Water vapor transmission properties

Matsuda Y, Kouzuki K, Tanaka M, Tanaka Y, TanigakiJ. Photostabihty of gelatin capsules effect of ultraviolet irradiation on the water vapor transmission properties and dissolution rates of indomethacin. Yakugaku Zasshi 1979 99(9) 907-913. 

A porous structure, which contains voids also called pores, is filled with a fluid (liquid and/or gas). Thus, mass transfer properties of textile materials can be studied at two levels water vapor transmission properties and liquid water transmission properties. 

GORE-TEX A trademark of the W.L. Gore Company for a material that has water vapor transmission properties (allows... 

ISO 1663 [461] Rigid cellular plastics - Determination of water vapor transmission properties... 

In conjunction with repellency tests, the air permeability and the water-vapor permeability (ASTM D 737-96 DIN 53 887) [153b] of a fabric are sometimes determined. Water-vapor transmission properties of a fabric are important variables affecting wearing comfort of repellent garments [173]. 

The much enhanced water vapor transmission property allows non-perforated film structure to offer high moisture breathability. This unique performance capability could be used in food packaging applications where protection against contamination and atmospheric moisture control are important. It also provides breathability and comfort to protective apparels where a continuous layer is essential for protection. 

Films or membranes of silkworm silk have been produced by air-drying aqueous solutions prepared from the concentrated salts, followed by dialysis (11,28). The films, which are water soluble, generally contain silk in the silk I conformation with a significant content of random coil. Many different treatments have been used to modify these films to decrease their water solubiUty by converting silk I to silk II in a process found usehil for enzyme entrapment (28). Silk membranes have also been cast from fibroin solutions and characterized for permeation properties. Oxygen and water vapor transmission rates were dependent on the exposure conditions to methanol to faciUtate the conversion to silk II (29). Thin monolayer films have been formed from solubilized silkworm silk using Langmuir techniques to faciUtate stmctural characterization of the protein (30). ResolubiLized silkworm cocoon silk has been spun into fibers (31), as have recombinant silkworm silks (32). 

Tensile properties and flexural modulus were determined on 20 mil pressed films in accordance with ASTM D882 and D790, respectively. Izod (notched) impact strength was determined on compression molded plaques in accordance with ASTM D256. Water vapor transmission was determined on 5 mil pressed films in accordance with ASTM E96. 

Primary interest was in the barrier properties obtained from plasma organo-silicones and from inorganic "SIN" coatings. Spectral grade HMDSO was used in the former case, while mixtures of SiH and NH were used to produce the SIN structures. The substrate in much or the work was DuPont Kapton type H polylmide film, 51 pm thick. Substrate temperatures extended to 450 C, as described earlier (6). The thickness of plasma-polymer deposits was about 0.5 pm. Moisture permeation was evaluated by the routine of ASTME-96-53 T (water vapor transmission of materials in sheet form). Additional, more precise data, were obtained with both a Dohrmann Envirotech Polymer Permeation Analyser, modified as previously described (6), and a Mocon "Permatran W" moisture permeation apparatus. 

In order to improve the water vapor barrier property of Ecoflex or Ecovio , a wax-based masterbatch can be used. Depending on the concentration, this masterbatch reduces the water vapor transmission rates of Ecoflex films by up to... 

The visual appearance, clarity in particular, of packed products with high water content (vegetables, fruits, various cheeses, fresh meat) in packaging can be impaired by fogging caused by condensation of water as small droplets on the inside surface of the plastic film. In applications where perforated films with effective water vapor transmission are undesirable, antifogging agents with the properties of surface active substances, such as poly(oxyethylene) sorbitan monooleate are effectively used. 

Spencer-Smith critically and thoroughly reviewed the physical basis of clothing comfort in four recent papers and discounted much of the previous work on heat and water vapor transmission through clothing assemblies (69, 70, 71, 72). In the first paper (69), he focuses on the special properties of hygroscopic fabrics such as linen and wool and points out that previous studies demonstrate that their buffering action affords comfort in moving from warm dry atmospheres to cold damp ones... 

The properties of SAN and rubber-modified SAN copolymers have also been evaluated for oriented films. Biaxial orientation can increase the glass transition temperature by up to 15 °C and decrease the water vapor transmission rate by 30% [105]. 

Rubber Property-Vapor Transmission of Volatile Liquids Oetermining Gas Permeability Characteristics of Plastic Film and Sheeting Water Vapor Transmission of Organic Coating Films... 

BS 4370, Part 2, Method 8 is related to ISO 1663. 1981 [25] and describes the determination of water vapor transmission rate (pg/(nr s)), water vapor permeance (ng/(m s Pa)) and water vapor permeability (ng/(m s Pa) for rigid cellular materials that have thicknesses of between 10 mm and 70 mm. The first two properties are specific to the specimen thickness, whereas the permeability is a property of the material if this is homogeneous. A table is included in this British Standard giving conversion factors for all three properties. The method described is suitable for materials having a water vapor transmission rate of between 200 to 3000 pg/(m" . s). 

Barrier Properties Exact Plastomers create controllable gas-permeable films for modified atmospheres, as well as gas-permeable films and packaging for such items as fresh vegetables, fhiits, flowers, and a growing range of other horticultural products. Users can select carbon dioxide and oxygen transmission rates (OTR) that meet their needs, with low water vapor transmission rates (WVTR) and high levels of clarity and gloss. " ... 

For the water-vapor transmission rate the ratios were lower R was 0.62 and R was close to 0.40 which means that the variability of the tested property depend on the variability of the input variables only in about 40%. Such model is not considered as satisfactorily compatible with the empirical data from the laboratory tests as the limit value is 0.65 [7]. 

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