Modification of Lignin
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Modification of Lignin book
L INTRODUCTION Lignin [8068-00-6] is a natural product produced by all woody
plants. It is second only to cellulose in mass of the natural polymer formed per annum (1). Lignin constitutes between 15 and 40 percent of the dry weight of wood with variation in lignin content being caused by species type, growing conditions, the parts of the plant tested, and numerous other factors (2). The data of Table 1 show the variation of lignin content by species type. Plants use lignin to 1. add strength and structure to their cellular composites; 2. control fluid flow; 3. protect against attack by microorganisms; 4. act as an antioxidant, a UV absorber, and possibly a flame retardant; and 5. store energy (3). When considering the present and future use of this biopolymer, it is important to realize that any archeological age, such as the iron age, starts and also ends before the participants realize it. We are currently at the end of the age of oil. The slow decline in available oil reserves during the early 21^ century will make lignin a more important source of chemicals for our future society. When fundamental technology within a society changes, decades of work preceding the change must have occurred to develop new technologies to replace those that are obsolete. As the age of oil changes to the age of biomass, some of the chemical modifications described below will become important industrial processes for producing the chemicals and materials that society needs.