Preparation And Application Of Ultrafine Chitosan Powders In Modification Of Calcium Alginate Porous Materials

In this paper, ultrafine chitosan powders and ultrafine chitosan powder/calcium alginateporous materials were prepared by high-energy impact grinding and cryogenic induced phaseseparation with chitosan and sodium alginate as raw materials. The effect of parameters on thepreparation of chitosan powders were studied, and the morphology, structure and performanceof chitosan were tested. Designed experimental to detect the pre-freezing conditions ofsodium alginate porous materials, and using ultrafine chitosan powders as addition agent tomodified calcium alginate porous materials, and then the performance of ultrafine chitosanpowder/calcium alginate porous materials were studied. Following results were obtained.The optimal preparation parameters of ultrafine chitosan powders were0.75ml ethanolper gram chitosan as process control agent, the volume ratio of chitosan and zirconium beadswas2:1, zirconium beads diameter was10mm, and impact grinding time was5h. Underthese conditions, which obtained the flour yield of chitosan powders was94%, and theproductivity of ultrafine chitosan powders with31%. On the basis of the optimal preparationparameters of ultrafine chitosan powders, the secondary impact milling to chitosan powderswas studied, the results showed that0.75ml ethyl alcohol per gram chitosan as PCA,according to the volume ratio of chitosan and zirconium beads was2:1, adding8mmzirconium beads, impact grinding time was1h, it obtained that productivity of ultrafinechitosan powders with58%. The particle size distribution of chitosan powders with less than6microns were tested, the results showed that the average diameter of chitosan powders were658nm. It can be seen that the secondary impact milling to chitosan powders could be furthersmashed chitosan and obtained nano chitosan powders.The ultrafine chitosan powders were prepared by high-energy impact grinding. Themorphology of powders was irregular spherical or sheet, the degree of crystallinity andviscosity-average molecular weight slightly reduced, the thermal stability had a little change,chitosan powders had the same absorption peak as chitosan on the infrared spectra. Theabsorbing water capacity and dissolving property of chitosan powders increased with theparticle size of powders decreased. When the particle size distribution of chitosan powderswere less than6microns, which absorbing water capacity and dissolving property were64.62%and8.31%, respectively. Its bulk density was0.341g/ml, and the minimum inhibitoryconcentration of ultrafine chitosan powders to Escherichia coli and Staphylococcus aureus were0.8g/L and1g/L, respectively.The porous materials were prepared by cryogenic induced phase separation. Sodiumalginate solution was coated handle before freezing, which was chosen in the preparation ofporous materials though analyzing the porous appearance of different factors. On the basis ofpre-freezing conditions of sodium alginate solution, influence of the particle size distributionand its content of ultrafine chitosan powders on the performance of calcium alginate porousmaterials had been systematically investigated. The results showed that when adding theweigh of powders relative to the weight of sodium alginate was7.5%, and its particle sizedistribution was43～55μm, it obtained the breaking strength of chitosan powder/calciumalginate porous materials was0.525MPa, and its elongation at break was26.51%, porositywas89.81%, water vapor permeability was66.93g/(g·m3·h), absorbing water capacity was32.48g/g, remaining water capacity was6.84g/g, and the inhibition rate of chitosanpowder/calcium alginate composite porous materials to Escherichia coli and Staphylococcusaureus were64.68%and74.25%, respectively. The porous materials had uniformity pore andsmooth surface, and had a better flexibility.