A modification of nonbiodegradable synthetic polymers with a biodegradable polymer producing environmentally friendly polymers. The main problem in modification of nonbiodegradable synthetic polymers with biodegradable polymers is compatibility between polymers mixtures with different properties. In order to investigate the aging process of PP/PCL blends without and with nTiO2 filler with UV irradiation samples were subjected to accelerated aging using a low-pressure mercury lamp unit (Suntest Heraeus Suntest CPS xenon light lamp) the changes of dynamic mechanical properties and phase transitions were investigated. The neat polymers, PP/PCL and PP/PCL/nTiO2 polymer blends were prepared by melt compounding with a twin screw extruder, the granules of the blends were compression moulding in hydraulic press. Because the aging process is extremely complex, to obtain a clearer picture of all processes that occur in the blends the technique of dynamic mechanical analysis (DMA) are used to determine the changes of dynamic mechanical properties and change of thermal properties was monitored using differential scanning calorimetry (DSC). The obtained results show that the particles of nTiO2 as filler in PP/PCL blends have the photocatalytic property and improves the photocatalytic degradation after UV irradiation. Furthermore, photodegradation process might occur through chain scission reactions, crosslinking and consequently photocatalytic degradation of polymers.