Cotton fibers from four varieties were washed with water using two procedures that included several combinations of temperatures and water volumes. Wettability of unwashed and washed fibers was determined by contact angle measurement and by a sink-float technique. The sink-float technique could be used to sort washed and unwashed cotton fibers.

Paper, although ubiquitous, is a complex material. We can classify paper as a basic network of self bonding cellulosic fibers; the chemical and physical characteristics of its surface are controlled by the raw materials, papermaking and converting processes used to produce it. Paper sometimes contains non-cellulosic fibers such as non-wood and synthetic fibers, chemical additives, fillers, and bonding agents. Other chemical additives used in the papermaking process, e.g., formation, drainage, and retention aids or coating materials may also change the physical and chemical characteristics of the paper's surface. With the greater use of recycled fibers we may expect additional changes in surface chemistry and structure.

X-Ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS) were used to study the chemical modification of polyphenylene sulfide (PPS) thin films on exposure to both oxygen and ammonia plasmas. The XPS results for the oxygen plasma treatment indicated a large oxygen increase with the incorporation of various oxidized carbon species as well as oxidized sulfur. For the ammonia plasma, both nitrogen and oxygen were incorporated. IRRAS proved to complement the XPS results, showing a wide range of C O and CO functionalities incorporated on oxygen plasma exposure. For the ammonia plasma treatment, an increase in hydrocarbon, alkene-type fragments, and possibly amine groups was detected. Both the XPS and IRRAS results indicated that exposure of plasma-treated surfaces to epoxy with subsequent carbon tetrachloride washes removed most of the modification originally present after plasma treatment. IRRAS analysis showed that a thin layer of epoxy remained after repeated solvent washes and that the film seemed to be cured. For untreated PPS films, a non-cured epoxy film adsorbed. This work suggests that the plasma-modified layer plays a role in the formation of a covalent interphase region between PPS and epoxy.

The surface of polyether ether ketone (PEEK) films was modified using plasma treatment, corona, or surface etching to improve their adhesion with regard to glued copper foils and copper layers generated by physical vapor deposition. After the pretreatments, surface chemical analysis was performed by X-ray photoelectron spectroscopy (XPS). The wetting behavior was qualitatively investigated by contact angle measurements. Surface topography was monitored by laser scanning microscopy (LSM). After coating, the adhesion strength of the copper layer was measured by a peel force test. Plasma treatment, corona discharge, or etching lead to a significant increase in adhesion. This increase is caused by a change in surface topography as well as by the incorporation of polar groups into the surface.

Polyethylene and polystyrene film surfaces have been plasma-oxidized and subsequently characterized by X-ray core level and valence band spectroscopies. The extent of polyethylene surface oxidation was found to be dependent on the power of the oxygen glow discharge employed and the length of time that the treated sample was left exposed to air prior to analysis. In marked contrast to these observations, plasma-oxidized polystyrene surfaces were much less dependent on the oxygen glow discharge power and were also found to retain their oxygenated character over much longer periods of ageing. These differences in oxidative behaviour are explained in terms of the molecular structures of the respective polymers.

This paper studies the effects on valid domain of contact angles and error limits of solid surface tension components and parameters (SSTCPs)/square roots of SSTCPs (SQSSTCPs) from the changes in liquid surface tension components and parameters (LSTCPs) when applying the van Oss–Chaudhury–Good (vOCG) approach. The results of maximum absolute errors and maximum relative errors (MREs) in SQSSTCPs/SSTCPs, induced by errors in LSTCPs or contact angles, show that most SQSSTCPs/SSTCPs can be evaluated at moderate accuracy from the lowest condition number liquid triplets, assuming that |Δθ_i| = 1° and  = 0.1 mN/m (i = 1, 2, 3, k = LW, +, −). This confirms the validity of the vOCG approach. The accuracy of each SQSSTSCP/SSTCP declines with increasing θ_i or decreasing parameter when θ_i > 0 or a critical value, provided the other two contact angles are kept fixed. This explains the underlying reasons for negative SQSSTCPs. At the scale proposed by vOCG, dimethyl sulphoxide is not suggested for use. Comparing with the MREs obtained at vOCG scale, considering the acidity of diiodomethane improves the accuracy of ; using the scales proposed by Lee and Shen do not affect the accuracy of SSTCPs, but using the scale proposed by Della Volpe et al. improves the accuracy of SSTCPs at low θ₂ and θ₃ while declines that at high ones. For a low , low surface tension apolar liquid is preferred for high accuracy. The dependence of the accuracy of SQSSTCPs/SSTCPs on contact angles suggests the importance of considering contact angle in accuracy evaluation.

In recent years, we have witnessed a remarkable growth in the use of the synthetic organic polymers in technology, both for high-technology and for consumerproduct applications (see Fig. 1 [1]). Polymers have been able to replace more traditional engineering materials such as metals, because of their many desirable physical and chemical characteristics (high strength-to-weight ratio, resistance to corrosion, etc.) and their relatively low cost. However, fundamental differences between polymers and other engineering solids have also created numerous important technical challenges, which manufacturing operations must overcome. An important example is the characteristic low surface energy of polymers and their resulting intrinsically poor adhesion [2–6]; the term “adhesion,” as it is used here and elsewhere in this text, may be briefly defined as the mechanical resistance to separation of a system of bonded materials [7]. Because adhesion is largely a surface property, often governed by a layer of molecular dimensions, it is possible to modify this near-surface region without affecting the desirable bulk properties of the material.

Low-pressure plasma processing of materials can be divided into three categories, namely (A) etching (removal of material),(B) deposition (addition of new material to a surface), and (C) modification (morphological, structural, and physicochemical change of the surface or near-surface region). In industries which make extensive use of low-pressure plasmas (for example, in the manufacture of integrated circuits-IC, the treatment of polymers for improved adhesion, etc), the above-named changes are deliberate and highly beneficial. However, there exist many instances where treatment can turn into a liability, or where plasma-chemical changes occur involuntarily and are a priori detrimental. The main objective of this chapter is to sensitize the reader to the existence of circumstances where plasma effects can be deleterious, for example:(1) Corona discharges, also known as silent discharges or dielectric barrier discharges, are a form of plasma which occurs when insulating materials are exposed to an alternating source of high voltage (~ 10 kV). Corona is comprised of multitudes of ultra-rapid (~ 100 ns), narrow (~ 100 μm) filamentary micro-discharges, which impinge upon the dielectric surface. Since the 1950s corona is being used commercially for treating polymeric webs up to 8 m in width, so as to render them printable (process category (C) above). However, corona treatment (like its low-pressure counterpart) can be detrimental if" overtreatment" occurs: If the reagent gas, like ambient air, contains oxygen, low-molecular-weight oxidized materials (LMWOM) form on the surface, and these can give rise to a weak boundary layer. This laboratory has compared corona and glow discharge treatment of LDPE and PET, using peel strength and XPS measurements, and has found similar" optimum" treatment criteria for both types of processes: High treatment (oxidation) levels could be correlated with elevated concentrations of acidic (O= C-O) reaction products and low peel strength.(2)

Low-temperature radiofrequency excited gas plasma was applied to the surfaces of a number of polymers. Polymers that are known to crosslink as well as those that only degrade under irradiation were included in the investigation. Surface changes were studied by viscosity, gel content, and contact-angle measurements. Changes in adhesive bond strength were used as a measure of overall practical effects of plasma treatment. In each case the response of the polymer surface to an oxidizing (oxygen) and a nonoxidizing (helium) plasma environment is discussed. Further indications of the nature of the surface changes were suggested by statistical treatment of the bond-strength data.

The study of the ionization of carboxylic acid groups at the interface between organic solids and water demonstrates broad similarities to the ionizations of these groups in homogeneous aqueous solution, but with important systematic differences. Creation of a charged group from a neutral one by protonation or deprotonation (whether -NH₃⁺ from -NH₂ or -CO₂- from -CO₂H) at the interface between surface-functionalized polyethylene and water is more difficult than that in homogeneous aqueous solution. This difference is probably related to the low effective dielectric constant of the interface (ε≃9) relative to water (ε≃80). It is not known to what extent this difference in ε (and in other properties of the interphase, considered as a thin solvent phase) is reflected in the stability of the organic ions relative to their neutral forms in the interphase and in solution, and to what extent in differences in the concentration of H⁺ and OH- in the interphase and in solution. Self-assembled monolayers (SAMs)-especially of terminally functionalized alkanethiols (HS(CH₂)_nX) adsorbed on gold-provide model systems with relatively well-ordered structures that are useful in establishing the fundamentals of ionization of protic acids and bases at the interface between organic solids and water. These systems, coupled with new analytical methods such as photoacoustic calorimetry (PAC) and contact angle titration, may make it possible to disentangle some of the complex puzzles presented by proton-transfer reactions in the environment of the organic solid-water interphase.

This paper reports on a three-part study: (1) to determine the effect of surface pretreatment of BDS, a siloxane/polyimide copolymer, on adhesion; (2) to determine the extent of segregation of components of BDS against metal substrates; and (3) to determine the properties of ultrathin polymer films against metal substrates.

Surface pretreatment of bds films with aqueous NaOH etched away the top siloxane layer, roughening the polymer surface and producing surface functional groups. These changes resulted in increased wettability and peel strength. Siloxane segregation when bds films were formed against metal surfaces was in the order: Al > Ti > Zn. The relative acidity of the metal oxides as measured by polyvinyl chloride adsorption was in the same order. Reflection-absorption measurements using Fourier transform infra-red spectroscopy were found to be useful in studying the crystallinity of thin polyphenylene sulphide (pps) films. X-ray photoelectron spectroscopy was used to show that failure occurred through a thin layer of residual pps polymer close to the copper oxide substrate.