The researchers are confident that this technique improves plastic's retention of water-based dyes and printing inks, such as those used on food labels, as well as reducing buildup of static charge. Commercial polymers such as polyethylene are hydrophobic, or water-repelling, until rendered otherwise (hydrophilic) with chemical reagents.
But according to ARS scientists FredFelker and George Fanta, coating such plastics with soluble starch -preparedby steam-jet cooking - could offer a cheaper, easier and safer alternative.
In studies since 2001 at the ARS National Center for AgriculturalUtilization Research in Illinois, the scientists showed that tinyparticles of starch comprising the one-micrometer-thick coating hold waterin place, preventing it from beading and rolling off the plastic's surface.And if a film of polyethylene is thin enough, the scientists observed, thecoating will temporarily change the film's shape when the coating dries.
The scientists made the hydrophilic coating as part of an ARS researcheffort to develop new, value-added products from agriculturalcommodities, especially cornstarch. The US supply of cornstarch - alongwith starches from rice, potato and other crops - often outpaces demand forthe commodity, the researchers note in a published paper describing theirinvention.
There is now a noteable trend towards manufacturing packaging from agricultural commodities that are both replaceable and biodegradable. PLA for example is a unique biodegradable material that is also processed from annually renewable resources, such as corn, meaning it uses less fossil resources compared to petroleum-based plastics. It offers excellent clarity and has an equivalent oxygen barrier to polypropylene.
The technology to produce NatureWorks PLA essentially "harvests" the carbon, which plants remove from the air during photosynthesis and store in grain starches. This is achieved by breaking down the starches into natural plant sugars.
The carbon and other elements in these natural sugars are then used to make plastic, called polylactide (PLA), through a simple process of fermentation, separation and polymerisation.
Many analysts believe that biodegradable packaging has a bright future. Growing environmental awareness and consumer power coupled with the inexorable rise in pre-packaged disposable meals means that food manufacturers and packagers are increasingly being targeted to improve their environmental performances.
Datamonitor statistics show that more than one-third of European consumers live alone and are spending €140 billion a year on food, drinks and personal care products. Single people spend 50 per cent more per person on consumer-packaged goods than a two adult household. Such trends underline why the environmental impact of food packaging has never been greater.
Felker and Fanta are hoping the hydrophilic starch coating will nibble awayat that surplus, either by making plastic films more water-friendly or byanother novel application.
Earlier this year, ARS obtained a patent (US Patent 6,709,763) on theinvention and is seeking to license it to a company that can explore suchpossibilities.
ARS is the US Department of Agriculture's principal scientific researchagency.