The preparation of a novel polymeric photostabilizer was carried out via the vibromilling of poly(vinyl chloride) (PVC) powder, a reactive light stabilizer (r-LS), and a peroxide initiator in ball-containing jars with a planetary ball mill for a certain time. The effects of the initiator content, milling time, and temperature on the grafting ratio were studied with gravimetric analysis and intrinsic viscosity measurements. Fourier transform infrared and ultraviolet visible spectra were used to investigate the structural development of the mixture of the r-LS and PVC during vibromilling. The results showed that the r-LS was grafted onto PVC chains successfully, and the aforementioned factors had a significant effect on the grafting ratio. The optimum preparation conditions were 0.5 wt % initiator, 8 h, and 20 degrees C. A grafting mechanism is proposed. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3079-3086, 2010