| Abstract: | Polyolefins (LDPE and HDPE) can be ozonized with ozone/air gas flow to create peroxide and hydroperoxide groups on polymers. These reactive groups can be used to initiate radical polymerization of vinylic monomers and produce graft copolymers. In this study, the optimization of the experimental conditions and the explanation of the phenomena occurring during the ozonization of polyolefins in a fluidized bed have been studied. The most reproducible methods for placing peroxide and hydroperoxide groups onto polyolefins are the iodometric method and indirect titration by thiol. This work shows that it is necessary to control the temperature of the fluidized bed to avoid the acceleration of the reaction and the degradation of the polymers. Then, we studied the effect of different parameters such as the crystallinity and the granulometry of polymers, the time of ozonization and the effect of the load of the reactor on the quality of ozonization. Infrared spectroscopy and steric exclusion chromatography were used to characterize the ozonized polymers. We show that double bonds of PE, particularly vinyl groups, are very reactive to ozone and that ozonized HDPE leads essentially to the formation of hydroperoxide groups, whereas ozonized LDPE leads to the formation of peroxide groups. |
