Лако-красочные материалы — производство

Cellulose is the principal structural material in the cell wall of all plants and is also found in algae, bacteria, and animals (tunicates). Approximately 1011 tons of cellulose is formed each year; this puts cellulose among the most important renewable resources in the world [1].

A. Cellulose Structure

Cellulose is a homopolymer of р-D-anhydroglucopyranose monomeric units that are linked via ether linkages between C-1 of one monomeric unit and C-4 of the adjacent monomeric unit (Fig. 1). As illustrated, every other monomeric unit is rotated approxi­mately 180° about the long axis of the cellulose chain when compared to its two neighbor­ing monomeric units. Because of this rotation, cellobiose is usually considered to be the

The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U. S. government employees on official time, and it is therefore in the public domain and not subject to copyright.

repeat unit of the cellulose polymer. Chain lengths in cellulose can range from 700 to 25,000 glucose units, depending on the source [2]. The two most common sources for cellulose are cotton linters and wood pulp, with approximate chain lengths of 1000­5000 and 500-2100 glucose units, respectively.

As a result of the large number of hydroxyl groups, cellulose molecules readily form hydrogen bonds with other cellulose molecules to give highly crystalline structures. Because the hydrogen bonding between cellulose molecules is not easily disrupted, cellu­lose does not dissolve in most common solvents. As a consequence, cellulose itself is not useful as an adhesive. Instead, cellulose is converted to various derivatives that can be used in the formulation of adhesives. Both esterification and etherification reactions can be carried out at the hydroxyl groups of cellulose. These cellulose esters and ethers can readily be dissolved into aqueous or organic solvents. Certain derivatives are thermoplas­tic and thus have been used in plastics and as hot-melt adhesives.