A Plastic That Behaves Like Glass | Chemical & Engineering News
Volume 89 Issue 51 | p. 16
Issue Date: December 19, 2011

Cover Stories: Chemical Year In Review 2011

A Plastic That Behaves Like Glass

Malleable material contains esters that swap positions in cross-links when the polymer is heated
Department: Science & Technology
Keywords: thermoset plastics, polymers, polyester, transesterification
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Localized heating allows researchers to shift the shape of a new polymer.
Credit: Cyril Fresillon/CNRS
This panel of photos show how a new polymer can be heated to change shape. It is malleable like glass, but holds its shape like plastic.
 
Localized heating allows researchers to shift the shape of a new polymer.
Credit: Cyril Fresillon/CNRS
[+]Enlarge
Esters swap positions in cross-links when this polymer is heated, allowing objects made from it to be reshaped.
This reaction shows how the esters and alcohols align in the polymer that allow for its malleablilty.
 
Esters swap positions in cross-links when this polymer is heated, allowing objects made from it to be reshaped.

Chemists in France unveiled this year a material that mimics the malleability of glass but retains the toughness and stability of thermoset plastics (C&EN, Nov. 21, page 5; Science, DOI: 10.1126/science.1212648). The polymer could be useful to make parts for the automotive and aerospace industries, among others. “Anywhere you have a complex shape, you can use this material,” said lead researcher Ludwik Leibler of the School of Industrial Physics & Chemistry, in Paris, part of France’s National Center for Scientific Research (CNRS). “It’s much lighter than metal or glass, it’s chemically resistant, and it’s recyclable.” Thermoset plastics, such as Bakelite, are stable to solvents and extreme temperatures. But they must be polymerized in a mold to give them a shape. And once they’ve been polymerized, thermosets can’t be reshaped or reprocessed, either with heat or with solvent. Leibler’s polymer retains the stability of a thermoset even as the material is heated and manipulated like glass into desired shapes. The key to the glassy behavior lies within the polymer’s molecular structure; it has an equal number of ester and alcohol groups. When the material is heated, it transesterifies—that is, its ester cross-links transfer from one region of the polymer to another, with the help of an embedded zinc catalyst. “You exchange links, but you never diminish the chemical bonding” that gives the polymer its strength, Leibler explained. His team has patented the material and hopes to see it commercialized soon. The chemical components, which include a bisphenol A derivative and a mixture of long-chain carboxylic acids, are inexpensive and readily available, Leibler said.

 
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