Research Articles

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.

Sponge gourd (Luffa cylindrica L.) fiber-reinforced cement composites were developed and analyzed. Dried sponge gourd fruit’s fibrous vascular system forms a natural 3D network that can reinforce matrices in composite materials, diverting cracks along the complex array of 3D interfaces between the fibers and the cementitious matrix. To avoid fiber deterioration, the cement paste was modified by incorporating pozzolanic materials. The fibers were mechanically characterized by tensile testing of strips of the 3D natural fiber array and of single fibers extracted from the array. The fibers had an average tensile strength of 140 MPa and an average Young’s modulus up to 28 GPa. Image analysis showed that the fiber spatial distribution inside the 3D network was random. The modified cement paste was characterized by its workability (flow table test) and mechanical behavior (compression and three-point bending tests), with average results of 430 mm, 62.7 MPa, and 6.2 MPa, respectively. Under bending, the cement matrix collapsed after the first crack. The sponge gourd-cement composite manufactured with 1 wt% of fibers showed an average flexural strength of 9.2 MPa (approximately 50% greater than the unreinforced matrix). Importantly, the composite also presented a limited deflection-hardening behavior. These results support sponge gourd’s possible use as reinforcement in cement matrix composites.

Sugar cane bagasse was delignified in a two-step process with peracetic acid and alkali. Peracetic acid pre-treatment with concentration of 25% based on oven-dry fiber at 60 min, with a liquor to wood (L/W) ratio of 9:1 and a temperature of 50 °C improved the second stage delignification, compared with soda pulping. The second stage was carried out at three levels of temperatures, times, and 20% sodium hydroxide based on oven-dry fiber. Soda pulping at 165 °C, 120 min, 20% sodium hydroxide based on oven-dry fiber, and L/W 10:1 was selected to compare with two-step delignification. The two-step delignification reduces the severity of pulping conditions, including temperature and pressure, and subsequent imposes less risks compared with the soda pulping at 165 °C. The advantages of this method are high delignification and reduction of kappa number with respect to lower temperature and pressure compared with soda pulping. The total time in two-step was increased from soda pulping. Two optimum conditions for alkali step were obtained at 120 °C and 140 °C and 90 min for pretreated bagasse pulping, and similar properties were achieved with soda pulping at 165 °C and 120 min. The yield of fibers, Kappa number, and data analysis using Duncan method were measured and recorded.

A verification experiment was performed to monitor the impact of technical, technological, material, and tool factors on the roughness of the milled surface (average roughness Ra) during plane milling of thermally treated spruce wood. The technological parameters were: four heat treatment temperatures (160 °C, 180 °C, 200 °C, and 220 °C; one sample kept in its natural state), three feed rates (6 m·min-1, 10 m·min-1, and 15 m·min-1), three cutting speeds (20 m·s-1, 40 m·s-1, and 60 m·s-1), three tool rake angles (15°, 20°, and 30°), and three types of used blades (HSS 18% W with AlTiCrN coating, tool steel knife 19 573 induction hardened, and steel knife MAXIMUM SPECIAL 55). The result of the experiments showed the individual effects of the parameters in the following order: used knife, heat treatment, angular geometry, cutting speed, and feed rate.

The biodegradability of a material has been an important measure in packaging design. Green biocomposites, which are made of natural fiber and biopolymer matrix, are promising alternative materials in single-use packaging to replace conventional materials. Selection of the most suitable natural fiber for reinforcement in green biocomposites is an initial attempt towards reducing resources depletion and packaging waste dumping. A selection system of analytic hierarchy process (AHP)-based method is proposed. Food packaging materials’ requirements and production factors are the basis of selecting 13 vital characteristics of natural fibers as the selection criteria. Nine natural fibers were assessed based on data gathered from recent literature. From the results, ijuk obtained the highest priority score (14%). Whilst, sisal had the lowest rank with a score of 8.8%. Sensitivity analysis was then performed to further validate the results, and ijuk remained at the top rank in four out of the six scenarios tested. It was concluded that ijuk is the most suitable natural fiber for reinforcement in green biocomposites for food packaging design. Nonetheless, for future development, more comprehensive selection criteria, such as fiber specific properties, fiber processing, and fibre treatment, are suggested to be included in the framework for more comprehensive results.

Potential application of Sembilang bamboo (Dendrocalamus giganteus) as a fuel source or an adsorbent was investigated, due to its large diameter, fast growth speed, and growth type. Samples of D. giganteus were carbonized at various temperatures, and then their physicochemical, fuel, and adsorption properties were analyzed and compared to the properties of Moso bamboo (Phyllostachys edulis), which is widely used as a raw material for charcoal in Northeast Asia. The volume, weight, and density of the D. giganteus samples were greatly reduced between carbonization temperatures of 200 °C and 400 °C. It is possible that the high levels of SiO2 and K in D. giganteus may cause a high electric conductivity value in Dendrocalamus giganteus charcoal, which is a poor fuel source because of its high ash content and low calorific value. The acidity of D. giganteus disappeared at a carbonization temperature of 400 °C and the pH of D. giganteus increased up to 10.3. The adsorption power of D. giganteus, in terms of iodine and methylene blue, was higher than that of P. edulis. Based on the results of this experiment, the proper utilization of Sembilang bamboo charcoal was suggested as a chemical adsorbent.