Fire cracker

Nano research could lead to a new generation of fire-retardant textiles.

Researchers are close to producing a fire-retardant synthetic cloth using nano materials. So far a team of specialists in fire chemistry, polymers and textiles from three UK universities has developed a range of new, inherently flame- retardant polymers, and is now working on methods of turning them into fibres for weaving and knitting into textiles.

If successful the project will create a new generation of textiles with applications from soft furnishings to soldiers’ uniforms and, according to the project leaders, ‘in so doing will breathe new life into the UK’s declining textile industry’.

Synthetic fibres have always been much more flammable than their natural counterparts and are difficult to make fire retardant. Natural fibres tend to form a crust of char which retards the burning process; they do not melt or drip like burning synthetic fibres.

In 2003 the MoD and the EPSRC each granted £150,000 to a team of specialists from the universities of Bolton, Sheffield and Salford to investigate the use of nano composites in synthetic materials. It was believed that the barrier layer and char-forming properties of nano composites promised to improve fire resistance of synthetic fibres, while enhancing their physical and mechanical properties.

Since then the team has worked on existing and novel nano composites formed from polyamides, polyesters and polyacrylics; each has been assessed for flammability and its ability to be spun into fibres.

Researchers at the Centre for Materials Research and Innovation at BoltonUniversityare developing fire-retardant polypropylene, nylon and polyester fibre. Dr Baljinder Kandola, the principal investigator at Bolton, said that to protect these synthetics with a conventional flame retardant such as ammonium polyphosphate, it would be necessary for the polymer to be 20 per cent ammonium polyphosphate. At this percentage she said the team encountered problems with the viscosity of the material and it was impossible to extrude into fibre.

Kandola said that by including a certain amount of a silicate ‘nano glaze’, it was possible to reduce the level of conventional flame retardant to five per cent and still achieve the required protection. The nano particles made up two per cent of the material, from which Kandola’s team have produced 1kg batches of fibre, which is strong enough to be knitted.

Kandola said the objective is to produce a textile that will not ignite, but if it does catch fire can extinguish itself. ‘We have been successful in producing fibres but at the moment we are still experiencing problems with the dispersion of the nano glaze.’

The fibres are melt-extruded in a single continuous process and an even distribution of the nano glaze is necessary to achieve the required level of fire protection. The team hopes to get around the problem by experimenting with a new type of extruder in the near future.

Kandola said the new material, which would not melt or drip when subjected to flames or heat, would have uses in sectors including civil aerospace, domestic furnishings and the military.