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Epoxy resins represent an important class of thermosetting polymers that are extensively used in demanding applications like in scratch resistant coatings. Usually fillers, either hard (inorganic) or soft (rubbery), are added. Here we test hard and soft particle-filled epoxy systems in single asperity sliding friction experiments, and analyze the results with the hybrid numerical-experimental approach presented earlier. The focus is on the detailed modeling of the local deformation processes and it is confirmed that a rate-independent friction model proves appropriate to quantitatively model this complex process. The constitutive framework developed for amorphous thermoplastic polymers adequately describes also these thermoset systems. The materials response during scratching is likewise. Hard fillers decrease the penetration of the indenter into the surface, and consequently enhance scratch resistance; they cause the lateral friction force to decrease, since less material flows in front of the indenter tip. Soft fillers increase the penetration into the surface, according to expectations, but surprisingly also decrease the friction force. Simulations do not predict this, and suggest an alternative explanation. Migration of rubber particles during sample preparation to the surface could have occurred. Adding a thin rubbery layer to the surface makes the model quantitative, but SEM and TEM pictures of the cross-sections do not confirm this phase separation and instead show the presence of a large number of very small voids. Including these voids in the modeling allows to predict the penetration depth into the surface and lateral force quantitative for all sliding speeds.

In this work we report on the processing, melt-drawing, and performance of new vanillic acid based aliphatic-aromatic thermotropic polyesters. It is demonstrated that these materials are easily processed from their nematic melts yielding highly oriented products. Furthermore, we demonstrate that a molecular weight (M-w) of roughly 30 kg/mol is required in order to successfully perform spinning on these polymers. The application of a polymer with lower M-w results in poor mechanical performance and fiber breakage during the winding process. Wide-angle X-ray diffraction analysis has been performed on the fibers and it is demonstrated that the orientation parameter increases with increasing draw-ratio of the fiber. Although these polymers are readily processed from their thermotropic melts, the obtained fibers only retain their orientation up to temperatures in the range of 120-130 degrees C, after which they start to melt. In general, these fibers exhibit tensile moduli in the range of similar to 10 GPa and a tensile strength around similar to 150-200 MPa. FTIR and solid-state NMR experiments indicate that only the aromatic components are molecularly oriented during the spinning process. In contrast, the aliphatic moieties exhibit a high mobility, normally corresponding to a local isotropic motion. It is expected that the poor molecular orientation of the aliphatic moieties in these aliphatic-aromatic thermotropic polyesters contribute to the relatively low tensile modulus of the fibers, obtained after the extrusion and melt-drawing process.