•Industrial manufacture of 3-layered, beech-spruce hybrid CLT.•Rolling shear properties were tested with compression shear and bending tests.•Rolling shear modulus and strength exceed classic ...softwood CLT by 7 and 3 times.•Sufficiently accurate calculation as a rigid composite ignoring shear-lag.•Greatly enhanced load capacity and deflection behavior as compared to softwood CLTs.
A hybrid, three-layered, softwood-hardwood cross-laminated timber build-up with outer layers of European spruce (Picea abies) and a center cross-layer of European beech (Fagus sylvatica) has been investigated with regard to out-of-plane bending. The determination of the rolling shear properties of the beech cross-layer performed by different test and measurement methods comprising bending and compression shear tests was of primary interest. The shear capacity of the composite is significantly influenced by the spruce longitudinal shear strength at the beech-spruce interface. The characteristic values of rolling shear modulus and strength of the beech cross-layer from the bending tests were Gr,mean=350N/mm2 and fv,r,05=2.6N/mm2, respectively. Direct strain gauge measurements and compression shear tests resulted in 10–20% higher values. The high rolling shear properties render the shear lag implications of the softwood CLTs to a negligible quantity. The hybrid build-up can be designed as a rigid composite with small error versus a more exact analysis. The novel investigations reveal the great potential of mixed softwood-hardwood CLT build-ups for structural elements in the building sector.
In this work, steam explosion (STEX), microwave assisted extraction (MAE) and high voltage electrical discharges (HVED) pretreatments have been evaluated for their impact on the physicochemical ...characteristics of extracted hemicellulosic polymers and on the resulting hemicellulose-based films. Extraction was carried out on spruce sawdust pre-soaked in water (WPS) or 1 M NaOH solution (SPS). The results have shown that STEX pretreatment gave the highest hemicellulose yields (64 and 66 mg g−1 of dry wood from WPS and SPS respectively) followed by MAE and HVED whilst MAE pretreatment produced the highest molecular mass (Mw~66 kDa of arabinoglucoronoxylans from SPS and 56 kDa for galactoglucomannans from WPS). A relatively high acetylation degree was found for STEX WPS (acetylation degree ≈ 0.35) and a high lignin content for STEX SPS (≈12%). Films have been produced by casting using sorbitol as plasticizer. Low oxygen barrier and light transmittance properties were observed for the films obtained from hemicelluloses extracted from SPS due to their high molecular mass and to intermolecular bonding of hemicelluloses and lignin.
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•Physical pretreatments have been used for the extraction of hemicelluloses.•High selectivity of extraction was observed as a function of the pH of extraction.•Spruce hemicelluloses have a good potential in films application.•Hemicelluloses with high content of lignin gave films with a good barrier.
SUMMARY
Performance‐based design of the timber structures' fire resistance is often based on the reduced cross section and thus relying on empirical and numerical assessment of the charring ...propagation. The current work aims to construct models for the pyrolysis of spruce and pinewoods to allow coupled simulations of the cross‐section reduction and burning rate in fire models. Kinetic models are formulated based on thermogravimetric data and supported by the heats of pyrolysis and combustion measurements by differential scanning calorimetry and microscale combustion calorimetry, respectively. The results from these small‐scale measurements are consistent with each other, and the heats of pyrolysis and combustion are determined for the wood primary components by fitting the simulations to the experimental results. Heat release models are constructed based on the small‐scale tests, and cone calorimeter experiments are used for the estimation of the physical properties and for the heat release model validation.
•2D digital image correlation to estimate local displacements/strains under hydric solicitations.•Strains tangential to radial direction is about 1.5 times and about 4 times for latewood and ...earlywood.•We identify the local swelling coefficients with rather good precision.•Proposed 2D DICT instead of 3D microtomography correlation gives precise local behavior of different hygroscopic materials.
Spruce wood, as all biosourced materials, is very sensitive to relative humidity changes, which can cause dimensional variations. In some cases, it leads to eccentricity, degradation and deterioration of the wooden structures. The 3D methods of evaluation of the spruce wood hydric behavior needs important financial resources and investigation. That’s why, the main objective of this study is to develop the technics of 2D digital image correlation to estimate the local displacements and strains values under hydric solicitations and to follow the hysteresis phenomenon, anisotropy and swelling coefficient. In this context, cycles of sorption - desorption for relative humidity that vary from 0 to 100% were applied. Results represent swelling coefficients for early- and latewood as a function of wood directions. A particular attention was devoted to the uncertainty of the 2D digital image correlation technics for both earlywood and latewood. This study provides the literature and future research with promising results especially concerning the evolution of the microscopic morphology of biosourced materials when exposed to relative humidity variations, which can significantly affect their macroscopic behavior.
•Follow up and quantification of bound and free water sorption by NMR.•Evolution of the chemical constituents on the sorption cycle using XRD.•The fiber saturation point is reached between 78% and ...95% relative humidity.•Swelling of the hemicellulose leads to narrowing of the crystalline cellulose.
The quantification of the bound and free water within spruce wood and the water and solid matrix interactions are still unknown by the researchers.
Many specimens were firstly studied by Nuclear Magnetic Resonance function of the relative humidity. For each test, the bound and free water were calculated. After that, spruce wood specimens were studied by X-Ray Diffraction, function of the relative humidity. For each test, the crystalline and amorphous phases were quantified.
This paper presents innovative results concerning the bound and free water uptake within wooden materials, and the water and wooden solid matrix interactions.
Spruce wood samples were subjected to different conditions of thermal and hydro-thermal treatment by varying the temperature, relative humidity and period of exposure. The obtained treated samples ...were evaluated using near infrared spectroscopy (NIR), principal component analysis (PCA) and hierarchical cluster analysis (HCA) in order to evidence the structural changes which may occur during the applied treatment conditions.
Following this, modification in all wood components were observed, modifications which were dependent on the temperature, amount of relative humidity and also the treatment time. Therefore, higher variations were evidenced for samples treated at higher temperatures and for longer periods. At the same time, the increase in the amount of water vapours in the medium induced a reduced rate of side chains and condensation reactions occurring in the wood structure.
Further, by PCA and HCA was possible to discriminate the modifications in the wood samples according to treatment time and amount of relative humidity.
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•Thermal and hydro-thermal treatment at 130 and 150°C of spruce wood was performed.•NIR spectroscopy and chemometrics were used to evaluate the structural modifications.•The spectra indicate the modifications occurring mostly in amorphous polymers of wood.•PCA and HCA discriminate the group clusters according to treatment time and RH used.
The effect of thermal treatment temperatures on the dynamic and static modulus of elasticity (MOE) of Norway spruce wood (Picea abies (L.) H. Karst.) was evaluated. The dynamic MOE was measured using ...ultrasound and resonance methods in the longitudinal and transverse directions. The static MOE was determined by the three-point bending test. The dynamic MOE values determined by the ultrasound method were higher than the static MOE values in each case. As the temperature of the thermal treatment increased, the difference between the dynamic and static MOE values decreased. The MOE increased with increasing temperature, and it was more pronounced on a tangential surface. Increasing the sensor distance had a positive effect on the correlation between the static and dynamic MOE, and the effect from the increased temperature decreased. Measurement by the resonance method showed twice as high MOE values in the transverse direction than in the longitudinal direction. The thermal treatment caused a significant decrease in the MOE only in the transverse direction, and the differences were insignificant in the longitudinal direction. The dynamic MOE values measured by the resonance method were higher than the static MOE values but slightly lower than the values measured by the ultrasound method.
Xylan–lignin (XL), glucomannan–lignin (GML) and glucan–lignin (GL) complexes were isolated from spruce wood, hydrolyzed with xylanase or endoglucanase/β-glucosidase, and analyzed by analytical ...pyrolysis and 2D-NMR. The enzymatic hydrolysis removed most of the polysaccharide moieties in the complexes, and the lignin content and relative abundance of lignin–carbohydrate linkages increased. Analytical pyrolysis confirmed the action of the enzymatic hydrolysis, with strong decreases of levoglucosane and other carbohydrate-derived products. Unexpectedly it also revealed that the hydrolase treatment alters the pattern of lignin breakdown products, resulting in higher amounts of coniferyl alcohol. From the anomeric carbohydrate signals in the 2D-NMR spectra, phenyl glycoside linkages (undetectable in the original complexes) could be identified in the hydrolyzed GML complex. Lower amounts of glucuronosyl and benzyl ether linkages were also observed after the hydrolysis. From the 2D-NMR spectra of the hydrolyzed complexes, it was concluded that the lignin in GML is less condensed than in XL due to its higher content in β-O-4′ ether substructures (62 % of side chains in GML vs 53 % in XL) accompanied by more coniferyl alcohol end units (16 vs 13 %). In contrast, the XL lignin has more pinoresinols (11 vs 6 %) and dibenzodioxocins (9 vs 2 %) than the GML (and both have ~13 % phenylcoumarans and 1 % spirodienones). Direct 2D-NMR analysis of the hydrolyzed GL complex was not possible due to its low solubility. However, after sample acetylation, an even less condensed lignin than in the GML complex was found (with up to 72 % β-O-4′ substructures and only 1 % pinoresinols). The study provides evidence for the existence of structurally different lignins associated to hemicelluloses (xylan and glucomannan) and cellulose in spruce wood and, at the same time, offers information on some of the chemical linkages between the above polymers.
Spruce wood is widely used in outdoor applications, but its susceptibility to degradation under exposure to sunlight and moisture is a major concern. This study investigates the impact of accelerated ...aging on spruce wood's surface chemistry, microstructure, geometry, and discoloration. The study was performed in two outdoor aging modes: dry and wet. The accelerated aging effects were evident in the changes in spruce wood structure, as well as in the other studied properties. During aging, it developed significant discoloration. Under simulated rainless outdoor conditions (dry mode), spruce wood gradually became dark brown. Under conditions involving rain (wet mode), the discoloration was qualitatively different from the dry mode. FTIR spectroscopy showed that during the accelerated aging of wood, lignin was mainly degraded, especially in the early stages of the process. A linear correlation was found between the changes in lignin and the color changes in the wood. There was an increase in carbonyl groups in the dry mode, which contributed to the color change and was also influenced by changes in extractives. The wet mode caused the leaching out of carbonyl groups. The observed decrease in cellulose crystallinity, together with the degradation of hydrophobic lignin, may result in the increased hydrophilicity of photodegraded wood. For both modes, there were different changes in the wood micro- and macrostructure, reflected in the surface morphology. The roughness increased during the aging process in both modes. The slightest changes in the roughness parameters were identified in the grain direction in the dry mode; the most evident was that the roughness parameters increased perpendicular to the grain in the wet mode. The demonstrated mechanism backing up the aging-related changes to the spruce wood structure and the relations unveiled between these changes and the changes in the spruce wood surface properties can provide an issue point for seeking ways how to mitigate the negative effects of the environmental factors the wood is exposed to.
With the increase in water consumption and pollution resulting from the rising world population and industrial development, severe fresh water shortage has been regarded as one of the critical ...problems facing the world. Solar‐driven water purification is an environment friendly and promising technology to address the problem. However, low photothermal conversion efficiency impedes its practical application. Herein, a natural spruce wood‐based solar evaporator functionalized with zeolitic imidazolate framework (ZIF‐8) nanoparticles and polydopamine (PDA) layers is designed, which significantly reduces the equivalent evaporation enthalpy and substantially boosts solar evaporation efficiency. The evaporation rate of the optimized wood‐based evaporator reached 2.28 kg m−2 h−1 with a high evaporation efficiency of 87.5% under 1.0 sun. Furthermore, the integrated spruce wood/ZIF‐8/PDA hybrids can remove organic pollutants after solar evaporation. Notably, the constructed multifunctional solar evaporator takes advantage of sustainable solar energy, low‐cost biomass, and ZIF‐8/PDA nanostructures to acquire desirable performance in water evaporation and sewage purification.
An efficient metal–organic framework (MOF)‐functionalized natural spruce wood solar evaporator is constructed via polydopamine modification, achieving a high evaporation rate of 2.28 kg m−2 h−1 under 1.0 sun illumination. This study offers an ideal solution for the development of biomass‐based solar evaporators for freshwater production and sewage purification.
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