Volume 14 Issue 3

This paper studies the impact of refining heterogeneity on paper property development and pressability. Three trials were performed in different refining equipment. The results showed that the strength development was due mostly to the water retention value (WRV) and the fiber straightness. Curly fibers require more energy to reach a given strength property. A heterogeneous refining, which in this case was performed by mixing less refined and highly refined pulps in different proportions, increased the energy requirement to reach a given tensile index or tensile stiffness index. The pressability of the pulps was not affected by the refining heterogeneity. At a given WRV, the pulp had the same solids content after dynamic pressing independent of the degree of heterogeneity.

Selecting clones with the best genetic material is one goal of eucalyptus breeding programs. Understanding the variations between the wood from different hybrid clones during drying is necessary to process improvement. This study aimed to select eucalyptus clones for lumber production based on their drying defects. From a plantation in Brazil, 42 trees within the seven different clones were used. All trees were 13 years old. The effect of the genetic material on the apparent density of the clones was significant. It was possible to separate the clones into four groups. Even if the wood was from the same genotype, a load of boards made from Eucalyptus grandis × Eucalyptus urophylla wood exhibited heterogeneity in the drying rate due to factors inherent in the wood, especially the apparent density. The apparent density negatively affected the drying rate of the clones, i.e., approximately 70.5% of the drying rate was explained by the apparent density. Denser pieces exhibited lower drying rates. For a more homogeneous natural drying, it is recommended that the composition of the stacks use pieces with the same apparent density and thus similar initial moisture. The air-drying process is recommended to release any free water from eucalyptus woods.

Effects of bleaching and heat treatment were investigated for Indosasa angustata bamboo grown in Vietnam. Hydrogen peroxide (H2O2) at a concentration of 30% was used for the bleaching process. For the heat treatment, the bamboo strips were heat-treated at two different temperatures (120 °C and 140 °C) for 3 h. There was a slight increase in the lignin and hemicellulose contents of the samples treated at 100 °C for 1 h when H2O2 was used. The water absorption rate did not change much, and the treated bamboo strips became brighter after undergoing bleaching. For the heat-treated samples, the lignin content slightly increased after the samples were heated at both 120 °C and 140 °C for 3 h. Moreover, the higher heating temperature led to a lower hemicellulose content, a darker colored bamboo sample, and a lower water absorption rate for the treated bamboo strips.

This study applied response surface methodology for modeling and optimizing heat-treated wood dowel joints, the most used joint in furniture construction. The factors examined were dowel length, dowel diameter, and adhesive consumption. The bending moment capacity of the joints loaded in compression or tension were the responses. The load was applied at a constant speed until a major separation between the two parts occurred. To figure out the bending moment capacity, the ultimate failure loads and the moment arms were obtained during testing the joints. The joints were tested by using a universal testing machine. A two-factor interaction model was established to describe the relationship between the factors and the responses. An analysis of variance was employed to test the significance of the developed mathematical model. The dowel length, dowel diameter, and adhesive consumption had significant effects on the bending moment capacity of the heat-treated dowel joints. The dowel length was the main factor that affected the bending moment capacity of the heat-treated dowel joints.

Waste cotton-derived carbon materials were synthesized using various chemical activators, and their performance as solid acid catalyst supports was studied. The pore surface structures of the carbon materials were quantitatively characterized by surface fractal dimension, and the relationship between pore surface structure and the density of catalyst was also investigated. The pore sizes were grouped into four ranges, including fractal dimensions D1 (0.32 nm to 2.0 nm) and D2 (2.0 nm to 50 nm), as revealed by N2 adsorption and Frenkel-Halsey-Hill fractal theory. In addition, D3 (50 nm to1000 nm) and D4 (1000 nm to 200,000 nm) were revealed by mercury intrusion porosimetry and the Friesen-Mikula fractal theory. The surface fractal dimension D was found to be proportional to the density of SO3H groups from sulfonation at the same carbonization temperature. A larger D value corresponded to the exposure of more active sites, which was more favorable for improving the density of SO3H groups. With the rise of carbonization temperature, the surface fractal dimension also increased. However, the graphitization structure of carbon materials increased with the rise of carbonization temperature, which reduced the active sites of SO3H groups. Finally, the solid acid catalysts prepared via the sulfonation process were used in the esterification reaction of levulinic acid and n-butanol.

Factors influencing the vertical driving force magnitude applied to screws during the process of driving the screws into faces of particleboard materials were investigated. In particular, the screw penetration depth and screwdriver air pressure were evaluated relative to critical torques, such as seating and stripping torques. Experimental results indicated that vertical driving forces significantly affected the magnitude of critical driving torques when no pilot hole was drilled, but this influence became non-significant when 3.2-mm diameter pilot holes were drilled. Screw-driving power had no significant effect on the magnitude of critical driving torques in particleboard materials if no pilot hole was drilled, but if pilot holes were drilled, increasing the screwdriver air pressure from 0.45 to 0.62 MPa led to increases in stripping torques. Increasing the screw penetration depth from 12.7 to 19.1 mm can significantly increase seating and stripping torques.

Lumber is often air dried in an air drying yard prior to being placed in a dry kiln for final moisture content removal. The rate of the air drying process is dependent on local weather conditions and wood moisture content. Introduced more than 30 years ago, the Drying Index is a method to estimate the relative drying time using the difference in vapor pressures between the dry bulb and wet bulb temperatures. This paper extends its application and describes the development and use of an Air Drying Index to estimate the relative potential of a geographic location to air dry lumber based on the average monthly climate conditions for that location. The monthly Air Drying Index for 252 US locations is presented, and the annual mean for each location was used to develop an air drying map.

Bio-based flours derived from distiller’s dried grains with solubles (DDGS), Osage orange seed meal (OOSM), or defatted commercial soybean meal flour-Prolia (PRO) were employed as adhesives with Eastern redcedar (Juniperus virginiana L.) wood (ERC) to fabricate composite wood panels (CWPs). OOSM and DDGS were defatted, milled, and screened prior to use. PRO was employed as provided. DDGS, OOSM, or PRO flour were mixed dry with ERC wood to make CWPs using the following conditions: molding temperature of 185 °C, ERC particle sizes of ≤75 µm to 1700 µm, pressure of 5.6 MPa, and employed in flour dosages of 10% to 75%. Flexural properties of DDGS and OOSM flour-ERC composites were similar to composites fabricated using PRO as the resin/adhesive. The dimensional stability properties (water absorption and thickness swelling) of all composites were similar. ERC CWP properties satisfied several European Committee Industry Standards for commercially acceptable CWPs in terms of their flexural properties but were inferior in terms of thickness swelling when subjected to water immersion testing. Surface roughness and color analysis of CWPs were also conducted. Statistical correlations between surface roughness and color properties and the composition of the CWPs were conducted. ERC CWPs were found to have termite resistance.

The influence of selected technological aspects was studied relative to characteristics of oriented strand lumber (OSL) boards manufactured from pine strands. Six types of boards were prepared, differing in the strand fraction size, density (700 kg/m3 and 800 kg/m3), and adhesive used to glue the strands in the core layer. The adhesives compared were melamine-urea-formaldehyde (MUF) and polymeric diphenylmethane diisocyanate (pMDI). The results showed that the OSL boards had good physical and mechanical properties, even though pine strands of diverse characteristics, particularly in terms of their length and width, were used for their production. The influence of strand size was clear in the results of the bending and elongation tests. Both for the bending test and tensile strength in a direction parallel to the wood grain, the properties were on average 20% greater for boards made of larger strands compared to those made of smaller strands. However, the latter demonstrated greater internal bonding strength (IB). The weakness of OSL boards made from small strands was their low modulus of elasticity, particularly when the board density was simultaneously reduced.

The color changes of compression and opposite spruce (Picea abies L. Karst) wood were evaluated as a function of different drying conditions. Compression wood samples and their corresponding opposite wood samples from the opposite part of the log were compared after three different drying modes. The color of the samples before and after the drying was characterized using the color coordinates L*, a*, b*, C*ab, C, h*, Sab, and the color difference (ΔE*) in the standard color space according to the International Commission on Illumination (CIELAB). The drying temperature was the most remarkable factor for discoloration of the samples. The lightness (L*) of the samples decreased with increased temperature. However, darkening was more pronounced in the opposite wood samples. The overall color difference (ΔE*) was found to be higher in the opposite wood. The compression wood was more saturated in color with a deeper hue angle due to the drying process.