Epoxy resins are often used polymers because of their adjustable properties and the resulting numerous application possibilities. Some of these applications are use as coating material, structural composites, casting molds and adhesives. They are also used as composite material together with fibers for lightweight construction in the automotive, marine and aircraft industry. Epoxy resins without any additives are brittle and hard to handle. But the properties of the epoxy resins are adjustable by addition of various additives. To increase the toughness of the material, toughener systems, which generate phase separation are used. Due to the possible deformation of the rubber additives during fracture the toughness and impact resistance increase.
The aim of the present study was the characterization of epoxy resins with scanning force microscopy. Part one of the present thesis is focused on the determination of the cross-linking level of epoxy resins. Local thermal analysis using a scanning force microscope equipped with a heatable probe is introduced to determine the glass transition temperature of the resin in specific curing stages. This nano-thermal characterization method is compared to conventional methods like differential scanning calorimetry and Raman spectroscopy. An increase of the glass transition temperature is connected to the increasing cross-linking density. Local thermal analysis is correlated with Raman spectroscopy data. The network formation of the examined epoxy resin follows an exponential trend.
The second part of the work is focused on the influence of rubber additives on the obtained microstructure in epoxy resins. The influence of curing conditions and the amount of the rubber additive on the morphology is examined with scanning force microscopy. A phase separation between epoxy and rubber domains occurs. The accumulation of rubber phase in the epoxy phase and vice versa was examined with nano-mechanical experiments. Both, the distribution of the spherical rubbery particles and the enrichment in the other phase have impact on the elastic modulus of the whole epoxy system.