Enzymatic Modification Of Polylactic Acid Fiber

Polylactic acid (PLA) fiber is a new eco-fiber, which not only owns the basic characteristics of synthetic fibers but also is a nature fiber with biocompatibility and biodegradability. Polylactic acid fiber is more competitive than other textile products which using oil as raw material in many aspects. Yet as a kind of aliphatic polyesters, it contains large numbers of esters bonds in its molecular structure, which makes it low hydrophilicity.To improve some performances of PLA fiber, lipase L3126 and Lipex100L was chose to hydrolyze ester bonds of PLA fiber in this article. Through evaluation indexes such as weight loss, drop time, dyeing performance, UV absorbency, pH value, the content of lactic acid and by means of SEM, XPS, HPLC and so on, the performance changes of PLA fiber and enzymatic solution were analyzed. Effects of plasma pretreatment to hydrolysis were also pilot studied in this paper.Technics of treatment by the two lipases were investigated to educe the optimal conditions. And treatment effect with different lipases was compared also. The results showed that the optimal conditions for lipase L3126 were determined: enzyme concentration 0.5g/L, pH 8.5, treating at 45℃for 8 hours; the optimal conditions for lipase Lipex100L were determined: enzyme concentration 10mL/L, pH 7.5, treating at 40℃for 10 hours.After dyeing with reactive black S-EO, reactive blue HN-GR and basic blue X-GB, K/S value of the treated fiber was higher than untreated fiber obviously. The scanning electron microscopy confirmed that the two kinds of lipases we chose all had effects on the polylactic acid fiber. Through XPS analysis it was indicated that after treated with lipases, the content of C descended, the content of O ascended and the content of carboxyl and hydroxyl increased. pH value of lipase solution was taken on dropping current. The hydrolysis can produce lactic acid substance in terms of UV analysis and HPLC. The action to polylactic acid fiber of lipase L3126 was better than lipase Lipex100L.Plasma pretreatment was adopted in this paper. The longer plasma treatment time and the greater discharge power and the larger discharge pressure were, the bigger UV absorbency was. Hydrolysis production analysis and the change of dyeing performance all indicated the plasma pretreatment accelerated the reaction of hydrolysis catalyzed by lipases.