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Synthesis of Reprocessable Lignin-based Non-isocyanate Poly(imine-hydroxyurethane)s Networks
Received:October 27, 2020    Click here to download the full text
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Author NameAffiliation
Xue Danwei College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi Province, 710021, China 
Xue Bailiang College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi Province, 710021, China
Key Laboratory of Pulp and Paper Science & Technology of Ministry of Education, Qilu University of Technology (Shandong Academy of Sciences), Jinan, Shandong Province, 250353, China 
Tang Rui College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi Province, 710021, China 
Shen Chao College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi Province, 710021, China 
Li Xinping College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi Province, 710021, China 
Zhao Wei College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi Province, 710021, China 
 
Abstract:In this study, an environmentally friendly and non-toxic route to synthesize lignin-based non-isocyanate poly(imine-hydroxyurethane)s networks was explored. Specifically, the NH2-terminated polyhydroxyurethanes (NPHUs) prepolymer was first synthesized from bis(6-membered cyclic carbonate) (BCC) and diamine via the ring-opening reaction. Subsequently, the corresponding lignin-based non-isocyanate polyurethanes (NIPUs) with tunable properties were synthesized from NPHUs and levulinate lignin derivatives containing ketone groups via the Schiff base reaction. The structural, mechanical, and thermal properties of NIPUs with different stoichiometric feed ratios of BCC and levulinate lignin were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The results indicated that the tensile strength, Young's modulus, toughness, storage modulus, glass transition temperature, and thermal stability of lignin-based NIPUs gradually increased with increasing lignin content, and the highest Young's modulus of 41.1 MPa was obtained when lignin content reached 45.53%. With good reprocessing properties, this synthetic framework of lignin-based NIPUs also provides sustainable non-isocyanate-based substitutions to traditional polyurethane networks.
keywords:lignin  non-isocyanate polyurethane  Schiff base reaction  reprocessing
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