Systematic Studies on Lignin-Inclusion Thermoplastic Polyurethane Composites Based on the Structure and Properties of Lignin
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초록
내용
Lignin is an attractive candidate for a naturally derived filler. Still, further fundamental research is necessary to determine the best type of lignin for use in a polymer matrix as a filler material. Three different types of lignin extracted from various sources (softwood and hardwood) and different extraction methods (kraft and hydrothermal) were utilized as filler materials to fabricate polymer composites with thermoplastic polyurethane (TPU) through a melt mixing process. Systematic studies focused on the structure and properties revealed that the conservation of aliphatic hydroxyl groups in the lignin structure increases the ordered hydrogen bonds with the TPU matrix. Quantified by various NMR techniques, hardwood lignin extracted by the hydrothermal process (HW-HT) displayed the highest aliphatic hydroxyl group contents with the lowest condensation ratio. A small inclusion of 0.5 vol% of HW-HT in the TPU matrix demonstrated a 58% increase in toughness, and the thermomechanical properties were also improved.