The use of Carbon Nanotubes (CNT) has developed rapidly over the last years because of their great potential of improving material properties with only a small amount of filler. To achieve best physical and chemical properties, a very good dispersion of the nanofillers, the correct structure in the polymer matrix and a good bonding at the interface is essential. Previous research showed that with correct process settings as well as parameters thermal expansion can be reduced. A second part was the influence of alkalis on mechanical properties of the polymers. This study reports the effect of CNT on the thermal expansion an alkali resistance of unfilled Polypropylene and Polyamide and PP and PA reinforced with 50 % glass fibers%. Thermal expansion and alkali resistance of four different polymers (Rialene P10100ST, Rialene P101SGF50ST, Riamid 15000ST, Riamid 150GF50ST; RIA-Polymers) was tested and compared with their counterparts incorporated with different filling degrees (0.5, 1, 2 %) of CNT. Therefore test specimens of the different mixtures were prepared with a HAAKE Rheomix lab mixer followed by a forming process to produce testing plates of 2 mm thickness. Thermal expansion of the Plates was tested with a Mettler Toledo TMA. Alkali resistance was shown by comparison of tensile tests of untreated polymers and polymers inlayed in caustic potash for 28 days. Significant differences in thermal and chemical properties were shown between the different materials and different filling degrees. The coefficient of linear thermal expansion (CLTE) was reduced by the use of CNT to lower regions. Alkali Resistance of polymers didn’t change significantly. These results are relevant to evaluate the potential CNT for influencing thermal and chemical properties of different polymers.