Three different poly(vinyl chloride) (PVC) formulations were submitted to photo ageing.The influence of the different thermal stabilizers was evaluated by means of ultraviolet-visible (UV-Vis) spectra

fourier transform infrared (FTIR) spectra and differential scanning calorimetry (DSC).The gel content formed in exposed samples was estimated gravimetrically

and the color and mechanical properties changes of PVC during photoageing were studied.It was found that microstructures of three PVC/thermal stabilizer blends changed in the same tendency.As UV irradiation time increases

the conjugated polyene sequence

carbonyl group and the gel content increase

respectively.And the molecular weight decreases.Meanwhile

the yellowness index

the elongation at break and impact strength of the PVC sheets gradually decrease with increasing UV irradiation time.The main photochemical reactions include photo-dehydrochlorination

photooxidation

degradation and crosslinking.The degree and the kinetics of dehydrochlorination

oxidative

degradation and crosslinking during photoageing were different in three PVC/thermal stabilizer blends.Sn was the most efficient on restraining dehydrochlorination.Pb was the most stable in the reaction of oxidative degradation and crosslinking.As a result PVC/Sn blends showed higher color stability

and the retained percentage of impact strength and elongation at break of PVC/Pb blends were the highest among of the three blends.