Hygroscopicity


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Hygroscopicity

 

the ability of materials to absorb moisture from the air.

Hygroscopicity is a property of wettable (hydrophilic) materials of capillary-porous structure (such as wood and grain), in whose fine capillaries moisture condenses; of water-soluble substances such as table salt, sugar, and concentrated sulfuric acid; and especially of chemical compounds that form, with water, crystalline hydrates. The amount of water absorbed by a porous material (hygroscopic wetness, or Whyg) increases as the moisture content of the air increases, reaching a maximum when the relative humidity of the air is 100 percent. For wood, the maximum Whyg is about 30 percent (in terms of weight), whereas for wheat it is about 35 percent. It is important to know the hygroscopicity of a material in order to determine drying and wetting processes. Hygroscopicity is also considered in long-term storage and transportation of materials, especially by sea. Hygroscopicity explains the dampening and even deliquescence of a number of salts when stored in the open air. Some hygroscopic substances, such as concentrated sulfuric acid, are used to dry the air.

References in periodicals archive ?
TPV A is fully crosslinked but is known to have problems with hygroscopicity and color.
Therefore, when wood is oven-dried to determine its MC, its hygroscopicity has been reduced, so its EMC will be lower for any future environmental condition.
This new product line of thermoplastic vulcanizates (TPVs, dynamically vulcanized TPEs) -- termed the Santoprene Rubber 8000 Series -- offers value-added characteristics such as non- hygroscopicity (requires no drying) and ease of coloring.
The final product has a lower hygroscopicity and an improved dimensional stability in comparison with controls (Tjeerdsma et al.
A study was conducted on the various brands of Ranitidine as per this method to understand the differences in hygroscopicity.
It is further characterized by good heat and acid stability and low hygroscopicity.
C*Eridex has a high stability against heat and acid, medium solubility, low hygroscopicity and excellent crystalline properties.
ricinoloxazoline maleinate and bis-oxazoline) has been used to promote the compatibilization of blends of polyolefins with polar polymers and to yield new interesting polymeric materials, such as PE and PP with increased stiffness and good resilience: PA6 with reduced hygroscopicity, high impact strength, and very good ultrasonic attenuation: PA6 with increased dimensional stability and improved strength: and recycled post-consumer PET with good mechanical properties and high impact strength.
However, problems associated with hygroscopicity and dimensional stability limit their application.
However, some disadvantages are associated with the use of natural fibers as reinforcements of polymers, such as their hygroscopicity and the incompatibility between lignocellulosic materials and polymer matrices, which lead to poor dispersion levels and low mechanical properties.