In this work we studied the effect of surface treatment of PET films, which are widely used in food packaging, on the adhesion value of ink layers based on polyvinyl chloride. To give high barrier properties to packaging laminates, the films used in their structure are coated with a nanolayer of aluminum oxide (AlOx). However, these films have a disadvantage associated with the low adhesion of adhesive and ink layers to the AlOx nanolayer. To eliminate this disadvantage, aluminium oxide nanolayer is additionally coated with various polymer coatings. In this work we studied the effect of a polyacrylic coating applied on top of an AlOx layer on improving the adhesion of ink layers. For PET films used in food packaging, optical and surface properties are also important. In this regard, additionally we measured surface free energy, coefficient of friction, and optical properties of the studied PET films. We also highlight the relationship of contact angles of wetting and the work of adhesion for the printing ink with the measured adhesion of ink layers.

In packaging, plastic films are very often applied as overprinting materials. The printing properties of plastic films depend on the value of the surface free energy. Usually, during storage but before printing, the surface free energy is decreasing as a result of ageing. The aim of this study was to analyse the influence of elevated temperature and UV radiation on ageing properties and variation of the free surface energy for three commercially available plastic films: polyethylene, polypropylene and polyethylene terephthalate. The investigation was done experimentally, and the surface free energy was calculated using two approaches, Owens-Wendt and van Oss-Chaudhury-Good. The time change of polar fractions was also analysed. The calculation results were compared and it was concluded that UV radiation causes more changes in surface free energy than elevated temperature. In some cases, surface free energy values calculated with the applied methods show similar trends.

The atmospheric pressure He- H 2 O plasma jet has been analyzed and its effects on the Kapton polyimide surface have been investigated in terms of discharge power effect. The polyimide surfaces before and after plasma treatment were characterized using atomic force microscopy (AFM), X-ray photoelectrons spectroscopy (XPS) and contact angle. The results showed that, increasing the discharge power induces remarkable changes on the emission intensity, rotational and vibrational temperatures of He- H 2 O plasma jet. At the low discharge power ≤5.2 W, the contact angle analysis of the polyimide surface remarkably decrease owing to the abundant hydrophilic polar C=O and N–C=O groups as well as increase of surface roughness. Yet, plasma treatment at high discharge power ≥5.2 W results in a slight decrease of the surface wettability together with a reduction in the surface roughness and polar groups concentrations.

Antimicrobial packaging is currently one of the emerging technologies being pursued to extend the shelf-life of food products. Polyamides (PA) are widely used in food packaging, principally in laminate constructions, where they are used alone or combined with other materials. PA can be surface-treated using UV, plasma and corona treatments to create active film surfaces for various industrial applications. Scope and Approach the object of this article was to review different surface treatment methods for the potential manufacture of smart packaging materials including antimicrobial application in particular and to review the necessary spectral characteristics deemed necessary to achieve this. Key Findings and Conclusions XPS and AFM methods are useful tools in the identification of film surface analysis. For UV treatment, different light sources, including lasers, can be applied to create antimicrobially-active packaging materials. UV-treated PA films possess antimicrobial properties and offer potential for industrial and medical packaging applications, however, the application of such packaging materials to foods needs some special consideration. Different plasma treatment methodologies can be used for modification of PA surfaces, followed by attachment of antimicrobial coatings which are very limited in literature. Surface studies have shown that plasma-treated PA surfaces possess spectral properties similar to those for UV-treated samples. Corona treatment, like UV and plasma treatments, induce the modification of functional groups on PA film surfaces. Corona treatment has the capacity to activate polymeric surfaces for adhesion of a variety of functional coatings and should be explored further in terms of creating special antimicrobial coatings.

Aging phenomenon or hydrophobic recovery of plasma-treated surfaces is a major concern in various fields of application. Post-plasma decay of treatment level can lead to problems such as delamination and incompatibility. Considerable work has been done to understand the fundamental mechanisms of aging, from which several approaches have been developed to tackle it. Most of the released solutions require additional and further steps after or before the plasma exposure to stabilize the treatment level and prevent its downfall. This per se causes process difficulties and increases production costs. Herein, a single-step gliding arc plasma-based method is investigated for modification of biaxially-oriented polypropylene (BOPP). Findings approved post-treatment progressive hydrophilicity improvement in this method. Surface characteristics’ alterations were assessed instantly after the treatment and with intervals during five weeks via ATR-FTIR, XPS, AFM, FESEM, GIXRD, and contact angle measurement (static and dynamic) in order to explain the plasma effects and aging findings. Results indicated that this treatment approach could make a significant contribution to the field of plasma surface treatment via introducing a feasible and fast method that can be carried out in a single step and at the atmospheric pressure with minus aging effects and without the unfavorable hydrophobic recovery phenomenon.

Improvement of paint adhesion to aluminium surfaces is one of the main challenges in many industrial applications. In this paper, we introduce the atmospheric pressure air plasma jet as an appropriate candidate for preparation of 5052 aluminium surface alloy to improve paint adhesion in the industrial level. The employed plasma jet can promote paint adhesion to aluminium surface at the treatment velocity of 2 m/min and plasma size of 10 mm. Based on the cross-cut test, adhesion of polyurethane paint to the surface greatly increases from 1B to 5B level due to the plasma treatment. According to the results, the surface wettability increases under the influence of the plasma treatment so that water droplet contact angle reduces from 79.0°±2.0°–27.5°±2.0° after the treatment. Dyne test ink also denotes the increment of surface energy to the greater than 72 mN/m. Besides, we employ various analytical methods to investigate the physical and chemical changes arise from the plasma processing to the surface. Atomic force microscopy (AFM) results show a twofold increase in the roughness parameters of plasma treated surface which can result in a stronger paint and surface interlocking. Chemical analysis of the surface reveals that plasma treatment of the aluminium surface leads to the surface cleaning and formation of hydrophilic functional groups that attract much more water towards the surface and improves the paint adhesion.

Critical surface tension (CST) is a measure of solid surface tension and is mainly determined by measuring the contact angle of a droplet on a target solid surface. The concept of CST makes it possible to determine solid surface tension without any unprovable assumptions such as the Fowkes hypothesis. However, it requires somewhat special devices and skills for measuring the contact angle. In this work, we propose a simple method to determine the CST of a solid by measuring the droplet spreading area. This method is developed by combining the conventional CST with a simple analytical droplet model. The difference in estimated CSTs between our method and the conventional one is within 3.0%. Our method enables a quick and simple evaluation of the solid surface tension without special devices for measuring the contact angle.

An interpretation of solid surfaces is generated based on physical considerations and the laws of thermodynamics. Like the widely used Owens–Wendt (OW) method, the proposed method uses liquids for characterization. Each liquid provides an absolute lower bound on the surface energy with some uncertainty from measurement variations. If multiple liquids are employed, the largest lower bound is taken as the most accurate, with uncertainty due to measurement errors. The more liquids used, the more accurate is the greatest lower bound. This method links generalizations of the Good–Girifalco equation with a general thermodynamic inequality relating the three-interfacial tensions in a three-phase equilibrium system. The method always satisfies this inequality with better than a 65% certainty. However, the OW seldom, if ever, conforms to this inequality and even then, the degree of satisfaction is insignificant. A reconciliation of the two methods is proposed based on rescaling the OW surface energies to conform to the inequality. This enables interpretations of dispersion and polar components of the surface energy, which are thermodynamically self-consistent. The proposed method is also capable of dealing with material exchange between liquid and solid phases, when the surface tension and contact angle of the saturated liquids can be measured.

The wettability of materials depends strongly on their surfaces, and endowing them with expected wetting properties promotes their applications in various fields. In this work, the biodegradable and superhydrophilic poly(butylene succinate) (PBS) nanofibrous membranes were fabricated using a combination of electrospinning and oxygen plasma treatment for the first time. The surface morphologies, chemical composition and wettability of the PBS membrane were investigated. It was found that the plasma etched the fiber surface and the etching depth increased with the plasma treatment time. The membrane became superhydrophilic from hydrophobic upon treated with oxygen plasma and the water droplet could completely spread out within 0.5 s, which was mainly attributed to the introduction of oxygen-containing groups by plasma treatment rather than the enlarged surface roughness. Meanwhile, the speed of water spread out on the modified membrane was closely and reversely related to the density of membrane. The wettability differences between nanofibrous membrane and dense films were also pointed out, and the structure had great influence in the performance. Furthermore, the wetting stability of treated membrane was explored by monitoring the evolution of contact angle. The contact angle gradually increased with days due to the decreasing functional groups, and the ageing rate was dependent on the plasma exposure time. Even though the wettability of membranes changed fast in the first 10 days, surfaces were still remained moderately hydrophilic (contact angle ~50°) after a month. The investigation concentrated on the wettability of PBS nanofibrous membrane treated with oxygen plasma is beneficial to the creation of materials with desirable properties for various applications.