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- Hassani Khorshidi, Fatemeh, et al.
(författare)
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The extraction of polyol for the synthesis of lignin-based polyurethane coatings – a review
- 2024
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 19:3, s. 794-802
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Forskningsöversikt (refereegranskat)abstract
- Lignin, with its availability, aromatic structure, and abundant hydroxyl groups, presents a promising source of green bio-based polyols. The environmental implications of oil-derived polymeric materials have sparked interest in renewable biopolymers and composites from natural sources, including polyurethane composites. This review investigates optimal methods for lignin extraction for use in lignin-based polyurethane coatings, scrutinizes alternatives to oil-based polyols, compares existing chemical modification methods of lignin for use in polyurethane coatings and resins, and discusses the control of synthesis and final properties of lignin-based polyurethane, emphasizing the crucial role of the stoichiometric ratio of NCO groups in the isocyanate to the total OH groups in a lignin-based polyol. While numerous studies have focused on polyurethanes with and without isocyanate, this review describes the synthesis of lignin into bio-polyols and its potential as a substitute for petroleum-based polyols, highlighting organosolv and Kraft lignin as optimal choices for replacing oil-based polyols in polyurethanes due to their high purity.
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- Khorshidi, Fatemeh Hassani, et al.
(författare)
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Color and Gloss Changes of a Lignin-Based Polyurethane Coating under Accelerated Weathering
- 2024
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Ingår i: Journal of Renewable Materials. - 2164-6325 .- 2164-6341. ; 12:2, s. 305-323
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this research study was to investigate the properties of polyurethane coatings based on ligninnano-particles. For this purpose, the prepared coatings were applied to pine wood surfaces and weathered artificially.Subsequently, color and gloss of the coatings were measured before and after the weathering test. Fieldemission scanning electron microscopy (FE-SEM) micrographs prepared from the coatings showed that the averagesize of nano-particles in the polyurethane substrate was approximately 500 nm. Nuclear magnetic resonance(13C-NMR) spectroscopy showed that strong urethane bonds were formed in the nano-lignin-based polyurethane.Differential calorimetric analysis (DSC) test revealed that the glass-transition temperature (Tg) of lignin nanoparticlesmodified with diethylenetriamine (DETA) was 112.8°C and Tg of lignin nano-particles modified withethylenediamine (EDA) was 102.5°C, which is lower than the Tg of un-modified lignin (114.6°C) and lignin modifiedwith DETA (126.8°C) and lignin modified with EDA (131.3°C). The coatings modified with lignin nano-particleshad a greater change in gloss. The lignin nano-particles in the modified coating are trapping hydroxylradicals which reduces photoactivity and yellowing of the polyurethane by about 3 times compared to unmodifiedpolyurethane coatings. After weathering test, the nano-lignin-based coating had a rougher surface with a lowercontact angle (0.78°) compared to the unmodified polyurethane coating (0.85°).
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