Flame-retardant polymer

Materials World magazine
1 Jul 2007

Scientists from the University of Massachusetts Amherst, USA, have created a flame-retardant synthetic polymer that does not require conventional and potentially harmful halogen additives.

Most common plastics burn readily, adding fuel to the fire. Fire-resistant additives are therefore included in the plastic mix. But these additives are often halogenated molecules that contain reactive chemicals such as chlorine, bromine or phosphorous, and may be detrimental to human health and the environment. Other non-halogenated additives usually contain phosphorous-based molecules, such as aluminium, which restrict the mechanical properties of the polymer itself.

‘In an ideal world, you would have a polymer that has excellent properties, no halogen and is not flammable. That’s very hard to do, but that’s what we’re trying to do,’ says researcher Todd Emrick.

The material created by the Massachusetts team uses a bishydroxydeoxybenzoin (BHDB) monomer, which releases water vapour as it disintegrates in a fire.

‘When I started working on this programme, we were looking at a particular halogenated molecule called bisphenol-C (BPC), which goes through a degradation mechanism that prevents polymers from burning. That mechanism looked like the BHDB polymers (which we had come across in physical chemistry literature),’ explains Emrick. ‘It looked on paper that BHDB would degrade in a similar way to this material and lead to charring instead of a flame. And it appears that is what is happening,’ he adds.

The new polymer has a char yield of 70%, and seems to retain all the qualities of a halogenated polymer – transparency, flexibility, durability and affordable production. Emrick says it is still early days as far as research and testing are concerned, but he hopes to see the material commercially produced. The research group has created fibres from the new material, which Emrick believes can be spun into fibrous matts for textiles to create flame retardant clothing.

The team also aims to apply the polymer in the interior of aircraft and ships – anywhere where it is difficult to escape from a fire. ‘This material could make a real difference,’ says Emrick.