In the field of packaging, barrier layers are functional films, which can be applied to polymeric substrates with the objective of enhancing their end-use properties. For food packaging applications, the packaging material is required to preserve packaged food stuffs and protect them from a variety of environmental influences, particularly moisture and oxygen ingress and UV radiation. Aluminum metallized films are widely used for this purpose. More recently, transparent barrier coatings based on aluminum oxide or silicon oxide have been introduced in order to fulfill requirements such as product visibility, microwaveability or retortability. With the demand for transparent barrier films for low-cost packaging applications growing, the use of high-speed vacuum deposition techniques, such as roll-to-roll metallizers, has become a favorable and powerful tool. In this study, aluminum oxide barrier coatings have been deposited onto biaxially oriented polypropylene and polyethylene terephthalate film substrates via reactive evaporation using an industrial 'boattype' roll-to-roll metalliser. The coated films have been investigated and compared to uncoated films in terms of barrier properties, surface topography, roughness and surface 2 energy using scanning electron microscopy, atomic force microscopy and contact angle measurement. Coating to substrate adhesion and coating thickness have been examined via peel tests and transmission electron microscopy, respectively.

Articles you may be interested inFabrication of super-hydrophobic surfaces on aluminum alloy substrates by RF-sputtered polytetrafluoroethylene coatings AIP Advances 4, 031323 (2014); 10.1063/1.4868363 Low-temperature atomic layer deposition of Al2O3 on blown polyethylene films with plasma-treated surfaces J. Vac. Sci. Technol. A 31, 01A129 (2013); 10.1116/1.4768171 Nanotribological characterization of fluoropolymer thin films for biomedical micro/nanoelectromechanical system applications J. Vac. Sci. Technol. A 23, 804 (2005); 10.1116/1.1861939 Plasma polymerization and deposition of linear, cyclic and aromatic fluorocarbons on (100)-oriented single crystal silicon substratesAluminum coatings are widely used as oxygen and water barrier layers on food packaging materials to protect the product from contamination and to extend its shelf life. Thin layers of aluminum, of the order of a few tens of nanometers, are thermally evaporated onto polymeric web in high speed roll-to-roll vacuum metallizers. More recently, transparent barrier layers, based on silica or aluminum oxide, have been introduced to allow product visibility and provide retortable, sterilizable, or microwaveable packaging. In all cases, though, the barrier characteristics are critically dependent on both the structure and properties of the coating and the nature and surface properties of the polymer film substrate. This paper, therefore, reports on characterization trials of aluminum oxide (AlO x ) coatings deposited onto polyethylene terephthalate (PET) and biaxially oriented polypropylene (BOPP) film substrates. Coating structures and properties have been investigated by scanning electron microscopy and atomic force microscopy; the influence of process parameters on barrier levels has been determined; surface energies have been determined through contact angle measurements; and coating-to-substrate adhesion has been assessed using "pull-off" tests. The main findings of this study are that the barrier performance of AlO x coated PET and BOPP films strongly depends on the surface properties of the plain film and the aluminum oxide film growth. While AlO x coated PET films deliver consistent barrier results, BOPP reveals considerable variations, depending on the individual substrate.

Metallized films consisting of thin, vacuum-deposited inorganic layers are used for a wide range of packaging applications for foods, pharmaceuticals and other technical purposes. They are made as laminates and consist of a polymeric film (substrate), an inorganic layer, mostly aluminum (Al), and a top layer, laminated to the inorganic layer using a suitable adhesive. One major quality indicator in such flexible packaging materials is the adhesion strength between the inorganic layer and the substrate. In order to measure the adhesion strength of thin Al layers deposited on a substrate, the following procedure is often used: Ethylene acrylic acid (EAA)-films are thermally sealed to the Al layers. In a subsequent peel test, the EAA-film is peeled-off at 180 • peel angle, delaminating the Al layer from the substrate. This method shows weaknesses in cases of high bond strength: The sealed EAA-film is elongated or even torn during the measurements, whereby it is difficult to obtain reproducible and repeatable results. In this study two alternative approaches have been tested to overcome the weaknesses of EAA-peel test. One of them is to use thermally sealable polymeric films, such as amorphous poly(ethylene terephthalate) and amorphous polyamide (both having a high mechanical strength), instead of the EAA film. Although the adhesion forces might have been weakened during the heat lamination of these selected films onto the Al surface, a quantitative comparison between the three different types of metallized films (with low, medium and high adhesion strength) is found to be promising by this approach. The other approach is to perform the peel tests with the laminates of the metallized films. The laminates are produced by laminating a low density polyethylene film (PE-LD) on top of the metallized film using an adhesive via a bench lamination process. The laminated PE-LD film in this case replaces the EAA-film. In this approach, the laminate structure is similar to the final product in the end-use. The metal adhesion strength is found to be in good agreement with the strength measured for similar structures produced at pilot scale.

We introduced columnar defects into (Bi,Pb)2Sr2Ca2Cu3O10+δ Ag tapes by irradiation with 2.65 GeV 197Au ions to investigate the dimensionality of pinning for this compound. Samples were irradiated up to fluences of 3.5×1011 ions/cm2 at a temperature of 100 K. The ion beam was directed both perpendicular and under a tilt angle of −60° to the tape surface. Our samples showed homogeneous columnar line defects throughout the whole thickness of the superconducting core. As a novel result we found evidence for marked deviations from two-dimensional behavior at elevated temperatures both in magnetic and in transport measurements.