Hygroscopic barriers

Copper(II) sulfate monohydrate [10257-54-2] CuS04-H2 0, which is almost white in color, is hygroscopic and packaging must contain moisture barriers. This product is produced by dehydration of the pentahydrate at 120—150°C. Trituration of stoichiometric quantities of copper(II) oxide and sulfuric acid can be used to prepare a material of limited purity. The advantages of the monohydrate as opposed to the pentahydrate are lowered freight cost and quickness of solubilization. However, these advantages are offset by the dustiness of the product and probably less than one percent of copper sulfate is used in the monohydrate form. 

The blocking of cell wall micropores reduces diffusion of water and other molecules into the ceU waU. If effective blocking of the cell wall micropores occurs close to the lumen, then complete filling of the cell wall may not be required in order to provide decay protection, or reduce hygroscopicity. However, this barrier may be breached in time. 

Almost all tests carried out to study the starting process of atmospheric corrosion have been performed in a surface without corrosion products however, in real conditions, the metal is covered with corrosion products after a given time and these products begin to play its role as retarders of the corrosion process in almost all cases. Corrosion products acts as a barrier for oxygen and contaminants diffusion, the free area for the occurrence of the corrosion is lower however, the formation of the surface electrolyte is enhanced. Only in very polluted areas the corrosion products accelerate the corrosion process. Water adsorption isoterms were determined to corrosion products formed in Cuban natural atmospheres[21]. Sorption properties of corrosion products (taking into account their salt content-usually hygroscopics) determine the possibilities of surface adsorption and the possibility of development of corrosion process... 

Dissolution Profile SEPIFILM LP can efficiently improve the moisture barrier on moisture-sensitive active pharmaceutical ingredients (API) or hygroscopic cores. The breakthrough in this technology is that SEPIFILM LP does not modify the dissolution profile when compared to conventional coating (Figure 30). 

Stratum corneum, the nonliving layer of skin, is refractory as a substrate for chemical reactions, hut it has a strong physical affinity for water. The chemical stability of stratum corneum is evident in its mechanical barriers which include insoluble cell membranes, matrix-embedded fibers, specialized junctions between cells, and intercellular cement. The hygroscopic properties of stratum corneum appear to reside in an 80 A-thick mixture of surface-active proteins and lipids that forms concentric hydrophilic interfaces about each fiber. This combination of structural features and surface-active properties can explain how stratum corneum retains body fluids and prevents disruption of living cells by environmental water or chemicals. 

Permeability. As a diflFusion barrier, SC is most eflFective when dry, less eflFective when hydrated, and still less eflFective when treated with solvents such as dimethylsulfoxide (DMSO) (16, 92). The hydrating eflFect of increased relative humidity, occlusion, or immersion can be visualized as separation of hygroscopic and protein elements to create diflFusion channels containing free water (20, 69, 71). Obviously, water and its solutes should be more mobile in free-water channels than in bound water. The degree of hydration also can be influenced indirectly by organic solvents that hold water (glycol, DMSO) (18) or that modify surfaces (surfactants) (16, 18). 

Uses Film-former for pharmaceuticals, esp. aq. film coatings, barriers, texture modification, binding, adhesives filler, humectant for pharmaceutical cleansers film-former, encapsulation aid for spray drying Features Low hygroscopicity nonirritating low vise. 

Environmental Aquatic toxicity LC50 (96 h, fathead minnows) 7.8 mg/l Precaution Incompat. with strong oxidizers thermal decomp, produces extremely flam m. tetrahydrofuran, CO temps, as low as 100 C can cause dangerous pressure buildup in stored dmms Storage Hygroscopic can oxidize store in completely enclosed tanks under a diy nitrogen blanket store above 45 C to prevent solid. do not store in materials with a low barrier to oxygen Terathane 1000 [DuPont DuPont Canada]... 

D = weight (g) of hygroscopic blocking, cushioning and other material inside the barrier (including cartons, etc.),... 

In the past barrier screws were used only with PET pellets because pellets are not susceptible to air entrapment. Powders, however, are susceptible to air entrapment and do not process well on conventional barrier screws. The internally vented barrier screw developed by Eastman achieves higher throughputs of PET powder. This screw design can also be used for other hygroscopic resins like ABS. 

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