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Open AccessArticle

Producing Lignin-Based Polyols through Microwave-Assisted Liquefaction for Rigid Polyurethane Foam Production

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Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China
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State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510641, China
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Author to whom correspondence should be addressed.
Academic Editor: Naozumi Teramoto
Materials 2015, 8(2), 586-599; https://doi.org/10.3390/ma8020586
Received: 19 December 2014 / Accepted: 3 February 2015 / Published: 10 February 2015
(This article belongs to the Section Structure Analysis and Characterization)
Lignin-based polyols were synthesized through microwave-assisted liquefaction under different microwave heating times (5–30 min). The liquefaction reactions were carried out using polyethylene glycol (PEG-400)/glycerol as liquefying solvents and 97 wt% sulfur acid as a catalyst at 140 °C. The polyols obtained were analyzed for their yield, composition and structural characteristics using gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra. FT-IR and NMR spectra showed that the liquefying solvents reacted with the phenol hydroxyl groups of the lignin in the liquefied product. With increasing microwave heating time, the viscosity of polyols was slightly increased and their corresponding molecular weight (MW) was gradually reduced. The optimal condition at the microwave heating time (5 min) ensured a high liquefaction yield (97.47%) and polyol with a suitable hydroxyl number (8.628 mmol/g). Polyurethane (PU) foams were prepared by polyols and methylene diphenylene diisocyanate (MDI) using the one-shot method. With the isocyanate/hydroxyl group ([NCO]/[OH]) ratio increasing from 0.6 to 1.0, their mechanical properties were gradually increased. This study provided some insight into the microwave-assisted liquefied lignin polyols for the production of rigid PU foam. View Full-Text
Keywords: microwave heating; lignin; liquefaction; Polyurethane (PU) foam microwave heating; lignin; liquefaction; Polyurethane (PU) foam
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MDPI and ACS Style

Xue, B.-L.; Wen, J.-L.; Sun, R.-C. Producing Lignin-Based Polyols through Microwave-Assisted Liquefaction for Rigid Polyurethane Foam Production. Materials 2015, 8, 586-599.

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