Abstract: Chitosan fiber had great potential to be used as absorbent suture and dressing due to good biocompatibility.However,the weak mechanical properties limited its application.In order to expand its application range and value,chitosan fibers were modified by gallnut tannins.The effects of different finishing conditions on the adsorption capacity of chitosan fibers were studied by response surface methodology.The mechanical properties and fluorescence properties of chitosan fibers before and after finishing under optimum finishing conditions were compared.Results indicated that the thermodynamics of the adsorption of chitosan fibers by gallnut tannins conformed to the Langmuir adsorption isotherm model and the kinetics accorded with the quasisecondary kinetic model.In addition,the optimal conditions for the adsorption of chitosan fibers by gallnut tannins by response surface method were:pH=3,temperature was 70 °C,time was 32.1 min and the amount of gallnut tannins was 14.3%.Under this condition,the adsorption capacity of gallnut tannins was 127.1± 0.2 mg/g.Compared with chitosan fiber before finished,the breaking strength was increased by 7.4%,the initial modulus was increased by 30%,and the tensile strength at the certain elongation of 3% was increased by 32.4%.At the same time,the fluorescence intensity was also enhanced by about 3 times.This experiment provided a new way to improve the performance of chitosan fibers.

Key words: gallnut tannins, chitosan fiber, modification, functional fiber