Water vapor permeability WVP

Barrier Property—Water Vapor Permeability (WVP) Protein hlms are excellent gas barriers but poor moisture barriers because of their hydrophilic nature. Mechanical properhes and gas permeability depend on the relative humidity (1). 

Water vapor permeability (WVP) was determined gravimetrically at 25°C at the relative humidity of 33, 54, and 76% according to ASTM (American Society for Testing Materials) E 96 (ASTM E 96, 2001). Anhydrous CaCl2 of about 50 g (Baker, J.T., Deventer, The Netherlands), was used as a desiccant. WVP was calculated with Equation 24.2 where mass of water is WhjO/... 

Water vapor permeability (WVP) for starch-based films plasticized with different contents (a) and types (b) of binary polyol mixtures at various relative humidities at 25°C. 

Different sizes of films were formed. The samples were cut to measure film properties and to establish a film thickness control equation. The small-diameter films were used for the water vapor permeability (WVP) and puncture strength (PS) large ones for tensile strength and elongation at break (%) measurement. The volume of solution was added over PVC plates at volume constant using a thin layer chromatography spreader. The plates were placed on a leveled surface to achieve uniform films and dried at room condition (25 2°C and 58 3% HR) for 24 to 48 h. Films used for each property measurement were manufactured and stored under the same temperature but at different relative humidity conditions. 

Water vapor permeability (WVP) of sodium caseinate films with nutraceutical substances. Film thickness was controlled in a range of 70 to 90 /rm for all films tested. 

According to the Fick and Henry s laws the water vapor permeability (WVP) should not be function of thickness.18,22 However, WVP of hydrophilic films can be function of the thickness.19 Tomasula et al.23 studied films made from C02-precipitated casein (C02-casein), with thickness varying from 0.110 to 0.150mm, and observed that the WVP increased significantly from 2.22 to 3.80g mm/kPa h m2. The influence of the thickness on the WVP was also observed by Cuq et al.19 and Sobral24,25 that worked with films based on myofibrillar proteins from Atlantic sardines and gelatin and myofibrillar proteins from Tilapia, respectively. 

The water vapor permeability, WVP, is calculated based on the water vapor transmission rate ... 

Figure 5.3 Young s modulus, elongation at break, and water vapor permeability (WVP) of PLA films crystallized at different temperatures as a function of the degree of crystallinity. Adapted from Ref. [44], Copyright (2011), with permission from Elsevier.

Table 7.3 Water vapor permeability (WVP), water vapor transfer rate (WVTR), and strength properties of edible hemicellulose films. ...

Water Vapor Water vapor permeability (WVP) of amorphous PLA films (obtained by solution casting) with different L-lactide unit contents (PLLA, P(LLA-DLA) (77 23), and P(LLA-DLA) (50 50)) have been reported as 2.18 xl0 1.90 xl0 and 1.95 x lO- kgm/ (m sPa), respectively, at 25°C [14]. These results indicate that L-lactide unit content had little effect on the water vapor permeability of the PLA films. The values are comparable to those measured by Auras et al. [15] (1.98 x 10 " and... 

Bourtoom and Chinnan (2009) studied the effect of lipid types (oleic acid, palm oil, and margarine) and their concentrations (0, 10, 20, 30, 40, and 50 wt%) on the water vapor permeability (WVP) on rice starch-chitosan composite film. WVP of rice starch-chitosan composite film decreased with the addition of lipids. Oleic acid-incorporated films provided the films with smoother surface and lower WVP than margarine and pahn oil, respectively. Wrapping cracker samples in the rice... 

Water vapor permeability (WVP) is a critical parameter in food packaging applications as contact widi water vapor may cause certain food items to lose texture. Polymer-water interaction, that is hydrophilicity or hydrophobicity of the polymer, is a crucial factor affecting the WVP. In general, water would permeate preferentially through... 

Film forming materials, plasticizer type and amount and other additives affect film properties differently. Table 1 and 2 show the water vapor permeability (WVP) and oxygen permeability (OP) of different polysaccharide-, protein-, composite- and frait and vegetable-based films with various plasticizers using different processes. Comparisons among them are difficult because of different film compositions, test conditions (RH, temperature), methodology, and number of replications were used in each woik. 

TABLE 1 Water vapor permeability (WVP), oxygen permeability (OP), and mechanical properties (tensile strength, TS elastic modulus, EM and % elongation, %E) of various edible films from wet process (solution casting)... 

Recently, Fama et al. (2012) reported nanocomposites based on starch reinforoed with CNTs wrapped with a starch-iodine complex allows in getting starch based nanocomposites with very small amounts, which otherwise costs more. The resultant nanocomposites exhibited important improvements in storage modulus by 100% and water vapor permeability (WVP) properties lowered by 43% respect to the starch matrix. However, the so formed packaging film reinforced with CNTs carmot be used directly as food contact materials but could serve as secondary packaging apphcation. 

Water vapor permeability (WVP) was determined gravimetrically according to the standard method E96-00 (ASTM 2000). The films were fixed on top of test cells containing a desiccant (silica gel). Test cells then were placed in a relative humidity chamber with controlled temperature and relative humidity (25°C and 75% RH). After steady-state conditions were reached, the weight of test cells was measnred every 12 hours over three days. The water vapor transmission rate (WVTR) was determined using equation (2) ... 

FIGURE 6 Effects of clay type and clay content on water vapor permeability (WVP) of composite film (a) starch/PVOH/Na-MMT, (b) starch/PVOH/LRD, (c) starch/PVOH/C30B, and (d) starch/PVOH/ClOA. Error bars indicate the standard deviation. 

Biopolymer-nanoclay hybrid plastics - Polymer nanocomposites are used as packaging materials. Application of nanocomposites in the biopolymer packaging industry (e.g. films and bottles) potentially yields materials with low water vapor permeability (WVP) accompanied by a high transparency of the... 

Chitosan-based bionanocomposites with improved properties, namely barrier and mechanical properties, were also prepared by Moura et al. [200] who added chitosan/tripolyphosphate (CS-TPP) nanoparticles to hydroxypropyl methylceUu-lose (HPMC) edible films (Figure 11.14). Samples were characterized by FTIR, TEM, SEM, mechanical properties, water vapor permeability (WVP), and thermal stability. The authors reported that the incorporation of chitosan nanoparticles into the films improved their mechanical and film barrier properties significantly. This behavior was attributed to the chitosan nanoparticles that tend to occupy the empty spaces in the pores of the HPMC matrix, increasing the collapse of the pores and thereby improving film tensile properties and WVP. 

The term water vapor permeability (WVP, g.m . day ) is commonly used to measure the breathability of the fabric, which indicates the moisture transfer resistanee in the heat and mass transfer processes. This property can be obtained by the experimental measurement with the Evaporation... 

Table 15.3 Water solubility (S) and water vapor permeability (WVP) of chitosan-tapioca starch-based edible films.

Permeability is defined as the product of the diffusion constant and the solubility coefficient. Water vapor permeability (WVP] is defined as the time rate of water vapor transmission through unit area of flat material with a definite unit thickness induced by unit vapor pressure difference between two specific surfaces, and under indicated temperature and humidity conditions. (ASTM E 96, Standard Test Method for Water Vapor Transmission of Materials]. 

The water vapor transmission rate (WVTR], often erroneously called water vapor permeability (WVP], is defined as a mass of water vapor transmitted through a unit area in a unit time under specified conditions of temperature and humidity. The water vapor barrier properties for the packaged product, whose physical or chemical deterioration is related to its equilibrium moisture content, are of great importance for maintaining or extending its shelf life. The water vapor barrier is quantified by the water vapor permeability coefficients (WVPC] which indicate the amount of water vapor that permeates per unit of area and time in packaging materials (kgm/m s Pa] (Bangyekan etal., 2006]. 

Films based on above starch-cl composites/nanocomposites were made from ground extrudates and water vapor permeability (WVP) and tensile properties of the films were examined according to the ASTM standard methods E96-00 (ASTM, 2000) and D882-02 (ASTM, 2002). 

Figure 17. Water vapor permeability (WVP) of com starch-based nanocomposite films with 6% MMT using different plasticizers at 15% concentration. Error bars indicate the standard deviation. Columns with different letters imply significant difference (P<0.05) (Tang et al., 2008b).

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