| 1. |
- Laxminarayan, Tejasvi, et al.
(författare)
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Chemically-resistant epoxy novolac coatings : Effects of size-fractionated technical Kraft lignin particles as a structure-reinforcing component
- 2023
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Ingår i: Progress in organic coatings. - : Elsevier. - 0300-9440 .- 1873-331X. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- To provide protection against corrosion in harsh environments, high performance anticorrosive coatings are applied on steel structures at all scales. However, to also limit the use of fossil-based ingredients, there is a growing demand to incorporate renewable raw materials in the coating formulations. In this study, to replace pigments and fillers of an epoxy novolac coating, technical Kraft lignin particles were ground and size fractionated (i.e., sieved), and used for formulation work. The effects of sieved and unsieved Kraft lignin, as structure-reinforcing components, on the anticorrosive and mechanical performance of epoxy coatings were subsequently investigated using the following methods: size exclusion chromatography (SEC), phosphorous nuclear magnetic resonance spectroscopy (31P NMR), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), salt spray exposure, pull-off, König pendulum hardness, and chemical resistance tests. Compared to the unsieved-lignin reference (U-L EN), the coating based on lignin fines (S-L EN) showed about 31 % lower rust creep after 70 days of salt spray exposure. However, no surface defects or chemical degradation were observed for any of the coatings. For the S-L EN coating, excellent adhesion strength (23 MPa) and impact resistance (0.49 N), relative to reference values of 17 and 13 MPa and 0.41 and 0.07 N for commercial and lignin-based diglycidyl ether bisphenol F (L-DGEBF) coatings, respectively, were measured. The addition of lignin particles did not influence the chemical resistance, the hardness, and the glass transition temperature of the epoxy novolac coatings. In summary, chemically unmodified Kraft lignin particles, after grinding and sieving, can be incorporated in epoxy novolac coatings (up to 25 vol%), thereby providing a bio-based alternative to pigments and fillers in heavy duty coatings (primers in particular).
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| 2. |
- Truncali, Alessio, et al.
(författare)
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Microwave-assisted fractionation and functionalization of technical lignin toward thermoset resins
- 2023
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 140:45
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is the most abundant aromatic biopolymer, with a potential to serve as a building block of rigid and thermally stable bio-based materials. However, it is still underutilized because of the heterogeneous and not fully understood chemical structure. Here, technical softwood Kraft lignin is refined in to narrow-dispersity and relatively low molar mass fractions by microwave-assisted processing, followed by microwave-assisted allylation and further application in lignin-based thermosets. This microwave processing is carried out under non-catalyzed conditions using a low boiling point solvent and elevated pressure. The properties of the retrieved fractions are investigated by 31P-NMR, heteronuclear single quantum coherence spectroscopy-NMR, SEC, differential scanning calorimetry, and thermogravimetric analysis. The extraction yield of the selected lignin fraction is around 25%, with the number-average molar mass (Mn), weight-average molar mass (Mw), and dispersity (Đ) significantly reduced. The chemically modified lignin is characterized by 31P NMR and FTIR, which provides evidence of the introduction of the allyl moieties. The analyses demonstrate that 90 ± 3% of the hydroxyl groups in fractionated lignin are successfully allylated. Subsequently, the allylated lignin is cross-linked through thermally induced thiol-ene chemistry to produce lignin-based thermosets. The final thermosets exhibit a storage modulus of 4050 ± 60 MPa and a Tg of 105 ± 5°C.
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| 3. |
- Truncali, Alessio, et al.
(författare)
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Microwave-Assisted Fractionation and Functionalization of Technical Lignin Towards Thermoset Resins
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lignin is the main source of aromatic natural polymers, with a potential to serve as a building block of rigid and thermally stable bio-based materials. However, because of its heterogeneity differences and not fully understood chemical structure it is still underutilized. Therefore, in this paper, technical softwood Kraft lignin is refined in to narrow-dispersity and relatively low molecular weight fractions by microwave-assisted processing. This process was carried out under non-catalytic conditions using a low boiling point solvent and higher pressure. The chemical properties of the retrieved fractions were investigated by 31P NMR, HSQC NMR, SEC, DSC, and TGA. One of the retrieved soluble lignin fractions was successfully chemically modified by microwave processing. The chemically modified lignin was characterized by 31P NMR and FTIR, which provided evidence of the introduction of the allyl moieties. Subsequently, the allylated lignin was cross-linked through thermally induced thiol-ene chemistry to produce lignin-based thermosets.
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