Environmental and chemical ageing of epoxy resins cured with bio-based amino acids

To achieve efficient and sustainable use of raw materials and energy, structures made of lightweight composites and thermosetting polymers are widely used. For sustainability, it is especially mandatory to extend the operating life of structures and components even under harsh conditions. Recently, the transformation from petrochemical to biobased resources is ongoing, to further improve sustainability. However, because of the more polar state of many biobased raw materials, it should be ensured, that they are not lacking in long-term use. In this study, specifically, the evolution of absorption and thermo-mechanical properties such as tensile strength or glass transition temperature (Tg) are analysed after ageing in demineralised water and chemicals (acetone, isopropanol, hydraulic oil) for L-arginine-cured epoxy compared to fully petro-based epoxies. The changes in properties due to physical ageing (molecular relaxation) and diffusion reveal a complex interplay between plasticization, physical ageing and possible chemical degradation. In particular, water absorption promotes strength-reducing plasticization and strength-increasing molecular relaxation on different time scales. This complex interplay is found for both types of epoxies and is in good agreement with what was previously found for classical epoxy. At the same time, the plasticizing effect of water also significantly reduces the Tg, as the water ingress into the molecular structure which increases chain distances and facilitates molecular movements. Furthermore, the resistance of the arginine-cured epoxy against different chemicals is particularly high and the diffusion retarded. Evidence for chemical degradation due to acetone diffusion is detected for both epoxy types via FTIR-analysis.

DDC Class

330: Economics

540: Chemistry

620.1: Engineering Mechanics and Materials Science

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Environmental and chemical ageing of epoxy resins cured with bio-based amino acids