engleski

Improvement of the polymer stability by radiation grafting

Losses of the stabilizer due to extractability or volatility immediately affect ultimate performance of polymer product. New approach to increase the persistence of the stabilizer in final product is to chemically bind it to the polymer backbone. Radiation grafting or crosslinking could be efficient method for it, when the stabilizer is polymerizable. By mutual gamma irradiation method photoprotector 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone (HMB) has been readily grafted to low density polyethylene (LDPE) in benzene, tetrahydrofuran and methanol solution, respectively. Surface grafting occurs in methanol solution of stabilizer, while in benzene and tetrahydrofuran solutions of stabilizer grafting proceeds more or less in the inner parts of polymeric film as well. The grafted LDPE film in methanol and tetrahydrofuran (containing 1 w/w % of grafted HMB), 1 w/w % blended HMB with LDPE and nongrafted LDPE film, were all exposed to accelerated aging and natural weathering and their spectral changes expressed by the carbonyl index, were then compared. The change of elongation at break and tensile strength were measured in the course of aging. UV stability tests on aged films and change in mechanical properties indicate pronounced protective effect achieved by grafted stabilizer. Grafting in methanol solution appears to be efficient photostabilization treatment and most economical one with respect to the consumption of monomer, grafting yield being less than 0.5%. Surface grafting is efficient photostabilization method since grafted stabilizer is chemically bound to a polymeric surface and in this way the problem of evaporation of blended stabilizers during the prolonged use of polymeric materials is eliminated.

photostabilization of LDPE; radiation grafting; chemically bound stabilizer; artificial and natural grafting

Rad je kao pozvano predavanje prezentiran na skupu 13th International Meeting on Radiation Processing (IMRP-2003), održanom do 07.-12.09.2003.g., Chicago, SAD ; objavljen u Knjizi sazžataka / John Masefield (ur.) ; 2003. ; str. 173-173.