Physical Properties of Lignin

Table 3 Physical properties of lignin- or carbon black-loaded CB-BRs...

Wood is a composite material that is made, up basically of a mixture of three main constituents, cellulose, hemicellulose, and lignin (see Textbox 54), all of them biopolymers synthesized by the plants, which differ from one another in composition and structure (see Textbox 58). The physical properties of any type of wood are determined by the nature of the tree in which the wood grows, as well as on the environmental conditions in which the tree grows. Some of the properties, such as the density of wood from different types of trees, are extremely variable, as can be appreciated from the values listed in Table 71. No distinctions as to the nature of a wood, whether it is a hardwood or a softwood, for example, can be drawn from the value of its specific gravity. 

It is well known that the structure, distribution and properties of protolignin in cell walls vary according to cell type and morphological location. This is based upon extensive studies on topochemical properties of lignin using various methods such as ultraviolet microscopic photometry (1,2), bromination-SEM-EDXA (3) and other physical or chemical analyses of isolated tissue fractions (4). 

In woody gymnosperms, there are significant differences in the distribution, reactivity and physical properties of protolignins found in the compound middle lamella and the secondary wall (1-3). Additionally, variations between lignins in vessels and fibers have also been noted (3). All of these... 

The hydroxyl content of the lignin was incrementally eliminated by acetylation and ethylation according to previously described procedures (11). In addition, modification with propylene oxide was also used to alter the original lignin structure (12). Table I presents a summary of the hydroxy content, and pertinent physical properties, of the derivatized lignins. 

We have shown by our ISO brightness and Ak measurements that the lignin was attacked by the reactive species created by the y irradiation. The results indicate that the reactive species created attack indiscriminately the phenolic hydroxyl or coniferalde-hyde groups and the quinone groups. The decrease in physical properties is associated with die attack on the micro fibrils cellulose. However, at 3000 krad/h, the increase in the ISO brightness is smaller than the one observed around 300 krad/h for the TMP, while the physical properties of the pulp are affected more profoundly at 3000 krad/h than at 300 krad/h. The physical properties of the P-TMP behave similarly, while the increase in brightness is negligible at 3000 krad/h for P-TMP. 

Farrell RL, Murtagh KE, Tien M et al (1989) Physical and enzymatic properties of lignin peroxidase isoenzymes from Phanerochaete chrysosporium. Enzyme Microb Technol 11 322-328... 

Occurrence, formation, structure and reactions. Wiley-Interscience, New York,, 597- 637 Goring DAI (1962) The physical chemistry of lignin. Pure Appl Chem 5 233-254 Goring DAI (1971) Polymer properties of lignin and lignin derivatives. In Sarkanen KV, Ludwig CH (eds) Lignins. Occurrence, formation, structure and reactions. Wiley-Interscience, New York, 695-768... 

The degree to which physical properties of polyols depend on the nature and prior treatment of the lignin employed in the oxyalkylation reaction is indicated in Table IV. Polyols pre-... 

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