Accelerant
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Accelerants, or accelerators, are substances that increase the rate of a natural or artificial chemical process. They play a major role in chemistry, as most chemical reactions can be hastened with an accelerant. They are commonly used in contexts such as fire investigation where they can indicate arson, in construction to speed the curing of building materials, and in sulfur vulcanization to produce rubber products such as 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. Understanding accelerants is crucial in forensic science, engineering, and other fields where controlled chemical reactions are essential.
Accelerants function by either altering a
Vulcanization
The use of accelerators and activators lowers the
A vulcanization accelerator is typically used in combination with sulfur as the cross-linker, and with zinc oxide and stearic acid as activators. The various types of rubber used in tyre compounds all have different vulcanization characteristics, like speed and extent of cure (the number of cross-links). A typical passenger car tyre is vulcanized for 10 minutes at 170 °C (338 °F).
Classification
There are two major classes of vulcanization accelerators, primary accelerators and secondary or ultra accelerators.
Primary
The main primary accelerator group used in tyre manufacture is the
In the vulcanization of
Secondary
The main categories of secondary or ultra-accelerators are
Cement and concrete
Cement accelerators are available as
3)
2), calcium formate (Ca(HCOO)
2) and sodium nitrate (NaNO
3).[8]
Fire
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.
A fire is a self-sustaining, exothermic oxidation reaction that emits heat and light. When accelerants such as oxygen-bearing liquids and gases (like 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.
Fire investigation
Indicators of an incendiary fire or arson can lead
Types
Many accelerants are
The properties of some ignitable liquids make them dangerous fuels. Many ignitable liquids have high
Common household items and objects can be accelerants. Wicker and foam have high surface-area-to-volume ratios and favourable chemical compositions and thus burn easily and readily. Large fuel loads can increase the rate of fire growth as well as spread the fire over a larger area, thus increasing the amount of fire damage. Unusual amounts and types of fuel in a particular area can indicate arson. Whether available combustible materials constitute accelerants depends on whether they were intentionally burned.
See also
References
- ^ Roberts, A. D. (1988). Natural Rubber Science and Technology. Oxford University Press.
- S2CID 250881411.
- ^ "SafeRubber, an alternative for accelerators in the production of rubber". SafeRubber. Archived from the original on 2016-07-09.
- ISBN 978-3527306732.
- ^ 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. 433–442
- ^ ACI 306R-88: Cold Weather Concreting. "Cold Weather Concreting" (PDF). Concrete Contractors Association of Greater Chicago. Archived from the original (PDF) on 2011-07-25. Retrieved 2011-03-05.
- ^ Korhonen, Cortez & Durning 1997, p. 19.
- ISBN 9781428913158.
- ^ International Association of Arson Investigators, Massachusetts Chapter (1999). A Pocket Guide to Accelerant Evidence Collection (2nd ed.). The Association.