Editing Hygroscopy (section)

==Engineering properties==
[[File:FspFkt 100dpi en.png|thumb|Hygroscopic qualities of various materials illustrated in graph form; [[relative humidity]] on the X-axis and moisture content on the Y-axis. ]]
Hygroscopicity is a general term used to describe a material's ability to absorb moisture from the environment.<ref>{{Cite book |author=Neĭkov, Oleg Domianovich |url=http://worldcat.org/oclc/1077290174 |title=Handbook of non-ferrous metal powders : technologies and applications |date=7 December 2018 |publisher=Elsevier Science |isbn=978-0-08-100543-9 |oclc=1077290174}}</ref> There is no standard quantitative definition of hygroscopicity, so generally the qualification of hygroscopic and non-hygroscopic is determined on a case-by-case basis. For example, pharmaceuticals that pick up more than 5% by mass, between 40 and 90% relative humidity at 25&nbsp;°C, are described as hygroscopic, while materials that pick up less than 1%, under the same conditions are regarded as non-hygroscopic.<ref>James L. Ford, Richard Wilson, in Handbook of Thermal Analysis and Calorimetry, 1999, Section 2.13</ref>

The amount of moisture held by hygroscopic materials is usually proportional to the relative humidity. Tables containing this information can be found in many engineering handbooks and is also available from suppliers of various materials and chemicals.

Hygroscopy also plays an important role in the engineering of plastic materials.  Some plastics, e. g. [[Nylon#Bulk properties|nylon]], are hygroscopic while others are not.