Thermal modification lignin

New trends in the modification of lignins related to the formation of polymeric materials with such special properties as thermal stability, fire resistance and use as carriers for controlled release, bioactive compounds are discussed. Several properties of new polymeric materials, especially their thermal behavior, were studied. 

The modification of lignins with chlorophosphazenes allows the manufacture of products characterized by flame resistance and thermal stability. This can be attributed to the aromatic structure of the lignin-phosphazene polymer as well as to the presence of such flame inhibiting elements as phosphorous, nitrogen and sulfur. Other useful properties may also result from this combination. It has previously been reported (8-13) that the modification provides crosslinked products with suitably low chlorine content. This is a consequence of incomplete substitution of the phosphazenes cycles. Additional modification of the reaction products by chemical compounds with reactive hydroxyl or amine groups reduces the unreacted chlorine content and improves product properties (8-13). Some properties of the derivatives obtained are presented in Table I. 

Reaction of kenaf with succinic anhydride were done in xylene at 120°C and WPGs up to 80% were achieved [32]. Dynamic mechanical analysis was done on acetone-extracted esterified fibers in the WPG range of 30-80. The data showed that there was a reduced transition temperature from about 170°C down to about 135°C and that there was no change in this first transition temperature as the WPG increases. The data showed that complete modification of that melting species had taken place at a WPG of m35. This thermal behavior is similar to reported trends observed for water-plasticized lignin in wood. 

Modification of Polysaccharides and Oligosaccharides, and Uses of Modified Polysaccharides and Oligosaccharides Introduction.—A book entitled Polysaccharide Shapes has discussed how the units of polysaccharides link together to confer a unique set of properties on the chain. Papers presented at a symposium on the thermal uses and properties of carbohydrates and lignins have covered some aspects of the pyrolysis of natural polysaccharides. ... 

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