High-definition automated optical analysis was used to observe the morphological changes of bleached hardwood dissolving pulp during oxidation mediated by (2,2,6,6-tetramethylpiperidn-1-yl)oxyl ...(TEMPO). The effects of TEMPO treatment kinetics on fiber morphology and fibrillation degree at a constant reagent loading were studied. The pulp underwent significant swelling, and carboxyl groups were introduced in which the fiber cell walls loosened, which contributed to fibrillation and subsequently nanocellulose dispersion quality in terms of both viscosity and visible light transmittance. The use of an automated optical fiber analyzer facilitates process control, as it allows controlling the fiber morphology and preventing major losses in the form of pulp fines stemming from an unnecessarily long TEMPO oxidation time.
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IJS, KILJ, NUK, PNG, UL, UM
The main objective of our study was to investigate the possible differences in the chemical composition of extractives from the bark of silver fir (
) with respect to the location of the bark sample ...on the tree, viz. differences in extract composition between stem bark and branch bark samples. Extractives in the bark samples from branches, depending on the distance of the sample from the trunk, were also analysed, and the stem bark samples were analysed with respect to their inner and outer parts. The results of the chemical analysis of extractives were supported by information about their antifungal and antioxidant effects. After felling and sampling silver fir trees, the collected bark samples were ground and freeze-dried. Extraction of bark samples was followed by a system of accelerated extraction using only water as a solvent. The extracts were analysed chemically using gravimetry, spectrophotometry and chromatography. Free-radical-scavenging activity was measured using the DPPH method, and the antifungal effect towards three moulds and three wood-decaying fungi was investigated with antifungal assay using the agar well diffusion method. It was found that the moisture content in bark samples decreased intensively just after the bark samples were peeled off the stem. Detailed chromatographic analysis showed that the bark extracts contained 14 compounds, among which phenolic acids, flavonoids and lignans were found to be the characteristic ones. The content of hydrophilic extractives in the branch bark samples decreased with increasing distance of the sample location from the tree stem. The largest amounts of phenolic extractives were measured in stem bark, followed by branch bark sampled at the point at which the branch entered the tree. Analysis of the separated parts of the bark showed that the outer layers of stem bark contained larger amounts of phenolic extractives, as well catechin and epicatechin, compared to the inner layers. Concentrated extracts of branch bark showed the largest free-radical-scavenging activity among the investigated samples, while strong antifungal effects of the bark extract were not found.
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Different types of southern European hardwoods and softwoods were subjected to a liquefaction process with glycerol/diethylene glycol. The liquefied spruce wood was reacted in a condensation reaction ...in the hot press with different melamine–formaldehyde and melamine–urea–formaldehyde resin precursors and used as adhesives for wood particle boards. The mechanical properties of these particle boards and the determination of formaldehyde release, proved that addition of 50% of the liquefied wood to such resin precursors caused the product to meet the European standard quality demands for particle boards. Up to 40% reduction of the formaldehyde emission was achieved. The temperature of the press unit was lowered from 180
°C to 160
°C with no significant influence on the mechanical properties. On the basis of the presented results it was possible to conclude that liquefied wood can be used as substitute for synthetic resin precursors in adhesives that are used for the particle board production.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The main goal of the study was to examine and compare the inhibition effect of knotwood extractives of Scots (
Pinus sylvestris
) and black pine (
Pinus nigra
) against the two white-rot fungi and ...two brown-rot fungi. Knotwood was extracted in a Soxhlet apparatus. Extracts were chemically analyzed, and the inhibitory effect of purified pinosylvins and crude hydrophilic extracts was tested against growth of the white-rot fungi
Schizophyllum commune
and
Trametes versicolor
and the brown-rot fungi
Fibroporia vaillantii
and
Gloeophyllum trabeum
with the in vitro antifungal assay. Knotwood of Scots pine and black pine contained comparable amounts of total extractives. Pinosylvin, pinosylvin monomethyl ether and nortrachelogenin were characteristic compounds in knotwood extracts of both pines. Scots pine knotwood contained larger amounts of pinosylvin than black pine. The ratio between pinosylvin monomethyl ether and pinosylvin was higher in black pine knotwood. Purified pinosylvins and crude hydrophilic extracts inhibited the growth of all the white-rot and brown-rot fungi tested. Pure pinosylvins better inhibited fungal growth than crude knotwood extracts, whereas the efficiency was not unambiguous and relates to fungi species. Crude hydrophilic extracts of Scots pine more efficiently inhibited fungal growth than extracts of black pine. With the present investigation, hydrophilic extracts of pine knotwood were demonstrated as formulations of natural compounds with good antifungal properties. Broken tops of Scots pine, which can lie on forest grounds for a month or even more, still contain high amounts of phenolic extractives and are therefore a potential raw material for recovery of bioactive compounds.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The chemical composition of extractives in the sapwood (SW), heartwood (HW), knotwood (KW), and branchwood (BW of silver fir (
Mill.) was analyzed, and their antifungal and antioxidant properties ...were studied. In addition, the variability of extractives content in a centripetal direction, i.e., from the periphery of the stem towards the pith, was investigated. The extracts were analyzed chemically with gravimetry, spectrophotometry, and chromatography. The antifungal and antioxidative properties of the extracts were evaluated by the agar well diffusion method and the diphenyl picrylhydrazyl radical scavenging method. Average amounts of hydrophilic extractives were higher in KW (up to 210.4 mg/g) and BW (148.6 mg/g) than in HW (34.1 mg/g) and SW (14.8 mg/g). Extractives identified included lignans (isolariciresinol, lariciresinol, secoisolariciresinol, pinoresinol, matairesinol) phenolic acids (homovanillic acid, coumaric acid, ferulic acid), and flavonoids epicatechin, taxifolin, quercetin). Secoisolariciresinol was confirmed to be the predominant compound in the KW (29.8 mg/g) and BW (37.6 mg/g) extracts. The largest amount of phenolic compounds was extracted from parts of knots (281.7 mg/g) embedded in the sapwood and from parts of branches (258.9 mg/g) adjacent to the stem. HW contained more lignans in its older sections. Hydrophilic extracts from knots and branches inhibited the growth of wood-decaying fungi and molds. KW and BW extracts were better free radical scavengers than HW extracts. The results of the biological activity tests suggest that the protective function of phenolic extracts in silver fir wood can also be explained by their antioxidative properties. The results of this study describe BW as a potential source of phenolic extractives in silver fir.
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Nanocellulose gels were prepared by a new chemical crosslinking approach. Carboxy group containing cellulose nanofibrils, which were prepared by (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO) ...mediated oxidation, were reacted with two different diiodoalkanes and one triiodoalkane in DMSO/water dispersions at elevated temperatures. Mechanically stable gels were obtained that were characterized with respect to chemical and physical properties. It was confirmed by FTIR spectroscopy that crosslinking of TEMPO oxidized cellulose nanofibrils (TCNF) occurs by the formation of ester bonds. The kinetics of gel formation were evaluated by oscillatory rheology experiments. For long alkyl chain cross-linkers, namely 1,4-diiodobutane and 1,10-diiododecane, the initial gel was formed within a short time (gel point < 5 min) and further evolved upon time for about 0.5–2 h. For the short crosslinker triiodomethane, gel formation was slower and resulted in lower mechanical strength.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The interest in nanocellulose made from woody biomass has been growing rapidly; however, detailed studies on the environmental performance of nanocellulose have only been reported on a few occasions. ...To fulfill this gap, the environmental performance of nanofibrillated cellulose fabricated from thermo-groundwood (removal of extractives, lignin and hemicelluloses, TEMPO oxidation and homogenization processes were included) was evaluated by means of a Life Cycle Assessment. The results show that the purification process contributes more than 95% of the impact. It is associated with a relatively high consumption of electrical energy and ancillary chemicals, i.e., cyclohexane and acetone. The global warming potential of 1 kg of nanofibrillated cellulose is as high as 800 kg CO2 equivalents. Even in the case that in addition to the extractives and the hemicelluloses also lignin is considered as a potentially valuable co-product, and the latter takes over some of the burden, the impact of nanofibrillated cellulose remains relatively high, at around 400 kg CO2 equiv. per kg of nanocellulose. While the primary energy consumption is around 19.000 MJ per kg of nanofibrillated cellulose, or 10.100 MJ in the case that the lignin is considered as a potentially valuable co-product. The study also had a methodological goal, i.e., the impact indicators were calculated using the three most relevant evaluation methods: ILCD/PEF, CML 2001 and ReCiPe 2016. These three methods show similar results for the impact on global warming and acidification. However, in the case of impacts on some other indicators, significant deviations in the obtained impact scores were observed with respect to the results for the three methods. Taking into account the background data of the methods, ReCiPe 2016 was found to be the most up-to-date method and can currently be considered as the preferable Life Cycle Impact Assessment method.
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•Environmental footprint of the nanocellulose is considerable (e.g. 800 kg CO2 eq.).•The purification contributes 95% to the environmental footprint of the nanocellulose.•Three the most relevant LCIA methods results were compared.•Current LCIA methods could be improved with regard to AP and ODP models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Research Highlights: The antifungal assay confirmed that knotwood extractives of Scots pine inhibit the growth of wood decay fungi. Heartwood extracts of black locust were found to be much stronger ...free radical scavengers than the extracts of Scots pine. The extracts were deposited in the lumina and on the wall surface of cells in the impregnated sapwood. Impregnation of the sapwood blocks with Scots pine and black locust extracts reduced the fungal decay of wood. Objectives: Hydrophilic extracts of Scots pine knotwood and black locust heartwood were chemically analyzed, tested for antifungal and antioxidant properties and used for impregnation of beech and Scots pine sapwood. Materials and Methods: Scots pine knotwood and black locust heartwood were extracted, and obtained hydrophilic extractives were chemically analyzed. Extracts were analyzed for antifungal properties with the in vitro well-diffusion method. The free radical scavenging activity of wood extracts was measured colorimetrically. The retention of the extracts in the impregnated sapwood blocks was evaluated with microscopy and gravimetry. A decay test was performed with the mini block test. Results: Almost half of both Scots pine knotwood and black locust heartwood hydrophilic extracts obtained were described by phenolic compounds. The extracts were deposited in the lumina of cells and on the cell wall surface. Extractives of Scots pine knotwood had good inhibitory properties against white- and brown-rot fungi. On the other hand, extractives of black locust heartwood were found to be good radical scavengers, better than knotwood extractives of Scots pine. The extracts of Scots pine knotwood and black locust reduced the fungal decay of the tested sapwood blocks. Conclusions: The results of this research show that the less-valued knotwood of Scots pine and heartwood of black locust are a potential source of antifungal and antioxidant agents for bio-based wood preservatives.
•Development of bacterial cellulose colloid dispersions using ultrasound irradiation.•Self-assembled film formation of the supernatant phase via solvent evaporation.•Purification treatment had a ...critical effect on the removal of bacteria impurities.•Ultrasound and drying processes had an important effect on the morphology and properties of bacterial cellulose films.
Bacterial cellulose (BC) film formation could be a critical issue in nanotechnology applications such as biomedical or smart materials products. In this research, purified pretreated BC was subjected to high intensity ultrasound (HIUS) and was investigated for the development of BC films. The morphological, structural and thermal properties of the obtained films were studied by using FE-SEM, AFM, FT-IR, XRD, TGA and DSC characterizations. Results showed that the most favorable purification treatment was the 0.01M NaOH at 70°C for 2h under continuous stirring. The most suitable ultrasound operating conditions were found to be, 1cm distance of ultrasonic probe from the bottom of the beaker, submerged in cold water bath cooling around 12±2°C. The power (25W/cm2), time (30min), BC concentration (0.1%w/w), amplitude (20μm) and frequency (20kHz) were maintained constant.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Cilj naše študije je bil razviti več različnih formulacij biokompozitnih in bionanokompozitnih filmov na osnovi polivinil alkohola (PVA) z dodatkom ojačitvene komponente – celuloznih nanofibril (CNF) ...in različnih tipov biološko aktivnih taninov – taninske kisline (TA), galne kisline (GA) in kostanjevega tanina (KT). CNF smo dodali v utežnem deležu 2 %; TA, GA in KT pa v utežnem deležu 4 % glede na PVA. S 4 % dodatkom TA v PVA matrico smo pripravili biokompozitni film, ki je izkazoval več kot 25 % višjo natezno trdnost v primerjavi z osnovnim PVA filmom. Z dodatkom 2 % CNF in 4 % TA v PVA matrico smo pridobili bionanokompozitni film (P2C4T) z izboljšanim modulom elastičnosti in natezno trdnostjo, hkrati pa smo z omenjenima dodatkoma povečali tudi fleksibilnost pripravljenega nanokompozita, saj je bila vrednost raztezka pri pretrgu za končni formulirani film (P2C4T) več kot 50 % višja od raztezka pri pretrgu za osnovni PVA film. Hidrofilnost površine dvokomponentnih PVA filmov je bila nižja, trikomponentnih pa višja.
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