Lignin Chemical content

Symbol of Sample Symbol of Initial Product Type of Lignin Used Type of Modifying Compound Yield of Product3, g Chemical Content. P S % Cl Infrared Frequency of P-N Unit, crn l... 

The chemical content in pineapple fiber is similar to that in flax and jute fiber (Table 2.8), but the lignin content in pineapple leaf fiber is more than that in flax (2—7%) and less than that in Jute (10—18%). Composition and properties of pineapple leaf fiber and bundle fiber are shown in Tables 2.9 and 2.10 [11]. 

Chemical pulps are produced in a digester where the wood is cooked in pressurized vessels using heat and chemicals to break the intercellular stmcture of the wood and extractives. The objective is to remove the lignin from the fibers without degrading the carbohydrate content of the wood. 

Chemical charge, Hquor composition, time of heatup, and time at temperature of reaction are all functions of the wood species or species mix being digested and the intended use of the pulp. A typical set of conditions for southern pine chips in the production of bleachable-grade pulp for fine papers is active alkaH, 18% sulfidity, 25% and Hquor-to-wood ratio, 4 1. Time of heatup is 90 min to 170°C time at temperature of reaction, 90 min at 170°C. Hardwoods require less vigorous conditions primarily because of the lower initial lignin content. 

Softwoods are generally more resistant to acids than are hardwoods because they have high lignin and low hemiceUulose contents. In general, heartwood is more resistant to acids than sapwood, probably because of heartwood s higher extractive content and slower movement of Hquid into the heartwood. For these reasons, the heartwood of certain conifers has been widely used in the chemical industry. 

The viscosity range of CN products can be adjusted in advance by choosing the starting cellulose with an appropriate degree of polymerization (DP). A study of the different celluloses examined the impact of various cellulose properties, such as morphological factors (percent crystallinity, fiber length, and distribution), chemical composition (DP, ash content), and hemiceUulose and lignin content, on the nitration behaviors of cellulose (55). 

---