ARCHIVED - Ingredients for greener plastics: NRC overcomes major hurdles in producing plastic from vegetable sources

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September 07, 2007— Ottawa, Ontario

When is a food no longer a food? When it has been turned into plastic.

It's hard to imagine wheat, potato and other starchy staples showing up on your table as disposable plates, cutlery and cups, but that's the aim of NRC's research on bioplastics. A team led by Dr. Michel Huneault at the NRC Industrial Materials Institute (NRC-IMI) has reported major breakthroughs in their project to develop starch-based polymers from some of our favourite foods.

Corn, peas and plastic beads
Corn, peas and plastic beads

The main source of chemicals for plastic is fossil fuels. These petrochemical plastics are very durable but, once disposed of, they take a long time to biodegrade. "In comparison, materials made from starch-based polymers can be made to biodegrade rapidly. Or, if required, they can be made far more durable. They also take less energy during production than petroleum-based plastics," notes Dr. Huneault.

Since 2005, Dr. Huneault and his team in Boucherville, Quebec, have been working closely with the Canadian Biomass Innovation Network and the École Polytechnique de Montréal to make bioplastics, using the starch in peas, rice and wheat. "We're aiming to develop an alternative for the synthetic petroleum-based polymers used in throw-away products like packaging," says Dr. Huneault. "Starch is a promising candidate for this purpose because it is a natural polymer. But it has to be modified to make it water resistant and 'thermoplastic' — capable of being melted and shaped."

Bioplastics are plastics manufactured from biomass rather than petroleum.

Biopolymers are polymers present in, or created by, living organisms. Cellulose (from wood, cotton, corn, wheat), soy protein (from soybeans), and starch (from corn, potatoes, wheat, tapioca) are biopolymers.

Polylactic acid is a bioplastic but not a biopolymer. It is made from lactic acid produced by fermenting natural sugars but it is polymerized through a man-made chemical synthesis process.

Bioplastics is a growing field of research, especially in Canada where we have abundant biomass. The rising cost of petroleum, diminishing oil reserves, and the increasing quantity of plastic piling up in landfills are just some of the concerns driving this research. Manufacturers are facing increasing pressure to use environmentally friendly packaging, especially since the U.S. government purchasing policy now favours biobased products as do big companies including Wal-Mart and McDonald's.

With the help of their technical support staff, Drs Michel Huneault, Nathalie Chapleau and Hongbo Li have characterized selected types of starch, assessed the availability and suitability of various feedstocks, and blended thermoplastic starch with a variety of other polymers. They have successfully created polymer alloys that can potentially be used to manufacture a variety of the disposable plastic articles we use in our daily lives.

In the January 2007 issue of Polymer, the team reported its success in overcoming a major obstacle in blending thermoplastic starch with other polymers – an essential step to produce bioplastics with the right characteristics for a range of commercial applications. They determined how to "compatibilize" polylactic acid and thermoplastic starch (PLA/TPS) blends through a reactive extrusion technology. The team was the first in the world to successfully apply this particular blending strategy to polylactic acid and thermoplastic starch. Previously, thermoplastic starch and polylactide were known to be like oil and water – an immiscible blend. Thanks to this innovative technique, the team now has the key to producing a much more homogenous blend that will lead to more versatile bioplastics.

The team's research will be presented at BioPlastics 2007, the second annual International Symposium on Bioplastics and Natural Fiber Composites. Co-organized by NRC and the Quebec Materials Network, BioPlastics 2007 will be held in Montréal from September 19 to 21, 2007. For details, visit: http://www.reseaumateriauxquebec.ca/BioPlastics2007/html/home.htm

"Certain blends are fully biodegradable and offer the full range of properties depending on the starch and plasticizer content," notes Dr. Huneault. The PLA/TPS blends were found to be very stretchable, opening the way for manufacturing plastic films for use in the thermoformed trays used in packaging. The blends could be injection-molded in simple parts, opening the way for their use in injectable thermoplastics. Finally, the blends were also found to be foamable with carbon dioxide, which could lead to lower density packaging foams. The team reported these encouraging findings in the July 2007 issue of Macromolecular Bioscience, making the first page of this prestigious international journal.

"The day will soon come when consumers won't be able to distinguish biobased plastics from today's petroleum-based plastics," says Dr. Huneault. "Given the environmental and cost advantages of starch-based biopolymers, it won't be long before we see a far greater acceptance of biobased plastics."


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National Research Council of Canada
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