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Article

Enhancing Thermal and Mechanical Properties of Ramie Fiber via Impregnation by Lignin-Based Polyurethane Resin

1
Department of Forest Products, Faculty of Forestry and Environment, IPB University, Bogor 16680, Indonesia
2
Research Center for Biomaterials, National Research and Innovation Agency, Cibinong 16911, Indonesia
3
Faculty of Forest Industry, University of Forestry, 1797 Sofia, Bulgaria
4
Faculty of Wood Sciences and Technology, Technical University in Zvolen, 96001 Zvolen, Slovakia
5
Department of Forest Product, Faculty of Forestry, Universitas Sumatera Utara, Medan 20155, Indonesia
*
Authors to whom correspondence should be addressed.
Academic Editor: Francisco Javier Espinach Orús
Materials 2021, 14(22), 6850; https://doi.org/10.3390/ma14226850
Received: 18 October 2021 / Revised: 4 November 2021 / Accepted: 10 November 2021 / Published: 13 November 2021
(This article belongs to the Special Issue Advanced Eco-friendly Wood-Based Composites)
In this study, lignin isolated and fractionated from black liquor was used as a pre-polymer to prepare bio-polyurethane (Bio-PU) resin, and the resin was impregnated into ramie fiber (Boehmeria nivea (L.) Gaudich) to improve its thermal and mechanical properties. The isolated lignin was fractionated by one-step fractionation using two different solvents, i.e., methanol (MeOH) and acetone (Ac). Each fractionated lignin was dissolved in NaOH and then reacted with a polymeric 4,4-methane diphenyl diisocyanate (pMDI) polymer at an NCO/OH mole ratio of 0.3. The resulting Bio-PU was then used in the impregnation of ramie fiber. The characterization of lignin, Bio-PU, and ramie fiber was carried out using several techniques, i.e., Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), pyrolysis-gas-chromatography-mass-spectroscopy (Py-GCMS), Micro Confocal Raman spectroscopy, and an evaluation of fiber mechanical properties (modulus of elasticity and tensile strength). Impregnation of Bio-PU into ramie fiber resulted in weight gain ranging from 6% to 15%, and the values increased when extending the impregnation time. The reaction between the NCO group on Bio-PU and the OH group on ramie fiber forms a C=O group of urethane as confirmed by FTIR and Micro Confocal Raman spectroscopies at a wavenumber of 1600 cm−1. Based on the TGA analysis, ramie fiber with lignin-based Bio-PU had better thermal properties than ramie fiber before impregnation with a greater weight residue of 21.7%. The mechanical properties of ramie fiber also increased after impregnation with lignin-based Bio-PU, resulting in a modulus of elasticity of 31 GPa for ramie-L-isolated and a tensile strength of 577 MPa for ramie-L-Ac. The enhanced thermal and mechanical properties of impregnated ramie fiber with lignin-based Bio-PU resins could increase the added value of ramie fiber and enhance its more comprehensive industrial application as a functional material. View Full-Text
Keywords: fractionated lignin; bio-polyurethane resin; ramie fiber; impregnation; thermal stability; mechanical properties fractionated lignin; bio-polyurethane resin; ramie fiber; impregnation; thermal stability; mechanical properties
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MDPI and ACS Style

Handika, S.O.; Lubis, M.A.R.; Sari, R.K.; Laksana, R.P.B.; Antov, P.; Savov, V.; Gajtanska, M.; Iswanto, A.H. Enhancing Thermal and Mechanical Properties of Ramie Fiber via Impregnation by Lignin-Based Polyurethane Resin. Materials 2021, 14, 6850. https://doi.org/10.3390/ma14226850

AMA Style

Handika SO, Lubis MAR, Sari RK, Laksana RPB, Antov P, Savov V, Gajtanska M, Iswanto AH. Enhancing Thermal and Mechanical Properties of Ramie Fiber via Impregnation by Lignin-Based Polyurethane Resin. Materials. 2021; 14(22):6850. https://doi.org/10.3390/ma14226850

Chicago/Turabian Style

Handika, Sucia O., Muhammad A.R. Lubis, Rita K. Sari, Raden P.B. Laksana, Petar Antov, Viktor Savov, Milada Gajtanska, and Apri H. Iswanto. 2021. "Enhancing Thermal and Mechanical Properties of Ramie Fiber via Impregnation by Lignin-Based Polyurethane Resin" Materials 14, no. 22: 6850. https://doi.org/10.3390/ma14226850

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