Microscopic in-situ characterisation of the local viscoelastic phase properties of thermoplastic vulcanisates for investigation of the recipe and processing effects on the micromechanical phase interactions

• Applicant: Professor Dr. Rainer Dahlmann
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Plastics Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 533837197

Among the thermoplastic elastomers (TPE), the group of thermoplastic vulcanizates (TPV) is found predominantly in applications. In TPVs, the cross-linked elastomer phase is finely dispersed in a continuous thermoplastic phase. The local constitution of the material, particle size, cross-linking degree of the elastomer phase, chain degradation in the thermoplastic phase, is determined in the manufacturing process, the dynamic vulcanization. In the subsequent injection moulding process, the local configuration of the polymer blend is determined in dependence on the flow and cooling conditions. The most important parameters in this regard are the distortion and the orientation of the elastomer particles. Both processes significantly influence the resulting macroscopic mechanical material properties of the TPV. These effects result in complex interactions that have not yet been fully understood and investigated. Especially the compounding process affects the mechanical properties of the individual phases. This results from the dispersion of additives, such as plasticizer oils and the cross-linking system. In the literature, a concentration equilibrium of additives between both base polymers is assumed. In addition, the mechanical properties are influenced by chemical processes. Cross-linking takes place in the elastomer phase. In the thermoplastic phase, the cross-linking system causes a degradation of the polymer chains. Due to this strong change of the mechanical phase properties in the compounding process, it is not possible to determine the material properties using macroscopic mechanical tests. Thus, in this project, local mechanical tests using an atomic force microscope are used to determine the mechanical properties in-situ. From these tests, input data for viscoelastic material models of the individual phases will be generated. These models will be used in micromechanical models based on representative volume elements to gain a deeper understanding of the interaction mechanisms occurring in the TPV under mechanical loading.

• DFG Programme: Research Grants