Porous Ultrahigh Gas‐Permeable Polypropylene Film and Application in Controlling In‐pack Atmosphere for Asparagus

Porous polypropylene (PP) films with greater gas permeability and lower permeability ratios (β) than existing commercial films were developed for fresh produce packaging. PP containing high content of beta‐form crystal was biaxially stretched under controlled conditions. Resulting porous films with uniquely high oxygen transmission rate (OTR) of 2 659 000 cm³?m^?2?d^?1, water vapor transmission rate of 67 g?m^?2?d^?1, and β value of 0.76 was used as a “breathable window” attached to the less permeable commercial BOPP (biaxially oriented PP) lidding film. Various sizes/areas of the breathable windows were designed and tested on packaging asparagus of 400 g, at 5°C. Results demonstrated that in‐pack O₂ and CO₂ concentrations could be practically controlled and modified by changing areas of the breathable windows. Altered porous high OTR area directly affected total gas permeation of the package. Optimum gas composition of Ο₂ and CΟ₂ within the recommended controlled atmosphere for asparagus, stored at 5°C, was effectively created and maintained in the package containing 25 cm² breathable window (15% of total film lid's area). The shelf life of asparagus under optimum modified atmosphere was extended to 29 days, as compared with <3 days in the normal, low OTR tray sealed with BOPP lidding film. Clearly, these developed porous ultrahigh permeable PP films can be useful materials in designing high OTR package with desirable in‐pack O₂ and CO₂ concentrations. Copyright © 2013 John Wiley & Sons, Ltd.     

Oxygen barrier properties of thermoformed trays manufactured with different drawing methods and drawing depths

A comparison was made of oxygen barrier properties and wall thickness distribution of different thermoformed trays. The thermoformed trays were manufactured with three drawing depths and two different thermoforming methods; with and without plug‐assist. Four different polymer combinations were evaluated. The oxygen transmission rate (OTR) [cm³/(package/day)] was measured at three conditions (23°C/50% relative humidity (RH) with 0% RH inside, 6°C/80% RH with 0% RH inside, and 6°C/80% RH with 100% RH inside. Wall thickness was measured at five different positions in the trays. In general, temperature had more influence on the oxygen transmission rate (OTR) than the humidity. The OTR in the packages increased with increasing drawing depth, but the increase was not linear. Other effects besides thinning, such as orientation, may have influenced the OTR, since the relationship between OTR, given as cm³/(m²/day), and the drawing depth was not linear. Plug‐assisted thermoforming only had an effect on the OTR in trays with 70 mm drawing depth made of 600 µm thick laminate of PP/PE, which was probably due to exceeding the maximum drawing depth of this material. There was no correlation between the OTR value in the packages and the wall thickness in either of the positions, but a quite high correlation between the drawing depth and the relative wall thickness in all measured positions was observed. Copyright © 2004 John Wiley & Sons, Ltd.     

Comparison of New Dynamic Accumulation Method for Measuring Oxygen Transmission Rate of Packaging against the Steady‐State Method Described by ASTM D3985

A new dynamic accumulation method for measuring the oxygen transmission rate (OTR) of packages and packaging films using robust and inexpensive fluorescence oxygen sensing technology has been developed. The method allows for oxygen to transfer through a given area of packaging or sample film and accumulate over time. The test volume incorporates a fluorescence‐based oxygen sensor that does not consume oxygen and therefore does not interfere with the real‐time measurement of oxygen concentration. The new method was tested against a widely used, commercially available instrument (Mocon Oxtran 2/20; Mocon, Inc., Minneapolis, MN, USA) designed around the steady‐state gas permeation measurement approach described by ASTM D3985. Sample films were chosen to provide comparison over several orders of magnitude of OTR. Specifically, sample films with OTR values in the range of 10¹, 10³ and 10⁴ ml O₂/m²/day were measured, and results using the two methods were compared. Results showed that the new dynamic accumulation method provides comparable results with the steady‐state method (ASTM D3985). Copyright © 2012 John Wiley & Sons, Ltd.     

Oxygen‐ and light‐barrier properties of thermoformed packaging materials used for modified atmosphere packaging. evaluation of performance under realistic storage conditions

The oxygen transmission rate (OTR) of packaging materials used for modified atmosphere packaging (MAP) of chilled products varies extensively with temperature, relative humidity (RH) and material thickness after the thermoforming of packages. Two different polymer combinations were studied: APET/PE (tray) and PA/PE (lid). A temperature reduction of 8°C (in the interval 7–23°C) caused an OTR reduction of 26–48% depending on material type, degree of thermoforming and RH. A 2–3‐fold increase in OTR was observed for PA/PE film when measured at 100/100% RH compared to 0/100% RH, whereas the APET/PE trays were not affected by RH. Increased OTR was observed as a result of material thinning; however, the increase was not always directly proportional to the degree of material thinning. Even very small amounts of oxygen have, in combination with light exposure, significant effects on oxidative quality deterioration of many products. Consequently, the changes in OTR observed in this study emphasize the necessity of evaluating the performance of packaging materials under realistic storage conditions, in order to estimate the real oxygen content of a chosen package solution. The light transmission through the packaging material was found to be reduced to 0–30% (300–800 nm) by dyeing of the lid and/or addition of labels. Thus, it is easy to protect the products from light, at least partly. Copyright © 2005 John Wiley & Sons, Ltd.     

Prediction of oxygen transmission rate for thermoformed trays

There is a desire in the food industry to be able to estimate the oxygen transmission rate (OTR) of packages by knowing the permeability data of unconverted sheet/film, instead of measuring the OTR of packages. Due to thermoforming, the permeability of a material changes and therefore it is difficult to estimate the permeability (OTR) of converted trays from the OTR values of unconverted material. This paper evaluates the possibilities and limitations of predicting the OTR of thermoformed trays. Different methods for the calculation of OTR due to thickness measurements were compared. The use of theoretical thickness was satisfactory in the calculation of OTR of trays based on the OTR of unconverted sheet, area and thickness. Both linear and quadratic regression models were evaluated. Validation of the regression models was made by comparing the measured and calculated OTR of trays made of PS/EVOH/PE, A‐PET/PE, PS/PE and PP/PE. These trays were manufactured on different thermoforming machines, different processing parameters and different sizes of mould. None of the models (linear and quadratic) were suitable for the calculation of OTR of trays made of PS/PE and PP/PE. Both linear and quadratic models gave satisfactory agreement with measured values for trays made of both PS/EVOH/PE and A‐PET/PE. This case study indicates that a general equation for the calculation of OTR for different polymer combinations was not possible to generate. The equations presented in this paper are strictly applicable only for the polymer combinations used in this experiment, and can not be considered as general equations. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of biaxial‐simultaneous stretching conditions on OTR and CO2 permeation of CO2 laser perforated poly(lactic acid) film

The biaxially oriented poly(lactic acid) films prepared using simultaneous biaxial stretching were perforated by CO₂ laser with the power of 60 W. The focal spot diameter was fixed at 103 μm. Pulse durations were varied from 1 to 30 μs, which corresponds to the fluence from 1.4 to 42.6 J/cm². The perforated microhole size increased with increasing laser energy. The shape of microholes was circular for the films of equi‐biaxial stretching, whereas elliptical microholes were formed with its long and short axes corresponding to the directions of higher and lower stretch ratios, respectively. Comparing the laser perforation behavior of the as‐drawn films and annealed films, the opening of a microhole in the annealed films started at higher laser fluence, and at the same fluence the size of microhole was smaller. Gas transmission rates of the biaxially oriented poly(lactic acid) films with different thicknesses were examined. The oxygen transmission rates (OTR) of film improved with increased microhole diameter. The OTR of films containing 1 microhole/103 cm² (hole diameter of ~110 μm) was 184, 150, and 98 cm³/d in comparison with the OTR for the original films without microhole of only 16, 10, and 8 cm³/d, respectively. Packaging films with OTR higher than 100 cm³/d (equivalent to the 9700 cm³/m²/d) are required to create a modified atmosphere inside the package of fresh produce for shelf‐life extension. Measured OTR and CO₂TR values of the 3 different shapes of microhole were compared and discussed.     

Influence of Active Packaging on the Shelf‐life­ of Minimally Processed Fish Products in a Modified Atmosphere

The effectiveness of an innovative foam plastic tray, provided with absorbers for volatile amines and liquids, on the shelf‐life of different fish products packed under a modified atmosphere (40%CO₂:60%N₂), was evaluated in comparison with a standard tray. Fillets of sole (Solea solea), steaks of cod (Merluccius merluccius) and whole cuttlefish (Sepia fillouxi), placed in the two different kinds of trays, were kept at 3°C. Microbiological (TBC‐, Gram‐negative‐, H₂S‐producing bacteria and lactic acid bacteria) and chemical (surface pH, TMA headspace) analyses were carried out after 3, 7 and 10 days of storage. The new packaging, associated with a rigorous control of storage temperature, increased the shelf‐life up to 10 days. In fact, the innovative tray sequestrated the greater part of trimethylamine from the headspace and led to delayed microbial growth, especially of Gram‐negative and H₂S‐producing bacteria, and in addition it favoured the growth of bacterial strains such as Moraxella phenylpiruvica , which are not involved in off‐flavouring production (especially H₂S), because of their lypolitic activity. Copyright © 2001 John Wiley & Sons, Ltd.     

Carbon stripper foils held in place with carbon fibers

The Spallation Neutron Source (SNS) currently under construction at Oak Ridge National Laboratory, Oak Ridge, Tennessee, is planned to initially utilize carbon stripper foils having areal densities approximately 260 μg/cm². The projected design requires that each foil be supported by only one fixed edge. For stability of the foil, additional support is to be provided by carbon fibers. The feasibility of manufacturing and shipping such mounted carbon foils produced by arc evaporation was studied using two prototypes. Production of the foils is described. Fibers were chosen for satisfactory mechanical strength consistent with minimal interference with the SNS beam. Mounting of the fibers, and packaging of the assemblies for shipping are described. Ten completed assemblies were shipped to SNS for further testing. Preliminary evaluation of the survivability of the foils in the SNS foil changer is described.     

Effect of impurities in charge-exchange carbon foil on foil thickness reduction

Carbon thin foils are commonly used as a charge stripping material in particle accelerators. Depending on the original foil thickness, changes in thickness during beam irradiation vary: thin foils (∼10 μg/cm²) thicken by build-up, medium thickness foils (∼15 μg/cm²) remain unchanged, and thick foils (∼20 μg/cm²) become thinner. The thickness reduction differs even under identical manufacturing processes and conditions.The factor causing foil thinning is unknown. On the basis of the low sputtering rate of carbon, it can be said that impurities contained in the foil cause foil thinning.Carbon foils contain impurities such as water. These impurities dissociate and combine with carbon and then evaporate. Taking this into consideration, we examined the gas composition during beam irradiation, to determine which impurity causes foil thinning. As a result, we found that oxygen contained in the foil plays a role in foil thinning.     

Low O2 Master Bag for Beef Patties: Effects of Primary Package Permeability and Structure

The contribution of the structure and permeability of case‐ready units on the colour changes of ground beef patties during low O₂ storage in master bags, aerobic blooming and display life was investigated. We selected the following case‐ready solutions: PVC 8000 + closed‐cell expanded polystyrene (EPS) tray, PVC 20000 + closed‐cell EPS tray, linear low‐density polyethylene (LLDPE) 26000 + closed‐cell EPS tray and PVC 20000 + open‐cell EPS tray. Patties packaged onto a closed‐cell tray and wrapped with PVC 20000, but never stored in master bag, were taken as a control. We monitored oxygen depletion in the headspace of the master bags, the microbiological indexes and the appearance of the patties (colorimetric measurements and scanning images). During the storage in master bags, the use of a very high permeability wrapping film and an open‐cell EPS tray allowed the best colour stability of the bottom and upper sides of patties through 7 days. After master bag opening, the same combination of materials favoured the blooming of the upper surface pigments of the product and the stability of the oxygenated pigments during the display life. Moreover, the open‐cell trays helped in reducing the discolouration of the bottom side of patties. Hence, this low O₂ master bag system can enhance the colour stability of ground beef patties and therefore extend their distribution life. Copyright © 2013 John Wiley & Sons, Ltd.     

Silicon oxide diffusion barrier coatings on polypropylene

In this study the influence of process conditions for the plasma-enhanced chemical vapor deposition of SiO_x diffusion barrier coatings on polypropylene (PP) is investigated and compared to results obtained on polyethylene terephthalate (PET). It was observed that the thermal load during deposition is much more crucial in the case of PP. If the thermal load is not the limiting factor, the composite parameter (CP) energy input per mass of precursor showed to be valuable to describe plasma conditions at constant oxygen to monomer ratio. Low oxygen transmission rates (OTRs) of 5.1 ± 3.6 and 0.3 ± 0.1 cm³/m²day/atm were achieved on PP and PET foil, respectively, for an optimal CP of 4.1 × 10⁵ J/g. Fourier transform infrared (FTIR) spectroscopy revealed that low carbon and silanol content is necessary for good barrier performance. Low RF power, necessary to reduce thermal load on PP, can be compensated by increasing the oxygen to monomer ratio.For favorable plasma conditions, the dependence of the OTR on the coating thickness follows a similar trend for both substrate materials with a critical thickness of approximately 12 nm. The residual permeation can be correlated to the defect density at each stage of film growth by means of a simple correlation. Further support for permeation through defects is found by the activated rate theory, since the apparent activation energy of oxygen permeation is below typical values of amorphous glasses and remains unchanged due to the deposition of SiO_x on both substrates.     

Measurement of carbon sputtering yield by N ion beam and lifetime dependence of resulting foils on thickness

Carbon stripper foils with a higher nitrogen content were made by ion beam sputtering with reactive nitrogen gas. Such foils seem to be very useful as strippers for high-intensity heavy ion accelerators. To know further characteristics of the lifetime of such carbon foils, we have measured the sputtering yield of the carbon source material at a sputtering voltage of 4–15 kV and the lifetime dependence of such foils on thickness. Lifetime measurement was performed with a 3.2 MeV Ne⁺ ion beam. The sputtering yield on average showed 0.75 atoms/ion at over 9 kV sputtering voltage. The lifetime of the foils noticeably depends on the foil thickness, and the thickness range as practical stripper foil is to be around 15 to 33 μg/cm². Two foils made at 13 kV showed extremely long lifetimes of 6800 and 6000 mC/cm² at maximum and the foils made above 10 kV lived longer than about 900 mC/cm², which correspond to about 270 and 40 times longer than commercially available best foils. We measured the thickness ratio of nitrogen to carbon in each foil made at the different sputtering voltages and at the different irradiation stages (mC/cm²) by RBS method. We also inspected the structure of a nitrided carbon foil by transmission electron microscopy.     

Microperforation of Three Common Plastic Films by Laser and Their Enhanced Oxygen Transmission for Fresh Produce Packaging

Three different plastic films of biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET) and low‐density polyethylene (LDPE) were perforated using Nd‐YAG laser. Effects of laser pulse energy were examined by varying energies from 50 to 250 mJ where the pulse duration and pulse repetition were kept constant at 10 ns and 1 Hz, respectively. It was found that perforation diameters of all films increased with increasing pulse energies. Observed perforations were different among the three film types. Explanation was contributed to material inherent property and its interaction with laser. Incorporation of an inorganic filler (i.e. silica based anti‐blocking agent used in packaging film) of 0.5 wt% into the LDPE films (0.5Si‐LDPE) could improve perforation performance for LDPE. This was attributed to an increased thermal diffusivity of the 0.5Si‐LDPE film. Commercial BOPET and BOPP films containing 97 microholes/m² (hole diameter of ~100 µm) showed an improvement in oxygen transmission rates (OTR) of 18 and 5 times that of the neat films without perforation. In the case of perforated 0.5Si‐LDPE films having similar perforations of 97 microholes/m² and perforation diameter of 100 µm, a two‐fold increase of OTR was obtained. Gas transmission rates of the microperforated films were measured based on the static method. Measured OTR and CO₂TR values of the three films with varying perforation diameters in a range of ~40–300 µm were compared and discussed. Overall results clearly indicate that perforation by laser is an effective process in developing breathable films with tailored oxygen transmission property for fresh produce packaging. Copyright © 2014 John Wiley & Sons, Ltd.     

Toughening MoSi2 with niobiúm metal—effects of morphology of ductile reinforcements

Morphology effect of ductile reinforcements was evaluated using a four-point bend test on chevron-notched MoSi₂ composites reinforced with 20 vol. % niobium. The niobium used had three different morphologies, i.e., fibre, foil and particle. The thickness of the foils was 250 m, while the fibres and particles had diameters of 250 and 200 m, respectively. Toughness of MoSi₂ composites was increased from 3.3 MPa m^1/2 for the matrix to 15 MPa m^1/2 with the incorporation of the Nb fibres or foils. The particulate composites also exhibited an increase in toughness (7 MPa m^1/2). The toughening achieved was mainly attributed to ductile phase bridging in all the composites tested. The relatively small toughness improvement in the particulate composites was ascribed to the embrittlement of the Nb particles. The results indicate that toughening by crack bridging depends mainly on the intrinsic properties of the ductile bridging ligaments rather than on their morphology, and that the embrittlement of the bridging ligament is detrimental to the toughening of the composites.Previously known as L. Xiao.     

Evaluating elevated release liner adhesion of a transdermal drug delivery system (TDDS): A study of Daytrana™ methylphenidate transdermal system

Background: Complaints from healthcare providers that the adhesive on the Daytrana? methylphenidate transdermal drug delivery system (TDDS) adhered to the release liner to such an extent that the release liner could not be removed prompted this study. Daytrana? has a packaging system consisting of a moisture-permeable pouch contained within a sealed tray containing a desiccant; the tray is impermeable to ambient moisture. The objective of this project was to determine if the Daytrana? packaging system influenced the difficulty in removing the release liner.

Method: Both a sealed tray and an open tray containing sealed pouches were placed into an environmental chamber at 25°C and 60% relative humidity for 30 days; afterwards, release liner removal testing using a peel angle of 90° and a peel speed of 300?mm/min was performed.

Results: TDDS from open chamber trays required less force to remove the release liner than did TDDS from closed chamber trays. For the 10?mg/9?h TDDS and the 15?mg/9?h TDDS (the dosages examined), there were substantial differences in release liner removal force between an old lot and a new lot for closed chamber trays but not for open chamber trays.

Conclusion: The results demonstrate that for this particular TDDS, storage conditions such as humidity influence release liner adhesion. This project also demonstrates that, to ensure adequate product quality, adhesion needs to become an important design parameter, and the design of a TDDS should consider the ability to remove the release liner under anticipated storage conditions.     

Comparison of carbon and corrugated diamond stripper foils under operational conditions at the Los Alamos PSR

To accumulate high-intensity proton pulses, the Los Alamos Proton Storage Ring (PSR) uses the charge-exchange injection method. H⁻ ions merge with already circulating protons in a bending magnet, and then are stripped off their two electrons in a carbon stripper foil. The circulating protons continue to interact with the foil. Despite efforts to minimize the number of these foil hits, like “painting” of the vertical phase space, they cannot totally be eliminated. As a result, foil heating and probably also radiation damage limit the lifetime of these foils. In recent years, LANL has collaborated with KEK to improve the carbon foils in use at PSR, and these foils now last typically for about 2 months. Recently, an alternative in the form of corrugated diamond foils has been proposed for use at SNS. These foils have now been tested in PSR production for a year, and have already shown to be at least as enduring as the LANL/KEK carbon foils. Advantages of the diamond foil concept, as well as some noteworthy differences that we observed with respect to the LANL carbon foils, will be discussed here.     

Effect of Pasteurization and Retort Processing on Spectral Characteristics,Morphological, Thermal,Physico‐Mechanical,Barrier and Optical Properties of Nylon‐Based Food Packaging Materials

The effect of pasteurization and retort processing on spectral, morphological, thermal, physico‐mechanical, barrier and optical properties of three different packaging materials viz., PP/N6/PP, PET/N6/cPP and SiO_x‐PET/N6/cPP were studied. These packaging materials were packed with distilled water, which acted as a food simulant. Subsequently, these pouches were subjected to different thermal processing conditions such as pasteurization and retort processing. Both the processing techniques found to have retained the mechanical properties of all packaging materials. Water vapour transmission rate (WVTR) and oxygen transmission rate (OTR) of nylon‐based combinations were increased after processing. Gloss found to decrease invariably irrespective of the material and increases with the severity of the treatment. XRD diffractogram shows changes in crystal structure as a result of thermal processing, and SEM analysis shows the crystal fragmentation. Absorption of water by the amide group of nylon 6 was observed, which could be a reason for the increase in OTR and WVTR. Copyright © 2014 John Wiley & Sons, Ltd.     

Polymer coating method developed for carbon stripper foils

The problem of handling the fragile carbon foils (mounting on the frame, placing in the stripper changer) that easily break when self-supporting has been solved by coating carbon foils with poly-monochloro-para-xylylene. It was found that the polymer-coating method could also be used to produce carbon foils thicker than 100 μg/cm² by alternated deposition of carbon and poly-monochloro-para-xylylene layers. Carbon foil of 500 μg/cm² thick and 10 cm in diameter was produced by this method and mounted to a foil holder. Results of lifetime measurement for singly coated foils are also presented.     

Skin-Inspired Thermosensitive Tactile Sensor Based on Thermally Conductive and Viscous Interface Composites for Rocks

Achieving high thermal conductivity and exceptional interfacial adhesion simultaneously in thermosensitive tactile recognition sensors poses a significant challenge. A copolymer, poly([[(butylamino)carbonyl]oxy]ethyl-ester)-co-polydimethylsiloxane (referred to as PP), is synthesized and subsequently complexed with alumina particles coated with liquid metal (LMAl₂O₃) to prepare a composite material called PP/LMAl₂O₃ with high thermal conductivity and strong interfacial adhesion to address this challenge. The best thermal conductivity (4.43 W m⁻¹ K⁻¹), electrical insulation (10⁻⁶–10⁻⁷ S m⁻¹), and adhesion properties derived from hydrogen bonding (1316 N m⁻²) are obtained by adjusting the volume fraction of PP and LMAl₂O₃ in PP/LMAl₂O₃. PP/LMAl₂O₃ with high thermal conductivity and high interface adhesion can efficiently transfer heat between thermal flux sensors and the objects being sensed, reliably detecting small thermal flux variations and ensuring accurate thermal flux measurements. In this study, PP/LMAl₂O₃ is used to make up thermosensitive tactile sensor. Surprisingly, PP/LMAl₂O₃ demonstrates high thermal signal sensitivity for tactile recognition applications, allowing the smart thermosensitive tactile sensor system to distinguish unknown rock materials even in the dark. Overall, PP/LMAl₂O₃ may function as a fundamental material in thermosensitive tactile sensors for lithology identification.