Biodegradable at last

Use of organic catalysts to usher in a new range of plastics  

By Ruhi Kandhari
Published: Saturday 04 July 2015

scientists from the International Business Machine Corp’s (ibm) and Stanford University in the US announced the discovery of plastics that could be biodegradable, biocompatible and completely recyclable. Organic catalysis is the new mantra in what is seen as a complete shift towards green polymer chemistry.

Three ingredients make plastic: a monomer of the organic molecule, solvent and catalyst. Metal oxide or metal hydroxide catalysts are generally used to ensure that the monomer readily binds to other monomers to form chains that continue to grow. The researchers have achieved this by using an organic catalyst which rivalled metal-based catalysts without significant impact on the cost or the performance of plastics.

When plastics are created using metal catalysts, metallic remnants of the catalyst remain in the final polymer. Their lingering presence weakens the recycled plastic over time. But polymers created using a new family of organic catalysts that are free of metal are fully recyclable, said chemist Robert Waymouth from Stanford University. The paper was published in Macromolecules on March 10.

“The development of new families of organic catalysts brings more versatility to green chemistry and opens the door for novel applications, such as improving the recycling process and drug delivery,” said ibm vice president Josephine Cheng in a press release.

ibm has announced this research could be used to recycle commonly used pet (polyethylene terephthalate) plastic to its original form; it is used for packaging soft drinks and food. While disposable plastic bottles are one of the biggest challenges today, recyclable ones have their drawbacks. For example, pet is recyclable but the resulting materials are for limited second generation use only, such as in carpets. This recycled product has nowhere to go except landfills after its use. ibm has tied up with scientists from King Abdulaziz City for Science and Technology in Saudi Arabia to launch a pilot pet recycling project.

Shyamala Mani, national coordinator of Waste and Resource Management at the Centre for Environment Education in New Delhi argues that no post-consumer plastic is fit for food or medicine packaging. “In its journey from virgin plastic to its second recycled avatar, no one knows what the plastic has picked up. How do you know kerosene, petrol or pesticides were not put into it?,” she said.

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