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Starch-based Polymers

Boosting biodegradability means plastic bottles like these won't hang around our environment for quite so long.

iStockphoto/Thinkstock

As a totally biodegradable, low-cost, renewable and natural polymer, starch has been receiving lots of attention for developing sustainable materials lately. When it comes to replacing plastic, however, starch can't cut the mustard; its poor mechanical properties mean it has limited use for the sturdy products that plastics generate.

What one of the hottest trends in biodegradable plastic development can do is make polymer composites more biodegradable. You name it, and starch has probably been combined with it, albeit with varying degrees of success.

To make completely biodegradable starch-based plastics, the components usually blended with starch are aliphatic polyesters, such as PLA and PCL, and polyvinyl alcohol. Adding in starch also shaves plastic manufacturing costs. Starch needs to exceed 60 percent of the composite before it has a significant effect on degradation; as the starch content increases, the polymers become more biodegradable [source: Nolan-ITU Pty Ltd]. Keep in mind that adding more starch also affects the properties of the plastic. If you put wet leaves in a starch bag for a bit, you'll have a mess when you go to pick up the bag.

So, while there is no silver bullet for making plastics greener, a combination of revitalizing old ideas and revolutionizing plastic technology is a step in the right direction.

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