Editing Accelerant

{{Short description|Substance increasing the rate of a chemical process}}
{{More citations needed|date=April 2024}}
{{Use Oxford spelling|date=April 2024}}

'''Accelerants''', or '''accelerators''', are [[chemical substance|substances]] that increase the rate of a natural or artificial [[chemical process]]. They play a major role in [[chemistry]], as most [[chemical reaction]]s can be hastened with an accelerant. Understanding accelerants is crucial in [[forensic science]], [[engineering]], and other fields where controlled chemical reactions are essential. Accelerants function by either altering a [[chemical bond]], speeding up a chemical process, or changing the reaction conditions. Unlike [[catalyst]]s, accelerants may be consumed during the process.

They are commonly used in contexts such as [[fire investigation]] where they can indicate [[arson]], in [[construction]] to speed the [[curing (chemistry)|curing]] of building materials, and in [[sulfur vulcanization]] to produce rubber products such as [[tire|tyres]]. In fire investigation, accelerants are often detected through laboratory analysis of fire debris. Various types of accelerants exist, including liquids, solids, and gases, each with specific properties and applications. 

== Applications ==

=== Vulcanization ===
{{See also|Sulfur vulcanization#Accelerants}}

Vulcanization of rubber can be categorized primarily into two types: sulfur and peroxide vulcanization. Both chemical processes are examples of using an accelerant.

Sulfur vulcanization, the more traditional method, uses sulfur to create cross-links between rubber polymer chains, enhancing flexibility and durability. Sulfur vulcanization is a chemical process crucial to the rubber industry, transforming raw rubber into a durable, elastic material. This process is suitable for a wide range of rubber products. 

On the other hand, peroxide vulcanization uses organic peroxides to form cross-links, resulting in rubber that withstands higher temperatures and chemical exposure better than sulfur-vulcanized rubber. Each method offers distinct properties to the rubber, tailored to specific applications and performance requirements.

=== Cement and concrete ===
{{Main|Cement accelerator}}

Cement accelerators are available as [[admixture (concrete)|admixtures]] for use in [[concrete]], [[mortar (masonry)|mortar]], [[cement render|render]], and [[screed]]. The addition of an accelerator speeds the setting time and thus [[curing (chemistry)|curing]] starts earlier.<ref name="Justnes">Justnes, H. (2000): Accelerator Blends for Portland Cement. Proceedings of Cement and Concrete Technology in the 2000s, September 6–10, 2000, Istanbul, Turkey, Vol. 1, pp.&nbsp;433&ndash;442</ref> This allows concrete to be placed in winter with reduced risk of [[frost damage (construction)|frost damage]].<ref name="ACI">ACI 306R-88: Cold Weather Concreting. {{cite web |title=Cold Weather Concreting |website=Concrete Contractors Association of Greater Chicago |url=http://www.ccagc.org/pdfs/ACI_306R-88_Cold_Weather_Concreting.pdf |access-date=2011-03-05 |url-status=dead |archive-url=https://web.archive.org/web/20110725150450/http://www.ccagc.org/pdfs/ACI_306R-88_Cold_Weather_Concreting.pdf |archive-date=2011-07-25}}</ref> Concrete is damaged if it does not reach a strength of {{convert|500|psi|MPa}} before freezing.{{sfn|Korhonen|Cortez|Durning|1997|p=19}} Typical cement accelerators are [[calcium nitrate]] ({{chem|Ca|(NO|3|)|2}}), [[calcium formate]] ({{chem|Ca|(HCOO)|2}}), and [[sodium nitrate]] ({{chem|Na|N|O|3}}).<ref>{{cite journal |last1=Korhonen |first1=Charles J. |last2=Cortez |first2=Edel R. |last3=Durning |first3=Timothy A. |date=1997 |title=Antifreeze Admixtures for Concrete |journal=[[Cold Regions Research and Engineering Laboratory]] |volume=Special Report 97-26 |isbn=9781428913158}}</ref>

=== Fire ===
{{Main|Fire accelerant}}
In [[fire protection]], the term ''accelerant'' is used differently from its use in chemistry, to refer to any material that initiates and promotes the development of [[fire]], including in cases of [[arson]], whether a chemical or not. Chemists distinguish an accelerant from a [[fuel]], such as gasoline. This usage of ''accelerant'' is also referred to by the term '''ignitable liquid'''.

A fire is a self-sustaining, [[exothermic reaction|exothermic]] oxidation reaction that emits heat and light. When accelerants such as oxygen-bearing liquids and gases (like [[nitrogen dioxide|{{chem|NO|2}}]]) are used, fires produce more heat, consume fuel more quickly, and spread quicker. Fires involving liquid accelerants like gasoline burn quicker, but at the same temperature as fires involving ordinary fuels.

==See also==
*[[Chemical kinetics]]
*[[Rate equation]]
*[[Retarder (chemistry)]]

==References==
{{Reflist}}
{{Wiktionary}}

[[Category:Firefighting]]
[[Category:Rubber]]