Inorganic impregnation strengthening of Chinese fir wood was carried out to improve the strength, dimensional stability, flame retardancy, and smoke suppression of Chinese fir wood. Sodium silicate was used as reinforcement, a sulfate and phosphate mixtures were used as a curing agent, and Chinese fir wood was reinforced by the respiratory impregnation method (RIM) that imitating human respiration and vacuum progressive impregnation method (VPIM). The weight percentage gain (WPG), density increase rate, distribution of modifier, bending strength (BS), compressive strength (CS), hardness, and water resistance of unreinforced Chinese fir wood from the VPIM and RIM were compared. It was found that RIM could effectively open the aspirated pits in Chinese fir wood, so its impregnation effect, strengthen effect and dimension stabilization effects were the best. RIM-reinforced Chinese fir wood was filled with silicate both horizontally and vertically. At the same time, the transverse permeability of silicate through aspirated pits was significantly improved. The chemical structure, crystalline structure, flame retardancy, smoke suppression, and thermal stability of VPIM- and RIM-reinforced Chinese fir wood were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), cone calorimeter (CONE), and thermogravimetric analysis (TGA). The results indicated that although the crystallinity of RIM-reinforced Chinese fir wood decreased the most, more chemical crosslinking and hydrogen bonding were formed in the wood, and the strengthen effect was still the best. Compared with VPIM-reinforced Chinese fir wood, RIM-reinforced Chinese fir wood had lower heat release rate (HRR), peak-HRR, mean-HRR, total heat release (THR), smoke production rate (SPR), and total smoke production (TSP), higher thermal decomposition temperature and residual rate. It was indicated that RIM-reinforced Chinese fir wood was a better flame retardant, and has a smoke suppression effect, thermal stability, and safety performance in the case of fire.
This study reports a new cellulosic material that maintains the original three-dimensional structure of bamboo and is produced by optimization of chemical treatments. Bamboo blocks were prepared from the current year culms of moso bamboo (Phyllostachys edulis) and subjected to three chemical treatments alone or in combination. Based on the color changes and Fourier transform infrared spectra, the combination of alkaline treatment with alcoholysis followed by Wise method was found to be an optimal treatment method. This serial treatment caused the blocks to become completely white and removed non-cellulosic components such as hemicellulose and lignin from the cell walls of the parenchyma as well as those of vascular bundles. This sample was named as “White-Colored Bamboo.” Extensive structural evaluations from anatomical- to nano- level were performed using X-ray computed tomography, X-ray diffraction, and transmission electron microscopy incorporated with the 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation technique. These multiple observations showed that the white-colored bamboo maintained its inherent hierarchical structure, thus encouraging to produce functional biomaterials.
It is well known the properties of resin impregnation wood is significantly influenced by the specific distribution pattern of resin in the modified wood. In this work, bamboo was furfurylated with an improved process. In addition to testing and evaluating its main physical, mechanical and durable properties, it was explored how the furfuryl alcohol (FA) resin is distributed in the furfurylated bamboo. To achieve this goal, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), nanoindentation, and imaging Fourier transform infrared microscopy (imaging FT-IR) were applied. SEM images demonstrates FA resin is mainly located in the parenchymal cell cavity of bamboo, however the existence of FA resin in the small cavities of the bamboo fibers is also observed by CLSM. In addition, the result of nanoindentation and imaging FT-IR both indicates that FA can penetrate and polymerize within the cell wall of the bamboo fiber. It is then concluded the heterogeneous but multi-scale distribution of FA resin should be responsible for the significant improvement of furfurylated bamboo in both dimensional stability and biological durability.
Density of wood can be increased by filling its porous structure with polymers. Such densification processes aim to increase hardness of wood and are particularly interesting for flooring applications. This study aims to evaluate efficiency of different polymers for chemical densification based on the polymer properties. Yellow birch (Betula alleghaniensis Britt.) was chemically densified with seven monomer mixtures through acrylate monomer impregnation and electron beam in-situ polymerization. Chemical retention and polymer content of densified woods were recorded. Hardness of treated and untreated Yellow birch was measured and compared to hardness of Jatoba (Hymenaea courbaril L.). All densified woods showed higher or comparable hardness to Jatoba. Hardness of densified wood was analyzed in relation to initial density of wood and polymer content of the material using multivariable linear mixed models. Efficiency of polymers for chemical densification was evaluated through effect of polymer content on hardness with interaction coefficients. Polymer films corresponding to monomer impregnating mixtures were prepared through low energy electron beam and characterized by their glass transition temperature, micro hardness, indentation modulus and crosslinking density. Polymers showed statistically significantly different efficiencies and were separated in two main groups. Overall, polymer efficiency increased with increasing glass transition temperature of polyacrylates.
The combinations of nano-ZnO with wood through simple and efficient physical methods to prepare environmentally friendly and versatile Nano-ZnO-coated Wood have important research and practical implications. In this paper, an environmentally friendly nano-ZnO-coated wood was prepared by physical magnetron sputtering using Pinus sylvestris L. var. mongholica Litv. The micro-characteristics, structure, wettability and colour change of the ZnO-coated wood were characterized and studied. For samples with a sputtering time of more than 3 min, the surface water contact angle exceeded 130° and had good hydrophobic properties. After a 168 h accelerated ultraviolet (UV) ageing test, the total colour difference (ΔE∗) of the sample with a sputtering time of 75 min (200 °C) was 77% lower than that of the original wood. When the substrate was at 200 °C, the ZnO films deposited on the surface of the wood were evenly and densely arranged, forming almost a continuous film. It could be seen that the deposition of a nano-ZnO film on the surface of wood could significantly improve its hydrophobic properties and anti-UV photochromic properties.
To clarify inheritance of static bending properties in relation to elastic and plastic regions, air-dry density, microfibril angle of the S2 layer in latewood tracheid (MFA), and static bending properties (modulus of elasticity [MOE], modulus of rupture [MOR] and bending work) were examined for juvenile wood of 18 full-sib families in 20-year-old Cryptomeria japonica. Heritability of all traits ranged from 0.12 (bending work) to 0.51 (air-dry density). Based on the results from principal component analysis (PCA) and cluster analysis, the families were classified into four groups with different types of load-deflection curves, suggesting that both elastic properties and deflection in plastic region differed among families. Furthermore, families included in a group were produced from specific parents, suggesting that deflection in plastic region as well as elastic property is inheritable. It can be concluded that mating parents may affect elasticity and plasticity of offspring.
Knotwood of softwood species is rich in secondary metabolites, especially lignans. These metabolites can be extracted with organic solvents, and are known to be valuable sources of natural bioactive molecules. Here, we examine the intraspecific variability of the yield and compositions of ethanol extracts from knotwood along the stems of three economically significant softwoods Abies alba, Picea abies and Pseudotsuga menziesii in view of further valorisation. Extractive yields from all three species were higher from knots at the base of the living crown than at the top. Lignans and terpenes were abundant in A. alba and P. abies extracts, and lignans were present in the highest concentrations at the crown base. Secoisolariciresinol and hydroxymatairesinol were the most abundant lignans in A. alba and P. abies, respectively. P. menziesii extract composition was more diverse than those of the other species, containing taxifolin, small amounts of the lignan nortrachelogenin, and smaller amounts of secoisolariciresinol. A cyclitol, D-pinitol, was found in high concentrations in extracts from knots at the very top of the crown, particularly in A. alba and P. menziesii. Lignans, taxifolin and D-pinitol are reported to have anti-tumour properties, and valuable food-supplement markets exist for these compounds suggesting possibilities of further valorisation.
The paper presents a novel approach to determine charring of wood exposed to standard and natural fire that is based on a new numerical model named PyCiF. The new model couples an advanced 2D heat-mass model with a pyrolysis model. A new charring criterion based on a physical phenomenon is implemented in the PyCiF model to determine charring of wood. This presents the main advantage of the new PyCiF model in comparison to common modelling approaches, which require an empirical value of the charring temperature that is often called the char front temperature. The fact that the char front temperature is not an explicit value as assumed by the isotherm 300 °C is advantageously considered in the presented approach where an assumed empirical value of the char front temperature is not directly required to determine the thickness of char layer. The validation of the PyCiF model against experimental results showed great model accuracy, meaning that the model is appropriate for the evaluation of charring depths of timber elements exposed to the standard fire as well as the natural fires. Additionally, as shown in the case study, the presented approach also enables to determine the char front temperature for various natural fire exposures. This will be especially important for the upgrade of the new design methods for fire safety of timber elements exposed to natural fire given in the various design codes such as Eurocode 5.
Adhesives based on vegetable tannins are already a reality in the market. However, their use is still limited due to their low mechanical resistance and weak humidity resistance. Cellulose nanofibrils (CNFs) are being used as reinforcing materials in various composites, resulting in an improvement of mechanical proprieties in general. The objective of this work was to evaluate the incorporation of CNFs in adhesives made of tannins obtained from the Angico tree (Anadenanthera peregrine). Concentrations of nanofibrils at 1, 5, and 10% were added to the adhesives on a dry basis. Tests of viscosity, pH, solids content, and gel time were performed to determine the physical proprieties of the adhesives. The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Raman spectra measurements were also determined to understand the interaction between tannins and CNFs. Thermogravimetric analyses (TGA) were carried out to determine the thermal resistance of the composite. The FTIR and Raman characterization identified some differences in the peaks in the chemical composition of the adhesives with different percentages of CNFs. The adhesives showed no different decomposition in the thermogravimetric analyses. The shear strength in the glue line of the adhesive with 5% of CNFs in Toona ciliata woods was determined. Among all the adhesives analyzed, the one with 5% of CNFs produced an improvement in the mechanical resistance and humidity resistance on the glue line.