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Using cheap and green lignin as a partial substitute for petroleum-based polyols is highly attractive for sustainable development of polyurethane elastomers (LPUes). However, the traditional synthesis process of LPUes inevitably uses toxic solvents that are difficult to remove or carcinogenic. Here, we reported a solvent-free synthesis method to prepare lignin-containing polyurethane elastomers (SF-LPUes) with high strength, high toughness and high elasticity. Most of the hydroxyl groups of lignin reacted with isocyanates to form a strong chemical cross-linking network, while the unreacted ones formed a dynamic hydrogen bond network with polyurethane matrix, contributing to the in-situ formation of lignin nanoparticles to build a nano-micro phase separation structure. Consequently, a dual-crosslinking network structure was formed and endowed SF-LPUes with excellent mechanical properties. Especially, the SF-LPUes prepared from low molecular alkali lignin possessed a tensile strength as high as 38.2 MPa, a maximum elongation at break of 1108 %, and an elastic recovery ratio of up to 98.7 %. Moreover, SF-LPUes showed impressing reprocessing performance and aging resistance. This work provides an industrial application prospect for the synthesis of lignin-containing polyurethane elastomers via a solvent-free synthesis process., Competing Interests: Declaration of competing interest The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. There's no financial/personal interest or belief that could affect our objectivity. Our manuscript was submitted only to the International Journal of Biological Macromolecules. All authors approved the submission., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Research on the use of bio-based material rather than fossil fuel-based synthetic polymers is of considerable value due to the increasing interest in biodegradable and ecofriendly products. This paper describes an in-depth analysis of the effect of cellulose nanocrystals (CNC), a promising nanomaterial filler derived from cellulosic biomass, on the mechanical properties of rubber latex thin sheets. Sheets of styrene butadiene rubber (SBR) and its bio-based alternative, natural rubber (NR) were tested and compared. Percolation of CNC was studied within the rubber matrices, where the tear strength, water permeability, and water absorption increased due to the formation of a continuous network of CNC within the polymer thin sheets. The rubber nanocomposites were resistant to tear propagation, caused by increased tortuosity along the tear path brought about by CNC dispersion and filler network formation. The CNC reinforcement yielded thin sheets that were much stronger and more durable than their non-reinforced counterparts. Additionally, the increased water uptake of the sheets could aid in the biodegradation of the polymer. Thus, CNC is found to be an excellent functional filler in rubber sheets, where its formation of a percolating network significantly improved their properties., (Copyright © 2020. Published by Elsevier B.V.)