From Table 4 it can be deduced that both the modulus of elas- ticity and the tensile strength were not significantly affected by the ageing process in the first reprocessing cycle, even after 600 h in the QUV chamber, which is equivalent to 22.1 years outdoors. Nevertheless, for samples reprocessed five times (Table 5) the mod- ule of elasticity decreased slightly, whereas the tensile strength decreased drastically during the first 400 h of residence in the QUV chamber (approximately 33% of its initial value), and remaining practically constant thereof.
These studies reveal that, in general, the major difference in the behaviour among the reprocessed materials took place in thefirst 50h of residence in the QUV chamber, i.e., in the first two years outdoors. After one reprocessing cycle the mechanical prop- erties of samples were reduced only slightly. Conversely, after the fifth reprocessing cycle the decrease could reach 30%. Therefore, from the point of view of the mechanical properties, it can be concluded that non-protected PC (without anti-UV additives) is seriously degraded after eight years outdoors only if it has been processed more than once. Therefore, depending on the mechani- cal requirements of the PC application, it should be replaced before that time.