Investigation of thiol-epoxy thermosets: Influence of polythiol hardeners on thermomechanical properties

A common curing agent for thermosets is based on anhydrides. Anhydrides are primarily used due to their excellent thermomechanical and mechanical properties. However, anhydrides also have their disadvantages; for example, they have a significant toxicological potential. One of the most promising alternatives is thiol-based hardeners; these can be produced sustainably, are highly reactive, and are less toxic, unlike anhydride systems. Considering these aspects, this thesis concentrates on the following topics/questions: 1. What influence does the stoichiometric ratio of a thiol-epoxy formulation have on the material behavior? 2. Do the thermomechanical and mechanical properties change when a different curing condition is used? 3. Can the material properties of a thiol-epoxy thermoset be made comparable to those of a conventional epoxy-anhydride system? Through the use of the following analytical methods: 1. Fourier-transformed infrared spectroscopy (FT-IR) 2. differential scanning calorimetry (DSC) 3. dynamical mechanical analysis (DMA) 4. tensile tests (TS) it was possible to analyze the curing behavior, thermomechanical, and mechanical properties of the different resin formulations. Furthermore, the different polythiol thermosets were compared with each other as well as with the reference sample, an epoxy-anhydride system. This study has demonstrated the following information: the stoichiometric ratio influences the thermomechanical and mechanical properties; furthermore, the amount of catalyst also influences the material properties. In addition, the material properties depend on the chemical structure of the thiols as well as on the curing conditions. The results indicate that there are significant differences in the material properties between the curing modes used. Additionally, it was demonstrated that there are gaps in the material properties between the thiol-epoxy thermosets investigated and the reference system based on anhydride.