Term: Accelerant
Vulcanization and Rubber Compounds:
– Accelerators lower activation energy in vulcanization reactions
– Accelerated sulfur vulcanization requires fewer sulfur atoms per cross-link
– Different rubber compounds in car tires require specific accelerators
– Vulcanization accelerators are used with sulfur, zinc oxide, and stearic acid
– Various types of rubber have different vulcanization characteristics
Accelerator Classification:
Primary Accelerators:
– Sulfenamides and thiazoles are main primary accelerator groups
– Thiazoles are used for vulcanization of thick parts and EPDM rubbers
– Ethylene thiourea (ETU) is significant in neoprene rubber vulcanization
– Conventional accelerators are problematic for curing CR rubbers
– European rubber industry researches safer alternatives to ETU
Secondary Accelerators:
– Thiurams and dithiocarbamates are main secondary accelerators
– Used to boost speed and state of cure in tire vulcanization
– Thiurams and dithiocarbamates have fast vulcanization speed
– EPDM rubber requires a rapid vulcanization system
– Latex compounds need a rapid accelerator due to low curing temperatures
Cement and Concrete Accelerators:
– Accelerators are admixtures used in concrete, mortar, rendering, and screeds
– Accelerators speed setting time and early curing
– Concrete must reach a strength of 500 psi before freezing
– Typical accelerators include calcium nitrate, calcium formate, and sodium nitrate
Accelerants in Fire:
– Accelerants in fire protection promote fire development
– Accelerants like oxygen-bearing liquids and gases increase heat production
– Liquid accelerants like gasoline burn faster in fires
Fire Investigation and Types of Accelerants:
– Indicators of arson lead investigators to look for fuel traces in fire debris
– Burning compounds and liquids leave evidence of their presence
– Presence of fuels in unusual areas can indicate incendiary fires
– Hydrocarbon-based fuels are common accelerants
– Ignitable liquids, such as gasoline and kerosene, leave irregular patterns
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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 chemical bond, speeding up a chemical process, or changing the reaction conditions. Unlike catalysts, accelerants may be consumed during the process.