Biobased structurally compatible polymer blends based on lignin and thermoplastic elastomer polyurethane as carbon fiber precursors

The production of carbon fibers based on lignin reduces the cost and the environmental impact associated with carbon fiber manufacture. However, the melt processing of lignin as a carbon fiber precursor is challenging due to its brittleness and limited thermoplastic behavior. For this reason we produce biopolymer blends based on Alcell organosolv hardwood lignin, hydroxypropyl modified Kraft hardwood and a thermoplastic elastomer polyurethane (TPU). Samples with TPU content greater than 30 % showed excellent melt processability and carbonization yield (35 % carbon yield for the samples containing 30 % of TPU). The thermal properties were analyzed by differential scanning calorimetry, rheology and thermogravimetric analysis. Fourier infrared measurements were utilised to explain the lignin/TPU interactions which governed the thermal and rheological behaviour of the blends. SEM analysis showed that the blends produce a homogeneous structure which was void free after carbonization. These structurally complimentary biopolymeric blends should open up new avenues for lignin valorization and bring closer the realization of the production of carbon fibers from biosources.