The surface of polyester grafted with acrylic acid has been characterized using contact angle measurements of a two-liquid phase system and FT-IR and ESCA spectroscopy as a function of the concentration of acrylic acid on grafting. The COOH groups on the polymer surface influence only the polar component γ_s ^p of surface energy and not the dispersive one γ_s ^d. Both the FT-IR and ESCA characterizations, showing the transformation of COOH to COONa by alkaline treatment, provide information with a high degree of surface sensitivity, comparable to that of contact angle measurements. The relative area ratios of the COONa peak to the COOR peak by FT-IR ( A_surface) and of the Na_1s peak to the C_1s peak by ESCA are linearly correlated to γ_s^p.

The use of plasma deposition to introduce sulfonate groups to the surface of a polyurethane was attempted. In previous work, the bulk incorporation of sulfonate groups was found to improve the blood contacting properties of the base polyurethane but physical properties in the hydrated state were adversely affected. Plasma deposition schemes involving ammonia and sulfur dioxide were utilized in an attempt to incorporate sulfonate groups. Surface characterization by X-ray photoelectron spectroscopy (XPS) and contact angle measurements was used to follow polymer surface rearrangement dynamics and to address the issue of plasma chemistry specificity. Concerns of reaction specificity were alleviated by using the plasma as a pretreatment which is followed by a chemical surface derivatization.

The effects of remote nitrogen plasma, remote oxygen plasma, and corona discharge treatments on linear low-density polyethylene were studied with regard to the chemical and physical surface modification, depth of modification, and surface stability. An attempt was made to correlate the type and the extent of modification with the printing and adhesion properties of the modified surfaces. Surface topography was studied using scanning electron microscopy. The relative percentages of nitrogen and oxygen on the surfaces were determined by X-ray photoelectron spectroscopy. Printing and adhesion tests were performed using standard, commercially available inks and adhesives.

A study has been undertaken in which both x-ray photoelectron spectroscopy (XPS) and Fast atom bombardment static secondary ion mass spectrometry (FAB-SSIMS) have been used to study the effects of remote nitrogen plasma treatment on polymers such as linear low-density polyethylene (LLDPE), poly(ethylene vinyl alcohol) (EVOH) and poly(ethylene terephthalate) (PET). For comparison, remote oxygen plasma treatment was also performed on LLDPE. A very rapid uptake of nitrogen was observed for all polymers. Negative FAB-SSIMS indicated CN⁻, CNO⁻ and C₂N fragments on each of the nitrogen plasma-treated polmers. Positive FAB-SSIMS spectra of plasma-treated LLDPE showed relatively high intensity, high mass fragments, thought to originate from additives. These were not observed for the other two polymers. Significant amounts of aromatic-type fragments were observed in the positive FAB-SSIMS spectra of all treated polymers. Surface stability studies have shown that for both nitrogen and oxygen plasma-treaed LLDPE there is a substantial decrease in the surface functionality on exposure to air. This effect was much less prevalent for EVOH and PET.

Oxygen plasma treatment can be used for increasing the hydrophilicity of polymer surfaces, however, it is widely known that this effect decays significantly with time. This ageing phenomenon is thought to be caused by both migration of low molecular weight fragments and reorientation of modified polymer chains. It has recently been shown that the aged surface becomes transiently hydrophilic before attaining a final surface energy significantly lower than the initially treated surface. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to monitor the changes in surface chemistry of plasma oxidized poly(ether ether ketone) (PEEK) during post treatment storage. The decay and transient increase in hydrophilicity were found to be dependent upon crystallinity and storage temperature.

Experimental results on plasma treatments of polysulfone and polyetherimide to improve the wettability of these polymers are presented. The plasma is characterized by optical emission spectroscopy. The wettability of the polymer surfaces were checked by contact angle measurements and ESCA is used to compare the surfaces before and after plasma treatment. Correlations between contact angle, concentration of oxygen at the surface, and optical emission intensity of the OH radical have been established. Optimization of operational plasma parameters leading to the best wettability of the treated samples is reported.

In the Flexographic printing of polyethylene films with waterbased flexo inks, the partitioning of the surfactants between film/ink, pigment/ water, ink/air interfaces plays a major role in determining the printability. In addition, in formulations containing nonionic surfactants the equilibrium surface properties are much different from the diffusion limited dynamic properties. Problems associated with the printability are examined from an analysis of the above surface chemical considerations.

We developed a new plasma treating method, incorporating the use of microwaves generated by an electronic cooking range. Using this method, polytetrafluorethylene (PTFE) and a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) were treated. Dialkylphthalates (DAP) were used as the standard liquids of contact angle measurements for evaluation of the wetting properties of plasma treated polymers. The components of surface tension (γ_L) due to the dispersion force (γ^d _L) and the polar force (γ^P _L) of DAP were calculated by Fowkes' equation from the contact angles (θ) on polypropylene. After plasma treatment cos θ of several standard liquids on PTFE and FEP increased. The linear relationship between γ_L(1 + cos θ)/(γ^d _L)^½ and (γ^P _L/γ^P _L)^½ was verified. γ_s and γ^d _s and γ^d _s of the plasma treated PTFE and FEP also increased. From the results of ESCA analysis, it was found that a significant amount of oxygen was introduced to the polymer surface by the plasma treatment. Peel strengths of a pressure sensitive adhesive bonded to PTFE and FEP increased approximately two-to threefold if the plasma treatment was used prior to bonding.

Wetting force at three-phase line was measured by the Wilhelmy technique using fibrous solids/liquid/liquid systems. Advancing and receding contact angles were calculated from the wetting forces during fiber immersion and emersion. The obtained results showed that contact angle hysteresis was due to the heterogeneity of the fiber surfaces. The dispersive and polar components of surface free energies of the fibers were determined from the advancing and receding contact angles, respectively. The Hamaker constants of the fibers were estimated from the dispersive components of their surface free energies.

Films of poly(methyl methacrylate) (PMMA) of both medium and high molecular weight have been prepared by casting onto clean glass. The difference in water contact angle of the surface originally in contact with glass. and air and the variation over time of this parameter have been studied. By use of the surface analytical techniques X-ray photoelectron spectroscopy (XPS) and, particularly, static secondary ion mass. spectroscopy (SSIMS), it has been shown that migration of low molecular weight impurities from the bulk of the film to the film/air interface is responsible for the contact angle behavior.

By measuring contact angles with water, glycerol and formamide on a number of polar surfaces, an estimate could be made of the electron-acceptor (γ⁺ ) and the electron-donor (γ⁻ ) parameters of glycerol (G) and formamide (F), relative to the parameters of. water (W), for which a reference value of γ⁺ _W = γ⁻ _W = 25.5 mJ/m² has been assumed. The values thus found are: γ⁺ _G ≈ 3.92 mJ/m² (which yields γ⁻ _G ≈ 57.4 mJ/m²) and γ⁺ _F ≈2.28 mJ/m² (which yields γ⁻ _F ≈ 39.6 mJ/m²).

With increasingly stringent EPA guidelines for controlling emissions of volatile organic compounds on the horizon, the desirability to move to water-based printing inks is evident This paper examines the effects of corona discharge treat ments which are commonly used to improve ink adhesion to polvethylene. Electron spectroscopy for chemical analysis (ESCA) was used to determine the surface chemi cal changes induced by corona treatments in pure polyethylene extruded films and in formulated resin systems This data was correlated with surface tension and ink adhesion measurements to show the effects of treatment and additives on the final printability of the films with particular emphasis on water-based inks. In addition, the effects of stonng treated film prior to printing and of retreating these films were also examined The results of these tests have shown that formulated linear low den sity polyethylene (LLDPE) films treat and print at least as easily as high-pressure low-density polyethylene (HP-LDPE) counterparts.

The reaction rates and products of remote oxygen plasma treatment, corona discharge, and ozone treatment of high and low density polyethylenes have been examined using x-ray photoelectron spectroscopy. The oxygen uptake by remote plasma treatment was faster than that of other surface treatments using excited oxygen species. A steady state concentration of 18 ± 1% oxygen can be attained within 1 s of exposure in the remote plasma.

A triode glow discharge system was used for the plasma treatment of polytetrafluoroethylene (PTFE) films and the formation of plasma polymerized hexamethyldisiloxane (PPHMDS) films on PTFE films. The nitrogen plasma increased the surface tension of the PTFE films to about 40 dyn/cm by applying an rf voltage to the substrate electrode. The contact angle of water on the PPHMDS films with the rf voltage was changed to 40°∼90° by corona discharge exposure for 30 s at 6 kV. This reduction is due to the decarbonization and the oxidation of PPHMDS films.