SHEAR-PRECIPITATED CHITOSAN POWDERS, FIBRIDS, AND FIBRID PAPERS - OBSERVATIONS ON THEIR FORMATION AND CHARACTERIZATION

Chitosan powders and fibrids were prepared by shear precipitation of d issolved chitosan in a coagulating solution of sodium hydroxide. Follo wing neutralization by washing and an alcohol dehydration step, the wh ite to off-white powders were fine and free flowing. The dried fibrids had a highly oriented, ribbon-like shape that in bulk gave a lofty ap pearance and soft hand. Chitosan fibrids were readily converted to she et structures by typical papermaking procedures. The resulting chitosa n papers were either smooth, flexible, and largely translucent when pr essed dry from the moist mat, or were soft and opaque white when the m oist mat was soaked in alcohol before drying. X-ray diffraction, SEM, and optical microscopy were used to characterize the different chitosa n powders, fibrids, and papers. Chitosan fibrid papers were found to h ave tensile properties comparable to that of cellulosic papers, though the wet strength and water sorption of chitosan fibrid papers was hig her than that of the cellulose controls. (C) 1995 John Wiley & Sons, I nc.