Bulk Grafting Modification Of γ-ray Activated Polymers In Supercritical Carbon Dioxide

Supercritical fluids, defined as any state point above critical temperature and critical pressure of one substance, have some properties of liquid and gases. Since carbon dioxide (CO₂), which has an easily accessible critical point is nontoxic, nonflammable and inexpensive, it can be used as environmentally benign solvent for replacing hazardous organic solvent and thereby has received much attention.In this thesis, a novel approach is presented for bulk uniform graft-modification of vinyl monomers to pre-existing polymeric materials by combining gamma (γ)-ray pre-irradiation-induced graft copolymerization and supercritical carbon dioxide (SC-CO₂) -swelling polymerization techniques.The bulk grafting modification of various polymeric materials such as isotactic polypropylene (i-PP), low density polyethylene (LDPE), poly(vinyl chloride) (PVC) and silicon rubber were succeeded in catching out in SC-CO2 with the use of diffirent vinyl monomers such as styrene, N-vinylpyrrolidone (NVP), methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH) and acrylonitrile (AN). The effects of reaction temperature, pressure and time on grafting yield have been investigated in detail. The result indicates the grafting reaction can be controlled by simple altering the experimental conditions.The graft-copolymers were characteristiced by means of FTIR, DSC, GPC, SEM, TEM methods, as well as element analysis and some of them were further measured their hydrophilic properties. The results show that grafting reaction predominant occured in the polymer backbone and grafting chains of 50nm length were uniformly distributed in the modified polymers.The graft-modification of hydrophilic vinyl monomers to polymeric materials resulted in an obvious increase in hydrophilicity as well as polarity.