Volume 72, Issue 12

To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70:30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48–51%). No difference in the mechanical properties of the produced CF was observed.

Viburnum macrocephalum f. keteleeri , not well explored in the pharmaceutical field, is a tall deciduous shrub and commonly used as folk medicines for the treatment of type 2 diabetes (T2D). In this study, the dried branches of V. macrocephalum f. keteleeri were extracted with 95% ethanol and the extract was fractionated on the basis of polarity with ethyl acetate and n -butanol. Among the different fractions, the ethyl acetate fraction exhibited the highest α -glucosidase inhibitory activity, and its bioassay-guided fractionation led to the isolation and identification of six compounds including a new 8- O -4′-neolignan glycoside ( 1 ), categorized as a rare 7-deoxy skeleton, three previously undescribed phenolic glycosides ( 2–4 ), together with two known secondary metabolites ( 5 , 6 ), which were found for the first time in Viburnum . Noticeably, compound 1 had almost the same intestinal α -glucosidase inhibitory activity as the positive control acarbose.

Conversion of lignocellulose into useful chemicals is an important research topic in the area of biomass utilization. In this study, microcrystalline cellulose (MC) was dissolved in a mixed-solvent system containing the ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl) and N -methyl-pyrrolidone (NMP), and the cellulose was directly converted into methyl glucoside (MG) by acid-catalyzed methanolysis aided by microwave irradiation (μWIr). Under moderate reaction temperature and pressure, and in the presence of acetyl chloride/methanol ( in situ formed HCl) as an acid catalyst, MG was obtained in a 42% yield. In contrast, in the absence of either IL or μWIr, the MG yield was only 5 or 21%, respectively. Both μWIr and the dissolution of cellulose in IL were quite effective for the conversion of cellulose into MG.

The reliability of diarylheptanoids as chemotaxonomic markers at inter- and intraspecific levels has been investigated. Six diarylheptanoids were quantified in bark ethanol extracts of four Alnus spp. populations by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The populations described here as locus classicus Alnus glutinosa (I) and locus classicus Alnus incana (III) are clearly differentiated. Compared to population I, individuals in population III have higher extract yields and hirsutanonol-5- O - β -D-glucopyranoside content and lower contents of hirsutanonol, rubranoside A and oregonin. Individuals from neighboring populations of A. glutinosa (II) and A. incana (IV) share similar contents of hirsutanonol. All the studied populations exhibit a high intrapopulation variability of the selected diarylheptanoids; they have a heterogeneous chemotype and they partially overlap. The geographical proximity of populations II and IV increases their chemical similarity. Principal component analysis (PCA) clearly shows that the biggest dispersion of individuals lies within population IV. The reason for its heterogeneity might be its physical proximity to population II, i.e. the appearance of hybrids. Also, geometric morphometrics of leaves was performed as a screening criterion for spontaneous hybrids.

Radiata pine wood (W) was modified with acetic anhydride and glutaraldehyde (GA) resulting in W Ac and W GA to various weight percent gains (WPGs), whereas in W Ac the effect is due to grafting and in W GA , crosslinking. The heat of vaporization of bound water (BW) of the modified woods was studied by differential scanning calorimetry (DSC) and the mass loss (due to water loss) of the samples by thermogravimetry (TG). The temperature program was in both cases from 25 to 40°C with 10°C min −1 . The adsorbed or condensed water in wood were observed via low-field nuclear magnetic resonance (LFNMR). At a comparable WPG level, the LFNMR analysis showed that the interaction of water with W GA was stronger than that with W Ac . In both modified woods, a considerable reduction in the vaporization heat of BW was visible due to cell wall hydrophobization and bulking. The reduction of condensed water in micropores was lower for W GA than W Ac , probably because BW needs more energy to evaporate from the crosslinked stiff W GA cell walls.

Density estimation by non-destructive or semi-destructive methods is applied mainly on softwood species. The instruments are expensive, the methods are complicated and the determination coefficients are low. In the present study, the simple core hollow drilling approach is revisited. Data of 600 cores or cylindrical specimens from 300 pieces of 10 different softwood and hardwood species were evaluated in the density range from 350 to 975 kg m −3 . The data were obtained from complete pieces and from the cores from core drilling, while the difference between the two data sets is 1.7%. At higher densities, the differences are greater. A model was proposed concerning the piece density estimation with a determination coefficient of 0.98. It is concluded that core drill is a cheap and reliable method for density estimation and the data are equally reliable for radial (R) or tangential (T) probing. The cylindrical cores obtained are suitable for moisture content (MC) and species determination.

To improve resin efficiency in plywood production, the veneer surface was modified by dielectric barrier discharge (DBD) plasma and the resin was applied by air spray atomization. The droplet size and coverage of resin droplets were evaluated by image analysis. This novel approach improved the resin efficiency. The shear strength of the produced plywood was improved along with a higher gluing speed. The surface energy of poplar veneer altered after plasma treatment, resulting in an increased size of resin droplets and increased resin coverage. Plywood produced at a plasma-processing power of 4.5 kW exhibited the highest shear strength and a 6 kW plasma-processing power did not bring about advantages. Under these circumstances, the lowest amount of resin necessary for fabricating quality products can be reduced to 50 g m −2 .

In an attempt to evaluate the effects of thermal treatment on wood cell walls (CWs), Masson pine ( Pinus massoniana Lamb.) wood was thermally modified (TM) at 150, 170 and 190°C for 2, 4 and 6 h, respectively. The chemical properties, cellulose crystallinity ( C r I) and micromechanics of the control and thermally modified wood (TMW) were analyzed by wet chemical analysis, X-ray diffraction and nanoindentation. The relative lignin content and C r I increased after the TM partly degraded the amorphous wood polymers. The relative lignin content was higher in TMW and the equilibrium moisture content decreased. Moreover, the elastic modulus ( E r ) and hardness ( H ) of TMW were lowered along with the creep ratio decrement ( C IT ) of CWs. However, a severe treatment (e.g. 190°C/6 h) may negatively affect the mechanical properties of CWs caused by the partial degradation of hemicelluloses and also cellulose.

The effects of moisture content (MC) and temperature (T) on the creep of Japanese cedar were investigated via a series of short-term creep tests, while MC had a higher effect than T, desorption of water caused more deformation. The results were separated into two distinct groups with MCs higher or lower than the equilibrium moisture content (EMC) and it was found that the mechano-sorptive effect is time-independent. The total creep strain of wood was explained by a model considering the instantaneous strain, creep strain and strain induced by the mechano-sorptive effect. The proposed model is in agreement with the creep master curves based on the time-temperature superposition principle (tTSP).

Air-seasoning is a simple method for moisture management in utility poles prior to treatment, but it involves the risk of fungal invasion during drying. These fungi can be eliminated by heat treatment, but fungi surviving in the installed poles are a quality problem. In this context, the incidence of decay fungi was investigated in 963 creosote-treated Scots pine ( Pinus sylvestris ) poles of varying ages in a utility system in Ireland. Thirty-seven percent of increment cores removed from the poles contained at least one viable basidiomycete. There was no relationship between pole age or distance above the groundline and fungal isolations. Phlebiopsis gigantea , a white rot fungus, was the most common isolate followed by Neolentinus lepideus and Sistotrema brinkmannii . The results highlight the importance of including a sterilizing process during treatment and maintaining quality controls when purchasing large numbers of poles.