No abstract
The influence of load on the cellulose microfibrils of single cells or thin wood foils is known. It can decrease the cellulose microfibril angles and, in turn, increase the stiffness. However, this modification of a piece of wood, which is made up of multiple cells, is unknown. The aim of this research was to study the effect of tensile creep on the longitudinal stiffness of radiata pine wood. The modulus of elasticity of each specimen was determined before and after being subjected to tensile creep. The samples were loaded at 1170 N and 1530 N for 20 min at 70 °C. The load was determined as a function of a percentage of the force at the proportional limit. The moduli of elasticity before and post-tensile creep showed no effect on the stiffness of wood at the macroscopic level, but neither were there damage to the cell structure. It can be assumed that there are changes at the microscopic level, but they are not enough to be reflected at the macro scale. It is also challenging to achieve the modifications that occur at the level of a single cell or in thin wood foils; however, the implications of this would be favorable for the development of stronger wood-based products.
In this work, the impregnation quality and mechanical properties of Pinus radiata D.Don treated with different copper nanoparticles (CuNP) solutions (named K1 and K2) and a commercial preservative (M) were studied. The impregnation quality of radiata pine wood was analyzed by two indicators, penetration and retention. The micro-distribution of preservative in the treated wood was qualitatively evaluated by SEM-EDS, both in the samples containing CuNP and in those treated with the commercial preservative. In addition, some mechanical properties were studied in the preserved wood including MOE, MOR and hardness. The results indicated values by ED XRF retention of 0.96 kg/m3 and 0.86 kg/m3 for K1 and K2, respectively, and 1.01 kg/m3 for M wood impregnated. In the penetration determined by colorimetric test, the wood samples impregnated (with K1, K2 and M) showed 100% penetration. The distribution of CuNP and micronized copper within the wood structure was confirmed by SEM EDS mapping. In mechanical properties, a reduction in MOE was reflected in all wood treated. The control samples were far superior to the K1 and M treated samples and slightly superior to the K2 samples, with no statistically significant differences. On the other hand, samples impregnated with K1 and K2 showed the highest values in hardness parallel and perpendicular to the grain, revealing that these preservative solutions tend to increase hardness. Overall, when it comes to the samples impregnated with micronized copper (M), the mechanical properties were considerably lower compared to the CuNP treated and control wood. Therefore, the CuNP-based preservative did not strongly affect the mechanical properties of the preserved wood.
The main objective of this study was to develop cellulose nanofibers from the thermomechanical pulp (TMP) of Radiata Pine (Pinus radiata D. Don), and for this, a one-step micro-grinding process was used. The newly developed material was called thermomechanical pulp nanofibers (TMP-NF). In the first instance, a determination of the constituents of the TMP was carried out through a chemical characterization. Then, TMP-NFs were compared with cellulose nanofibers (CNF) by morphological analysis (Scanning Electron Microscopy, SEM, and Atomic Force Microscopy, AFM), X-Ray Diffraction (XRD) and Fourier-Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR). In addition, films were developed from TMP-NF and CNF using a vacuum filtration manufacturing method. For this study, 0.10, 0.25, 0.50, and 1.00% dry weight of CNF and TMP-NF were used as continuous matrices without organic solvents. The films were characterized by determining their morphological, physical, surface properties, and mechanical properties. The main results showed that morphological analysis by SEM and AFM for the fractionated sample indicated a fiber diameter distribution in the range of 990-17 nm and an average length of 5.8 µm. XRD analysis showed a crystallinity index of 90.8% in the CNF, while in the TMP-NF, it was 71.2%, which was foreseeable. FTIR-ATR analysis showed the functional groups of lignin and hemicellulose present in the TMP-NF sample. The films presented apparent porosity values of 33.63 for 1.00% solids content of CNF and 33.27% for 0.25% solids content of TMP-NF. The contact angle was 61.50° for 0.50% solids content of CNF and 84.60° for 1.00% solids content of TMP-NF. Regarding the mechanical properties, the modulus of elasticity was 74.65 MPa for CNF and 36.17 MPa for TMP-NF, and the tensile strength was 1.07 MPa for CNF and 0.69 MPa for TMP-NF. Although the mechanical properties turned out to be higher in the CNF films, the TMP-NF films showed improved surface characteristics as to surface hydrophobic and apparent porosity. In addition, the easy and rapid obtaining of TMP nanofibers makes it a promising material that can be used in biologically based nanocomposites.
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