**5.1 Native lignin**

Lignin has many applications; one of them is direct combustion of lignin as black liquor as a fuel and power in paper and wood pulping industry. Also the native lignin increase combustion heat to bio-fire made of propane-1,3-diol and cellulose. In view of its binding stuffs, it is commonly used as a stabilizer in coal briquettes in which it raises the boiling speed and strength in packing paper material. Regardless of the importance of lignin for power generation, it has many other uses like as toluene or benzene, nontoxic binder in pelleted feeds, nonhazardous chelating agent, transporter of nutrients as lignosulfonate for the plants to discharge them gradually in the soil. Lignin can also

be use as a sequestrant of heavy metals (e.g. zinc, nickel, cadmium and mercury) for purification of polluted water due to chelating property [26, 52].

## *5.1.1 Polymers from native lignin*

Native lignin can be an outstanding preparatory material for making of polymer composites with other molecules through covalent bonds. Additionally, as an additive the native lignin can protect polymers from high temperature, light and oxidation. The most essential linkages are the hydroxyl groups in polymerization. Remarkably, the steric interruption decrease the reactivity of lignin and due to fairly small amount of free active hydroxyls, still the use of lignin in polymer materials has been successful. For example, in the reaction between phenol and formaldehyde for production of phenol-formaldehyde adhesives of chipboards, plywood etc., lignin is convenient as a substitute for phenol binding reagent. Similarly, lignin can be blended in polyethylene, polypropylene, to change its mechanical properties and improving the oxidative resistance. Kraft-lignin as an unmodified material used in polyesters as a reaction monomer has been reacted with sebacoyl chloride, increased the recycling of subsequent polymer. Native lignin has many other applications also, it can react with polyethylene glycol (PEG) and methylene diphenyl isocyanate to make polyurethanes, biodegradable foam, cheap composites, bioplastic materials mixed with cellulose fibers, cellulose-lignin based hydrogel, medical devices or controlled drug release exercises [26, 52].
