View source for Friability

{{short description|Property of materials which break into smaller pieces when rubbed}}
{{redirect|Indurated|the medical condition|Induration}}

In [[materials science]], '''friability''' ({{IPAc-en|ˌ|f|r|aɪ|.|ə|ˈ|b|ɪ|l|ə|t|i}} {{Respell|FRY|ə|BIL|ə|tee}}), the condition of being '''friable''', describes the tendency of a [[solid]] substance to [[Fracture|break into smaller pieces]] under [[Stress (mechanics)|stress]] or contact, especially by [[Abrasion (mechanical)|rubbing]]. The opposite of friable is '''indurate'''.

Substances that are designated hazardous, such as [[asbestos]] or crystalline [[silicon dioxide|silica]], are often said to be friable if small particles are easily dislodged and become [[Particulates|airborne]], and hence respirable (able to enter human [[lung]]s), thereby posing a health hazard.

Tougher substances, such as [[concrete]], may also be mechanically ground down and reduced to finely divided [[mineral dust]]. However, such substances are not generally considered friable because of the degree of difficulty involved in breaking the substance's [[chemical bond]]s through mechanical means. Some substances, such as [[polyurethane]] foams, show an increase in friability with exposure to [[ultraviolet]] radiation, as in [[sunlight]].

Friable is sometimes used metaphorically to describe "[[brittle]]" personalities who can be "rubbed" by seemingly-minor stimuli to produce extreme emotional responses.<ref>{{cite web |url=http://thecommonparlance.blogspot.ca/2008/01/friable-v-frangible.html |title=The Common Parlance |author=Lauren |work=thecommonparlance.blogspot.ca |date=9 January 2008}}</ref>

==General==
A friable substance is any substance that can be reduced to fibers or finer particles by the action of a small amount of [[pressure]] or [[friction]], such as rubbing or inadvertently brushing up against the substance. The term could also apply to any material that exhibits these properties, such as:

* [[Ionic bond|Ionically]] [[Chemical bond|bound]] substances that are less than 1&nbsp;kg/[[Litre|L]] in [[density]]
* [[Clay tablet]]s
* [[Cracker (food)|Crackers]]
* [[Mineral wool|Mineral fibers]]
* [[Polyurethane]] (foam)
* [[Aerogel]]

==Geological==
''Friable'' and ''indurated'' are terms used commonly in soft-rock [[geology]], especially with [[sandstone]]s, [[mudstone]]s, and [[shale]]s to describe how well the component rock fragments are held together.

Examples:
* Clumps of dried [[clay]]
* [[Chalk]]
* [[Perlite]]

==Medical==
The term ''friable'' is also used to describe [[tumor]]s in medicine.  This is an important determination because tumors that are easily torn apart have a higher risk of malignancy and [[metastasis]].

Examples:
* Some forms of [[cancer]], such as [[atrial myxoma]]
* [[Cholecystitis|An inflamed gallbladder]]

==Pharmaceutical==
{{see also|Tablet hardness testing}}
Friability testing is a [[laboratory technique]] used by the [[pharmaceutical industry]] to test the durability of [[Tablet (pharmacy)|tablets]] during transit.  This testing involves repeatedly dropping a sample of tablets over a fixed time, using a rotating wheel with a baffle. The result is inspected for broken tablets, and the percentage of tablet mass lost through chipping.  A typical specification will allow a non-zero percentage of chipping, and zero broken tablets.

==See also==
* [[Asbestos abatement]]
* [[Frangibility]]
* [[Spall]]

==References==
{{Reflist}}

==External links==
{{wiktionary}}
* [http://www.hse.gov.uk/aboutus/meetings/iacs/acts/211102/paper45.pdf UK Advisory Committee Treatise On Friable Ceramic Fibres] {{Webarchive|url=https://web.archive.org/web/20170706075430/http://www.hse.gov.uk/aboutus/meetings/iacs/acts/211102/paper45.pdf |date=2017-07-06 }}
<!-- I have changed the link to the HSE document so that it now works. However, this is an old document discussing a proposed MEL for Refractory Ceramic Fibres. A more up-to-date link might be more appropriate e.g. http://www.hse.gov.uk/ria/manufacture/ceramicfibres.pdf -->

[[Category:Materials science]]
[[Category:Geology terminology]]
[[Category:Tumor]]