Effect of high‐pressure processing on the permeance of selected high‐barrier laminated films

This study investigated the effects of high pressure processing (HPP) on the barrier properties of eight multilayer films. Pouches made from these films were filled with distilled water, sealed and then pressure processed at 600 and 800 MPa for 5, 10 and 20 min at 45°C. Controls were similarly prepared but exposed to atmospheric pressure. After processing, all pouches were dried and their oxygen, carbon dioxide and water vapour permeance determined. Films used in this study were PET/SiO_x /LDPE, PET/Al₂O₃/LDPE, PET/PVDC/nylon/HDPE/PE, PE/nylon/EVOH/PE, PE/nylon/PE, metallized‐PET/EVA/LLDPE, PP/nylon/PP and PET/PVDC/EVA. Results showed that metallized PET was most severely affected by HPP, as its permeance values for oxygen, carbon dioxide and water increased as much as 150%. Copyright © 2000 John Wiley & Sons, Ltd.     

高透气性LDPE/EVA薄膜的制备

通过对6种不同LDPE/EVA共混比例的薄膜进行DSC分析和阻隔性分析,结果表明随着EVA质量分数的增加,LDPE/EVA薄膜的结晶度下降,透气性增大,水蒸气透过率和氧气透过率也随改性薄膜中EVA质量分数的增加而增大.     

Development of a mathematical model for the effect of temperature and relative humidity on the water vapour permeability of plastic films

The water vapour permeability constants of three flexible films (LDPE, PET and a laminate of both films) were determined at 20, 30 and 40 °C and from 55 to 90% relative humidities. The relationship between permeability and temperature followed the Arrhenius model for the three films. The relative humidity also influenced the permeability of the films. A mathematical model describing permeance (P/X - the permeability of laminates or films) as a function of external relative humidity and temperature was developed. The model can be used to predict the permeance of the three films at different temperatures and relative humidities.     

Effect of organic vapour interaction on permeation rate through polymer films

The permeability coefficients (P) of linalool, citral ethyl butyrate, d-limonene and octanal permeating through LDPE and ionomer films were measured alone as individual and as a component of a mixture at a temperature of 23 °C and in saturated water vapour. Values of P for ionomer film were approximately two orders of magnitude below those for LDPE for the compounds tested. Both PET and PETG films were found to be much better barriers against the compounds tested than LDPE and ionomer films. In general, the permeability, diffusion and solubility coefficients (P. D, and S) values measured in mixture were substantially less than the values obtained individually. Permeability behaviour of these compounds at low concentrations in the mixture was similar to that of permanent gases. Reduction of solubility coefficients in mixture permeation was greater with the higher solubility coefficients. These results provide a better understanding of the mechanism of vapour diffusion through polymers.     

Effect of high‐pressure processing on the mechanical and barrier properties of selected packagings

This investigation focuses on the effect of high‐pressure processing (HPP) on possible changes of the mechanical properties and of the water vapour permeability of seven selected packaging materials. NOD 259 (PA‐PE), BB4L (Cryovac‐Grace packaging), PET/BOA/PE, PET/PVDC/PE, PA/SY, LDPE and EVA/PE were investigated (PET, polyester; PE, polyethylene; SY, surlyn; LDPE, low‐density polyethylene; EVA, polyethylene–vinyl acetate co‐polymer; BOA, biaxially oriented polyamide). These packaging materials were selected because of their interest to the food industry. All had an internal film of PE for food use. High‐pressure tests were realized at 10°C for 10 min at pressures of 200, 400 and 600 MPa, with water as a food‐simulating fluid. The depressurization rate was either rapid (pressure drop in <10s) or slow (20 MPa/min). Permeability to water vapour was realized using the NFF H 00 030–ASTM E96‐90 standard. Mechanical tests were carried out with a tensile testing machine (Lloyd LR5K), according to the NF 54‐102 standard. Maximal stress, rupture stress and strain at rupture were evaluated with non‐treated and treated samples. Obtained results showed that HPP minimally affects the mechanical strength of packaging material. The depressurization rate did not have any significant influence in our conditions. The barrier properties to water vapour were not significantly affected and were even slightly enhanced for LDPE, which is a packaging material commonly used for HPP applications and at least as a food contact material. Copyright © 2006 John Wiley & Sons, Ltd.     

Estimation of vapour pressure and partial pressure of subliming compounds by low-pressure thermogravimetry

A method for the estimation of vapour pressure and partial pressure of subliming compounds under reduced pressure, using rising temperature thermogravimetry, is described in this paper. The method is based on our recently developed procedure to estimate the vapour pressure from ambient pressure thermogravimetric data using Langmuir equation. Using benzoic acid as the calibration standard, vapour pressure-temperature curves are calculated at 80, 160 and 1000 mbar for salicylic acid and vanadyl bis-2,4-pentanedionate, a precursor used for chemical vapour deposition of vanadium oxides. Using a modification of the Langmuir equation, the partial pressure of these materials at different total pressures is also determined as a function of temperature. Such data can be useful for the deposition of multi-metal oxide thin films or doped thin films by chemical vapour deposition (CVD).     

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.     

Characterization of antimicrobial films containing basil extracts

The properties of low‐density polyethylene (LDPE)‐based films containing either linalool or methylchavicol as antimicrobial (AM) additives were evaluated. Slight decreases in transparency, water vapour and oxygen transmission rates were found in the extruded films containing 0.34% w/w linalool or methylchavicol. The infrared (IR) spectra of the AM films were similar to that of additive‐free LDPE film. However, carbonyl peaks could also be observed in the spectra of the AM films. There was no significant difference in the degree of crystallinity and the melting temperature range of the different films. Derivative thermogravimetry mass‐loss curves showed that the thermal decomposition temperatures of the AM films were marginally lower than that of LDPE film. Electron micrographs indicated that AM LDPE‐based films exhibited no evidence of changes in microstructure to suggest that linalool and methylchavicol were not evenly distributed in the film. Copyright © 2006 John Wiley & Sons, Ltd.     

Preparation and properties of quercetin‐incorporated high density polyethylene/low density polyethylene antioxidant multilayer film

High density polyethylene/low density polyethylene (LDPE) antioxidant multilayer films were prepared by the co‐extrusion method, and quercetin was incorporated in the LDPE layers as an antioxidant. The release rates of quercetin and the antioxidant activities of films were adjusted by changing the amount of ethylene vinyl acetate (EVA) and diatomite added into the LDPE active layer. The morphologies of the films were observed by SEM, and the release property of quercetin was characterized by a high‐performance liquid chromatography (HPLC) method. The mechanical properties and heat sealing performance of the films were influenced to a certain extent by the amounts of EVA and diatomite in the active layers, while the barrier properties of the films were almost unchanged. The release of quercetin from the active films to a food simulant (95% alcohol) at 37°C was measured over 55 days. When the EVA amounts were 30% and 40% to 50%, the diffusion coefficients, D, were 10^?14 and 10^?13 cm²/s, respectively. In addition, the antioxidant activity values of the films were enhanced as the EVA amount increased. When adding diatomite into the active layer with 50% EVA, the diffusion coefficient, D, was 10^?11 cm²/s, and the quercetin was almost completely released with a partition coefficient, K, of less than 1. Meanwhile, the antioxidant activity values of the films exceeded 95%. The antioxidant release rate could be adjusted within a wide range; thus, these active films could be used for food antioxidant protection.     

射频等离子体化学气相沉积(RF-PECVD)制备Si-O-N特种阻隔包装材料的研究

采用13.56MHz射频等离子体聚合装置,以六甲基二硅氧烷(HMDSO)和四甲基硅氧烷(TMDSO)为单体、氧气以及氮气为反应气体、氩气为电离气体,在载玻片、单晶硅片、PET等基材上沉积硅氧氮薄膜.在薄膜的制备工艺研究中,通过改变放电工作压强、放电功率、沉积时间和氧气、氮气、氩气和单体的比例等,研究所制备硅氧氮薄膜的性能.通过傅立叶红外光谱仪(FTIR)表征分析沉积膜的化学组成;采用透湿、透氧测试仪测试薄膜的阻隔性能,探讨工艺参数的变化对薄膜表面的成分和阻隔性能影响以及氮的加入对薄膜柔韧性的影响.     

High Rate Growth of a-Si and μc-Si Thin Films with Facing-target PECVD

The first investigation on high rate growth of uniform a-Si and μc-Si thin films with facingtarget plasma enhanced chemical vapour deposition (FTPECVD) has been presented here. It has been shown that by employing FTPECVD both a-Si and μc-Si thin films can be fabricated with rates of up to 10μm/h and l μm/h, respectively, around 10 times higher than those of the conventional PECVD, and the correspondent gas utility is about 20 times higher. As indicated by Raman spectroscopy measurement, the crystallinity of the materials is as high as 85%. A columnar structure in the films has been revealed by TEM analysis, a reflection of epitaxial growth in the deposition process.     

Gas transmission properties of polyvinyl chloride (PVC) films studied under subambient and ambient conditions for modified atmosphere packaging applications

This study was undertaken to determine the gas transmission properties of three polyvinyl chloride (PVC) films mostly used as overwrap for fresh produce under subambient and ambient conditions (5–40°C). Three different kinds of curves or groups of data are presented: gas transmission rates, activation energy measurements and the permeability coefficient. Hydrophobic by nature, the PVCs are not affected in their gas transmission properties (O₂, CO₂) by the moisture level. Reliable gas transmission data were obtained with method variability (≤9%) over a wide range of temperature. Regression constants, activation energies for prediction equations and permeability ratios (CO₂/O₂) are presented for the three films. Greater uniformity in test procedures, and the presentation of permeability data normalized to 1 μm instead of 1 mil would simplify comparative studies within and between countries, laboratory services and from the scientific literature. More research is needed to study the wide variety of polymers available under subambient conditions.     

Aufgedampfte SiOx Barriereschichten unter monoaxialem Stress

SiO_x barrier layers under uniaxial stress For the study of the impact of defined mechanical uniaxial load on the gas barrier effect of a PET (Polyethylenterephthalate) film coated with silicon oxide SiO_x a measurement device was designed. The developed system is modular and can be combined to measure both water vapour and oxygen transmission rate. The gas permeation was measured after a given strain and after unloading the strain on relaxed films.The results show that strain above 1 % can be critical for the increase of gas permeation of coated films under constant stress and 4 % for relaxed film.     

Simple models for evaluating effects of small leaks on the gas barrier properties of food packages

A detailed theoretical analysis and calculations were made for providing a simple and explicit means to evaluate the effects of small leaks on the barrier properties of food packages. Small leaks, such as pinholes and channel leaks, were approximated as cylindrical pores with diameters of 50–300 μm. The first part of the current study proposes a simple mathematical model based on Fick's law of diffusion, which accounts for both the gas leakage across small leaks and the gas permeation across package walls. The model uses an effective permeability that depends on leak dimensions, type of diffusing gas, type of packaging material and gas conditions around the leak ends. In the second part of the study, three practical cases are presented to illustrate the application of the proposed model in examining the significance of leaks. These demonstrate in a simple and explicit manner that for LDPE packages: (a) leaks affect the oxygen transfer more than the water vapour transfer; (b) leak effects are more significant at lower storage temperatures; and (c) that for high gas barrier packages, the effect of leaks is very important and should not be neglected. The model can be also used to arrive at conclusions about the significance of leaks in other packaging situations (e.g. other than LDPE packaging materials) and to correct the shelf‐life estimation of gas‐ and water vapour‐sensitive foods for errors from package leaks. Copyright © 2003 John Wiley & Sons, Ltd.     

硅藻土填充PE保鲜膜的研制与性能研究

以LDPE/EVA(质量比为4∶1)共混薄膜为基材,选择具有透气调湿性能的硅藻土为无机填充剂,针对薄膜透气性和透湿性的改善,制备了不同处理方式的硅藻土填充保鲜膜。结果表明:偶联处理使填料与偶联剂很好的结合在一起;煅烧处理可以使填料表面的微孔孔径增大。随着不同处理方式的硅藻土添加量的增加,薄膜的力学性能和热封性能有所降低,但薄膜的透氧和透湿性能却有所提高。     

Characterisation of SiOxCyHz thin films deposited by low-temperature PECVD

SiO_xC_yH_z thin films were deposited from hexamethyldisiloxane (HMDSO)/O₂ mixtures in a parallel plate, capacitively coupled, RF plasma reactor. Polyethylene terephthalate (PET), Si(1 0 0) wafers and KBr tablets were chosen as substrates. Effect of HMDSO/O₂ ratio, total treatment pressure and power input on the properties of the deposited films were investigated. The structure and bondings were studied by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Wettability characteristics of the deposited thin films were investigated by means of water droplet contact angle measurements. Surface morphology was investigated with atomic force microscopy. Barrier properties of the SiO_xC_yH_z thin films were investigated by measuring the water vapour transmission rate of the coated PET substrates. Correlations between the characteristics of the deposited film and their barrier properties were discussed.     

Simplified Approach Based on Polynomial Equations to Predict the Permeability of Micro‐perforated Polymeric Films

A simplified approach to predict the mass transport properties of micro‐perforated films was presented in this work. In particular, the proposed mathematical model was based on a second‐degree polynomial function. Different types of micro‐perforated films with two thicknesses (35 and 25 µm) were tested for gas and water vapour permeability, under proper conditions. The films differed in both number of holes per unit area and hole diameter. Corresponding non‐perforated films were also tested. The experimental data obtained were used to validate the model. Moreover, the surface response plot of the interactions between hole diameter and number of holes per area relative to oxygen, water vapour and carbon dioxide permeability were determined. Results of the mean relative deviation modulus (E%) between the experimental and predicted data confirmed the ability of the proposed model to predict the permeability of micro‐perforated films. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of high‐pressure food processing on the mass transfer properties of selected packaging materials

The effect of high‐pressure processing (HPP) on the total migration into distilled water and olive oil and on the barrier properties of four complex packaging materials were evaluated. The films were polyethylene/ethylene‐vinyl‐alcohol/polyethylene (PE/EVOH/PE), metallized polyester/polyethylene, polyester/polyethylene (PET/PE), and polypropylene‐SiOx (PPSiOx). Pouches made from these films were filled with food simulants, sealed and then processed at a pressure of 400 MPa for 30 min, at 20 or 60°C. Pouches kept at atmospheric pressure were used as controls. Prior to and after treatment, all films were evaluated for their barrier properties (oxygen transmission rate and water vapour transmission rate) and ‘Total’ migration into the two food simulants. In the case of water as the food stimulant, a low ‘Total’ migration was observed and even a lower one after the HPP treatment. In the case of oil as the food simulant, a higher ‘Total’ migration was found compared to the control as a result of damage to the structures during the HPP treatment. The gas permeability of the films increased after the HPP, compared to the control, due to damages in the structure caused during the treatment. The PET/PE film presented minimum changes in properties after HPP. Copyright © 2010 John Wiley & Sons, Ltd.     

Properties of antimicrobial plastics containing traditional food preservatives

Traditional food preservatives, sodium benzoate, sodium nitrite, potassium sorbate and sodium lactate, were incorporated into synthetic plastics, low‐density polyethylene (LDPE), poly(maleic acid‐co‐olefine), polystyrene (PS) and polyethylene terephthalate (PET), aimed at producing antimicrobial packaging material for foodstuffs. The study was undertaken on plaques (thickness 2 mm) and films (thickness 70–120 µm), whose antimicrobial test results clearly differed. Plaques containing 15% sodium nitrite inhibited both Aspergillus niger and Bacillus subtilis, whereas the same concentration of sodium benzoate and potassium sorbate had activity only against B. subtilis. Sodium lactate‐containing samples did not have any antimicrobial activity and none of the samples inhibited Escherichia coli. Antimicrobial substances added into PS and PET produced the strongest activities; however, due to the brittle structure of these materials, they were not tested further. Thus, more thorough tests for antimicrobial activity, migration and oxygen and water vapour permeability were carried out using LDPE films with 2.5–15% sodium benzoate and sodium nitrite. The effects of both substances on permeability properties were negligible. Although the total migration into food simulants measured from the films in many cases exceeded the limit value of 10 mg/dm², no antimicrobial activity was observed. Copyright © 2003 John Wiley & Sons, Ltd.     

Ultramicrohardness experiments on vapour-deposited films of pure metals and alloys

The ultramicrohardness of thin alloy films is determined by indentation experiments at very low loads. The indentation apparatus is briefly described. We measured the hardness of a number of pure metal films, either vapour deposited or magnetron sputtered. In addition, a detailed study was made of the composition dependence of the hardness of the six binary alloy systems of AgAuCu and AuCoNi. These films were prepared by high vacuum vapour deposition. The thickness of all the films was 1 μm.The hardness data were interpreted with the help of the metastable alloy phase diagram, e.g. as obtained by transmission electron microscopy. The results are discussed in terms of the blocking of the motion of dislocations, solid solution hardening, compound formation, grain size reduction due to alloying, and differences in atomic radii.