Evergreen by name, evergreen by nature

University of South Carolina scientists are working to give the term ‘evergreen’ a new meaning. Led by Chuanbing Tang, the research group is developing new plastics that are ‘green’ from the cradle to the grave, based on polymers from pine trees, firs and other conifers.

The plastic will use natural resins found in trees, especially evergreens. The rosin and turpentine from their wood is rich in hydrocarbons - similar, but not identical, to some components of petroleum.

Hydrocarbon-rich starting materials, whether from petroleum or tree resin, can be converted into various forms of plastics through polymerisation. Processes for developing plastics from renewable sources like rosin and turpentine are not nearly as developed as those using petroleum derivatives.

“Renewable polymers currently suffer from inferior performance in comparison to those derived from petroleum,” Tang said.

Molecules derived from wood products are particularly worthwhile targets, Tang says. “They’re a rich source of the cycloaliphatic and aromatic structures that make good materials after polymerisation,” he said. “They have the rigid molecular structures and hydrophobicity that materials scientists know work well.”

The materials are also suitable sustenance for the microbes responsible for biodegradation. “Most plastics from non-renewable resources are generally not biodegradable,” Tang said. “With a polymer framework derived from renewable sources, we’re able to make materials that should break down more readily in the environment.”

Tang’s review of terpenes, terpenoids and rosin - three components of tree resin - was published in Macromolecular Rapid Communications in January 2013.