Ammonia plasma treatments were performed on both thermoplastic plates and fabrics made of poly (ethylene terephthalate)(PET). The plates became more hydrophilic with improved adhesion properties as expected, whereas the fabrics became more hydrophobic, yet positively charged. Plasma treatments of PET fabrics using gas mixtures such as NH3/N2 and HZ/NZ were performed in order to simulate pure ammonia plasma treatments since such treatments are not always applicable in industrial applications, due to environmental and safety reasons. It was shown that the recommended and allowed gas compositions, 15% NH; in N2 and 5% H2 in N2, did not show any similarity with pure ammonia plasma treatments with respect to surface charge, wettability and chemical surface composition. At least 80% NH; in N; or 80% H2 in N2 is needed to simulate an ammonia-like plasma treatment of PET fabrics.

Ultra-high-molecular-weight polyethylene (UHMWPE) fibers (Spectra® 1000) were treated using pulsed XeCl excimer laser (308 nm) to improve their adhesion to epoxy resin. The la-ser treatments were carried out in air and in diethylenetriamine (DETA) environments with varying numbers of pulses and fluences. The effects of the laser treatments on the fiber surface topography, chemistry and wettability were investigated. The interfacial shear strength (IFSS) with epoxy resin was measured using a single fiber pull-out test. The surface roughness was characterized using scanning electron microscopy (SEM) and atomic force microscopy (AF M). The laser treatment introduced grooves along the fiber length and increased the fiber surface roughness up to 6-times the control value, as measured by AFM. The X-ray photoelectron spectroscopy (XPS) data indicated that oxygen and/or nitrogen were incorporated on the fiber surface afier the laser treatments depending on the environment in which the treatments were carried out. For some treatments the oxygen/carbon ratio increased by up to 2.5-times the control value. The dynamic wettability data showed that the laser treatments significantly increased the acid-base component of the surface energy and the work of adhesion. The UHMWPE fiber/epoxy resin IFSS increased by up to 400% for certain treatment conditions. The introduction of polar groups and higher surface roughness were found to be the two main factors that contributed to the significant increase in the adhesion of the UHMWPE fiber/epoxy resin system.

In this work, low pressure glow discharge O₂ plasma has been used to increase wettability in a LDPE film in order to improve adhesion properties and make it useful for technical applications. Surface energy values have been estimated using contact angle measurements for different exposure times and different test liquids. In addition, plasma-treated samples have been subjected to an aging process to determine the durability of the plasma treatment. Characterization of the surface changes due to the plasma treatment has been carried out by means of Fourier transformed infrared spectroscopy (FTIR) to determine the presence of polar species such as carbonyl, carboxyl and hydroxyl groups. In addition to this, atomic force microscopy (AFM) analysis has been used to evaluate changes in surface morphology and roughness. Furthermore, and considering the semicrystalline nature of the LDPE film, a calorimetric study using differential scanning calorimetry (DSC) has been carried out to determine changes in crystallinity and degradation temperatures induced by the plasma treatment. The results show that low pressure O₂ plasma improves wettability in LDPE films and no significant changes can be observed at longer exposure times. Nevertheless, we can observe that short exposure times to low pressure O₂ plasma promote the formation of some polar species on the exposed surface and longer exposure times cause slight abrasion on LDPE films as observed by the little increase in surface roughness.

Polyolefin surfaces, namely isotactic poly(propylene) (iPP) and low-density polyethylene (LDPE), were modified by corona discharge plasma. The chemical changes on the modified surfaces were observed, deeply affecting the surface and the adhesive properties of the studied materials. The hydrophobic recovery in the case of iPP is considerably dependent on the polymer crystallinity. The presence of the processing agents in the LDPE has a significant influence on the surface hydrophobization dynamics.

Atomic-force microscopy was used to study structural chemical transformations on the surface of polyvinyl chloride films subjected to modification with compounds based on acrylic acid derivatives, with preliminary activation of the polymer surface with a corona discharge.

PTFE surface modifications have been realized using low-pressure RFGD, DBD and APGD in different atmospheres. Compared to the RFGD NH₃ plasma, the DBDs operating in H₂/N₂ lead to similar surface concentrations of amino groups and similar surface damage, but with a much higher specificity. Both APGDs in H₂/N₂ and NH₃/N₂ lead to lower concentrations of amino groups, but with similar specificity, and with lower surface damage than the RFGD treatment. A method is proposed to evaluate the efficiency of the different discharges for amine surface functionalization of PTFE, and it is concluded that the NH₃/N₂ APGD discharge is the one that give the best results for an effective surface treatment.

The experimental work reported here is devoted to the electrical study of two atmospheric pressure dielectric barrier discharge (DBD) reactors operating at high gas flow, conceived for surface treatment applications in spatial afterglow conditions. Both reactors are of coaxial geometry with the dielectric covering the active electrode, and are driven by a power generator delivering quasi-sinusoidal voltage waveforms in the 100–160 kHz range. The influence of the gas flow value and of the input power on the electrical operation of these systems is investigated. The comparative study performed here, by means of electrical measurements, reveals the influence of parameters such as geometrical dimensions and dielectric material used on the operation of the DBD. Power factor measurements are used to quantify the reactors' electrical performance. Optical diagnostics and kinetic modelling reveal a high chemical activity of the systems appropriate for the treatment of surfaces at atmospheric pressure.

A review is presented of the adhesion between polymers with particular emphasis on the processes that occur during failure at the level of polymer chains and how these processes relate to the macroscopic interface toughness. The same processes at the chain level, pull-out and scission, occur in both glassy polymers and elastomers, but the two classes of material are considered separately because their deformation processes around a crack tip are so different. Emphasis is placed on the work in which the author has participated and so the review makes no attempt to be an unbiased survey of the field.

In atmospheric pressure corona systems, the densities of electrons and ions determine the level of treatments. Here, the electron and ion densities in a corona plasma are evaluated for a DC positive-polarity wire discharge in dry air at atmospheric pressure, in the coaxial wire-cylinder geometry. We use a new numerical iterative approach to solve the coupled equations for the electric field and charge densities. The role of electron diffusivity is discussed and the influence of the charge distribution between electrodes on the electric field strength and on the plasma region is analyzed.

In the last few decades there has been an intense development in non-equilibrium (“cold”) plasma surface processing systems at atmospheric pressure. This new trend is stimulated mainly to decrease equipment costs by avoiding expensive pumping systems of conventional low-pressure plasma devices. This work summarizes physical and practical limitations where atmospheric plasmas cannot compete with low-pressure plasma and vice-versa. As the processing conditions for atmospheric plasma are rather different from reduced pressure systems in many cases these conditions may increase final equipment costs substantially. In this work we briefly review the main principles, advantages and drawbacks of atmospheric plasma for a better understanding of the capabilities and limitations of the atmospheric plasma processing technology compared with conventional low-pressure plasma processing.

The performance of water-based acrylic flexographic inks laboratory printed on three different polymer-coated boards, namely coated with LDPE, OPP and PP, have been analysed and interpreted. The print quality and resistance properties obtained were related to varying ink formulation, in particular choice of emulsion polymer and presence of silicone additive in the vehicle, as well as varying levels of corona pretreatment. Print mottle and adhesion were worst on PP, while wet (water) rub and scratch resistance were worst on OPP and PE, respectively. However, these properties could be greatly influenced by the ink formulation, more so than corona level. In general addition of silicone improved scratch resistance, due to reduction in polar energy component of the print surface, but at the expense of worsened wet rub resistance. The emulsion polymer giving best resistance performance was generally found to give poorest optical properties, presumably due to more limited resolubility on press.

The capability of the PDMS based antiadhesion surface treatment strategy for high resolution unconventional lithography using hard or soft molds as representatives of imprint lithography or soft lithography was investigated. A thin film of PDMs was used as an antiadhesion release layer as PDMS has a fairly low surface energy and allows for the easy release of the mold from the patterned polymer on the substrates. The surface of the Si wafer was coated with a thin film of PDMS and using this PDMS-coated Si wafer as a hard mold line/space patterns were printed on the SU-8-coated PET substrates. Using this photoresist replica mold as a template for a soft mold the same PDMS-based coating strategy was applied. The imprinting of nanostructure-patterned mold onto a polymer composed of the same chemical as the mold led to pattern collapse during the release of the assembly because of the extremely strong adhesion between the mold and the polymer.

o optimize the effects of some discharge parameters on the surface wettability of polypropylene (PP) in atmospheric pressure dielectric barrier discharge, a surface modification model is created based on statistical theory and orthogonal experimental design method. Contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) are used to study the changes in the surface wettability, surface topology and chemical compositions of the samples. The results show that surface wettability has been improved due to roughness increasing and the introduction of oxygen-containing functional groups. High-resolution XPS of C1s peak deconvolution indicates that the types and contents of oxidized functional groups are different in different discharge conditions or plasma energy. Moreover, the model analysis reveals that it has better predictive ability, and different discharge parameters has selective influence on water contact angle and surface O atom percentage.

Methods for treating polymeric substrates by placing the substrate in a gaseous mixture and subjecting it to a dielectric barrier electrical discharge. The gaseous mixture, which has a pressure around atmospheric, contains a carrier gas, a reducing gas and an oxidizing gas. The amount of the oxidizing gas in the gas mixture is between about 50 ppm and about 2000 ppm by volume, while the amount of the reducing gas in the gas mixture is between about 50 ppm and 30000 ppm by volume.