Biopolymers & Biocomposites Workshop - August 14, 2012

Preparation and Properties of Lignin–poly(lactic acid) Graft Copolymer as a Binding Phase in Lignin-poly(lactic acid) Binary Blends

Mahendra Thunga, Ted Angus, Gauri Ramasubramanian, and Michael R. Kessler
Iowa State University

The production of carbon fiber from low-cost renewable resources like lignin has been deterred due to difficulties in processing fine lignin fibers. The complex interconnected structure of raw lignin constrains its ability to be spun and spooled into fibers without additional modifications. In this work, the influence of chemical modification and physical blending of lignin with poly(lactic acid) (PLA) biopolymer on the processability of lignin has been studied. Lignin-PLA graft copolymer was prepared in bulk by ring-opening graft copolymerization of L-lactide in a reactive extruder. The surface hydroxyl groups on lignin were reduced by esterification reaction prior to grafting to enhance miscibility during reactive extrusion. Fine fibers were extracted and spooled continuously from the grafted lignin with an overall lignin concentration of 50%. The influence of blending lignin-PLA graft copolymer in Lignin-PLA binary blends has also been studied to optimize the processing parameters and concentration of lignin for spinning fibers with higher lignin content. The morphology, phase behavior, and carbon yield from the blended fibers with different concentration of lignin have been characterized by transmission electron microscope (TEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA).