Plasmagestützte Flascheninnenbeschichtung

Application of substrate biasing for plasma enhanced inner coating of plastic bottles to improve barrier properties The article summarizes the results of a research project aiming at the improvement of the barrier performance of plastic beverage bottles by means of plasma enhanced barrier coatings. A pilot plant for the biased barrier coating of PET‐bottles was designed and successfully commissioned within the scope of the investigations. In the process, two excitation types are examined: the so‐called in‐plasma process and a single‐sided plasmaline process for the deposition of barrier coatings. Advantages as well as draw backs of both processes are investigated with respect to an industrial implementation. As a result, improvement of the barrier performance by adjustment of the substrate bias is estimated by a factor of 2‐3. At the same time, substantial challenges for the realization of the processes as well as possible approaches for their solution are identified with the support of gas flow simulations.     

涂层技术制备高阻隔性PET瓶的应用研究

对聚偏二氯乙烯、改性聚乙稀醇和环氧-胺等有机涂层材料及氧化硅、类金刚石等无机涂层材料在PET瓶上的应用工艺、阻隔性能及其在国内外市场的研究进展进行了综述,指出高阻隔PET瓶目前仅处于小规模的试用阶段,若要成功实现从玻璃瓶到PET塑料瓶的转化,不仅需要提高PET材料的阻隔性能,还应保证其具有较高的透明性、可回收性、技术易操作性及实用性等。     

On‐going solutions to environmental issues in plastic packaging

Recently, the consumption of polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) resins as packaging materials has been declining in the face of various environmental problems they pose. To replace PVC containers, the use of PET bottles and A‐PET containers is on the increase, but PVDC resins are still in wide use as gas‐barrier materials. For gas‐barrier purposes, however, ethylene vinyl alcohol co‐polymer (EVOH) films, polyvinyl alcohol (PVA)‐coated polypropylene films, and MX nylon or silica‐ or alumina‐coated PET films are becoming mainstream. The weight reduction of plastic bottles is considered to play an important role in tackling the waste disposal problem. Recently, a new type of stretch‐blow moulding system has been developed, which is effective in reducing the weight of PET bottles. This system is called COSMOS (complete stretch‐blow moulding system) or the two‐blow system. COSMOS PET bottles are now used to hold carbonated drinks containing fruit juice or lactic acid. Copyright © 2001 John Wiley & Sons, Ltd.     

Dekontamination von Primärverpackungen mittels Atmosphärendruckplasmen

Decontamination of primary packaging by means of atmospheric plasmas The increasing demand of perishable products in urban areas as well as the globalisation of the markets also rises up the requirements for packaging. The storage life of these products is provided by microbial reduction in food and packaging, which is realized by aseptic filling or diffusion barriers. Furthermore, in pharmaceutical products it is recommended that preserving agents should not be added to avoid allergic reactions. Therefore packaging with low microbial load up to sterility is needed. Sterilization in wet (peracetic acid) or dry (hydrogen peroxide) set ups are currently available and used in the beverage industry. Pharmaceutical and food industry would prefer decontamination methods without hazardous substances. The possibility of plasma to generate antimicrobial effective components such as UV light, charged particles (ions, electrons) and reactive radicals offers an alternative to common decontamination methods. Plasmas can be separated in two main groups, the low‐pressure plasma and the atmospheric pressure plasma which have advantages and disadvantages. However, both are expected to require lower total process times than the current chemical methods. The construction for bottle treatment used in this study is based on microwave‐driven self propagating discharge. A careful design of the plasma source by using simulation tools is necessary to avoid hot spots during the bottle treatment. Minimization of process times before and after the decontamination treatment is necessary for industrial processes. The lock in and lock out of the bottles into the microwave area may be a limitative factor. Therefore the development of a barrier‐free transport system for 200 ml PET bottles was realized in this work. Temperature investigations of the material PET showed a critical temperature range above 60 °C at 4 cycles of 1000 W. After an 1 second plasma treatment a maximal reduction rate of 2 log10 was observed. A longer treatment time of 5 minutes led to an inactivation of 4 to 5 log10 for vegetative bacteria and of 2 to 3 log10 for Bacillus spores. Moreover an optimization of plasma generation inside the bottles may increase the microbiological inactivation. An optimization of the antimicrobial efficiency is necessary and detailed investigations of inactivation mechanisms of atmospheric pressure plasma should follow.     

Quantification of the Sorption Behavior of Polyethylene Terephthalate Polymer versus PET/PA Polymer Blends towards Organic Compounds

Polyethylene terephthalate (PET) bottles are widely used for beverages. Oxygen‐sensitive beverages, however, often require the use of barrier materials or oxygen‐scavenging additives incorporated into the PET material, which is in most cases polyamide (PA). As a consequence, small amounts of polyamide are entering the PET bottle‐to‐bottle recycling feedstream. Aim of the study was therefore the determination of the sorption behavior of bottles made of different PET/PA blends in comparison with a PET reference. As a result, PET test bottles containing blended PA amounts of up to 1000 ppm do not show a sorption behavior for the investigated model compounds, which is different from pure PET material. Therefore, polyamide impurities in the recycling streams coming from polyamide barrier bottles will not lead to a different sorption/remigration behavior as pure PET bottles. Consequently, evaluations of PET recycling processes will still be valid for feedstream materials containing such small amounts of polyamide from barrier bottles. On the other hand, the introduction of 8% of polyamide decreases significantly the sorption of organic compounds into the bottle wall. Copyright © 2011 John Wiley & Sons, Ltd.     

Single‐ and Double‐Sided Chemical Functionalization of Bilayer Graphene

An experimental study on the interaction between the top and bottom layer of a chemically functionalized graphene bilayer by mild oxygen plasma is reported. Structural, chemical, and electrical properties are monitored using Raman spectroscopy, transport measurements, conductive atomic force microscopy and X‐ray photoelectron spectroscopy. Single‐ and double‐sided chemical functionalization are found to give very different results: single‐sided modified bilayers show relatively high mobility (200–600 cm² V^?1 s^?1 at room temperature) and a stable structure with a limited amount of defects, even after long plasma treatment (>60 s). This is attributed to preferential modification and limited coverage of the top layer during plasma exposure, while the bottom layer remains almost unperturbed. This could eventually lead to decoupling between top and bottom layers. Double‐sided chemical functionalization leads to a structure containing a high concentration of defects, very similar to graphene oxide. This opens the possibility to use plasma treatment not only for etching and patterning of graphene, but also to make heterostructures (through single‐sided modification of bilayers) for sensors and transistors and new graphene‐derivatives materials (through double‐sided modification).     

Experimental direct evaluation of functional barriers in PET recycled bottles: comparison of migration behaviour of mono‐ and multilayers

Recycling of used bottles into new bottles is associated with possible migration of pollutants arising from the previous life of the packages. To reduce or delay such migration, the recycled resin is depolluted or a functional barrier layer made of virgin plastics is used. Testing migration from such recycled bottles relies on the use of model pollutants (surrogates). In order to enable modelling of migration kinetics, each step of the use of surrogates is carefully investigated here in the case of PET. First, criteria underlying the selection of surrogates are carefully examined; together with volatility, polarity and diffusion behaviour, it is shown here that their solubility in the food simulant and their chemical stability strongly influence migration results. For aqueous test media, 2,4‐pentanedione and phenol should be used as surrogates. Second, a procedure is developed to impregnate surrogates at very large concentrations (several thousands of mg/kg PET) which are necessary to monitor migration kinetics. This procedure, which uses dichloromethane as solvent, allows a quick and reproducible impregnation, not sensitive to temperatures between 11–23°C, factors which favour its use at a plant scale. Third, flakes impregnated with this procedure are processed into bottles, and their physicochemical properties are compared to those of commercial bottles. Last, monolayer and tri‐layer polluted bottles (model pollutants in inner layer) are tested for migration for more than 1.5 years. With multilayers, the migration lag time of the fastest surrogates is 6 months with 3% acetic acid and 3 months with ethanol as the simulant, due to plasticization of PET by ethanol. The sequence of migration of surrogates is different with monolayer and multilayer bottles, which shows that partition effects (solubility) play an essential role, especially with monolayer materials. Copyright © 2005 John Wiley & Sons, Ltd.     

Evaluation of a bio‐coating as a solution to improve barrier,friction and optical properties of plastic films

The present research dealt with evaluating barrier, friction and optical properties of three different plastic films after deposition of a gelatin‐based bio‐coating. The composite films showed improved barrier properties against oxygen and UV radiation. The oxygen transmission rate decreased in the order of 73% for oriented polypropylene (OPP), 56% for low‐density polyethylene (LDPE) and 40% for polyethylene terephthalate (PET). The increased UV barrier characteristics ranged from 20% for OPP to 12% for both LDPE and PET. Static and kinetic coefficients of friction significantly decreased both in the film‐to‐film and in the film‐to‐metal tests, leading to a desirable value for many applications. However, bio‐coated films showed lower optical performances in terms of transparency and haze. Transparency decreased mainly for LDPE (36%), whereas the haze index increased especially for OPP (85%). Non‐significant differences were observed as far as the water vapour permeability was concerned, except for a slight reduction for PET (from 15.78 to 13.53 cm³/m²/day at 23°C and 90% of relative humidity), suggesting that non‐meaningful effects arose from the addition of a hydrophobic component in the original formulation. Finally, the solubility of the coating in water was around 25% for all the three plastic substrates. The obtained data suggest that the lipid protein coating tested in this study, in spite of its great potential for enhancing some characteristics of plastic packaging films, still exhibits negative aspects which necessitate further improvement. Copyright © 2008 John Wiley & Sons, Ltd.     

低温等离子体技术及其在塑料包装中的应用

介绍了低温等离子体技术及其特点,论述了低温等离子体技术在改善塑料薄膜印刷适性、提高粘接性及增强PET瓶阻隔性等塑料包装中的应用.     

Migration of Aluminum and Silicon from PET/Clay Nanocomposite Bottles into Acidic Food Simulant

Poly(ethylene terephthalate) (PET)/clay nanocomposite samples were prepared by melt blending PET and Cloisite 20A nanoparticles. A stretch blow‐moulding machine was used to produce bottles from neat PET and PET nanocomposite. Tests were performed on the migration of aluminum and silicon from PET nanocomposite bottles into acidic food simulant. The samples were stored at room temperature (about 25°C) and 45°C for time durations ranging from 7 to 90 days. A specific surface of sheets (prepared from PET/clay nanocomposite) immersed in acidic food simulant, and two‐sided migration of Al and Si was investigated. According to X‐ray diffraction analysis, the nanoclays show intercalated structure in the PET matrix. Transmission electron microscopy and atomic force microscopy micrographs displayed both intercalation and exfoliation morphology for PET/clay nanocomposites. Inductively coupled plasma was used to quantify amounts of Al and Si that had migrated into the acidic food simulant. It was observed that the migration process is dependent on storage time and temperature, and the molar ratio of aluminum and silicon in the acidic aqueous solution (Al/Si)_aq to the ratio in the solid phase of prepared nanocomposites (Al/Si)_solid was about 23% higher in the samples stored at 45°C. Copyright © 2013 John Wiley & Sons, Ltd.     

Beschichtung und Reinigung von Oberflächen mit Atmosphärendruck‐Plasmen. Coating and cleaning of surfaces with atmospheric pressure plasmas

Since long time dielectric barrier discharges have been in use for technical applications such as ozone synthesis and surface activation treatment of polymers for subsequent printing, pasting, or laquering. A new field of applications for these discharges is opened by their use for plasma‐based coating and cleaning processes at atmospheric pressure. By introducing gaseous monomers (like hydrocarbons, fluorocarbons, silicon‐organic compounds) into the discharge zone, coatings can be deposited on electrically conductive or insulating substrates. Barrier discharges in oxygen containing gases can also be used for the degreasing of surfaces. Owing to the possibility, to sustain barrier discharges in very small volumes, new perspectives are opened for the geometrically structured modification of chemical and physical properties of surfaces as well as for the modification or coating of internal surfaces in microfluidic devices.     

Simulation of the Decontamination Efficiency of PET Recycling Processes based on Solid‐state Polycondensation

The recollection rates for postconsumer poly(ethylene terephthalate) (PET) bottles and the recycling capacities are increasing year by year. The postconsumer PET bottles were recycled either to fibres or to new packaging applications. For packaging applications, the so‐called super‐clean recycling technologies are applied to decontaminate the postconsumer PET pellets. Most of these processes are based on solid‐state polycondensation processes. Because experimental determination of the cleaning efficiency is a time‐consuming and expensive procedure, it would be useful to predict the cleaning efficiencies, e.g. for process development and optimization. Within this study, the decontamination kinetics of a PET super‐clean recycling process based on solid‐state polycondensation was determined. From the decontamination kinetics, the diffusion coefficients were calculated. By use of the diffusion coefficients, the decontamination kinetics was simulated using migration modelling approaches for spherical pellets. The result of this study shows that the decontamination of PET pellets in solid‐state polycondensation processes follows Fickian laws. The diffusion coefficients of the investigated migrants are not influenced by vacuum or inert gas process conditions. The diffusion equations used in commercially available software packages for migration calculation can be used for the simulation of the decontamination efficiencies of PET recycling processes. Copyright © 2012 John Wiley & Sons, Ltd.     

Mineral Oil Barrier Testing of Cellulose‐Based and Polypropylene‐Based Films

Recycled cardboard has been identified as a major source of mineral oil hydrocarbon (MOH) contamination of foods. Identifying and using appropriate functional barriers is a mechanism through which this problem can be addressed. A number of cellulose‐based and biaxially oriented polypropylene (BOPP) films were evaluated as potential functional MOH barriers. The films were tested using a donor material, a paper containing MOH placed on one side of the film barrier and a paper which acted as the receptor on the other. Testing was performed at accelerated conditions of 60°C, the receptor analysed periodically for MOH. The results demonstrated that the cellulose‐based film types provided an MOH barrier of >3.5 years. This contrasted with the BOPP selected films, for which only the proprietary acrylic‐coated BOPP film provided an effective barrier to MOH migration. Further investigation of the MOH barrier properties of the proprietary acrylic‐coated BOPP film was undertaken. Various coating strategies were employed including increasing the coating application weight, increasing the number of coating lay downs and coating one or both surfaces of the film. It was found that an MOH barrier of 1.5 years when tested at 40°C could be achieved for the proprietary acrylic‐coated BOPP film; however, barrier effectiveness was dependent on the coating integrity of the film. Further work with a vertical form filler packaging machine and the use of a staining technique with transmission microscopy proved effective at highlighting and assessing the coating integrity of packets during a typical packaging operation. Copyright © 2014 John Wiley & Sons, Ltd.     

Mikrowellen‐PECVD für kontinuierliche Großflächenbeschichtung bei Atmosphärendruck

Microwave PECVD for continuous wide area coating at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are coatings to achieve an improved corrosion and scratch protection, or surface cleaning. Normally, these processes are vacuum based and therefore suitable to only a limited extend for large area industrial applications. By use of atmospheric pressure plasma technology integration in continuously working manufacturing lines is advantageously combined with lower costs and higher throughput. Microwave plasma sources present powerful modules for plasma enhanced chemical vapour deposition at atmospheric pressure. At Fraunhofer IWS processes and equipment as well as application specific materials are developed. The coatings are suitable for scratch resistant surfaces, barrier and corrosion protective layers or anti‐reflex layers on solar cells. The film properties achieved are comparable with those produced by low pressure processes.     

Long‐time Performance of Bottles Made of PET Blended with Various Concentrations of Oxygen Scavenger Additive Stored at Different Temperatures

Blending of poly(ethylene terephthalate) (PET) with oxygen scavenger additives is a way to reduce ingress of oxygen into PET bottles made of these blends. The objective is to reduce oxidation of packaged beverages and oils. However, few studies were performed about the long‐time influence of temperature on PET bottles with oxygen scavenger additives. Such knowledge is relevant for the development of accelerated tests. In this study, the influence of temperature on oxygen permeation of PET bottles with the oxygen scavenger additives MXD6 or Oxyclear® was examined. PET bottles made of blends of PET with 2, 5 and 8 wt.?% MXD6, respectively, or with 2 wt.?% Oxyclear® were filled with deoxygenated water. The bottles were stored at 5, 23, 38 and 55 °C up to 5 years. Oxygen partial pressure of the water in the bottles was measured regularly. As expected, oxygen partial pressure increased earlier at higher temperature because of faster exhaustion of the oxygen scavenger. Oxygen partial pressure of water in PET bottles with 8 wt.?% MXD6 was below 10 mbar even after 5 years storage time at 5 and 23 °C. Oxygen absorption capacity of activated MXD6 was at least 76 mg/g. This study shows that PET bottles with oxygen scavengers are able to reduce the oxygen ingress for several years, even at elevated temperatures. Copyright © 2017 John Wiley & Sons, Ltd.     

Acetaldehyde in Mineral Water Stored in Polyethylene Terephthalate (PET) Bottles: Odour Threshold and Quantification

The use of PET bottles for packaging soft drinks and mineral waters is still growing world wide. The production process for these bottles is improving constantly. These improvements are focussed on bottles with better barrier properties, higher inertness and higher heat stability. One of the factors determining the quality of PET bottles is the release of acetaldehyde into the product during storage. A literature survey was conducted on the odour and taste detection threshold of acetaldehyde in water. A method is described to rapidly determine the concentration of acetaldehyde in water up to a level of 1 μg/l. This method was used to determine the concentration of acetaldehyde in mineral water during storage in PET bottles. In still water no acetaldehyde could be found, whereas the concentration of acetaldehyde in carbonated mineral water increased steadily upon storage. Model experiments were performed to find an explanation.     

Roll‐to‐Roll Cohesive,Coated, Flexible,High‐Efficiency Polymer Light‐Emitting Diodes Utilizing ITO‐Free Polymer Anodes

This paper reports solution‐processed, high‐efficiency polymer light‐emitting diodes fabricated by a new type of roll‐to‐roll coating method under ambient air conditions. A noble roll‐to‐roll cohesive coating system utilizes only natural gravity and the surface tension of the solution to flow out from the capillary to the surface of the substrate. Because this mechanism uses a minimally cohesive solution, the roll‐to‐roll cohesive coating can effectively realize an ultra‐thin film thickness for the electron injection layer. In addition, the roll‐to‐roll cohesive coating enables the fabrication of a thicker polymer anode film more than 250 nm at one time by modification of the surface energy and without wasting the solution. It is observed that the standard sheet resistance deviation of the polymer anode is only 2.32 Ω/□ over 50 000 bending cycles. The standard sheet resistance deviation of the polymer anode in the different bending angles (0 to 180°) is 0.313 Ω/□, but the case of the ITO‐PET is 104.93 Ω/□. The average surface roughness of the polymer anode measured by atomic force microscopy is only 1.06 nm. Because the surface of the polymer anode has a better quality, the leakage current of the polymer light‐emitting diodes (PLEDs) using the polymer anode is much lower than that using the ITO‐PET substrate. The luminous power efficiency of the two devices is 4.13 lm/W for the polymer anode and 3.21 lm/W for the ITO‐PET. Consequently, the PLEDs made by using the polymer anode exhibited 28% enhanced performance because the polymer anode represents not only a higher transparency than the ITO‐PET in the wavelength of 560 nm but also greatly reduced roughness. The optimized the maximum current efficiency and power efficiency of the device show around 6.1 cd/A and 5.1 lm/W, respectively, which is comparable to the case of using the ITO‐glass.     

Overestimated diffusion coefficients for the prediction of worst case migration from PET: application to recycled PET and to functional barriers assessment

This paper defines parameters that can be used to predict worst‐case migration from recycled PET bottles, with and without a functional barrier. Starting with a set of diffusion coefficients determined in well‐defined experimental conditions (temperature, presence or not of a solvent, with and without swelling effect), empirical equations for the diffusion coefficient of a migrant or a pollutant in PET at 40°C are given as a function of its molecular weight. An equation is also derived for migration from PET into water. Surrogates representative of worst‐case migrants are identified and are discussed in terms of molecular weight, structure and interaction with the PET matrix. In the second part of the paper, the empirical equations have been used to simulate the migration from monolayer bottles and from multilayer bottles with different geometries of functional barrier, as a function of the pollutants' molecular weight. Since the diffusion coefficients are overestimated, the calculated migration is also overestimated, which provides a margin of safety. The advantage of the functional barrier technology is compared to the direct food contact route, as a function of food contact time. In the last part of the paper, the effect of testing temperature is investigated. Based on a literature survey, the activation energy of pollutants is shown to increase roughly with their molecular weights. A worst‐case activation energy of 80 kJ/mol is proposed, allowing extrapolation of migration data from a higher temperature (values calculated at 40°C or determined at 60°C) to room temperature. The possible use of this activation energy to design tests for functional barriers is discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Packaging‐related properties of protein‐ and chitosan‐coated paper

The mechanical and gas‐barrier properties of paper and paperboard coated with chitosan–acetic acid salt (chitosan), whey protein isolate, whey protein concentrate and wheat gluten protein were studied. Paper sheets were solution‐coated using a hand applicator. In addition, bi‐layer composites of wheat gluten and paper or paperboard were produced by compression moulding, and the chitosan solution was also applied on paperboard using curtain coating. Young's modulus, fracture stress, fracture strain, tearing strength, air permeance and oxygen permeability were assessed. The mechanical and air permeance measurements of solution‐coated paper showed that chitosan was the most effective coating on a coat weight basis. This was due to its high viscosity, which limited the degree of penetration into the paper. The proteins, however, also enhanced the strength and toughness of the paper. Compression‐moulded wheat gluten/paper or paperboard, as well as curtain‐coated chitosan paperboard laminates, showed oxygen barrier properties comparable to those of paper and paperboard coated with commercial barrier materials. None of the composites could be delaminated without fibre rupture, indicating good adhesion between the coatings and the substrates. Copyright © 2005 John Wiley & Sons, Ltd.     

Numerical simulation of fluid flow and temperature field in keyhole double‐sided arc welding process on stainless steel

Double‐sided arc welding process powered by a single supply is a type of novel high‐production process. In comparison with the conventional single‐sided arc welding, this process has remarkable advantages in enhancing penetration, minimizing distortion and improving welding production. In this paper, a three‐dimensional steady numerical model is developed for the heat transfer and fluid flow in plasma arc (PA)–gas tungsten arc (GTA) double‐sided keyhole welding process. The model considers the surface tension gradient, electromagnetic force and buoyancy force. A CCD camera is used to observe the size and shape of the keyhole and weld pool. The acquired images are analysed through image processing to obtain the surface diameters of the keyhole on the two sides. A double‐V‐shaped keyhole geometry is then proposed and its characteristic parameters are derived from the images and cross‐section of weld bead. In the numerical model, the keyhole cavum within the weld pool is treated as a whole quality, whose temperature is fixed at the boiling point of the workpiece material. The heat exchange between the keyhole and weld pool is treated as an interior boundary of the workpiece. Based on the numerical model, the distributions of the fluid flow and temperature field are calculated. A comparison of cross‐section of the weld bead with the experimental result shows that the numerical model's accuracy is reasonable. Copyright © 2005 John Wiley & Sons, Ltd.