Contact time of activated gas with polymer film of as little as 1 sec. under these relatively mild conditions resulted in greatly improved adhesive joint strength for polyethylene. Longer contact times were required for polymers such as polytetrafluoroethylene. Helium, argon, krypton, neon, and xenon, and even hydrogen and nitrogen were all effective crosslinking agents although the latter also changed wettability of the surface. Adhesive joints were prepared by sandwiching 1041 films of polyethylene (Marlex 5003, Phillips Petroleum Co., Bartlesville, Oklahoma) and polytetrafluoroethylene (G-80, Allied Chemical Co., Morristown, New Jersey), before and after CASING, between epoxy-coated aluminum strips (3). The values obtained for tensile shear strengths of these joints are shown in Figure 1. In these instances, the polyethylene film was treated for 10 sec. and the polytetrafluoroethylene film was treated for 10 min.

The surface energetic properties of different areas of the offset printing plate are the key factors of this printing process, since they control the ink transfer during printing. The importance of these factors is discussed for both waterless offset and conventional offset. The printing process is highly dynamic. New surfaces are created and their lifetimes are short. From recent theories of dynamic wetting, it has been concluded that spontaneous removal of ink films from nonimage areas is a very slow due to the high ink viscosity and the low dynamic contact angle. Thus it is of less importance.

The apparatus described provides a direct-reading instrument for the measurement of the spreading coefficient of a liquid on a solid surface. The determination is based on the measurement of the maximum height of a sessile drop of the liquid-solid system.

The article throws light on the physical methods to modify natural fibers to be used in composites. Physical methods in natural fiber processing are used to separate natural fiber bundles into individual filaments and to modify the surface structure of the fibers so as to improve the use of natural fibers in composites. Steam explosion and thermomechanical processes fall in the first category while plasma, dielectric barrier techniques and corona fall in the second. The physical treatments have also been used to modify the thermoplastic polymeric films like polyethylene and polypropylene in a bid to impart reactivity. Reviewing such developments, the areas for further research are suggested.

Titanium films, 1 μm thick were electron‐beam evaporated onto polyethylene (PE) that had been pretreated in situ by 2 keV Ar⁺ bombardment. A measure of the film adhesion was obtained by measuring the pull strength required to remove the Ti films. A strong dependence of the adhesion on the ion dose was found. The pull strength had a maximum of approximately 20 MPa after a dose of 6×10¹⁴ ions/cm² but decreased for higher ion doses. Without any ion bombardment prior to deposition, the adhesion was very poor with a pull strength of approximately 2 MPa. XPS analysis was used to examine the effect of the ion bombardment on the chemistry of the PE substrate and the Ti/PE interface. Untreated PE samples were contaminated with surface impurities and probably also with low molecular weight hydrocarbons. As the adhesion is maximized, most of the impurities are removed by the ion bombardment. The strong adhesion is suggested to be due to formation of a carbidelike Ti–C interfacial layer, detected by XPS.

Surface composition, fluorine distribution, and morphology were determined for polyimide films modified downstream from microwave plasmas containing CF₄/O₂. Complementary analytical techniques including x‐ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, and scanning electron microscopy yielded a more complete understanding of polyimide fluorination and subsequent etching of the modified film. Depth of fluorination increased nonlinearly with treatment time for films exposed downstream from a CF₄‐rich plasma. Exposure downstream from an O₂‐rich plasma resulted in a reduction of thickness in both the fluorinated layer and the unmodified polyimide during etching. Finally, a model for fluorination of polyimide and subsequent removal is proposed.

Surface chemical modification of polymer thin films induced by sputter etching was studied by x‐ray photoelectron spectroscopy (XPS) and infrared reflection–absorption spectroscopy (IRRAS). The polymers studied were polystyrene, polypropylene, and poly(ethylene terephthalate) (PET). Oxygen and argon sputter etching of these polymers causes surface oxidation and possibly crosslinking; trends in polymer oxidation can be correlated with the etchant gas, etch power, and initial material properties. For polystyrene and polypropylene, the predominant new functionalities formed are CO and CO groups; the breadth of the infrared absorption bands suggests that many different types of these groups exist. For PET, the predominant damage mechanism is crosslinking, with only a slight degree of oxidation resulting from oxygen sputter etching. This work suggests that the information provided by XPS and IRRAS is highly complimentary and will be useful in future studies of polymer functionalization and derivatization.

The effects of ion irradiation on polyimide surfaces have been studied using x‐ray photoemission techniques. Ion bombardment with energies in the range 0.5–2.0 keV and doses between 8×10¹³ and 1×10¹⁵ ions/cm² were carried out in situ in the x‐ray photoelectron spectrometer and the chemistry of the modified surface was monitored using core level spectral changes. At low doses and energies, carbonyl groups were preferentially sputtered keeping the rest of the monomer intact. Loss of nitrogen was insignificant compared to losses of carbon and oxygen. At higher energies and doses, the polymer undergoes extensive bond scission, restructuring of various functional groups and species, together with radical and anion formation. High resolution spectra indicated a binding energy scale shift to a lower value, which increased with ion energy and dose, and which was related to the creation of a surface negative charge. The effects of exposure to moisture in the ambient on the surface charge, on the surface structure, and on the surface chemistry was studied.

Remote argon plasma (RP) and ozone in the presence of ultraviolet light (UV–O₃) were used to render polystyrene (PS) surfaces hydrophilic in a controlled manner for eventual application in cell‐surface interaction studies. X‐ray photoelectron spectroscopy (XPS) was used to characterize both methods of modification. The degree of modification on PS was measured by an increase in surface oxygen and concomitant change in C 1s binding energies as a function of time. Both remote plasma and UV–O₃ are shown to be partially surface destructive, producing polymer fragments which are easily washed away to leave stable modified surfaces of oxidized polymer comprising of distributions of C–O, C=O and O—C=O type groups. Of the two methods, UV–O₃ is shown to be more versatile and conducive to preparing PS surfaces with controllably varying degrees of modification. UV–O₃ modified polystyrene is shown to be stable in air for at least eight months. Contact angle methods were used in correlation with XPS in characterizing UV–O₃ modified surfaces. It is shown that changes in surface tension and total surface oxygen content were related, however, not directly connected.

Emission spectroscopy was applied to observe the reaction process of poly (ethylene terephthalate) (PET) in an oxygen (O2) plasma generated by a microwave discharge. As the PET was exposed in the O2 plasma flow, light emitted from the PET surface was monitored. In the diagnosis measurement, several emission peaks assigned to the Hα atomic line at 652 nm, Hβ at 486 nm, OH (2Σ→2Π) transition near 244–343 nm and CO (b3 Σ→a3 Σ) near 283–370 nm were observed and measured at various discharge times. These results indicated that after the plasma etching, the PET sample was decomposed by the oxygen plasma reaction, and then, hydrogen abstraction and carbon oxidation processes. We also observed the time profile of oxygen atom, as the atom-emission intensity at 777 nm was monitored. As Hβ atomic and OH molecule lines appeared in the presence of PET, the O atom intensity was significantly reduced. In the surface analysis on Fourier transform infrared and x-ray photoelectron spectroscopy measurements, it was found that for the PET surface treated by O2 plasma containing excited atomic oxygen species, ester bands were broken and carbonization formed on the PET surface.

The control of the surface wettability of poly (methyl methacrylate) (PMMA) substrates has been successfully demonstrated using an Ar2* excimer lamp radiating 126 nm vacuum ultraviolet (VUV) light. Each of the samples was exposed to 126 nm VUV light in air over the pressure range of 2×10−4-105 Pa. Although at the process pressures of 10, 103, and 105 Pa, the PMMA surfaces became relatively hydrophilic, the degree of hydrophilicity depended markedly on the pressure. The minimum water contact angles of the samples treated at 10, 103, and 105 Pa were about 50°, 33°, and 64°, respectively. These values were larger than those of PMMA substrates hydrophilized through 172 nm VUV irradiation conducted under the same conditions. On the other hand, after 126 nm VUV irradiation conducted under the high vacuum condition of 2×10−4 Pa, the PMMA substrate surface became carbon-rich, probably due to preferential cross-linking reactions, as evidenced by x-ray photoelectron spectroscopy. This surface was hydrophobic, showing a water contact angle of about 101°. Although the 126 nm VUV-irradiated surfaces appeared relatively smooth when observed by atomic force microscope, very small particles with diameters of 30-60 nm, which probably originated from the readhesion of photodecomposed products, existed on all of the sample surfaces.

The plasma source ion implantation (PSII) was utilized to improve the wettability and the stability of surface layer formed in the modification of polymeric materials. Polystyrene was treated with different kinds of plasma ions to render the surface more hydrophilic or hydrophobic. Hydrophobic recovery of PSII-treated polystyrene was also observed as a function of aging time, aging temperature, and treatment parameters. Treatment parameters involve kinds of gases, pressure, plasma power, pulse frequency, pulse voltage, etc. To study the effect of inert gas on hydrophobic recovery, polystyrene samples were prepared by helium, argon, or gas-mixture treatment. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been used to interpret the PSII-treated polystyrene surface and its hydrophobic recovery, with the assistance of x-ray photoelectron spectroscopy and water contact angle measurements. TOF-SIMS spectra of O218 PSII-treated samples showed the presence of O18-containing peaks from the modified surfaces. PSII modifications provide more stable surfaces of polystyrene as a function of aging time than plasma treatments. The comparison of aging behavior data allowed for examination of the differences in the stability of the functionality introduced by the two different treatment techniques.

Mild plasma cleaning of metal surfaces was shown to be effective in removing organic contaminants. Auger electron spectroscopy and surface wettability measurements were used to evaluate the plasma cleaning procedure and to provide a comparison with conventional solvent cleaning methods.

Poly(methylmethacrylate) (PMMA), poly(2-hydroxyethyl methacrylate (PHEMA), and poly(2-hydroxypropyl methacrylate) (PHPMA) were modified to improve the wettability by two techniques: plasma and plasma source ion implantation. The modified surfaces were characterized to investigate the dependence of the modification and hydrophobic recovery on the polymer structure. The differences obtained under optimal experiment conditions among the polymers were interpreted in terms of their polymer structures including the glass transition temperature. The surface free energy, calculated from the contact angle measurements, revealed that its polar component was a dominant factor in improving the wettability. The PSII treatment created more functional groups on the surface and extensively modified the polymer layer than the plasma treatment.

Modification of a selective area of a fluororesin surface was accomplished by using ArF excimer laser radiation and a boron complex with oleophilic or hydrophilic functional groups. The chemical stability of fluororesin is attributed to the presence of C-F bonds. The F atoms were abstracted by B atoms selectively from the area irradiated with excimer laser radiation and were replaced with the desired functional groups. In this modification, B(CH₃)₃ and B(OH)₃ were used: a boron compound with methyl groups to generate an oleophilic surface, and one with hydroxyl groups to generate a hydrophilic surface. As a result, the resin surface exposed to ArF laser radiation becomes oleophilic or hydrophilic. Both samples were bonded to stainless steel plates with an epoxy bonding agent and the tensile shear strength was 1.2 x 10⁷ Pa in both cases.