Qualitative and quantitative analysis of lignins from different sources and isolation methods for an application as a biobased chemical resource and polymeric material

Abstract

Lignins in general have been extensively studied, though the relation between source, isolation method and application is rarely described. In the present work, lignin from different sources (wheat straw and beech wood) and isolation methods (steam explosion, Organosolv) has been characterized regarding their application as a chemical resource and polymeric material. A range of analytical methods were applied including elemental analysis, FT-IR, 31P NMR, SEC, Py-GC-MS and HPLC to gain information about establish the purity, structure, molecular weight, thermal behavior and to determine carbohydrate residues according to the NREL protocol. TGA and DSC were used to study the thermal behavior of the isolated lignins and showed relatively low glass transition temperatures around 120 °C and decomposition temperatures between 340 and 380 °C. NREL analysis presented a carbohydrate-free lignin fraction derived from beech wood via Organosolv process which has not been achieved to date. The finding of this work supports Organolsolv as an efficient method to isolate pure lignin fractions from beech wood with practical value in industry, in particular for application in polyurethanes and phenolic resins.