It is important to note that there are no carbon deposits and no indication of polymer decomposition at the inner surface. For both polymeric materials, no chemical degradation of the material is observable and no structural changes could be seen near the embossed catalyst particles. These results indicate that under the prevailing reaction conditions between 160 and 220 °C over 100 h, the catalytic material does not initiate chemical degradation reactions of the polymer. Certainly, the results should be interpreted in the way that the polymers are most probably not chemically decomposing, but the mechanical stress might lead to structural damage of the surface. This is potentially critical for the mechanical integrity of the reactor, since the small notches induced by glass fibers or catalyst particles result in stress concentration. Phenomena like these can finally lead to reactor failure and need further investigation, in order to consider these effects in the derivation of criteria for the design of polymeric reactors.