Probing multifunctional materials
Flame-retardant coatings and anti-bacterial bedsheets are just two outputs of a pan-European research project to develop multifunctional products from paper and
textiles for buildings, transport, health and personal protection.
Flexifunbar was an 11m euro, four-year project that began in 2004 and involved 44 partners. It was set up to create flexible materials that combine at least two barrier properties such as flame retardancy, thermal and sound insulation, or protection against UV, bacteria and odours. By altering their micro- or nanostructures, researchers hoped to combine several functions into a single material.
The textiles industry instigated the programme to create ‘value added’ products that could compete against cheaper imported materials.
One example is a project led by Devan Chemicals of Ronse, Belgium, to develop anti-microbial textiles for hospital sheets and uniforms. As well as being resistant to microbial attack, the materials had to withstand multiple industrial washing cycles at 80ºC.
The aim was to reduce hospital-acquired infections, around one-sixth of which are picked up from textiles. The partners tested several formulations incorporating two of its proprietary molecules – Aegis, a quaternary silane anti-bacterial treatment, and Nanolink, a polymer pre-coat that helps the Aegis molecules adhere to the surface.
‘Aegis kills lots of bacteria types, but does not migrate from the surface,’ says Patrice Vandendaele, CEO of Devan Chemicals. ‘Nanolink improves the way that the Aegis molecules stick to the fibre, and helps the material get through many wash cycles.’
The cotton/polyester sheets were trialled at Douai Hospital in France and the staff uniforms at Alessandria Hospital in Italy. The Pasteur Institute in Lille, France, tested both for bacterial growth. Treated sheets were found to reduce bacteria by at least 80% – even after 50 washes. A similar effect was revealed with the uniforms.
Devan now has commercialisation agreements with a range of companies who will make sheets, pillow cases, uniforms and other hospital textile products using this technology.
Work on a second project to develop a cheap anti-bacterial, anti-viral facemask is underway. Devan is also looking to understand the exact mechanism behind Nanolink’s efficacy.
Within transport, Irish polyester fibre specialist Wellmann International and worldwide automotive supplier Mecaplast have developed an engine air filter that combines filtration and flame retardancy. Mecaplast was also involved in testing a polyester for passenger car upholstery that combines flame retardancy and recyclability.
Though Flexifunbar has come to an end, many of the researchers are continuing their projects, such as Professor Peter Hornsby of Queen’s University Belfast, UK. In conjunction with Swedish company Inca, he will explore new fillers for polyester fibres.
‘When fibres are spun to around 20µm, you can’t add normal fillers because they are the same size,’ he says. ‘So we are using nanoparticles.’
Hornsby and his team are using nanoclay, which enhances stiffness and flame retardancy, and graphite, to create anti-static and electrically conductive fibres.
Inca has also developed a flame-retardant film containing carbon particles for products such as wallpaper and other wall coverings. It works on the principle of intumescence, so that it chars as it burns to restrict the spread of fire.
Some other promising projects that will continue are activated carbon panels to absorb hydrocarbons within car engines and reduce emissions, and a plasma surface treatment to improve the barrier properties of flexible polypropylene packaging.