Study On Surface Grafting Polymerization Of PP Tower Packings

In this thesis, surface grafting polymerization of cast polypropylene (CPP)/acrylic acid(AA) system was studied with the two-step method and the suspend solid-phase grafting method, and the effects of various factors were explored. Furthermore, these results were used to guide the grafting polymerization of PP tower packings, in order to improve the surface hydrophilicity of tower packings.The two-step method consists of two steps. Firstly, dormant groups were introduced on the CPP, and then, AA was grafted on the substrate surface by thermoactivating polymerization. The results show that acetic anhydride is an ideal solvent for CPP/AA surface grafting system; grafting yield increases with the growth of photosensitizer and monomer concentration; and polymerization temperature has positive effect on Grafting Yield. The contact angle of grafted CPP film against water decreases with the increase of Grafting Yield. The crystallity of PP slightly increased after grafting polymerization.The suspend solid-phase grafting method includes two procedures in this study. PP film was dipped in solution of benzoperoxide (BPO)previously, and then the PP film containing BPO was grafting polymerized in AA aqueous solution. The results show that:toluene is more effective to make PP film swelling than acetone dose, if used as the solvent of BPO; lengthening the dipping time and enhancing temperature lead to increased amount of BPO absorbed by PP film. To the grafting polymerization, both increasing the concentration of BPO and the concentration of AA, and enhancing the temperature enable grafting polymerization to take place more smoothly. The contact angles of the grafted films against water decrease obviously, indicating the surface hydrophilicity of the grafted PP film is improved markedly. The crystallity of PP was influnced by crosslinking and grafted chain.Because of their complicated configuration, the two-step method is limited to PP tower packings. When the above conditions of suspend solid-phase grafting polymerization were applied, the grafting yield of tower packings was low. It was found that the grafting yield could be enhanced by thermoswelling the tower packings with xylene in advance. Simultaneously, the swelling temperature and time, the reaction time and temperature have great effect on grafting yield. So the affinity of packings for water is improved.The existence of the dormancy groups on PP film was identified by UV-Vis spectra. The grafted chains of PAA were determined with FTIR spectra. The state of the PP's surface was measured by SEM. The photosshowed the primitive PP film was smooth, while the surface of grafted film was globular. The hydrophilicity of PP film was measured by contact angle. The crystal structure and thermal behaviour of PP-g-AA was studied by WAXD and DSC.