Abstract: Effect of ultraviolet light (UV) irradiation on the structure and properties of PVC was studied by means of FT-IR，UV spectrum, SEM, GPC, stress-strain curves, yellow index, and water contact angle tests, etc. With the increasing UV irradiation time, the molecular weight of PVC increased to a maximum then decreased，polydispersity index increased from 1.771 to 1.919.The carbonyl groups and the conjugated double-bond sequences were generated on PVC chains. Surface of PVC samples became coarse, lots of cracks formed and enlarged，yellowness index increased from 40.7%to 90.28%，and the color turned to dark gradually. The weight loss of PVC samples increased to 0. 22%during UV ir-radiation.At initial UV irradiation，the contact angle to water decreased from 63.3to 55 rapidly and then leveled off to about 50 .The tensile strength of PVC samples increased slightly from 55 MPa to a
maximum 57 MPa and then decreased，while the elongation at break decreased from 35.5%to 11.8%with UV irradiation time.

Key words: polyvinyl chloride), ultraviolet light, aging, molecular structure