Volume 15 Issue 2

Fresh bark from spruce Picea abies was milled and extracted with hot water. The extracts were purified in a number of steps in order to get tannin-extracts pure enough to prepare tannin-based carbon foams. The chemical composition of the extracts were analyzed. The foams were maturated and thermally treated to obtain desired properties, such as specific surface area, porosity, and compressive strength. It was possible to produce carbon foams even if they contained carbohydrate impurities. Differences in the properties of the carbon foams such as compressive strength, specific surface areas, and pore size distributions might be related to the compositions of the extracts. The foams were finally activated chemically and physically and were tested in adsorption of methylene blue. Results from the adsorption tests showed that adsorption was highly related to the total pore volume and the amount of mesopores created inside the foam structure during the thermal treatment.

The aim of this work was to determine the effect of propolis extract and propolis-silane formulations on the color of wood. Additionally, the aim was to assess the influence of accelerated aging (water leaching and UV+IR radiation) on the color change of the treated wood. Scots pine wood was treated with the ethanolic extract of propolis and two propolis-silane formulations. The first formulation contained the propolis extract and silanes, 3-(trimethoxysilyl)propyl methacrylate, and tetraethyl orthosilicate. The second formulation comprised propolis extract, vinyltrimethoxysilane, and tetraethyl orthosilicate. The wood impregnation with the propolis extract and propolis-silane formulations had a significant effect (p ≤ 0.05) on the color change. This effect involved decreasing the L* parameter and the displacement of a* and b* coordinates in the red and yellow direction, respectively. The propolis extract and the propolis-silane formulations were characterized by low durability relative to the effect of light. Nevertheless, the examined formulations based on natural substances (propolis) and low toxicity chemical compounds (silanes) may be used to impregnate wood elements for indoor applications.

Wood engineered products are alternatives to the use of timber for civil construction, manufacturing, and the furniture industry. One of these products is the medium density particleboard (MDP) panel, which is made of wood particles and resin under high temperature and pressure. This research produced a prototype to evaluate the use of MDP panels waterproofed by castor oil-based polyurethane resin and Pinus sp. residues treated with CCB preservative for use as a wall coating. The influence of weathering, position of wood panel, and waterproof treatment were evaluated. Panels were made under the requisites of Brazilian Standard ABNT NBR 14810 (2013) and evaluated with international standards. MDP panels met standard requisites, with properties similar to that reported in the literature, indicating the possibility of use as wall coating. Statistical analysis indicated the only significant factor was weathering, which influenced physical and mechanical properties.

Bacterial cellulose acetate (BCA) at a low degree of substitution (DS) was prepared using acetic anhydride in the presence of N-methylimidazole (NMIM) as a catalyst. The acetylated reaction was studied in both solvent-free (heterogeneous) and N,N-dimethylacetamide/lithium chloride (DMAc/LiCl; homogeneous) systems, where the DS ranges of BCA obtained from heterogeneous (BCA-HE) and homogeneous (BCA-HO) systems were recorded as 0.31 to 0.95 and 0.4 to 1.5, respectively. The DS values could be effectively controlled by adjusting the reaction conditions. Compared to the heterogeneous reaction, the homogeneous reaction could be processed under a mild condition within a short time. The BCA-HE and BCA-HO displayed good water solubility at a DS value less than 0.95 and 1.09, respectively. The structural and the characteristic changes were confirmed by scanning electron microscopy, Fourier transform infrared, X-ray diffraction, 13C cross-polarization magic angle spinning nuclear magnetic resonance, and thermogravimetric analyses. The present study may offer a convenient, mild, and green catalyzed-processing to tailor low DS of cellulose acetate.

Strong alkaline hydrolysis is usually employed to enhance fermentative production of volatile fatty acid (VFA) from plant biomass. However, this method is not ecofriendly due to the large consumption of energy/chemicals. In this study, a special henna plant biomass (Lawsonia inermis) containing the chemical compound lawsone, served as a fermentation substrate (without any pretreatment) for high VFA production under mild alkaline conditions (pH 9). The results indicated that the fermentative VFA production was 0.31 g per gram of henna biomass, which was comparable to other plant biomass pretreated with hydrothermal, strong acidic, and/or alkaline methods. Acetate was the main VFA component, and accounted for 69% to 82% of the COD fraction. The soluble lawsone concentration in the fermentation system ranged from 8.5 mg/L to 31.2 mg/L, which mediated the potential fermentation process. Thus, in this study henna was established as a feasible plant biomass for high fermentative VFA production in mild alkaline conditions.

Chopped corn straw is a viscoelastic material that can rebound after compression. Pressure maintenance and strain maintenance are two key processes that enhance the dimensional stability of post-compression straw blocks. To study the effects of stabilization processes on the dimensions of post-compression straw blocks, the authors comparatively explored the relationships of strain and stress with time during constant-speed compression (CC), constant-speed compression followed by strain maintenance (CCS), constant-speed compression followed by pressure maintenance (CCP), and constant-speed compression, pressure maintenance followed by strain maintenance (CCPS), and uncovered the reasons for these relationships. The Burgers constitutive model fit well to the data during the pressure maintenance stage (R2>0.990), and the effects of pressure maintenance on strain and dimensional stability of post-compression straw blocks were investigated. The Wiechert model B (R2>0.990) was the constitutive model that best represented the strain maintenance stage. Additionally, the effects of strain maintenance during CCS and CCPS on relaxation rate and dimensional stability of post-compression straw were compared. The relaxation density of post-compression straw blocks was compared among different stabilization processes. The relaxation density of post-compression straw blocks was the largest after CCPS, followed by CCS and CCP.

Pyrolysis of coconut cloth was investigated with the influence of pyrolysis process parameters on the maximum products yield and their chemical compositions. With the microwave reactor, the process parameters were as follows: temperature (450 °C to 650 °C), heating rate (10 °C/min to 30 °C/min), and nitrogen flow rate (80 °C/min to 120 cm3/min). The highest liquid yield of 38.3% was observed at 550 °C for the heating rate of 20 °C/min. The characteristics of bio-oil and biochar were analyzed using chromatographic and spectroscopic techniques, such as nuclear magnetic resonance spectroscopy (HNMR), Fourier transformed infrared spectroscopy (FTIR), gas chromatography-mass spectroscopy (GC-MS), scanning electron microscopy-energy dispersive X-Ray (SEM-EDX), X-ray powder diffraction (XRD), and elemental analysis. The bio-oil contained a higher amount of phenolic compounds at 79.6%. The obtained biochar had a calorific value of 27.8 MJ/kg, which made it a promising candidate for solid fuel.

The quantitative difference in the antibacterial response was measured for pine rosin and propolis against Staphylococcus aureus ATCC 12598. The activity was studied for fibrous networks that form entirely bio-based cellulose-acetate (CA) materials. The analysis considers the effects of bacterial input, additive dosage, solvent type, variation in preparation, as well as the effect of storage time. Based on the results, the electrospun network structure is dependent on the solvent and the concentration of rosin and propolis. Both rosin and propolis improved the cellulose acetate solution processability, yet they formed beads at high concentrations. Rosin and propolis created strong antibacterial properties when these material systems were immersed in the liquid for 24 h at room temperature. The response remained visible for a minimum of two months. The electrospun networks of water and DMAc solvent systems with 1 to 5 wt% rosin content were clearly more efficient (i.e., decrease of 4 to 6 logs in colony forming units per mL) than the propolis networks, even after two months. This efficiency is likely due to the high content of abietic acids present in the rosin, which is based on the Fourier transform infrared spectra. The results of the additional analysis and cell cultivation with dermal fibroblast cells indicated an impairing effect on skin tissue by the rosin at a 1 wt% concentration compared to the pure CA fibers.

Particles from waste laminated particleboards were recovered using various thermo-hydrolytic treatments. The size distribution and three main chemical properties, such as pH, buffer capacity, and nitrogen content of the control and resulting particles were determined. The effects of treatment temperature and duration on the chemical properties of recycled particles were investigated. The effects of the resulting particles on the gel time of urea-formaldehyde (UF) resin were also measured. The test results suggested that the pH of particles after hot water soaking pre-treatment and the different thermo-hydrolytic treatments increased to different extents, with the exception of the particles treated at 140 °C for 50 min and 160 °C for 20 min. The acid buffer capacity and base buffer capacity of particles treated at 140 °C for 50 min and 160 °C for 20 min had no statistical difference, but they were much higher than those of other types of treated particles. A high treatment temperature facilitated the decomposition of wood polymers and UF resin. Both temperature and treatment duration had significant effects on pH, acid buffer capacity, and base buffer capacity of wood particles. Wood particles recycled at a high temperature had a negative effect on the gel time of UF resin.

Dynamic and static elastic properties beech wood joints were assessed. Conventional joints, namely dovetail, tongue and groove, dowel, and halving joints were prepared with beech wood (Fagus orientalis Lipsky) using polyvinyl acetate and cyanoacrylate adhesives. The results of the dynamic and static modulus of elasticity of the joints in this research indicated the highest reduction trends in halving, dowel, tongue and groove, and dovetail joints, respectively. The modulus of dovetail joint elasticity, its homogeneous joint texture, and lack of an extended adhesive line, corresponded to that of the jointed samples. The average static modulus of elasticity was approximately 10.5% lower than that of the dynamic modulus of elasticity. The results of the Student’s t-test indicated a significant difference between the mean of dynamic and the mean of static modulus of elasticity, significance at 5% level and the Pearson correlation test indicated that the dynamic and static modulus of elasticity of the samples were significant at the 5% level and indicated a positive correlation. Based on the observed correlation in the dynamic and static tests’ results, using these methods, dynamic assessment of NDTs may be regarded as an appropriate alternative in standardizing destructive static testing for wood assessment and categorization.