Water-vapor resistance

Poly(vinylidene chloride). Poly(viayHdene chloride) [9002-85-1] (PVDC), most of which is produced by Dow Chemical, is best known in its saran or PVC-copolymerized form (see Vinylidene chloride and poly(VINYLIDENE chloride)). As solvent or emulsion coating, PVDC imparts high oxygen, fat, aroma, and water-vapor resistance to substrates such as ceUophane, oriented polypropylene, polyester, and nylon. 

Chemical Surface Modification. In considering the interface, one must contemplate not only the possibility of moisture disrupting the bond but also the possibility of corrosion of the substrate. Corrosion can quickly deteriorate the bond by providing a weak boundary layer before the adhesive or sealant is applied. Corrosion can also occur after the joint is made and, thereby, affect its durability. Mechanical abrasion or solvent cleaning can provide adhesive joints that are strong in the dry condition. However, this is not always the case when joints are exposed to water or water vapor. Resistance to water is much improved if metal surfaces can be treated with a protective coating before being bonded. 

We next examine a simplified expression for the total water vapor resistance that often adequately describes diffusion of water vapor from the sites of evaporation in cell walls to the turbulent air surrounding a leaf and is useful for considering diffusion processes in general. We will consider the case in which nearly all of the water vapor moves out across the lower epidermis and when cuticular transpiration is negligible. By Equations 8.11 and 8.12, the total resistance then is... 

AvenaBustillos, R.D., Krochta, J.M., and Saltveit, M.E. (1997). Water vapor resistance of red delicious apples and celery sticks coated with edible caseinate-acetylated monoglyceride films. J. FoodSci. 62(2), 351-354. 

Famworth, B., Lotens, W.A., Wittgen, P.P.M.M., 1990. Variation of water vapor resistance of microporous and hydrophilic films with relative humidity. Text. Res. J. 60, 50-53. 

Features Exc. water/water vapor resist., antibiocking fuiiy repuipabie Regulatory FDA approved for food contact Properties Clear Tykote WTR-AF [Reichhold]... 

More recently, the monofunctional cyanopentadienoates (2) were shown to improve the heat resistance of cyanoacrylate adhesives. In one case, when more than 50 weight % of 2 was combined with a standard cyanoacrylate monomer, the impact, peel, heat, and water resistance were greatly improved. " The improved heat resistance was attributed to the crosslinking of the residual olefin (28) after the anionic polymerization of 2 (see Eq. 8). The cyanopentadienoate was used in 50-90% concentration. The slow cure rate of the dienoate was overcome by the addition of an accelerator, in this case, a small quantity of an alcohol. Improvements in the heat, water, and water vapor resistance of alkyl cyanoacrylates can also... 

The COj and water sorptions indnce similar trend for PHBV polymers due to the affinity of the backbone structure and the crystalhruty degree exhibited. A major challenge for the material manufactnring concerns the resistance to moisture conditions. However, when comparing the water vapor resistance of various PHBV polymers to materials based on mineral oil, it becomes clear that it is possible to produce bio-based... 

Military uniforms for cold environments can be designed for specific climatic conditions and physical activity using existing test procedures and standards. The thermal insulation and the water vapor resistance of the whole garment are important. A low water vapor resistance ensures sweat evaporation and results in a dry insulation layer, and thus less heat loss. The improved overall comfort ensures the mental and physical performance of the soldier in extremely cold environments. 

ISO 11092, 2014. Measurement of thermal and water vapor resistance under steady-state condition using sweating guarded hot plate. 

It was found that this additive effectively absorbs water and ensures an adequate hydration of the cement minerals (45). In the mixture of plaster, when the sand is changed by clinoptilolite in an amount of 15% the structure becomes slightly compact and the compressive and flexural strength of the hardened plaster increase by 47% and 12%, respectively. Further, the adhesion to a surface of the autoclaved aerated concrete element increases by 44%. In contrast, the drying shrinkage, the water vapor resistance factor and the coefficient of capillary absorption do not change (45). 

TABLE 2 Typical water vapor resistance (WVR) of fabrics [1]. 

Scientists reported a strong dependency of water vapor resistance of hydrophilic membranes or coatings the higher the relative humidity at the membrane, the lower the water vapor resistance (i.e., the higher the water vapor permeability or bieathability). 

ISO 11092, Measurement of Thermal and Water-vapor Resistance under Steady-state Conditions (Sweating Guarded-hotplate Test), 1993. 

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