Volume 14 Issue 4

Autonomous self-repairing properties can prolong the service life of materials. In this paper, galactomannan hydrogel with high mechanical strength was prepared by graft copolymerization of galactomannan with acrylamide and octadecyl methacrylate in aqueous solution. The microstructure, water absorption property, self-healing behavior, and mechanical properties of the hydrogels were investigated using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), etc. The galactomannan hydrogel had the highest tensile strength of 49 KPa and strain of 3000%. The water absorption reached 2340%, and the removal rate of methylene blue was more than 80%. Galactomannan hydrogels demonstrated significant self-healing properties. The cut hydrogel was quite effective in self-repairing in a few minutes, and the self-repairing strength increased with increasing contact time of hydrogel cut surfaces. The healing efficiency of fracture strain could reach 92.7% of the original sample in 10 h. The maximum water absorption of hydrogel reached 2340%. The maximum removal rate of methylene blue by hydrogel reached 80.5%, and the maximum adsorption capacity was 19.3 mg/g. The novelty of the work lies in octadecyl methacrylate being used for galactomannan cross-linking with the ability to self-repair after fracture. The galactomannan self-healing hydrogel has potential in water treatment and sealing technology.

Natural lignocellulosic biomass is a valuable feedstock for soluble-grade cellulose (α-cellulose > 90%) with advantageous features such as abundance, high strength, rigid structure, low weight, and it is biodegradable. The bagasse from Agave tequilana Weber var. azul is the main agroindustrial waste from the tequila industry and poses an environmental threat. However, due to its high cellulose content, Agave tequilana bagasse is an excellent candidate for the extraction and utilization of its components. In this study, alkaline cooking, followed by five stages of bleaching, was employed to obtain soluble-grade cellulose pulp. The obtained soda pulp material had a Kappa number (KN) of 23 ± 3, viscosity (μ) of 11.53 to 10.18 cp, degree of polymerization (DP) of 830 to 750, brightness of 87.5%, and percentage of alpha-cellulose (α) of 81 ± 3 at 94 ± 3%. The obtained material was characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy to compare its properties with published information. The waste of A. tequilana Weber var. azul produced pulp with a high percentage of alpha cellulose and a high crystallinity degree. This methodology is novel and simple for the production of soluble-grade cellulose pulp, a raw material for the production of cellulose nanocrystals.

Flexural properties were evaluated of blockboard with spruce (Picea abies Mill) core and faces made of 2.5-mm fromager (Ceiba pentandra) veneer and 3-mm high-density fiberboard (HDF). For these two types of structures, fiber glass, jute, gauze, and cotton fabrics, were separately bonded under the face layers to improve the strength performance. Flexural properties, modulus of rupture (MOR), and modulus of elasticity (MOE) were determined under laboratory conditions. Improved values were found for MOR and MOE tested in the parallel to core grain direction compared to those perpendicular-to-grain. They were 32% to 49% (MOR) and 39% to 95% (MOE) improvements in case of veneer faces and 142% to 161% (MOR) and 134% to 245% (MOE) improvements in case of HDF faces. The best results of MOR and MOE were obtained for glass fiber used as insertion material, the higher ones being reached for specimens tested in the parallel direction to grain, which were 56.1 N/mm2 (MOR) and 6704 N/mm2 (MOE) for HDF faces. Generally, the improvements were more evident on the blockboard structures with veneer faces oriented perpendicular-to-core grain (30% for MOR and 18% MOE) and for HDF faces with parallel core grain orientation (16% for MOR and 6% MOE).

Foam forming is an innovative process for papermaking that yields various paper products with excellent formability and porosity. The stability of the foam is a critical factor in foam forming technology. The effects of different surfactants and gases (N2 and CO2) on the ability of the foams to coalesce and the stability of the foams were studied. The properties of the liquid film were investigated via high-speed camera observation and infrared spectrum. The CO2 foam was less stable than the N2 foam under the same conditions, especially for the polyvinyl alcohol surfactant. The infrared spectra and high-speed camera observation showed that the main factor that resulted in CO2 foam instability was the bubble coalescence caused via the gas diffusion in the foam column, although the process of liquid film thinning was performed simultaneously. The greater the liquid film permeability coefficient of the foam, the easier the gas was able to spread throughout the liquid film. Foam forming technology will likely be employed in many potential pulp and papermaking mill processes.

The use of particleboards (PB) has increased quickly as an alternative engineered wood product mainly due to its having a better ratio of resistance to weight and more elimination of wood defects, such as the presence of knots. Although the panel industry has been constantly growing, innovations are still necessary to improve the final product. The use of metallic oxide nanoparticles on the wood-based panels has the potential to increase the heat transfer process and improve the physico-mechanical properties. The aim of this work was to evaluate the influence of the addition of zinc oxide (ZnO) nanoparticles in PB, correlating the physical and mechanical properties of the panel with the heat transfer process at 180 °C. The results were compared with the Brazilian standard ABNT NBR 14810-2 (2013) and the European standard EN 312 (2010), as well with works found in literature. The results showed a homogenous heat distribution during the pressing, which improved physical properties, decreasing the 24h swelling from 22.2% to 14.9% and the 24 h absorption from 30.29% to 21.0%. Besides that, MOR values was increased from 11.3 MPa to 14.5 MPa and the MOE from 1880 MPa to 2510 MPa.

Ethylene glycol and caprolactam were added during the synthesis process of melamine formaldehyde (MF) resins to develop a new MF formulation with high flexibility, storage stability, and low formaldehyde emissions that can be used for the impregnation of papers. It was demonstrated that the MF resins with amounts of ethylene glycol (molar ratio of ethylene glycol to melamine was 1.0) and caprolactam (molar ratio of caprolactam to formaldehyde was 0.12) achieved higher storage stability, flexibility, and lower free formaldehyde content. The impregnated papers made from these MF resins displayed good dry and wet tensile strength and passed the relevant standard specifications for decorative paper on wood-based panels. The size exclusion chromatography (SEC) and Fourier transform-infrared spectrometry (FT-IR) studies showed that the MF resins produced via incorporation of ethylene glycol and caprolactam had a different molecular weight distribution and polymeric structure.

Extractives, such as carvacrol, play a major role in the durability of Alaska yellow cedar (Callitropsis nootkatensis) heartwood. However, it is a slow and complicated process to identify the levels of these compounds in individual timbers. This study investigated the feasibility of attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and near-infrared (NIR) spectroscopy, coupled with hierarchical cluster analysis (HCA) and principal component analysis (PCA), for detecting carvacrol in wood. Alaska yellow cedar was extracted using sequential Soxhlet extraction with toluene-ethanol, followed by ethanol and hot water. The extracted samples were milled, and the powders were treated with different concentrations of carvacrol. The spectral analysis of the wood that contained carvacrol was conducted using ATR-FTIR and NIR spectroscopy, and the peaks indicative of carvacrol were identified. The chemometric analysis on the spectral data using PCA and HCA distinguished the wood with high (> 34%) and low (< 3.5%) carvacrol concentrations. The results suggest that infrared spectroscopy can be a non-destructive tool for the qualitative and quantitative evaluation of extractives, and possibly for the rapid assessment of Alaska yellow cedar durability.

In order to realize the resource utilization of the Pinus koraiensis pine cone, the polysaccharides were obtained by a traditional hot water extraction process, and the optimal extraction process was confirmed. The effects of a traditional hot water, alkali, and ultrasound assisted extraction on the yield and properties of polysaccharides were studied. The structure, monosaccharide composition, and content of polysaccharides obtained by different extraction methods were analyzed by means of Fourier infrared chromatography and liquid chromatography. Effects of polysaccharides extracted by different methods on the antimicrobial activity of Staphylococcus aureus and Escherichia coli were studied. The scavenging effect of DPPH free radicals were also examined. The optimum condition of the hot water extraction was identified as an extraction temperature of 100 °C, a ratio of material to water at 1:16 (w/v), an extraction time of 4 h, and a yield of polysaccharide at 10.2%. In comparison, the yield of the pine cone polysaccharide was improved significantly to 29.1% by using NaOH solution extraction method. The FTIR spectra of polysaccharides showed that the samples possessed the typical chemical structure of a polysaccharide.

Intense droughts and extreme precipitation events are likely to occur more frequently with global climate change. These drying-rewetting (DW) cycles affect the soil carbon (C) cycle. Biochar addition are reported to affect SOC mineralization and soil organic carbon (SOC) storage. However, the effects of biochar application on SOC mineralization during DW cycles are poorly understood. Two wheat straw (WS25) biochar produced at 300 °C (WS300) and 600 °C (WS600) were used to explore the effects of biochar on SOC mineralization under artificial DW cycles as compared to constant moisture (CM). It was found that biochar had different effects on SOC mineralization depending on biochar type or drying/rewetting period of DW cycles. Just like CK and WS25, WS600 application decreased SOC mineralization under DW cycles compared to CM. To some extent, SOC mineralization during DW cycles was similar to CM for WS300. The results suggested that WS300 addition diminished the reducing effect of DW cycle on SOC mineralization. In addition, biochar exhibited different effects on SOC mineralization depending on the drying and rewetting period under DW cycles. Biochar (WS300) addition during the drying period had less effect on SOC mineralization but increased the flush effect of SOC mineralization during the rewetting period. In conclusions, biochar application significantly affect SOC mineralization following DW cycles.

Biomass seedling containers were prepared from agricultural field wastes (i.e., rice straw and corn stalk) and cow manure, mixed with a starch adhesive. Based on the ratio of raw materials, different models of seedling containers were designed and tested. The performance of the seedling containers was characterized by measuring their forming ability in the mold, water absorption, air permeability, density, and various physical and chemical properties. The results showed that the percentage of well-shaped containers formed in the mold could reach as high as 98% when the ratio of rice straw to cow dung was 1:15, and the moisture content of the containers was approximately 15%. As the straw or stalk content increased, the percentage of seedling containers having good shape and compactness decreased, whereas the air permeability and water retention values increased. At the same mixture ratio, rice straw seedling containers were better than corn stalk seedling containers. The nutrient content of the seedling containers was over 10 times that of the soil surrounding the container, which could contribute to the conservation of soil fertility, as well as the seeding and transplanting of species in the process of ecological restoration.