Additive-free nucleation of PLA for accelerated crystallization

• Applicant: Dr. Regine Boldt
• Subject Area: Polymeric and Biogenic Materials and Derived Composites
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 573882006

The aim of this project is to modify polylactic acid (PLA) to accelerate its crystallization without the addition of external additives. The scientific hypothesis posits that the use of high-energy electrons will induce long-chain branching in the polymer, which can act as nucleation sites. Systematic studies are required to validate this hypothesis, focusing on the detailed analysis of the effects of high energy radiation on the molecular structure of PLA, particularly concerning chain scission and chain formation. This project will involve comprehensive studies on the influence of electron irradiation on PLA with varying molecular weights and D-isomer content, considering the crystalline state during irradiation, irradiation temperature, and the applied dose. These investigations aim to provide a detailed understanding of the relationship between structural modifications and the resulting material properties. Another goal is to expand the scientific understanding of the crystallization kinetics of electron beam-modified PLA under shear, as well as under isothermal and non-isothermal crystallization conditions. This will lead to a profound understanding of the crystallization behavior of electron beam-modified PLA as a function of structural and process parameters. To achieve these objectives, expertise in electron beam modification of polymers will be combined with capabilities in structural characterization and visualization of polymer structures. The existing equipment and extensive knowledge in correlative, multiscale investigations of polymer structures and morphologies provide an excellent foundation for addressing these topics. A specific subgoal of the project involves studying crystallization kinetics using Xray diffraction. For this purpose, the developed FlowCell developed at the IPF will be modified to enable various cooling rates by using a liquid-based cooling system instead of the current air cooling. Additionally, temperature-dependent changes in the polymer structure will be analyzed using a Raman spectrometer coupled with a differential scanning calorimeter (DSC). The outcome of this project is a fundamental scientific understanding of a sustainable, additive-free modification of PLA using high-energy electrons to effectively control crystallization. Different crystalline morphologies are generated by varying the irradiation parameters. The resulting material properties will be investigated using classical materials science methods, and the relationships between irradiation parameters, altered structure and material properties will be elucidated based on the knowledge gained in this project.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Michael Thomas Müller