First part of our series was dedicated to polymeric compatibilisers and impact modifiers showing versatility of polymers and function. The second part is dedicated to : flame retardants, surface modifiers (like matting agents, antistatic agents…) and polymeric processing aids.
Halogenated (Cl or Br or F) compounds in combination with antimony trioxide are very well known systems providing polymers with flame retardant properties. In principle any halogenated molecule containing high halogen content can be used for this purpose. Halogenated polymers are also good candidates. Their high molecular weight provide numerous advantages such as :
* Low volatility
* Low migration rates at surface
* Low toxicity
* Easy to handle.
High molecular weight silicone (HMW silicone) rubber appears to be a good halogen free flame retardant.
Silicone rubber is used in low energy cables EVA/PE based. Pure HMW are very visco-elastic and consequently very difficult to handle and feed. Generally the use of a masterbatch is recommended.