Effect of Lignin Obtained From Ionic Liquid Pretreated Poplar Wood On the Thermomechanical Properties of Polypropylene

The scarcity of petroleum and resulting variable costs of its derived products coupled with environment consciousness and increased usage of resources due to continued growth of population has triggered the research in the development of sustainable alternatives. Thus, scientists around the world have been focusing on plant biomass which is a rich carbon source and is available abundantly on earth. In addition, being renewable and carbon dioxide neutral added to its increased attention.

Biomass predominantly consists of cellulose, hemicellulose and lignin. Cellulose is a highly crystalline polymer of glucose while hemicellulose is a polymer of xylose and other sugar derivatives. Lignin is a high-molecular weight polyaromatic macromolecule that structurally binds both cellulose and hemicellulose. These three components are intertwined with complex linkages to form a structurally rigid and chemically resistant substance, which makes it very difficult to break them down for further development of bioproducts. However, over the past few decades lots of research is being conducted in breaking down biomass into its individual constituents either by pretreating the biomass with acids, bases or ionic liquids. Among them ionic liquids pretreatment methodology has gained increased attention especially owing to its environment-friendliness.

In this work, the byproduct of ionic liquid based cellulosic ethanol platform viz. lignin was studied to investigate its ability as reinforcement in polypropylene based composites. The composites were fabricated via micro-extrusion and micro-injection molding processes and the thermomechanical properties have been evaluated using various characterization techniques such as tensile testing, differential scanning calorimetry, thermogravimetric analyzer etc. For comparison, polypropylene-organosolv lignin (model lignin) composites have also been fabricated and tested.