Effect of lignin on bio-based/oil-based polymer blends

Lignin is one of the most abundant biodegradable and renewable natural biopolymers after cellulose. The main source of lignin comes from the by-product of the pulp and paper industries. Lignin has been added to various polymers to give blends, while in other cases, composites, depending on the involved interactions. The blending process of lignin with polymers is not easy, since the polarity of lignin molecules results in strong interactions. Moreover, lignin has a complex structure and it is difficult to characterize. Therefore, lignin is often modified in order to improve its miscibility with other polymers. Lignin can be introduced into bio-based polymers (polysaccharides, natural rubber, proteins, and polylactic acid), oil-based polymers (polyester, polyether, polyethylene, and polypropylene), and bio-based/oil-based polymers. The combination of the three materials (lignin, bio-based polymers, and oil-based polymers), such as in the case of polypropylene/polylactic acid/lignin (PP/PLA/lignin), is one of the most interesting cases of blends and composites. This chapter focuses on the effect of lignin on bio-based polymers and oil-based polymers, and special attention is given to the bio-based/oil-based polymer blends and composites.