Next generation vacuum deposited ALOx clear barrier coatings for flexible food packaging materials

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. In the case of food packaging applications, the packaging material is required to preserve packaged foodstuffs and protect them from a variety of environmental influences. Amongst others, the impermeability of the packaging material to substances including water vapour, oxygen and aromas is an important requirement for successful food packaging. Polymer films, vacuum coated with thin transparent barrier layers of aluminium oxide or silicon oxide, are very attractive candidates for food packaging applications due to the oxide film imparting attractive properties, including good barrier performance, transparency, microwaveability and recyclability. In this project, aluminium oxide barrier layers were deposited onto various commodity grade BOPP films via reactive evaporation of aluminium, using a modified industrial ‘boat-type’ roll-to-roll metalliser. Optimisation of the deposited coating, in some cases together with potential surface modifications of the BOPP films, was the main focus of the work. The effects of different film treatments (in-line and off-line); surface properties of the polymer film, such as topography and chemistry; coating stoichiometry and thickness; as well as conversion processes; on barrier properties were investigated using a broad variety of analytical techniques. Furthermore, critical parameters for the convertibility of vacuum coated films, including coating adhesion and coating surface energy, were assessed. This project has demonstrated that the barrier performance of aluminium oxide coated BOPP is heavily dependent on the plain film surface and the growth/nucleation conditions of the deposited film, both of which can vary to a large extent on standard packaging grade BOPP film. Whilst acceptable oxygen barrier levels were achieved on some of the standard BOPP film types, others did not match the requirements, despite investigating a wide range of coating parameters. This was found to be due to the presence of defects (permeation pathways) in the coating, which were reproduced from defects in the underlying polymer film surface. With regards to the barrier performance after aluminium oxide coating, the polymer film surface chemistry was identified as an important parameter. Furthermore, oxygen barrier performance was significantly enhanced when a high surface energy polymer skin layer was co-extruded onto the BOPP film. Nevertheless, water vapour barrier improvement for aluminium oxide coated BOPP films was only achieved through the use of different polymer skin layers or via depositing coatings with reduced oxygen content, thus obtaining grey coatings that can no longer be classified as transparent. Peel tests indicated very high levels of adhesion of the aluminium oxide coating to the BOPP film, with cohesive failure taking place within the polymer, rather than adhesive failure at the coating-substrate interface. Examination of the time related change of surface energy revealed a distinct decay with ageing time, most probably due to transfer of polymeric material and film additives from the reverse side of the film onto the coating and also migration through defects in the coating. Finally, the application of acrylate under- and topcoats, as well as adhesive lamination, was found to have the capability to significantly enhance the barrier performance of the aluminium oxide coated BOPP film. In the case of acrylate undercoats, this was attributed to the change in surface chemistry, whilst for topcoats and lamination processes, the barrier properties of the acrylate/adhesive play an important role, together with a possible ‘pore filling’ effect

Conversion of aluminium oxide coated films for food packaging applications—From a single layer material to a complete pouch

© 2019 Elsevier Ltd Transparent barrier films based on vacuum deposited aluminium oxide (AlOₓ) layers are continuing to create large interest in the market with regards to their use as food and healthcare packaging materials. Nevertheless, their post-metalliser conversion to the final packaging material still presents challenges to current AlOₓ producers and the wider converting industry. In this work, AlOₓ coated polyethylene terephthalate (PET) films have been converted in long duration industrial-scale trials via topcoating, printing, lamination and finally pouch making. Throughout this process, each conversion step has been investigated for its effects on the barrier performance. It was found that the printing processes, especially, induce significant damage to the ceramic barrier layer. However, by the use of a protective topcoat prior to any conversion step, the barrier properties of the AlOₓ coated film were preserved, or could even be significantly enhanced, depending on the topcoat material. Furthermore, for a barrier topcoat, remarkable stretch- and flex-durability properties were achieved in the final laminate

Aluminium oxide barrier films on polymeric web and their conversion for packaging applications

In recent years, inorganic transparent barrier layers such as aluminium oxide or silicon oxide deposited onto polymer films have emerged as an attractive alternative to polymer based transparent barrier layers for flexible food packaging materials. For this application, barrier properties against water vapour and oxygen are critical. Aluminium oxide coatings can provide good barrier levels at thicknesses in the nanometre range, compared to several micrometres for polymer-based barrier layers. These ceramic barrier coatings are now being produced on a large scale using industrial high speed vacuum deposition techniques, here, reactive evaporation on a 'boat-type' roll-to-roll metalliser. For the thin barrier layer to be useful in its final packaging application, it needs to be protected. This can be either via lamination or via an additional topcoat. This study reports on acrylate topcoats, but also undercoats, on aluminium oxide coated biaxially oriented polypropylene films. The effect of the acrylate layer on barrier levels and surface topography and roughness was investigated. The acrylate was found to smooth the substrate surface and improve barrier properties. Furthermore, the activation energy for water vapour and oxygen permeation was determined in order to investigate barrier mechanisms. The oxide coated film was, additionally, converted via adhesive lamination, which also provided improvement in barrier levels. © 2013 Elsevier B.V. All rights reserved

Amorphous Alumina Barrier Coatings on Glass: MOCVD Process and Hydrothermal Ageing

Amorphous alumina coatings are applied on the inner surface of glass containers aiming at improving their hydrothermal ageing barrier properties. A direct liquid injection technology is implemented in a metal-organic chemical vapor deposition (MOCVD) process to feed the reactor in a controlled and reproducible way with a solution of aluminum tri-isopropoxide (ATI) in anhydrous cyclohexane. Amorphous alumina coatings are characterized by X-ray diffraction, electron probe microanalysis, scanning electron microscopy, atomic force microscopy and scratch-test method. They are amorphous and hydroxylated at process temperatures between 360 and 420 °C and close to Al 2 O 3 stoichiometry between 490 and 560 °C. Hydrothermal ageing simulated by a standard sterilization cycle results in the increase of the root mean square of the surface of the coatings from ≈17 to 61 nm and in the increase of the porosity without affecting the adhesion of the coatings on the glass substrates

Aluminum oxide barrier coatings on polymer films for food packaging applications

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 'boat-type' roll-to-roll metallizer. The coated films have been investigated and compared to uncoated films in terms of barrier properties, surface topography, roughness and surface 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. © 2013 Elsevier B.V

Proposal of a Standardized Questionnaire to Structure Clinical Peer Reviews of Mortality and Failure of Rescue in Pancreatic Surgery

Background: Quality management tools such as clinical peer reviews facilitate root cause analysis and may, ultimately, help to reduce surgery-related morbidity and mortality. This study aimed to evaluate the reliability of a standardized questionnaire for clinical peer reviews in pancreatic surgery. Methods: All cases of in-hospital-mortality following pancreatic surgery at two high-volume centers (n = 86) were reviewed by two pancreatic surgeons. A standardized mortality review questionnaire was developed and applied to all cases. In a second step, 20 cases were randomly assigned to an online re-review that was completed by seven pancreatic surgeons. The overall consistency of the results between the peer review and online re-review was determined by Cohen’s kappa (κ). The inter-rater reliability of the online re-review was assessed by Fleiss’ kappa (κ). Results: The clinical peer review showed that 80% of the patient mortality was related to surgery. Post-operative pancreatic fistula (POPF) (36%) followed by post-pancreatectomy hemorrhage (PPH) (22%) were the most common surgical underlying (index) complications leading to in-hospital mortality. Most of the index complications yielded in abdominal sepsis (62%); 60% of the cases exhibited potential of improvement, especially through timely diagnosis and therapy (42%). There was a moderate to substantial strength of agreement between the peer review and the online re-review in regard to the category of death (surgical vs. non-surgical; κ = 0.886), type of surgical index complication (κ = 0.714) as well as surgical and non-surgical index complications (κ = 0.492 and κ = 0.793). Fleiss’ kappa showed a moderate to substantial inter-rater agreement of the online re-review in terms of category of death (κ = 0.724), category of common surgical index complications (κ = 0.455) and surgical index complication (κ = 0.424). Conclusion: The proposed questionnaire to structure clinical peer reviews is a reliable tool for root cause analyses of in-hospital mortality and may help to identify specific options to improve outcomes in pancreatic surgery. However, the reliability of the peer feedback decreases with an increasing specificity of the review questions

A survey among physicians in surgery and anesthesiology departments after the first surge of SARS-CoV-2 infections in Germany

Summary Background The SARS-CoV‑2 pandemic has extensively challenged healthcare systems all over the world. Many elective operations were postponed or cancelled, changing priorities and workflows in surgery departments. Aims The primary aim of this cross-sectional study was to assess the workload and psychosocial burden of surgeons and anesthesiologists, working in German hospitals during the first wave of SARS-CoV‑2 infections in 2020. Methods Quantitative online survey on the workplace situation including psychosocial and work-related stress factors among resident and board-certified surgeons and anesthesiologists. Physicians in German hospitals across all levels of healthcare were contacted via departments, professional associations and social media posts. Results Among 154 total study participants, 54% of respondents stated a lack of personal protective equipment in their own wards and 56% reported increased staff shortages since the onset of the pandemic. While routine practice was reported as fully resumed in 71% of surgery departments at the time of the survey, work-related dissatisfaction among responding surgeons and anesthesiologists increased from 24% before the pandemic to 36% after the first wave of infections. As a countermeasure, 94% of participants deemed the establishment of action plans to increase pandemic preparedness and strengthening German public health systems a useful measure to respond to current challenges. Conclusion The aftermath of the first wave of SARS-CoV‑2 infections in Germany has left the surgical staff strained, despite temporarily decreased workloads. Overall, a critical review of the altered conditions is indispensable to identify and promote effective solutions and prudent action plans required to address imminent challenges.Open Access funding enabled and organized by Projekt DEAL.Eberhard Karls Universität Tübingen (1020