Which additive in plastics acts to reduce the risk of combustion?

Flame retardants are specifically designed to decrease the flammability of materials, including plastics. They work by either preventing ignition or slowing down the progression of flames once a fire starts. This occurs through various mechanisms, such as forming a protective char layer on the surface of the material, releasing water vapor to cool the burning material, or interfering with the combustion process itself.

In comparison, plasticisers are used to increase the flexibility and workability of plastics but do not have any impact on combustion resistance. Stabilisers help protect the material from degradation due to environmental factors like UV light and heat, while anti-static agents reduce static electricity build-up but do not serve any purpose related to fire resistance. Thus, flame retardants are the most effective additive for reducing the risk of combustion in plastics.