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The current study demonstrates that methacrylate and acrylate poly(ethylene glycol) (PEG) functional oligomers can be effectively impregnated into wood blocks, and cured efficiently to high conversions without catalyst by e-beam r...
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The current study demonstrates that methacrylate and acrylate poly(ethylene glycol) (PEG) functional oligomers can be effectively impregnated into wood blocks, and cured efficiently to high conversions without catalyst by e-beam radiation, allowing for less susceptibility to leaching, and favorable properties including higher Brinell hardness values. PEG based monomers were chosen because there is a long history of this water-soluble monomer being able to penetrate the cell wall, thus bulking it and decreasing the uptake of water which further protects the wood from fungal attack. Diacrylate, dimethacrylate. and dihydroxyl functional PEG of M_w 550-575. of concentrations 0. 30. 60. and 100 wt % in water, were vacuum pressure impregnated into Scots Pine blocks of 15 X 25 x 50 mm in an effort to bulk the cell wall. The samples were then irradiated and compared with nonirradiated samples. It was shown by IR. DSC that the acrylate polymers were fully cured to much higher conversions than can be reached with conventional methods. Leaching studies indicated a much lower amount of oligomer loss from the cured vinyl functional PEG chains in comparison to hydroxyl functional PEG indicating a high degree of fastening of the polymer in the wood. The Brinell hardness indicated a significant increase in hardness to hardwood levels in the modified samples compared to the samples of hydroxyl functional PEG and uncured vinyl PEG samples, which actually became softer than the untreated Scots Pine By monitoring the dimensions of the sample it was found by weight percent gain calculations (WPG %) that water helps to swell the wood structure and allow better access of the oligomers into the cell wall. Further, the cure shrinkage of the wood samples demonstrated infiltration of the oligomers into the cell wall as this was not observed for methyl methacrylate which is well-documented to remain in the lumen. However, dimensional stability of the vinyl polymer modified blocks when placed in water was not observed to the same extent as PEG.
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The search for sustainable material solutions has put lignin as one of the prime candidates for aromatic building blocks in macromolecular materials. The present study aimed to demonstrate how lignin-based thermoset resins can be ...
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The search for sustainable material solutions has put lignin as one of the prime candidates for aromatic building blocks in macromolecular materials. The present study aimed to demonstrate how lignin-based thermoset resins can be utilized in combination with different cross-linkers. Kraft lignin was used to produce thermosets with tunable mechanical and morphological properties. The lignin-based thermosets were obtained via a thermally induced thiol–ene reaction. The first part of this work was focused on Kraft lignin solvent fractionation and chemical modification of the ethanol soluble fraction. Chemical analysis indicated that the allylation process was selective toward phenolic hydroxyl groups. SAXS and SEM studies demonstrated that solvent fractionation and allylation processes affected the molecular and nanoscale morphological characteristics of lignin. The second part’s focus was on how the properties of thermosets can be tuned by using three different cross-linkers. The dynamic mechanical and morphological properties of three different thermosets were investigated via DMA, SAXS, and WAXS techniques. The three different thermosets exhibit similar molecular morphology but different storage modulus and glass transition temperature. In this work, it was shown that despite lignin’s heterogeneity it was possible to produce thermosetting materials with tunable properties.
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It is shown that the isolation of nanocellulose in a biorefinery approach adds value to the bark and its components. The utilization of a chlorine-free delignification and the preparation of cellulose oxalate in a solvent-free pro...
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It is shown that the isolation of nanocellulose in a biorefinery approach adds value to the bark and its components. The utilization of a chlorine-free delignification and the preparation of cellulose oxalate in a solvent-free process are an economic and environmentally advantageous way of applying the biorefinery concept and to use the bark in a sustainable way. The properties of cellulose oxalate from delignified bark were determined, and the morphological structure of the isolated nanocellulose was characterized. The chemical composition and thermal properties were monitored during the extraction and separation steps, and it was possible to prepare cellulose oxalate in a yield of 82% with a degree of substitution of 0.3 and surface charge of 1.53 mmol g~(–1). The isolated nanocellulose was found to be a mixture of rodlike nanocrystals and nanofibrils. Initial thermal analysis of the isolated nanocellulose shows promising properties. The results show that the bark is a potential inexpensive source of high-value nanocellulose that can be isolated in high yield, for use in cosmetics or as reinforcement in nanocomposites. Since the isolated nanocellulose contains two different morphological types, it can be used where the properties of both cellulose nanocrystals and cellulose nanofibrils are required.
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? 2023 The AuthorsSelective, active, stable, and general catalysts for the controlled ring-opening polymerization of (macro)lactones are central in our pursuit of a more benign material economy. Within, we explore the formation of...
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? 2023 The AuthorsSelective, active, stable, and general catalysts for the controlled ring-opening polymerization of (macro)lactones are central in our pursuit of a more benign material economy. Within, we explore the formation of an activated lactone initiator (ALI) based on ZnEt2-1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as an air-stable and selective initiator/catalyst, yielding linear polymers with one ?-keto ester and one alcohol end-group. Ring-opening polymerization (ROP) with high activity and control was found for unsubstituted (macro)lactones (ω-pentadecalactone (PDL), hexadecanolide (HDL), δ-valerolactone (δVL), and ε-caprolactone (εCL)) and cyclic carbonate trimethylene carbonate (TMC). A particular focus was placed on studying the ALI for the polymerization of strainless PDL and strained εCL. In contrast, ALI-ROP could not polymerize lactones containing substituents on the terminal carbon, indicative of the coordination insertion features of the polymerization. This work explores selective catalysts with high control, fast kinetics, and superb air stability towards the next generation of greener materials.
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Hemicelluloses as major components of plant cell walls are acetylated to different extents. The biological functions of acetylation are not completely understood but suggested that one reason is to decrease the microbial degradabi...
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Hemicelluloses as major components of plant cell walls are acetylated to different extents. The biological functions of acetylation are not completely understood but suggested that one reason is to decrease the microbial degradability of cell walls. Model seed galactomannan and glucomannan, which are structurally similar to an abundant class of wood hemicelluloses, were acetylated to various degrees and used as sole carbon source on agar plates for microbial growth. When soil samples were inoculated on the plates, significantly fewer strains grew on the agar plates with highly acetylated mannans than with slightly acetylated or non-acetylated mannans. One filamentous fungus isolated and identified as a Penicillium species was shown to grow faster and stronger on non-acetylated than on highly acetylated mannan. The data therefore support the hypothesis that a high degree of acetylation (DSac) can decrease the microbial degradability of hemicelluloses. Possible mechanisms and the technological significance of this are discussed.
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? 2023 The Author(s)A series of different technical hardwood lignin-based resins have been successfully synthesized, characterized, and utilised to produce thiol-ene thermoset polymers. Firstly, technical lignin was fractionated a...
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? 2023 The Author(s)A series of different technical hardwood lignin-based resins have been successfully synthesized, characterized, and utilised to produce thiol-ene thermoset polymers. Firstly, technical lignin was fractionated and allylated, whereafter it was crosslinked with a trifunctional thiol. Structural and morphological characteristics of the lignin fractions were studied by 1H NMR, 31P NMR, SEC, FTIR, DSC, TGA, and WAXS. The hardwood lignin fractions have a high content of C5-substituted OH groups. The WAXS studies on lignin fractions revealed the presence of two π-π stacking conformations, sandwiched (4.08–4.25 ?) and T-shaped (6.52–6.91 ?). The presence of lignin superstructures with distances/sizes between 10.5 and 12.8 ? was also identified. The curing reaction of the thermosets was investigated by RT-FTIR. Almost all thermosets (excepting one fraction) reached 95% of the thiol conversion in less than 17 h, revealing the enhanced reactivity of the allylated hardwood lignin samples. The mechanical properties of the thermosets were investigated by DMA. The curing performance, as well as the final thermoset properties, have been correlated to variations in chemical composition and morphological differences of lignin fractions. The described results clearly demonstrate that technical hardwood lignins can be utilized for these applications, but also that significant differences compared to softwood lignins have to be considered for material design.
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Here we report the synthesis of thermosetting resins from low molar mass Kraft lignin fractions of high functionality, refined by solvent extraction. Such fractions were fully characterized by ~(31)P NMR, 2D-HSQC NMR, SEC, and DSC...
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Here we report the synthesis of thermosetting resins from low molar mass Kraft lignin fractions of high functionality, refined by solvent extraction. Such fractions were fully characterized by ~(31)P NMR, 2D-HSQC NMR, SEC, and DSC in order to obtain a detailed description of the structures. Reactive oxirane moieties were introduced on the lignin backbone under mild reaction conditions and quantified by simple ~(1)H NMR analysis. The modified fractions were chemically cross-linked with a flexible polyether diamine (M _(n) ≈ 2000), in order to obtain epoxy thermosets. Epoxies from different lignin fractions, studied by DSC, DMA, tensile tests, and SEM, demonstrated substantial differences in terms of thermo-mechanical properties. For the first time, strong relationships between lignin structures and epoxy properties could be demonstrated. The suggested approach provides unprecedented possibilities to tune network structure and properties of thermosets based on real lignin fractions, rather than model compounds.
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Cellulose acetate (CA) is subjected to different aqueous environments (e.g., lake water, seawater, artificial seawater) under controlled laboratory conditions to investigate the degradation potential in natural water systems. The ...
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Cellulose acetate (CA) is subjected to different aqueous environments (e.g., lake water, seawater, artificial seawater) under controlled laboratory conditions to investigate the degradation potential in natural water systems. The main changes in the CA films are detected during the first months of the 12-month study. Approximately 5% and 10% weight losses are observed during the first month of aging at RT and at 60 °C, respectively. The temperature effect is rather negligible and the weight loss also does not significantly increase on prolonged aging. A quantitative high-performance liquid chromatography analysis shows that this weight loss is mainly caused by deacetylation and depending on the aging conditions, 10–30% of the acetate groups are lost during the first 1–3 months of aging. Fourier transform infrared and nuclear magnetic resonance analyses further support this. It is well established that a high degree of substitution (DS) is the bottleneck for biodegradation of CA and a significantly higher biodegradation rate has been demonstrated for CA materials with degree of substitution, DS<2, compared to those with DS>2. The degree of deacetylation observed here is enough to decrease the DS to below 2, which can therefore have a significant effect on the subsequent biodegradation.
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The interest in the bark and the attempt to add value to its utilization have increased over the last decade.By applying an integrated bark biorefinery approach,it is possible to investigate the recovery of compounds that can be u...
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The interest in the bark and the attempt to add value to its utilization have increased over the last decade.By applying an integrated bark biorefinery approach,it is possible to investigate the recovery of compounds that can be used to develop green and sustainable alternatives to fossil-based materials.In this work,the focus is on extracting Norway spruce(Picea abies)bark lignin via organosolv extraction.Following the removal of the extractives and the subcritical water extraction to remove the polysaccharides,a novel cyclic organosolv extraction procedure was applied,which enabled the recovery of lignin with high quality and preserved structure.Main indicators for low degradation and preservation of the lignin structure were a high β-O-4'content and low amounts of condensed structures.Furthermore,high purity and low polydispersity of the lignin were observed.Thus,the obtained lignin exhibits high potential for use in the direct development of polymer precursors and other bio-based materials.During the extraction sequence,around 70% of the bark was extracted.Besides the lignin,the extractives as well as pectic polysaccharides and hemicelluloses were recovered with only minor degradation,which could potentially be used for the production of biofuel or other high-value products such as emulsifiers or adhesives.
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Aromatic material constituents derived from renewable resources are attractive for new biobased polymer systems. Lignin, derived from lignocellulosic biomass, is the most abundant natural source of such structures. Technical ligni...
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Aromatic material constituents derived from renewable resources are attractive for new biobased polymer systems. Lignin, derived from lignocellulosic biomass, is the most abundant natural source of such structures. Technical lignins are, however, heterogeneous in both structure and polydispersity and require a refining to obtain a more reproducible material. In this paper the ethanol-soluble fraction of Lignoboost Kraft lignin is selectively allylated using allyl chloride by means of a mild and industrially scalable procedure. Analysis using 1H-, 31P-, and 2D HSQC NMR give a detailed structural description of lignin, providing evidence of its functionalization and that the suggested procedure is selective toward phenols with a conversion of at least 95%. The selectively modified lignin is subsequently cross-linked using thermally induced thiol–ene chemistry. FT-IR is utilized to confirm the cross-linking reaction, and DSC measurements determined the Tg of the thermosets to be 45–65 °C depending on reactive group stoichiometry. The potential of lignin as a constituent in a thermoset application is demonstrated and discussed.]]>
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