Polymers play an increasing role in manufacturing processes and their production keeps on growing, especially in the packaging industry [1]. However, the decline of fossil resources, along with the raise of collective awareness about the impact that waste may have on the environment, impose to look for possible alternatives to petroleum-based polymers with reduced environmental risks. For these reasons, bio-sourced and/or biodegradable polyesters have attracted much attention from both academic researchers and industrials. Industrial processing techniques such as injection molding or additive manufacturing (laser bed fusion, 3D-printing, etc.) often involve extremely high cooling rates, with major consequences on polymer microstructure and molecular mobility. Controlling the cooling rate and understanding its consequences on polymer properties remain a major challenge. Conventional calorimetric measurements provide scanning rates generally limited to a few tens of degrees per minute. Fast Scanning Calorimetry (FSC) allows the extension of the experimental window of several orders of magnitude in terms of scanning rate, giving access to cooling rates up to 40 000 K s-1, which is ideal to reproduce industrial processing conditions [2]. A series of biodegradable and potentially bio-based thermoplastic polyesters was synthesized from trans-1,4-cyclohexanedicarboxylic acid and diols of different lengths [3]. These materials have interesting barrier and mechanical properties for food packaging applications [4-8], but also a very different aptitude to crystallize depending on the number of methylene groups in their repeating unit (odd-even effect). The cooling rate required for full quenching is thus very different for each one of these materials, with different consequences for the ones being able to crystallize compared to the ones that cannot. This work illustrates how to estimate the critical cooling rate for fast-crystallizing polyesters [9], and the possible consequences of a fast-quenching process on an amorphous polyester [10], taking the example of poly (alkylene trans-1,4-cyclohexanedicarboxylate) (PCHs) with a number of methylene groups varying from 3 to 6.

References

1. R. Geyer, J.R. Jambeck, K.L. Law Science Advances, 2017, 3, e1700782.
2. K. Hallavant, M. Mejres, J.E.K. Schawe, A. Esposito, A. Saiter-Fourcin J. Phys. Chem. Lett. 2024, 15 (16), 4508.
3. G. Guidotti, C. Fosse, M. Soccio, M. Gazzano, V. Siracusa, L. Delbreilh, A. Esposito N. Lotti Polym. Degrad. Stab. 2024, 230, 111050.
4. L. Genovese, N. Lotti, M. Gazzano, L. Finelli, A. Munari EXPRESS Polym. Lett. 2015, 9, 972.
5. M. Gigli, N. Lotti, M. Gazzano, V. Siracusa, L. Finelli, A. Munari, M. Dalla Rosa Ind. Eng. Chem. Res. 2013, 52, 12876.
6. G. Guidotti, M. Soccio, V. Siracusa, M. Gazzano, A. Munari, N. Lotti Polymers 2018, 10, 866.
7. M. Soccio, N. Lotti, L. Finelli, M. Gazzano, A. Munari Polymer 2007, 48, 3125.
8. V. Siracusa, L. Genovese, C. Ingrao, A. Munari, N. Lotti Polymers 2018, 10, 502.
9. K. Hallavant, M. Soccio, G. Guidotti, N. Lotti, A. Esposito, A. Saiter-Fourcin Polymers 2024, 16 (19), 2792.
10. M. Mejres, K. Hallavant, G. Guidotti, M. Soccio, N. Lotti, A. Esposito, A. Saiter-Fourcin J. Non-Cryst. Solids 2024, 629, 122874.

Acknowledgments

The authors acknowledge: Thomas Flammang, Brigitte Djuiga Wabo and Silvia Quattrosoldi for contributing to polymer synthesis and preliminary characterizations; Erasmus+ for Kylian Hallavant’s mobility to Bologna; Région Normadie for Kylian Hallavant’s PhD financial support; Mettler-Toledo for lending a DSC 3+ apparatus; LabEx EMC3 for financing the acquisition of a Flash DSC2+ apparatus; Graduate School Materials & Energy Sciences (GS-MES) for Marouane Mejres’ internship.