Permeation of water vapor, carbon dioxide, and oxygen in polymeric materials (original) (raw)
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Packaging Technology and Science, 2009
The low oxygen permeability of the ethylene-vinyl alcohol copolymer, EVOH, is outstanding, but is also known to be very sensitive to moisture uptake and cannot be used as a monolayer packaging material. In this paper, theory is presented in order to calculate the average water activity of the EVOH layer at steady state and the corresponding oxygen barrier for different multilayer structures using various polymer types and layer thicknesses. Multilayer materials can be designed for different food packaging applications and storage conditions, in order to keep the relative humidity of the barrier below recommended 75%, by varying the thickness of the outside versus the inside protective layers and/or varying the water vapour transmission rate of the outside versus the inside layer. The conclusion reached is that to retain the optimal barrier properties and thereby the optimal protection of the food, asymmetric multilayer structures are necessary.
Water Vapor Permeability of Packaging Materials (LDPE) and Fabricated Package Systems
Low-density polyethylene (LDPE) films were investigate to the water vapor transmission rate (WVTR) of packaging material, fabricated package. And also to evaluate the influence factor of temperature and Relative humidity on WVTR. The permeation of water vapor through film was evaluated by two different approaches i.e. for WVTR of pouch by ASTM E96-08 at 37.50C 85%RH and for package system (ASTM F 1249) at 200C &400C with 60%RH &100 %RH. It was seen that as the temperature increase the value of permeability increases, The value of experimental and predicted permeability of the LDPE was compared and analyzed.
Evaluation of Water Vapour Permeability of Some Food Grain Packaging Materials
Journal of scientific research and reports, 2024
The properties of any packaging material are essential parameters to know before storage of any kind of food materials. Physical properties are prerequisites for selecting proper packaging materials to obtain the desired shelf-life during the storage and distribution chain of food commodity. At the village/household level for packaging of food grains and other Non-Timber Forest Produce (NTFP) commodities, generally used packaging materials namely, low-density polyethylene (LDPE), polypropylene (PP), earthen pot (EP), polypropylene woven sack (PPWS), and gunny sack (GS) were evaluated for their physical properties such as strengths (grammage and thickness) and water vapour permeability using the standard gravimetric method. The thickness was determined to be 0.065 mm, 0.056 mm, 0.168 mm, 3.530 mm, and 0.849 mm for LDPE, PP, PPWS, EP, and GS respectively. Similarly, grammage was found to be 6.03 x 10-5 g m-2 , 4.94 x 10-5 g m-2 , 9.59 x 10-5 g m-2 , and 3.70 x 10-4 g m-2 for LDPE, PP, PPWS, and GS respectively. Results revealed a significant difference between the permeability of packing materials. The highest water Original Research Article
Important Factors for Selecting Food Packaging Materials Based on Permeability
2004
of the critical factors in selection of food packaging materials is permeability and/or transmission rate to help maintain food quality. Conditions of product/material use such as temperature and relative humidity are critical for determining optimal testing conditions to determine permeability rate. Basics of permeability, interpretation of data and relationship to selection of materials for specific applications will be discussed. In addition, the relationship of permeability to aroma and flavor retention will also be covered. Introduction The type of food, chemical composition, size, storage conditions, expected shelf life, moisture content, aroma/flavor and appearance are just a few of the characteristics that must be taken into consideration when selecting the right material for a food product. A continuing trend in food packaging is the design of packages to extend the shelf life of foods while maintaining fresh-like quality. This places a high demand on selecting materials th...
23) MODIFIED ATMOSPHERE PACKAGING
The shelf-life of perishable foods as meat, poultry, fish, fruits and vegetables and bakery products is limited in the presence of normal air by two principal factors-the chemical effect of atmospheric oxygen and the growth of aerobic spoilage micro organisms. These factors either individually or in association with one another bring about changes in odour, flavour, colour and texture leading to an overall deterioration in quality. Chilled storage will slow down these unde sirable changes but will not necessarily extend the shelf -life sufficiently for retail distribution and display purposes.
Journal of Food Science, 1977
A method for accelerated stability tests was developed, which is applicable to isothermal storage of moisture-sensitive dehydrated products packaged in water-vapor-permeable containers. The method does not require prior knowledge of the kinetic model of the effect of moisture on rate of deterioration. The method can be applied to dehydrated products when the index of deterioration [defined as J -(dc/cn) where c is reactant concentration, and n is the order of reaction] is dependent only on moisture content, which changes continuously during storage. The accelerated tests are based on monitoring quality changes in the product, which undergoes rapid deterioration because of a high, albeit controlled, rate of moisture gain. Theoretical considerations based on I kinetic theories indicate that the rate at which the index of deterioration changes at any given moisture content is inversely proportional to the rate of moisture gain. This fact provides a basis for the mathe-I matical procedures of extrapolation and prediction of storage stability of the same product at the same temperature under any given rate of moisture gain. The method successfully predicted the loss of ascorbic acid in stored tomato powder and the extent of browning in dehydrated cabbage.
Moisture effects on a system in package carrier
EuroSimE 2009 - 10th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 2009
We have investigated the behaviour of moisture absorption in various humidity environments at constant temperature of two types of epoxy novolac polymers. In addition, we examined the effects of moisture on the viscoelastic properties. The water absorption is carried out in an adjustable thermal and humidity chamber at different temperature and humidity. The diffusion coefficients at different conditions were obtained through early stage moisture absorption tests. The moisture absorption was revealed to be of the Fickian type of diffusion for both types of samples and to shift the creep compliance to the left of that of a dried sample, as an effect of plasticization. The relationship between loga H and the equilibrium water content is analogically described by the WLF-type equation on the timetemperature superposition. The time-moisture superposition was confirmed to hold at various equilibrium moisture contents at constant temperature. The more moisture in the sample, the more plasticization will happen for the epoxy. 3. Sunil K. Karad, et al "Mechanisms of moisture absorption by cyanate ester modified epoxy resin matrices: the clustering of water molecules," Polymer
Aroma compound and water vapor permeability of edible films and polymeric packagings
Journal of Agricultural and Food Chemistry, 1994
The permeability of water vapor and aroma compounds through low-density polyethylene packagings and edible films was measured with a dynamic method coupled with a gas chromatograph. Volatile fluxes were analyzed and quantified with two detections: thermal conductivity and flame ionizing detectors. The effects of overpressure and aerodynamic conditions inside the permeation cell were determined, and vapor concentration differentials were only used to measure permeability. Water vapor and aroma permeabilities increase with the penetrant sorption within the film, particularly for hydrophilic films such as cellophane or edible films. Whatever the nature of the penetrant, polar (water vapor) or apolar (l-octen-3-01), the behavior of edible films and the activation energy of permeation are identical. However, aroma transfer through methylcellulose-based films strongly increases with the water vapor transfer rate WVTR) due to the plasticization of the polymer network by water. WVTR directly depends on the hydrophobicity of the polymer, but not for 1-octen-3-01 flux. Abstract published in Advance A C S Abstracts, October 15, 1994.
Defect and Diffusion Forum, 2010
This work present a model for prediction of moisture gain over storage time for individually packaged, which considered both the moisture transfer through the polymeric film to the headspace and from the headspace to the product. The transport of moisture between the headspace and each product was assumed to be controlled by external resistance. No interaction between the packaged components was considered. Moisture content within the product was assumed to be uniform for a given time and to relate to the headspace humidity by the GAB sorption isotherm. The isotherm parameters were determined by equilibrating samples at different relative humidity. The transient period of these experiments was used to estimate the mass transfer coefficients. The model was validated by monitoring the moisture take up by breakfast cereal and chocolate powder packed individually in different materials, oriented polypropylene (OPP) and low density polythelene (LDPE), during storage at 25ºC and 75% RH (relative humidity). The model provided very good fits for the products packaged individually (with r 2 above 0.99).