Self-destructing plastic

A biodegradable plastic is now available for wrapping

 
Published: Sunday 15 April 2001

-- (Credit: swagata Bose)biodegradable plastic is now a reality. Environmental Polymers Group (epg), a us-based private company, has created a biodegradable plastic wrapper that is soluble in water under the right conditions. In coming up with its product, the company claims, it has beaten some of the big plastic manufacturers, such as Du Pont, in manufacturing a 'green' plastic.

Polyvinyl alcohol (pvoh), a polymer already being used to coat drug capsules, was found to posses all the desired characteristics. But the challenge was to suitably alter it for commercial use. pvoh cannot be made into pellets. Most plastic polymers need to be processed in the form of pellets to preserve their characteristics. epg's achievement has been to modify pvoh for use in conventional equipment. "All the polymer scientists said it couldn't be done but we found a way to do it," says Phil Smith, chief executive of epg . "The process allows us to produce pvoh to meet the market demand with the quality required for commercial applications," he is reported saying in a news report published in Financial Times, London.

pvoh , water, glycerol and a little bit of silica are mixed together to form a 'pre-blend'. This pre-blend exists as flakes, which then must be melted into pellets. "The secret lies in the melting process," says Smith. The pellets, made in various shapes and sizes, are then shipped to plants that, with minor modifications, can process them through standard melt-processing equipment into all sorts of products.

The temperature at which the plastic product dissolves in water is determined when the pellets are made from the flakes. So, once the product has served its purpose it can be dissolved in water at a specified temperature. Microorganisms and enzymes in waste streams then eat it. They decompose pvoh and convert it into carbon dioxide, water and biomass.

The pellets, named 'depart', are currently being processed into biodegradable dustbin bags, irrigation pipes and hospital laundry bags.

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