This paper deals with the effect of carbon nanotubes (CNT) on the basic characteristics and the global aging behaviour of beta-nucleated polypropylene random copolymer absorber material for overheating protected solar thermal collectors. Hot air aging experiments at an elevated temperature of 135 degrees C were carried out using micro sized specimens with a thickness of 100 gm. The unaged specimens were characterized as to the antioxidant content and the mechanical and thermal properties. The CNT pigment affected the semi-crystalline morphology (less beta-content) and increased the stiffness significantly. The aging indicators strain-at-break, average molar mass, primary antioxidant content and oxidation temperature were monitored for up to 4000 h. A more pronounced degradation was deduced for the compounds with CNT. Compared to carbon black modified grades a higher deterioration rate was ascertained for the CNT compounds. The amount of CNT should be kept at low levels (< 0.1 wt%) just needed to achieve sufficient solar absorbance (> 90%) of the absorber sheet.