Oxygen plasma-treated quenched and annealed polypropylene (PP) films with different crystallinities were investigated to characterize the surface rearrangement behavior during aging using contact-angle measurements and X-ray photoelectron spectroscopy. Optimum plasma conditions were examined by varying the power, time and pressure. Less crystalline quenched PP showed a larger increase in water contact angle and a larger decrease of oxygen atomic concentration during aging than the more crystalline annealed PP, since the oxygen species, such as hydroxyl groups, introduced by oxygen plasma treatment, oriented towards or diffused faster into the bulk with lower crystallinity. The degree of crosslinking on the surface was enhanced after plasma treatment and, in addition to increased crystallinity, the crosslinked structure induced by plasma treatment restricted chain mobility and lowered the aging rate of the PP surface.

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.

The physical and chemical principles of the process of polymeric material surface layer (WW) modification using corona discharge (WK) in an air were discussed. The phenomenon of low temperature plasma formation and the way of its interaction with polymer surface were described. Basic aims of the process of modification with WK were presented as well as the results obtained this way for particular polymers, among others PE, PP, PVC, PET. In case of PE and PP also the composite materials with polyolefine matrix or fiber filler were considered. The possibilities of corona discharge use in graft polymerization were noticed. Also numerous directions of practical use of the changes of polymers' surface layers caused by corona discharge were marked.

A new method of analysis of differences in the surface free energy (SFE) values of a solid, calculated using the methods of Owens-Wendt (OW) and Neumann and two measuring liquids, water and diiodomethane, is presented. The concept of the analysis bases on the differences in SFE, which occur objectively and regardless of both the precision and the performing conditions of the contact angle (CA) measurements. These differences result from utilizing of different mathematical relations between CA and SFE in each of the methods. The results obtained with these two methods are compared with one another over the SFE range common for polymeric materials (20-50 mJ/m 2). It is calculated that the relative difference in SFE between the results from the OW and Neumann methods can reach 19.9 % over this range.

In the article the analysis of the main methods of calculations of interfacial free energy and surface free energy (SEP) values of solids, in which contact angle measurements' results play a key role, has been presented. The importance of Young's equation and Berthelot's hypothesis as the scientific basis of these methods has been indicated. Various methods of calculations of interfacial free energy values for solid-liquid systems, including calculations of this energy on the basis of state equations or SEP divide to independent components, (especially for polymers) were discussed. The most important methods of calculations of SEP values for polymeric materials on this basis were characterized. The methods of calculations of contact angle values for porous materials, granulated products, powders or fibers on the basis of Washburn equation, what is a base for calculations of SEP of these materials, were presented.

The selected problems related to investigations of surface layers (WW) of solids were presented. The analysis of essential limits of van Oss - Chaunhury - Good's (vOCG) method, used for calculation of surface free energy (SEP) of polymeric materials, has been done. Some reasons of discrepancy between the results of calculations, obtained by various authors, were discussed in details. Namely, the need of use of algebraic analysis for selection of the set of three measured liquids, which are necessary in vOCG method, has been pointed. It makes possible to eliminate the sets of liquids being the reasons of bad conditioning of the sets of equations for SEP calculation. The effect of the proper selection of scale of components (acidic and basic ones) of SEP of water on the right evaluation of selected properties of the materials investigated was also presented (Table 1&2). General conclusions concerning the causes of controversy over van Oss - Chaunhury - Good's method were formulated.

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.

Influence of the unit energy (E_u) of corona discharge used for modification of pure polylactide (PLA) and polylactide nanocomposite (PLAC) containing 5 wt% of an aluminosilicate nanofiller (Cloisite 30B) on water (Θ_W) and diiodomethane (Θ_D) contact angles as well as on surface free energy (γ_s) of these polymers was studied. Θ_W and Θ_D as advancing contact angles were measured with use of a goniometer while γ_s was calculated by the Owens–Wendt method. It was found that Θ_W increased with the rising E_u while Θ_D remained approximately constant. Assuming E_u = const, it could be stated that the increase in γ_s was much more evident for PLA than for PLAC. This increase resulted practically from the change in the polar component of γ_s because the dispersive component for the two materials only slightly decreased with increase in E_u.

The paper investigates the effect of corona discharge (CD) treatment on the properties of surface layer (SL) of polylactide (PLA) film. The modification of PLAwas carried out in the air and helium atmosphere and the results were compared on the basis of the assessment ofwettability, surface free energy (SFE) calculated using Owens-Wendt method aswell as the degree of oxidation (O/C) of the modified SL, determined by photoelectron spectroscopy.

The effects of the electron radiation dose and of compatibilizers on the contact angle and surface free energy (SFE) of the composites made of low-density polyethylene (PE-LD), high-density polyethylene (PE-HD), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were studied. Use of the high-energy electron radiation with doses up to 300kGy and of compatibilizers was done to reach better mechanical and adhesion properties of the composites studied and, at the same time, to investigate the possibility of applying of this technique in the processes of polymeric materials recycling. The compatibilizers were the styrene-ethylene/butylene-styrene elastomer grafted with maleic anhydride (SEBS-g-MA), added at the amounts of 5, 10 or 15 wt.%, and trimethylol propane trimethylacrylate (TMPTA), added at the amounts of 1, 2 or 3 wt.%. The effects, discussed in the present article, are: enhancement of wettability and increase in SFE of the composites studied. It was found that the contact angle steadily decreased and SFE of the composites increased with the rising dose of the electron radiation and that TMPTA intensified these tendencies.

Without any preprocessing, polyester fabric has a lower ability to hold on water and inks due to the smooth morphology and chemistry property of polyester fibers. Therefore, patterns directly printed with pigment inks have poor color yields and bleed easily. Plasma surface treatment of polyester fabrics was carried out in composite atmosphere with air and 10% Ar under different experimental conditions. After plasma treatment the samples were printed with pigment inks. The results show that surface-modified polyester fabrics exhibited enhanced color yields and excellent pattern sharpness. SEM and XPS analyses indicated that this improved color performance was mainly contributed by not only the etching effect but also oxygen-containing polar groups induced onto fiber surfaces through plasma treatment. Thereby the surface modification of polyester fabrics using air/Ar plasma offers a potential way to fabric pretreatment for pigment inkjet printing with the advantages of environmental friendly and energy saving over traditional pretreatment methods.

Semi-crystalline polyetheretherketone (PEEK) is of interest for providing hermetic sealing of implantable medical devices. Self bonding or autohesion is achieved by mild temperature and pressure treatment and is potentially useful to form joints in the encapsulation of active medical implants. The surfaces of PEEK films were treated in a radio-frequency (RF) plasma containing one of the gases Ar, N₂ and O₂, to achieve surface activation. The bond strength developed over the interface of PEEK films was evaluated by lap-shear testing. The effects of plasma conditions on the surface morphology, composition, and properties were determined using the profilometer, contact angle measurements, X-ray photoelectron spectrometry (XPS) and scanning electron microscopy (SEM). Results obtained show that plasma treatment of the PEEK films enhances their bonding strength, with the Ar treated films exhibiting the highest bond strength and nitrogen the lowest. Bond strength was shown to correlate positively with total oxygen content, with C–O group concentration and with the polar component of surface energy. Bond strength correlated negatively with CO group concentration.

To prevent the loss of fiber strength, ultrahigh-molecular-weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corona-discharge treatment. The physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance. The gel contents of the fibers were measured by a standard device. The mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE-fiber-reinforced vinyl ester resin composites were investigated with tensile testing. After 20 min or so of ultraviolet radiation based on 6-kW corona treatment, the T-peel strength of the treated UHMWPE-fiber composite was one to two times greater than that of the as-received UHMWPE-fiber composite, whereas the tensile strength of the treated UHMWPE fibers was still up to 3.5 GPa. The integrated mechanical properties of the treated UHMWPE fibers were also optimum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 463–472, 2004
https://onlinelibrary.wiley.com/doi/10.1002/polb.10727

The influence of corona treatment on the near-surface structures of treated ultra-high-molecular-weight polyethylene (UHMWPE) fibers was studied first by atomic force microscopy (AFM). AFM pictures showed that the pits on the corona-treated PE fiber surfaces had different change characteristics in depth compared with in length and breadth with variations of corona power. Then the UHMWPE fibers were subjected to chemical modification following the corona treatment, named the two-stage treatment. Surface morphologies and chemical properties of the treated fibers were analyzed by scanning electron microscopy (SEM), FT-IR–ATR spectroscopy and Raman spectroscopy. The results obtained suggested that some carbon–carbon double bonds had been introduced on the surfaces of the PE fibers after the two-stage treatment. These unsaturated groups could participate in free-radical curing of vinylester resin (VER), and this resulted in improvement of interfacial adhesion strength in the PE fiber/VER composites. In addition, the mechanical properties of the UHMWPE fibers reduced after corona treatment did not reduce further after subsequent chemical treatment with increase of corona power. In short, the two-stage treatment proved to be effective in improving the interfacial adhesion of the composites and maintaining the high mechanical properties of the PE fibers, as this treatment method did not destroy the bulk structure of the UHMWPE fibers.

Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (PET) film surface for improving hydrophilicity using the non-thermal plasma generated by atmospheric pressure glow discharge (APGD) in air is conducted. The discharge characteristics of APGD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena, and the surface properties of PET before and after the APGD treatment are studied using contact angle measurement, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEh4). It is found that the APGD is homogeneous and stable in the whole gas gap, which differs from the commonly filamentary dielectric barrier discharge (DBD). -4 short time (several seconds) APGD treatment can modify the surface characteristics of PET film markedly and uniformly. After 10 s APGD treatment, the surface oxygen content of PET surface increases to 39%, and the water contact angle decreases to 19°, respectively.