Control of degradation rate of biodegradable polymers (The application of corona discharge treatments)

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Effects of corona discharge treatment on the degradation rate of poly (L-lactic acid) (PLA) and Poly(ε-caprolactone) (PCL) and Poly(butylenesuccinate・adipate) (PBSA) have been investigated The treatment introduced oxygen containing functional groups onto the polymer surfaces The contact angles of these polymers decreased by 30〜60゜ indicating an increase in hydrophilicity on the polymer surfaces The composting degradation tests were carred out for both treated and untreated PLA, PCL and PBSA The treatment depressed the degradation of PLA, while it promoted the degradation of PCL and PBSAThe affinity between microorganisms (general bacteria, actinomycetes, fungi) and the polymer surfaces have also been estimated by a film-contacting method The results showed that the treatment decreased the affinity for PLA due to the production of lactic acid having antibacterial activity by the corona discharge treatment On the contrary, the corona treatment increased the affinity for PCL ~and PBSA Especially, Aspergillus sp rapidly adsorbed to the treated surfaces and has a significant degradation activity for PCL and PBSA The adsorption of lipase (from Aspergillus sp) onto the polymer surface was also increasedTo depress the degradation for several weeks, natural antibacterial substance, which was extracted from Japanese horseradish, was oated on the PCL and PBSA films The sinigrin (extracted from Japanese horse-radish) coated PCL and PBSA films were successfully depressed the degradation for 3 weeks, and then degraded immediately The PLA/starch blends coated with pure PLA and PCL were also made by a conventional coating method to control the degradation rate The degradations of the coated blends were depressed for 2〜4 weeks, after that they degraded immediately