New efforts were made to produce photodegradable polyethylene by mixing partially degraded polymer (PDP) containing carbonyl groups as initiators for molecular degradation with virgin polymers. In the current work the influence of PDP of varying amount on the photodegradation process of a virgin polymer under natural and artificial weathering conditions is investigated. The degree of degradation expressed by average values of the molar mass of the polymer is measured by size exclusion chromatography and correlated with the number of carbonyl groups in the polymer system estimated by Fourier Transform Infrared Spectroscopy. Molecular degradation is also accompanied by an increase in the degree of crystallinity of the polymer which affects the processability of films and is measured by Differential Scanning Calorimetry. Correlation of these measurements helps to judge about the efficiency of a certain PDP in degradation process under various weathering conditions. Furthermore, predictions of the processability and mechanical properties of films containg PDP can be made.