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An introduction to flame retardants
Theories of flame retardant performance
In the polymer burning process, first, the polymer (solid phase) is destroyed in the presence of sufficient heat, producing flammable volatile gases (gaseous phase) and the produced gases are oxidized in the presence of oxygen and sufficient heat. Based on this, the flame retardant works by chemical and/or physical intervention in the gaseous and/or solid phase. The main theories governing the performance of all types of delay devices include the following:
Gas theory: reducing the concentration of oxygen and other oxidizing substances on the surface of the polymer by producing neutral gases such as water, carbon dioxide and ammonia
Thermal theory: the destruction of the retarder during the endothermic reaction and the cooling of the environment involved in the fire
Chemical theory: turning retarders into free radical absorption components and disrupting oxidation reactions (radical trap)
Coating theory: the formation of a carbon layer, a liquid or glass coating and as a result reducing the penetration of oxygen and heat to the surface of the polymer
Based on this, five categories of flame retardants have been introduced so far:
Halogen flame retardant
Mineral retarder
Compounds containing phosphorus
Nitrogen containing compounds (melamine)
Inflator retarder
The choice of the type and amount of flame retardant depends on the flammability, mechanical, health and environmental standards expected from the part. Achieving the desired standards is dictated by different characteristics of the part and environment.
Generally, retarders are consumed in the form of slow burning compound or retarder masterbatch by the parts maker. Choosing the right mixing method and equipment is essential to achieve a uniform product.
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This post is written by MZ140005