtained underline the very high reactivity of such species in the discharge, but are encouraging in respect of the possibility of the implantation or generation of functional groups other than oxygen-related ones at the surface of interest. The processing conditions concerned simulate 'real' continuous high speed processing, allowing the planning of further experiments, where various gaseous mixtures of the type X + N₂ will be used for controlled surface functionalization.

The synthesis of ozone from oxygen in a cylindrical ozonizer operating under surface discharge conditions with a plasma electrode was studied. The conditions of ozone synthesis were optimized. The dependence of ozone concentration and specific energy consumption on gas pressure in the plasma electrode and on distance between the coils of a corona electrode was determined. The results were compared with data obtained with the use of classical surface barrier discharge.

Polytetrafluoroethylene (PTFE) surfaces were treated by oxygen and nitrogen species generated either in a remote (filtered) RF plasma or in an ion gun. In the first case, the majority of the species reaching the surface are neutral molecules, whereas in the second case, ions are the reactive agent. In this paper, we show that ions alone do not lead to a significant grafting of new functions on the PTFE surface. The XPS analysis of the treated surface show identical behaviour with oxygen and nitrogen ion treatment, and the evolution of the C1s peak shape suggest a progressive sputtering, leading to defluorination of the surface. The nitrogen plasma treatment lead to a subsequent grafting that is attributed mostly to the “excited neutrals”, but we suggest here that the ions could play a significant role in the activation process of the surface. The exposure of PTFE to an oxygen plasma lead to chemical etching of the surface, different from the physical sputtering induced by the ion treatment, that lead to a super-hydrophobic behavior of the surface attributed to an increase in the surface roughness.