Influence of alkali-freezing treatment on the solid state structure of chitin.

Chitin was soaked in frozen sodium hydroxide for further modification. The solid state structural changes of the resulting chitin powders were studied by X-ray diffraction (XRD) and infrared spectroscopy measurements. During the alkali-freezing process, the crystal space parameters of chitin changed, and the order of the hydrogen bonds of chitin was modified. The study explains how the treatment is beneficial for further modification of chitin. The crystallinity of chitin was assessed according to XRD results. It decreased by half after the alkali-freezing treatment for the first 3 days, and then a few changes happened on the following days while the crystallinity of chitin was kept in the scale of 13.5-18%. That means that the alkali-freezing treatment of chitin for several days is suitable and sufficient.