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. Some silicone suppliers are proposing up to 60% masterbatch in PE carrier. Be aware that addition of silicone rubber may modify significantly the rheology behavior of the product and disturb processing in some cases.
In technical polymers silicone rubber has been used in combination with Zinc Borate as flame retardant.