Researchers in the United Kingdom report the first use of bacteria to deposit sticky coatings of cellulose on the surfaces of plant fibres, a process that may expand the use of natural fibres in renewable plastic composites used as strong, lightweight materials for cars, airplanes, and other products. The coated fibres provide strength and will make composites more durable without affecting their biodegradability. They are more suitable for recycling (or compositing) than commonly used petroleum-based composites, the researchers say. Their study is scheduled for the June issue of ACS' Biomacromolecules, a monthly journal.
In the new study, Alexander Bismarck and colleagues point out that synthetic composite materials now in use are made from non-renewable, petroleum sources which are becoming more expensive. These materials not only are difficult to break down, they also create environmental hazards when disposed. Existing composites made from natural fibres show poor adhesion qualities and must be strengthened by using other synthetic coupling agents, some of which are toxic, the researchers note.
The researchers coated hemp and sisal fibres with nano-sized particles of bacterial cellulose through a special fermentation process. The coated sisal fibres showed much better adhesion properties than the original fibres without losing their mechanical properties, ideal properties for their use in composites, the researchers say. The modified hemp fibres also had improved adhesion properties but showed a loss of strength, they note.