Original Research ARTICLE
The Effect of Plant Source on the Properties of Lignin-based Polyurethanes
- 1University of Tennessee at Knoxville, United States
This work increases our understanding of the effect of plant source on the mechanical and morphological properties of lignin-based polyurethanes. Lignin is a polymer that is synthesized inside the plant cell wall and can be used as a polyol to synthesize polyurethanes. The specific aromatic structure of the lignin is heavily reliant on the plant source from which it is extracted. These results show that the mechanical properties of lignin-based polyurethanes differ based on lignin’s plant source. The morphology of lignin-based polyurethanes was examined using atomic force microscopy and scanning electron microscopy and the mechanical properties of the lignin-based polyurethane samples were measured using dynamic mechanical analysis and Shore hardness (Type A). The thermal analysis and morphology studies demonstrate that all polyurethanes prepared form a multiphase morphology. In these polyurethanes, better mixing was observed in the wheat straw lignin polyurethane samples leading to higher moduli than in the hardwood lignin and softwood lignin polyurethanes whose morphology was dominated by larger aggregates. Independent of the type of the lignin used, increasing the fraction of lignin increased the rigidity of polyurethane. Among the different types of lignin studied, polyurethane with wheat straw soda lignin exhibited storage moduli ~2-fold higher than those of polyurethanes incorporating other lignins. This study also showed that during synthesis all hydroxyl groups in the lignin are not available to react with isocyanates, which alters the number of cross-links formed within the polyurethane and impacts the mechanical properties of the material.
Keywords: Lignin based polyurethanes, lignin structure, Biomaterials, renewable polymers, lignin plant source
Received: 16 Oct 2017;
Accepted: 01 Feb 2018.
Edited by:Chang Geun Yoo, Oak Ridge National Laboratory (DOE), United States
Reviewed by:MARIA GONZALEZ ALRIOLS, University of the Basque Country (UPV/EHU), Spain
Muhammad Waqas, King Abdulaziz University, Saudi Arabia
Copyright: © 2018 Lang, Shrestha and Dadmun. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Prof. Mark Dadmun, University of Tennessee at Knoxville, Knoxville, United States, email@example.com