Tuning Reprocessing Temperature of Aliphatic Polyurethane Networks by Alkoxyamine Selection.

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Polyurethanes (PUs) are a significant class of thermosets with reprocessing potential due to dynamic carbamate linkages.
• Current reprocessing methods for PUs, especially aliphatic ones, require high temperatures, leading to undesirable side reactions.
• There is a need for efficient reprocessing techniques for PUs under milder conditions.

Purpose of the Study:

• To explore the use of alkoxyamine bonds in polyurethane networks for reprocessing under mild conditions.
• To design and synthesize novel alkoxyamine-based diols for creating dynamic PU networks.
• To investigate the impact of these dynamic blocks on the reprocessing capabilities of aliphatic polyurethanes.

Main Methods:

• Design and synthesis of two distinct alkoxyamine-based diols.
• Incorporation of these dynamic diols into polyurethane networks, replacing 50 mol % of a nondynamic diol chain extender.
• Evaluation of the relaxation times and reprocessing temperatures of the resulting PU networks.

Main Results:

• The developed alkoxyamine-based PU networks exhibit enhanced relaxation times.
• Reprocessing of these modified polyurethanes was achieved at significantly lower temperatures (as low as 80 °C).
• The structural modifications effectively facilitated dynamic bond exchange under mild conditions.

Conclusions:

• Alkoxyamine bonds offer a viable strategy for creating recyclable aliphatic polyurethanes.
• This approach enables efficient reprocessing of PUs at reduced temperatures, minimizing thermal degradation and side reactions.
• The study demonstrates a promising pathway towards more sustainable polyurethane materials.