Preparation And Release Properties Of Ethrel/Chitosan Complex Film

A complex film containing chitosan as a carrier and ethrel as a release agent was fabricated via a casting method. The structure, mechanical property and moisture absorption of complex film were characterized by fourier transform infrared spectroscopy(FT-IR), X-Ray diffraction(XRD), thermo-gravimetric analysis(TG), polarizing microscope(POM), scanning election microscopy(SEM) and universal materials tester; the release property of the complex film in the air dielectric and buffer solution was studied respectively, and the release mechanism was analyzed; The banana ripened by complex film was controllable at room temperature. The relationship between release property and controllable ripening of complex film was studied. The results showed that:1. The mechanical property of chitosan film was changed with the increase of ethrel. The tensile strength was enhanced and the elongation at break was reduced when the content of ethrel was less than25%. The moisture absorption rate of complex film was decreased with the increase of ethrel when the content of ethrel was less than20%.2. The results of FT-IR、XRD、TG、SEM and POM indicated that ethrel and chitosan were not a simple physical adsorption but combined with salt bond. The molecular chain structure and crystal type of chitosan were not changed, but there were some impacts on crystallinity and smoothness of the complex film. The appearance of complex film was changed clearly when the ethrel content reached30%. The decomposition temperature of complex film was lower than pure chitosan film by65℃.3. The release rate of ethylene of complex film was positively correlated with the relative humidity and was negatively correlated with the content of ethrel. When the ethrel content of complex film was20%and the relative humidity raised from54.5%to97.7%, the half-life of ethrel in complex film dropped from16.6days to5.9days. In buffer solution the release rate was positively correlated with the pH value of buffer solution, and the half-life of ethrel in complex film was unconnected with the concentration of ethrel.4. The controllability of release rate was based upon the alkalescence of amine groups of chitosan and the controllability of moisture absorption rate of complex film. The release reaction of ethrel in the buffer solution showed up the kinetics characteristic of a first order. The structure and smoothness of the surface were badly affected by the release of the ethlyene, but had no effect on the chemical component and crystal type of chitosan. And we found mineral crystal grown on the surface of the complex film during the release of ethylene.5. The ripening effect of complex film on banana was controllable, The bananas which were close to the complex film matured in2days, but it needed4days when bananas were away from the complex film. As the banana matured, soluble sugar increased by11.5%and soluble protein increased by10%. This ripening method was different from conventional method, for example, the film was not in direct contact with the garden stuff when used in practice, a large reduction of pesticide residue could be observed, and the ripening rate was controllable in this way.