Photo-oxidative degradation of some water-soluble polymers in the presenceof accelerating agents

The unsolved problem of plastic waste utilization has led to a great intere st in the development of studies of accelerated degradation of polymers. In this work the course of photo-oxidative degradation of some water soluble polymers such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA) and poly(vinylpyrrolidone) (PVP) in the presence of hydrogen peroxide has been investigated. The following methods have been applied: viscometry, LR and UV-Vis spectroscopy, gel permeation chromatography and chemical analysis. T he hydrogen peroxide is an unstable compound which undergoes photolysis upo n UV irradiation. Free radicals (HO. and HO2.) formed in this process are e fficient initiators of polymer degradation. The changes of the viscosity an d the average molecular weighs indicate that the rate and efficiency of pho todegradation of PAA, PMA and PVP in the presence of H2O2 is much higher in comparison with respective values obtained in the absence of this agent. S pectroscopic data show that some simultaneous competitive processes (degrad ation, oxidation and chromophores formation) take place in UV irradiated po lymers. In PAA photocrosslinking reaction occurred. The efficiency of this reaction was estimated by the amount of formed insoluble gel. Contrary to d egradation, photocrosslinking of PAA was hampered by H2O2 It was found that photochemical reactions in polymers depend on the concentration of H2O2 an d dose of UV irradiation. The mechanisms of reactions occurring in the stud ied systems have been discussed. Moreover, the influence of the chemical st ructure of macromolecules on the course of photo-oxidative degradation has been considered. It has been also shown that acceleration of PVP photodegra dation by H2O2 is larger than that by FeCl3. Some additional data indicatin g the changes of physical properties of photodegraded polymers have been pr esented. It can be concluded that hydrogen peroxide may significantly accel erate the decay of water soluble polymers present in municipal sewers.