Switchable adhesives made from renewable resources make carpet tiles more environmentally friendly, say UK scientists. 

70 million kilograms of carpet tiles are incinerated or landfilled every year in Europe alone representing a huge environmental burden. Powerful latex adhesives used to bind layers of nylon, polyester and bitumen make it impossible to recycle the components of the tile. Now James Clark and colleagues at the University of York have developed a starch-based adhesive that can be easily removed at the end of the carpet's life. 

Starch adhesives are used to bind paper in packaging and as wallpaper paste but its water solubility has limited its applications. Clark acetylated corn starch to make it hydrophobic and insoluble in water, then added glycerol triacetate to give improve the adhesive properties. The adhesive is also switchable so that it could be completely removed using steam under controlled conditions, allowing complete separation of the layers for full recycling. The carpet can still be cleaned using normal methods including steam cleaning, says Clark, as the adhesive is below the surface and tests show that any water that may reach it will be too low temperature to cause a problem. 

'The mechanical and physical properties [in our adhesive] are comparable to or better than current carpet tiles,' comments Clark. The new adhesive also provides a remarkable degree of flame retardancy to the tile eliminating the need for synthetic flame retardants and further adding to the environmental benefits, he adds. 

Giulio Malucelli, an expert in the field of adhesion, from the Polytechnic University of Turin, Italy, says the work is 'of interest to members of the general population' due to its novelty and environmental impact. 

'Our results show how we can reduce a massive product-specific waste problem and also demonstrate a more general approach to greener product design,' adds Clark. 

Ben Merison 

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