Global Challenges/Chemistry Solutions

Our Sustainable Future: Biodegradable plastic from
milk and clay

January 12, 2011

Marshmellows

Lighter-than-a-feather, this new material, made
from milk protein and clay, could become a new biodegradable substitute for traditional
foamed plastics.
Credit: Tassawuth Pojanavaraphan

Summary

Amid ongoing concern about plastic waste accumulating in municipal landfills, and reliance on imported oil to make plastics, scientists are reporting development of a new ultra-light biodegradable foam plastic material made from two unlikely ingredients: The protein in milk and ordinary clay. The new substance could be used in furniture cushions, insulation, packaging, and other products, they report in the ACS’ Biomacromolecules, a monthly journal.

With continuing concern about plastic waste accumulating in municipal landfills, and reliance on imported oil to make plastics, scientists have created an ultra-light biodegradable foam plastic material made from two unlikely ingredients. A study in ACS’ Biomacromolecules, reports that researchers have actually used the protein in milk and ordinary clay. Here is lead author David A. Schiraldi, Ph.D. of Case Western Reserve University:

“We believe this new ‘green’ foam plastic can have a wide range of uses. For example, we can see it in furniture cushions, insulation, packaging and many other products. By replacing standard foam this could have an important impact on better protecting the environment from debris.”
An advantage of this new technique is that the materials are readily available and producing the biodegradable foam would be rather easy.

“About 80 percent of the protein in cow’s milk is a substance called casein, which already is used in making adhesives and paper coatings. But casein is not very strong, and water can wash it away. To beef up casein, and boost its resistance to water, we simply blended in a small amount of clay and a reactive molecule called glyceraldehyde. This process links casein’s protein molecules together.”

The team tested it’s creation and concluded that is strong enough for commercial use.

“We freeze-dried the resulting mixture, removing the water to produce a spongy aerogel, one of a family of substances so light and airy that they have been termed ‘solid smoke.’ To make the gossamer foam stronger, we cured it in an oven, then tested its sturdiness. We concluded that not only is it strong enough for commercial uses, but is biodegradable. Almost a third of the material breaks down within 30 days.”

“About 80 percent of the protein in cow’s milk is a substance called casein, which already is used in making adhesives and paper coatings. But casein is not very strong, and water can wash it away. To beef up casein, and boost its resistance to water, we simply blended in a small amount of clay and a reactive molecule called glyceraldehyde. This process links casein’s protein molecules together.”

Smart Chemists/Innovative Thinking

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st Century. Be sure to check our previous Global Challenges podcast episodes by visiting www.acs.org/globalchallenges. Today’s podcast was written by Michael Bernstein. I’m Adam Dylewski at the American Chemical Society in Washington.

David A. Schiraldi, Ph.D.
Case Western Reserve University