Release of biocides from polymeric carriers coated with soluble polymers
Beads of crosslinked dextran gel with an average diameter of 9.6x10-2mm containing about 5% 2,4,5-trichlorophenol, 8-hydroxyquinoline or codeine have been coated with a layer of polymer soluble in the medium used in tests (water or dilute solution of hydrochloric acid): polyvinylpyrrolidone (PVP) or a copolymer of dimethylaminoethyl methacrylate and methyl methacrylate (DAMA/MM A). The kinetics of release of biocide from such systems and from system coated with two polymer layers: insoluble of poly(vinyl acetate) (PVAC) and soluble — of PVP or DAMA/ MM A copolymer, has been investigated. In general, the kinetics of release is well described by an exponential equation (1). The polymeric coating decreases the rate of biocide release. The initial period of release during which dissolution of soluble polymer layer takes place, obeys the kinetic equation of О-order. The kinetics of release of codeine during 6 hours to dilute hydrochloric acid from Wofatit KPS ion exchanger resin, uncoated or coated with a layer of PVAC or DAMA/MMA copolymer or with two layers: PVAC and DAMA/MMA copolymer, has been also determined. In the case of these systems no effect of the coating layer on the rate of biocide release has been observed.
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