Structural investigations of crosslinked cellulose derivatives
Аннотация
Abstract Electron microscopy methods are used for investigation of the structure of cellulose fibers modified by some bifunctional reagents (dimethylolurea, formaldehyde, acrolein, epichlorohydrin, and propylene oxide). For sample preparation, mechanical and ultrasonic dispersion, ultrathin sectioning, and treatment by some reagents were used. Some data were obtained indicating extensive changes of the fiber supermolecular structure as a result of crosslinking between the structural elements. These changes are expressed in redistribution of the effective dimensions of structural elements toward their increasing (increase in layer thickness and diameters of fibrillar bundles) and even in the alteration of mutual arrangement of structural elements under very high degrees of substitution, as compared with the untreated fibers. Modification may proceed not only in the most accessible regions of the fiber, between the microfibrils as well as between the secondary wall layers, but also inside the microfibrils themselves, and in some cases affects the most dense fiber regions—crystallites. All these changes of the supermolecular structure after modification leads to essential alterations in the mechanical properties of the fibers.