Thermo-hydro-mechanical (THM) treatments can be used to improve certain properties of underutilized wood species, especially those with low densities. These treatments densify the wood by softening the cell walls using heat, pressure, and moisture but are subject to set-recovery (recovery of compressive deformation) when exposed to humidity. Phenol-based resins have been successful in mitigating this issue when impregnated into the wood. This work explores the use of a new phenol-based resin combined with a THM treatment to limit set-recovery and produce products with the potential for flooring applications. Scratch resistance, hardness, and glue-line shear strength were used to assess the performance. The THM treatment and impregnated phenol resin used in this study increased the scratch resistance, density, and hardness of natural poplar wood and created satisfactory bonding conditions for flooring purposes. With optimization of THM parameters and resin solids content, the resulting product could provide a high-quality flooring material used alone or as a thin laminate from a low-density species like poplar.Abstract
The effective use of agricultural residues is desirable. In this study, the manufacturing of mouldings using sweet sorghum bagasse powder and citric acid as an adhesive was attempted. The effects of the application method and citric acid content on the bending properties and water resistance of the mouldings were investigated. Powder and liquid applications were used. The citric acid solid content based on the total weight of the mouldings was adjusted to 0, 15, 20, 25, and 30 weight percent. The dumbbell-shaped moulding was manufactured at 200°C and 4 MPa for 10 minutes. The relationship between the bending properties and citric acid content differed depending on the application method; the powder application was effective for obtaining high bending properties with a lower citric acid content. The water resistance of the moulding was greatly affected by the application method when a low citric acid content was used, and it was affected by the citric acid content when a high citric acid content was used. According to the data measured from Fourier-transform infrared spectroscopy, it was easy to contain unreacted citric acid in the moulding with the powder application, and an ester linkage formed easily when the liquid application was used. It was suggested that the citric acid tends to work as an adhesive in the powder application, and it tends to modify the bagasse powder in the liquid application.Abstract
The organic material of wood treated with inorganic nanoparticles has gained significant improvements in its stability against ultraviolet (UV) light and moisture degradation. Here, a new method was proposed to modify Chinese fir (Cunninghamia lancellata), which was treated by high-temperature steam and coated with titanium dioxide (TiO2) nanoparticles. Due to the synergistic effect, the treated Chinese fir can obtain the properties of surface hydrophobicity and photoaging resistance that can prevent the invasion of moisture and the damage of UV light from sunlight. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction were used to characterize the morphology, structure, chemical composition, hydrophobicity, and light-aging resistance of the treated Chinese fir. By means of comparative experiments, the Chinese fir was treated with 5 percent nano-TiO2 solution and annealed at 300°C. The surface water contact angle reached to about 130°, indicating the strong hydrophobicity. In addition, the total color difference (ΔE*) after accelerated light aging for 120 hours was only 45 percent of the control sample.Abstract
An approach for implementing statistical process control and other statistical methods as a cost-savings measure in the treated-wood industries is outlined. The purpose of the study is to use industry data to improve understanding of the application of continuous improvement methods. Variation in wood treatment is a cost when higher-than-necessary chemical retention targets are required to meet specifications. The data for this study were obtained in confidence from the American Lumber Standard Committee and were paired, normalized assay retentions for charges inspected by both the treating facility and auditing agencies. Capability analyses were developed from this data for three use categories established by the American Wood Protection Association (AWPA), including UC3B (above ground, exterior), UC4A (ground contact, freshwater, general use), and UC4B (ground contact, freshwater, critical structures, or high decay hazard zones). Agency and industry data indicate that between 4.45 and 9.82 percent of the charges were below the lower confidence limit of the passing standard (LCLAWPA), depending on use category. A Taguchi loss function (TLF), which is quadratic based and decomposes the monetary loss into shift and variation components, was developed to estimate the additional cost due to process variation. For example, if a treatment input cost of $1.00/ft3 is assumed for UC3B, reducing the variation in total retention allows lowering treatment targets, e.g., 1.45 to 1.38, reducing costs to $0.76/ft3. The study provides some important continuous improvement tools for this industry such as control charts, Cpk, Cpm capability indices, and the one-sided TLF.Abstract
Copper remains one of the key biocides for protecting timber in soil contact. Historically, copper-based preservatives relied on solubilized copper. Over the past decade, micronized copper systems have largely replaced soluble copper systems in this application. While micronized copper chemistries have been shown to perform well over time with reduced copper leaching compared to solubilized copper, data are lacking on the effects of repeated leaching cycles on resistance of the timber to fungal attack. The potential effects of repeated leaching cycles of micronized copper azole–treated southern pine (Pinus spp.) blocks on both copper losses and resistance to fungal attack were explored over 20 leaching cycles using Gloeophyllum trabeum and Rhodonia placenta as test fungi. Copper losses during leaching were elevated for the first two cycles and steadily declined with additional cycling. There were no noticeable differences in fungal-associated weight losses in blocks exposed to G. trabeum. There was only a slight increase in average block weight losses with R. placenta, although blocks exposed to this fungus experienced higher weight losses with increased leaching cycles. The results suggest that repeated leaching exposures may produce some localized increases in susceptibility to fungal attack, but the overall effects were minor.Abstract
As China is the largest importer of wastepaper in the world and is highly dependent on the international market, the relationship between the Chinese and international wastepaper markets affects the stability of both markets. The purpose of this study was to investigate the impact of China's newly implemented wastepaper polices on the degree of integration between the Chinese and international wastepaper markets and analyze the dynamics of the relationship between the two markets over time. We developed both the static and dynamic total spillover indices to analyze the degree of integration in average and in time-varying perspectives and performed E-Divisive with Medians (EDM) on the dynamic total spillover index to evaluate the impacts of the new policies. The results revealed that the Chinese and international wastepaper markets were integrated. The calculated dynamic total spillover index varied widely during the studied period and presented an overall declining trend, indicating that these policies have disrupted the integration relationship between the two markets. The results of EDM detected structural breaks in the dynamic spillover index due to the new policies, further confirming and describing the negative impacts of the new policies on the integration relationship between the two markets. Since mutual dependence exists between the Chinese and international wastepaper markets, the interventions on the integration relationship have led to dramatic fluctuations and expanding price differences between the two markets, imposing risks and uncertainties on the stable development of China's paper industry and the global recycling industry.Abstract
Density (D) and moisture content (MC) are two important physical properties of wood and bamboo, which are highly correlated with many other physical and mechanical properties. In this study, the X-ray computed tomography (CT) technique was used to determine the D and MC of poplar (Populus xiangchengensis) and bamboo (Phyllostachys edulis). There was a statistically significant difference in the CT-measured numbers for D and MC between these species. The D-CT and MC-CT linear models for both species were independently established: Dpoplar = 0.00098 × H + 1.02603, Dbamboo = 0.00118 × H + 0.98684, MCpoplar = 0.00309 × H + 1.89982, and MCbamboo = 0.00131 × H + 0.31488, where H is the CT number. The determination coefficients, R2, of the models were all higher than 0.97. Additionally, the R2 values obtained for model validation were also all higher than 0.97. These results indicated that it is feasible to reliably determine D and MC of wood and bamboo using the X-ray CT technique. This study aims to provide reference data for CT detection of the D and MC of wood and bamboo.Abstract
West Virginia's forest products industry (FPI) has long been viewed as an important industry to the state. However, there is a lack of recent data regarding the economic contribution of the industry to the state's economy. The housing market collapse of the mid-2000s, subsequent recession, continued increasing global competition, natural gas boom, and other macroeconomic trends have affected the FPI in the state. The continuing evolution of the state economy necessitates a reexamination of the role the FPI plays in the state. Thus, this article examines the historical contribution of the FPI to West Virginia's economy using 2006, 2010, 2015, and 2017 data. Both the direct and total economic contributions of the industry substantially declined from 2006 to 2010. The largest declines were experienced in the secondary solid-wood products and wood furniture sectors. Between 2010 and 2015, the industry's direct and total contributions rose for all measures evaluated. Between 2015 and 2017, all measures of direct and total contributions of the industry also increased but at a much slower pace and remained lower than 2006 levels. The inability of the FPI in the state to return to 2006 levels of direct contributions suggests that long-term industry trends such as the continued offshoring of value-added forest products sectors and increased industry automation are still putting negative pressure on direct industry growth. Additionally, the industry is facing new challenges such as uncertainty about the future availability of the foreign markets and competition for resources from emerging industries.Abstract
Southern pine lumber 2 by 8s and 2 by 10s from across the Southeast were used as the parent material source for this study. Fundamental data were collected for each piece of lumber: growth rings per inch (RPI), presence of pith, and specific gravity (SG), among other information. After mechanical property evaluation through static bending, small clear specimens were cut from the lumber pieces and tested for compression perpendicular to grain (C⊥). Those values were then compared with 2 by 8 and 2 by 10 average RPI and density. The results were significant for both tests. Therefore, a segmentation of the growth ring data into groups of <3, 3 to 5, and >5 RPI was conducted. Correlations were run specific to each group, per both lumber sizes, and still significance was found. Segmentation of SG was not significant only for 2 by 8 SG <0.4. The results suggest that SG is a better predictor of C⊥ than RPI alone due to statistical significance found during these analyses.Abstract
The drying characteristics of urea formaldehyde (UF) resin–impregnated Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) wood were determined by the 100°C-test method and scanning electron and fluorescence microscopies to predict an optimal drying schedule. Compared with the untreated sample, the UF resin–impregnated Chinese fir wood presented a lower grade of initial checks and a faster initial drying velocity, but a higher grade of internal checks and a slower drying velocity at the later stage. The average drying velocity of the UF resin–impregnated wood was 38.9 percent lower than that of the untreated sample. The predicted drying schedule was applied to the UF resin–impregnated wood and the resulting grades of the drying characteristics were in good agreement with the required national standard values. The resulting dried UF resin–modified composite would become a potential candidate for a shallow depth rock mining supportive system with its stable mechanical performance.Abstract
Encapsulation of cellulose with wax and surfactant is a physical way to restrict cellulose-to-cellulose attraction. Because wax is often used in the wood composite process, industrial manufacturers would not have to upgrade or add expensive equipment to handle cellulose addition. The encapsulated cellulose particles could easily be transported to composite and polymer facilities and blended in a homogeneous fashion for a multitude of products and composites. It was the objective of this study to utilize differential interference contrast (DIC) microscopy to characterize the wax and surfactant coverage and encapsulation morphology of the wax–surfactant–cellulose composite. The lengths and widths of the cellulose particles were significantly changed after encapsulation. DIC microscopy found that we could fine-tune wax coverage to control homogeneity and reduce fiber bundling during dispersion. It was found that surfactants were not necessary to enhance coverage if a 1:4 ratio of wax to microcrystalline cellulose was used. However, if more wax is desired, then surfactants may be necessary to suppress fiber bundles during dispersion.Abstract
In this article, the surfaces of 2D and 3D polypropylene (PP) membranes were sanded with different brush-type sanding belts and a waterborne primer and topcoat were applied; the effect of the sanding process on the adhesion of the waterborne paint film on a PP decorative membrane surface was tested. A contact angle meter was used to determine the effect of the sanding process on the hydrophilicity of a PP decorative membrane surface. A scanning electron microscope and a roughness tester were used separately to observe the changes in the surface microfeatures and the roughness on PP decorative membranes before and after the sanding process. A 3D profilometer was used to test the changes in the surface roughness and 3D microtopography on PP decorative membranes before and after the sanding process, and a crosscut tester was used to test the changes in the surface adhesion of waterborne paint film on PP decorative membranes before and after the sanding process so as to research the effects of different sanding parameters on the adhesion of waterborne paint films on PP decorative membrane surfaces. The research results showed that the surface sanding process could be used to decrease the surface contact angle, increase the roughness, and improve the wettability of PP decorative membranes. In general, under experimental conditions, a 400-grit sanding belt and two sanding passes were the suitable parameters for 2D PP decorative membranes, and a 320-grit sanding belt and two sanding passes were suitable for 3D PP decorative membranes.Abstract