Water vapor and oxygen permeability of wax films

The water vapor (WVP) and oxygen (O₂P) permeabilities of beeswax (BW), candelilla wax (CnW), carnauba wax (CrW) and microcrystalline wax (MW), formed as freestanding films, were determined. CnW and CrW both had small values for O₂P (0.29 and 0.26 g·m⁻¹·sec⁻¹·Pa⁻¹ × 10⁻¹⁴, respectively), which are less than half the value for high-density polyethylene and about a decade greater than the value for polyethylene terephthalate. O₂P values for BW and MW were about 6−9× greater than those of CnW and CrW. WVP of CnW was 0.18 g·m⁻¹·sec⁻¹·Pa⁻¹ × 10⁻¹², which is about one-half the value for CrW and MW and about one-third the value for BW. The WVP of CnW was somewhat less than that of polypropylene and somewhat greater than that of high-density polyethylene. Differences in permeabilities among the wax films are attributed mainly to differences in chemical composition and crystal type as determined by X-ray diffraction.     

Barrier and mechanical properties of carrot puree films

The edible films based on carrot puree, carboxylmethyl cellulose (CMC), corn starch and gelatin were developed. Glycerol was added as plasticizer. Hydrocolloids and plasticizer content effects on film properties were investigated. CMC and gelatin contents did not significantly affect film %elongation (%E), oxygen permeability (OP) and water vapor permeability (WVP) but significantly enhanced film tensile strength (TS). Corn starch content significantly enhanced film TS and WVP but not significantly affected film %E and OP. Increasing glycerol content decreased film TS and increased film %E (p < 0.05), OP and WVP. Moreover, the L, a and b values of carrot films increased with the increase of the glycerol and decreased with the increase of the corn starch.     

Water vapor permeability and mechanical properties of fabrics coated with shape‐memory polyurethane

Water vapor permeable fabrics were prepared by coating shape‐memory polyurethane (PU), which was synthesized from poly(tetramethylene glycol), 4,4′‐methylene bis(phenylisocyanate), and 1,4‐butanediol, onto polyester woven fabrics. Water vapor permeability and mechanical properties were investigated as a function of PU hard‐segment content or polymer concentration of the coating solution. Water vapor permeability of PU‐coated fabrics decreased dramatically with increased concentration of coating solution, whereas only a slight change was observed with the control of PU hard‐segment content. The coated fabric showed the clear appearance of a nonporous PU surface according to SEM measurements. Attainment of high water permeability in PU‐coated fabrics is considered to arise from the smart permeability characteristics of PU. Mechanical properties of coated fabrics, although there was some variation depending on the concentration of coating solution, were primarily affected by PU hard‐segment content. Fabrics coated with PU hard‐segment content of 40% showed the lowest breaking stress and modulus as well as the highest breaking elongation, which could be interpreted in terms of the dependency of mechanical properties of coated fabrics on PU hard‐segment content and the yarn mobility arising from a difference in penetrating degree of coating solution into the fabric. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2812–2816, 2004     

Influence of sorghum wax,glycerin, and sorbitol on physical properties of soy protein isolate films

Sorghum wax, sorbitol, glycerin, and soy protein isolate (SPI) composite films were prepared. Effects of sorghum wax, sorbitol, and glycerin concentrations on various films were evaluated using response surface methodology. All independent variables significantly (P<0.05) affected film water vapor permeability (WVP), tensile strength (TS), elongation at break (E), total color difference, and total soluble matter (TSM). Increasing the sorghum wax concentration decreased WVP and E. As sorbitol content increased in the composite films, WVP and TS increased. Sorbitol had a critical point of 2–5 g/5 g SPI for low values of TSM. The addition of sorbitol contributed more to the properties of the film than did glycerin.     

Water vapor permeability of the polyurethane/TiO2 nanohybrid membrane with temperature sensitivity

A novel thermal‐sensitive polyurethane (TSPU)/TiO₂ nanohybrid membrane was successfully prepared via in situ process and used for controllable water vapor permeation. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) were employed to reveal the nanohybrid mechanism between TSPU and TiO₂ and the thermal sensitive characteristics of TSPU/TiO₂ nanohybrid membranes. FTIR analysis demonstrates that the highly active nano‐TiO₂ particles produced by the hydrolysis of the nanoprecursor (tetrabutyl titanate) have reacted with the active groups of TSPU. And some new peaks assigned to the Ti? O? C, Ti? C, and Ti? O? Ti bonds occur in the FTIR spectra of TSPU/TiO₂ nanohybrid membrane; these chemical bonds are believed to contribute to the higher mechanical properties of nanohybrid samples. DSC study indicates that nanohybridization does not disrupt the intrinsic phase‐separated structures and thermal‐sensitive characteristics of pure TSPU, the difference in behavior is the phase transition temperature (defined as switch temperature, T_s) of the reversible phase shifting from 50.1 to 53.4°C. SEM analysis shows that the nano‐TiO₂ particles are evenly distributed in TSPU and the size of the nano‐TiO₂ is lower than 100 nm. In addition, the water vapor permeability (WVP) of nanohybrid membrane is found to depend on the TiO₂ content. To be specified, when TiO₂ content is lower than 5.0 wt %, the nanohybrid samples show lower WVP at low temperatures and higher WVP at high temperatures than pure TSPU. Especially, when the temperature exceeds the T_s, for example from 50 to 60°C, the WVP of pure TSPU show improvement by 114%, whereas the WVP of the nanohybrid TSPU with 5.0 wt % TiO₂ content shows improvement by 145%, the latter shows more sensitivity to thermal stimuli. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of soy protein isolate films modified with sorghum wax

The effect of increasing the concentration of sorghum wax paste on the characteristics of soy protein isolate (SPI) films was investigated. Water vapor permeability (WVP), tensile strength (TS), elongation at break (E), and total soluble matter (TSM) of cast SPI films were determined. Sorghum wax paste extracted with ethanol was added to film-forming solutions of SPI at 5, 10, 15, or 20% w/w of protein. As the concentration of wax paste increased, mean WVP, E, and TSM values of SPI-sorghum-wax-paste composite films decreased and were lower than those of control SPI films. Mean TS values were lower than the control upon addition of 5 and 10% wax paste; however, TS values increased at 15 and 20% was concentrations. Although no differences in components of sorghum wax were observed between paste extracted with ethanol and wax extracted with hexane, paste extracted with ethanol was miscible with the filmforming solution. SPI-sorghum wax paste films had better water barrier and physical properties compared to control films.     

Influence of preparation conditions on the physical properties of zein films

Zein is a hydrophobic protein produced from maize. Biodegradable zein films without additional reagents were prepared using various controlled drying conditions. The zein films were transparent. Mechanical properties (tensile strength and puncture strength), gas permeability, and water vapor permeability (WVP) of the zein films were measured. The tensile strengths of the zein films were between 7 and 30 MPa and the puncture strengths between 37 and 191 MPa. The zein films had higher oxygen permeability than carbon dioxide permeability. The lowest WVP of the zein film was 0.012×10⁻⁹ g·m/m²·s·Pa. We found differences in the WVP between the sides of the zein films; i.e., the air side of the zein film had a higher WVP than the basal side of the zein film when the films were exposed to high humidity during testing. This indicates a relationship between the WVP of the zein film and the contact angle of the zein film. The mechanical properties of the zein film depended on the drying conditions during preparation. Zein films with various useful physical mechanical properties were produced.     

Morphology and water vapor permeability of temperature‐sensitive polyurethanes

A series of segmented polyurethanes (PUs) were prepared, in which five different polyols and hexamethylene diisocyanate were used as soft segments, and 4,4′‐diphenylmethane diisocyanate, hydrophilic segment poly (ethylene glycol) 200 (PEG 200), and chain extender 1,4‐butanediol were used as hard segment. Morphology of the PUs was investigated using differential scanning calorimetry, wide angle X‐ray diffraction, polarizing microscopy, and transmission electron microscopy. Water vapor permeability of the membranes as a function of temperature was tested accordingly. Results show that the presence of PEG200 interferes the crystallization of hard segment in these PUs, and at the same time, increases phase compatibility between soft and hard segment in the PET‐PU. It leads to a lower crystal melting temperature and degree of crystallinity of soft segment in the segmented PU than those of pure polyols, and no crystallization existing in hard segment. A morphological model is proposed, that is, aggregated soft‐segment‐rich domains can be observed clearly in the PUs with high crystallinity in soft segment, while identifiable hard domains are well‐distributed in the soft segment domains in the PU with low crystallinity. Within the temperature range of crystal melting, water vapor permeability of the PU membranes increases significantly with increase of temperature. Such temperature‐sensitive property is triggered by crystal melting of soft segment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚氨酯—丙烯酸酯复合乳液的表征及对复合薄膜的粘结作用

通过预聚体分散法制备出阴离子自乳化型聚氨酯-丙烯酸酯共聚乳液,对乳液粒径、贮存稳定性进行了表征,对共混型和共聚型复合乳液胶膜进行了DSC表征,测试了乳液胶膜的耐水性,并且研究了该乳液对PVC/PVC、PET/PE等复合薄膜的粘结作用。     

Permeation of oxygen and water vapor through EVOH films as influenced by relative humidity

The transport properties of oxygen and water vapor through EVOH films as functions of relative humidity (RH) and temperature were studied. The results of oxygen and water vapor permeation demonstrated that temperature and RH markedly affected barrier properties of these films. In general, the EVOH films had minimal oxygen and water vapor permeabilities at a low RH, attributed to the reduced mobility of the polymer resulting from strong interactions between small water molecules and the polymeric matrix at low RH. Beyond 75% RH, the permeabilities increased considerably. In addition, the barrier performance of the EVOH films was found to be dependent on their ethylene content and orientation. From the experimental data, semiempirical equations describing oxygen transmission rates (O₂TR) as functions of RH and temperature were developed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1866–1872, 2001     

大米蛋白可食性膜的制备工艺研究

大米蛋白膜是一种绿色包装膜,它具有良好的阻气性、阻油性、保香性、防湿性和防紫外线性,因此开发大米蛋白膜具有重大的意义.作者对大米蛋白的成膜条件进行了研究.结果表明,大米蛋白在质量分数80％乙醇中溶解效果良好,在40℃恒温条件下,可以在光滑的不锈钢板上形成具有一定强度的可食性薄膜.此外,添加油酸与甘油可以对膜的透明度与抗...     

Investigation of water vapor permeability and antimicrobial property of zinc oxide nanoparticles‐loaded chitosan‐based edible film

This study is focused on the investigation of moisture uptake properties of chitosan films. The GAB isotherm model is found to fit well to the experimental moisture uptake data obtained at 10, 25, and 37°C. The water vapor permeability is found to increase with temperature. The use of plasticizer enhances the water vapor permeability. Finally, the films have been loaded with ZnO nanoparticles and characterized by X‐ray diffraction, differential scanning calorimetry, surface plasma resonance, and scanning electron microscopic analyses. The crystal size as determined using Scherrer's equation is found to be around 15 nm. The films have shown excellent antibacterial action against the model bacterium Escherichia coli. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Desiccant films made of low-density polyethylene with dispersed calcium oxide: Water vapor absorption,permeation and mechanical properties

Polymers with dispersed desiccants are relevant for various packaging applications to protect packaged goods from water vapor. The intention of this study was to analyze and to describe a relevant system. Therefore, films with calcium oxide (CaO) were investigated, because such materials are hardly described in scientific literature. Monolayer films with 0.14 to 0.51 g dispersed CaO per 1 g film (PE-LD) were prepared and they absorbed up to 0.2 g water vapor per 1 g of film. The water vapor absorption was described by effective diffusion coefficients. By the use of effective diffusion coefficients and the absorption capacity, the absorption behavior of layers with various thicknesses can be estimated. The steady state (effective) water vapor permeation coefficients of the films with dispersed CaO were a factor of 2 to 24 (8.4 to 101.5 mg cm [cm² s Pa]^–1 × 10¹², at 23 °C) higher than for pure PE-LD films (4.26 mg cm [cm² s Pa]⁻¹ × 10¹², 23 °C). The tensile stress changed only slightly (pure PE-LD: 9.5 N mm⁻²; PE-LD with 0.14 g dispersed CaO per 1 g film: 8.1 N mm⁻²; PE-LD with 0.51 g dispersed CaO per 1 g film: 10.5 N mm⁻²), while the tensile strain at break was reduced with higher CaO concentration from 318% (pure PE-LD) to 10% (PE-LD with 0.51 g dispersed CaO per 1 g film). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47460.     

PU型防水透湿层压复合织物的制备工艺及研究进展

介绍了聚氨酯薄膜的制备工艺和防水透湿机理,综述了聚氨酯型防水透湿层压复合织物的制备方法和研究进展,并对聚氨酯型层压复合织物的发展方向进行展望。     

室温交联聚丙烯酸酯乳胶膜的制备及其渗透性能

以双丙酮丙烯酰胺（DAAM）为官能性单体合成了带酮羰基的聚丙烯酸酯核壳乳液,将其与己二酸二酰肼（ADH）在室温下交联制备了聚丙烯酸酯多孔乳胶膜,考察了乳液壳层组成、ADH用量、致孔剂用量及种类对乳胶膜渗透性能的影响。研究结果表明,当壳层组成BA/(MMA+AA+DAAM)质量比为2.5/2.5时,乳胶粒子没有完全变形,粒子间相互融接堆积,结合致孔剂的作用,形成了内部呈疏松多孔结构的乳胶膜,膜的渗透量较高;研究进一步揭示,限制大分子链段的热运动有利于维持乳胶膜的多孔结构,从而获得较高的渗透量;此外,发现以葡萄糖、聚乙二醇300（PEG300）为致孔剂时可使乳胶膜获得较高的渗透量。     

莲藕淀粉/乳清蛋白复合膜的制备、表征及性能

将莲藕淀粉与乳清蛋白按1∶0.3、1∶0.4、1∶0.5、1∶0.6、1∶0的质量比共混得到系列复合膜，探究不同比例乳清蛋白的添加对膜性能的影响。通过SEM、XRD、FTIR、DSC及TG对复合膜进行表征，在常温环境下对复合膜的机械性能和阻隔性能进行测定。结果表明，乳清蛋白的添加对膜的机械性能、阻隔性能均有所改善，特别当莲藕淀粉∶乳清蛋白=1∶0.5时，成膜基质间相互作用，紧密结合，相容性良好，且机械性能及阻隔性能最佳，抗拉强度和断裂伸长率分别达到11.66 MPa和14.71 %，热稳定性好。     

Water vapour permeability,diffusion and solubility in latex films

Water vapour diffusion D, solubility S and permeability P coefficients have been determined for films obtained from carboxylated styrene-butadiene (SB) copolymer latexes. The experimental method is water vapour sorption performed in the range 30–60d?C. Using the small angle neutron scattering (SANS) method and a selective labelling with D₂O vapour, it has been shown that water molecules mainly diffuse in the films through the particle-particle interfaces, which consist of a polar carboxyl-rich copolymer. It has been shown that the degree of cross-linking of the particles does not significantly affect the values of D and S. Moreover, the effect of neutralization conditions, regarding both the pH value of the initial latex and the nature of the neutralizing agent, has also been investigated. It has been found that D does not depend on these parameters, whereas S appears to be very sensitive to them. The results have been interpreted on the basis of the structural modifications of the films induced by neutralization. Finally, the hydrophilicity (or hydrophobicity) of the neutralizing agent has been identified as one of the key features for controlling the affinity of the latex film for water vapour and hence its permeability properties.     

The effect of relative humidity gradient on water vapor permeance of lipid and lipid-hydrocolloid bilayer films

The water vapor (WV) permeance of lipid and lipid-hydrocolloid films exposed to relative humidity (RH) gradients of 100–0%, 100–50%, 100–65% and 100–80% RH were determined. The lipids used were beeswax (BW) or a blend of BW and acetylated monoglycerides (AG). Hydrocolloids used were methylcellulose, carboxymethylcellulose or ethylcellulose (EC). All films, except those containing EC, exhibited increased water vapor permeance as the RH gradient was reduced by raising the low-end RH. This increase in permeance was apparently caused by hydration and swelling across the entire film thickness, thus facilitating water movement through the film. Because of its hydrophobicity, EC likely lessened this swelling. Knowledge of the WV properties of edible films at relatively small gradients in the upper half of the RH spectrum, such as those used in this study, is useful because these conditions are far more common to foods than are the 100–0% gradients that are often used when evaluating films. Even though the WV permeance of BW and BW/AG films increased greatly at the 100–80% RH gradient, as compared to gradients ranging from 100–65% to 100–0%, they still possess WV barrier properties sufficient to be useful for foods.     

Water vapor permeability of poly(lactide)s: Effects of molecular characteristics and crystallinity

Amorphous‐made poly(L ‐lactide) [i.e., poly(L ‐lactic acid) (PLLA)], poly(L ‐lactide‐co‐D ‐lactide)[P(LLA‐DLA)](77/23), and P(LLA‐DLA)(50/50) films and PLLA films with different crystallinity (X_c) values were prepared, and the effects of molecular weight, D ‐lactide unit content (tacticity and optical purity), and crystallinity of poly(lactide) [i.e., poly(lactic acid) (PLA)] on the water vapor permeability was investigated. The changes in number‐average molecular weight (M_n) of PLLA films in the range of 9 × 10⁴–5 × 10⁵ g mol^?1 and D ‐lactide unit content of PLA films in the range of 0–50% have insignificant effects on their water vapor transmission rate (WVTR). In contrast, the WVTR of PLLA films decreased monotonically with increasing X_c from 0 to 20%, while leveled off for X_c exceeding 30%. This is probably due to the higher resistance of “restricted” amorphous regions to water vapor permeation compared with that of the “free” amorphous regions. The free and restricted amorphous regions are major amorphous components of PLLA films for X_c ranges of 0–20% and exceeding 30%, respectively, resulting in the aforementioned dependence of WVTR on X_c. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Preparation and properties of waterborne polyurethane‐urea/sodium alginate blends for high water vapor permeable coating materials

To improve the water vapor permeability of coating materials, aqueous sodium alginate (SA) solution was blended with waterborne polyurethane‐urea (WBPU) dispersions synthesized by prepolymer mixing process. The content of SA for stable WBPU/SA dispersions was found to be below 30 wt %. As the SA content increased, the number and density of total micropores (tunnel‐like micropores/isolated micropores) formed after dissolution of SA in water increased, and the water vapor permeability of coated Nylon fabric also increased remarkably. These results clearly demonstrate that utilizing WBPU/water soluble polymer SA blends as coating materials and then dissolving SA in water surely facilitate obtaining prominent breathable fabrics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007