Research Articles

Composites made from annual plants, such as winter rapeseed, can be used as an alternative to wood-based composites because of their ecological character, low price, as well as physical and mechanical properties. The goal of this study was to prepare such boards and evaluate their properties. Unmodified material and chemically and hydrothermally modified rapeseed particles glued by powder polyester glue were used. The characteristics measured were the internal bonding, swelling and moisture uptake over time, and surface soundness. The results showed that modification of the raw material influenced the properties of the resulting composites. The highest swelling values were exhibited by the boards with particles that were alkaline-modified. Boards made from hydrothermally modified particles achieved the highest strengths compared with the commercially produced boards. The alkaline modification of the particles resulted in a stronger adhesive bond between the particle and adhesive. During the internal bonding test, the boards made from the alkaline-modified particles exhibited cohesive failures in the particles. Therefore, the modification of the particles increased the mechanical properties of the boards, but the physical properties deteriorated.

Much research has been carried out to improve the wettability and to overcome the low adhesion of tire rubber for use in developing new building materials, such as wood-cement panels. Corona surface treatment (air plasma) of rubber particles was used in this study with various application times to improve adhesion and the interface between the particles and the cementitious matrix. Another aspect evaluated in this study was the partial replacement of wood particles by tire rubber waste in wood-cement panels. The particulate rubber residue was subjected to various corona application times to determine the most suitable treatment; the samples showed the most desirable qualities after 20 min of air plasma treatment. Then, panels were produced using Pinus oocarpa particles associated with various contents of tire rubber after corona treatment. Overall, after 20 min of air plasma treatment, the wettability and adhesion properties of tire rubber waste improved. The use of 5% rubber to replace pine wood in wood-cement panels led to a substantial improvement in the physical-mechanical properties evaluated, making its production feasible and promoting the reuse of a material harmful to the environment.

Market globalization, with its accompanying higher living standards, food availability, and sedentary jobs noticeably affects the eating habits and lifestyles of people. Therefore, the body weight of populations is increasing globally. These changes must be taken into account when various everyday items (furniture, clothes, and shoes) are designed. Population-based studies dealing with measuring the height and body weight of adult male populations were analyzed (body mass index categories: 25 kg/m² to < 30 kg/m² (overweight), > 30 kg/m² (obese), > 35 kg/m² (severely obese)). Because of the analysis of anthropometric parameters in Central Europe, especially Slovakia, it is necessary to produce chairs with two weight categories for the common population (normal weight up to 110 kg) and a population with a higher weight. The aim of this research was to investigate the effect of the body weight of users on the load capacity and dimensions of structural elements of chairs. Following the static analysis of the load-carrying capacity of several chair types, it was calculated that the only suitable construction type for users with a higher weight is the construction with stretchers. The cross-section of the leg space and side rail increased by 20% and 25%, respectively, in the case of a 150-kg user and tenon dimensions of 10 mm × 60 mm × 30 mm.

This study investigated the dyeing methods (soaking and vacuum-pressure), types of dye (direct dye and reactive dye), and dyeing parameters (dye concentration, dyeing time, and temperature) in the veneer dyeing process for Eucalyptus globulus grown on plantations in Australia. The dyed veneers were assessed in two ways: dye penetration, which was determined using ImageJ software, and visual veneer grading for identifying any damage (curves or cracks). Veneers with different moisture content (MC) levels were used and were called green veneer (80% ± 5% MC) and dried veneer (12% MC). The study showed that the reactive dye Procion Brown P2RN at a concentration of 2% resulted in a significantly higher dye penetration than the other dyes. Soaking was not recommended as the dyeing method for this species because the dyed samples were severely damaged by the pre-treatments and high temperatures. A dye penetration of 100% was achieved when using the vacuum-pressure method with a dyeing time of 120 min, a pressure of 1000 kPa, and the addition of 20 g/L of sodium chloride. The results of this study can be applied in further research on the veneer dyeing process for this species.

Combustion characteristics of cattle manure (CM) and pulverized coal blends under oxy-fuel atmosphere were considered. Factors such as the furnace temperature, O2 concentration, and blending ratio were analyzed. The experiment under non-isothermal and isothermal conditions were used to study effects of the heating rate. Blended CM can improve the combustion characteristics of pulverized coal. However, a difference exists between the increase of the blending ratio of CM with Shanxi bituminous coal (SX) and Xiaolongtan lignite coal (XLT) under various O2 concentration conditions. More attention should be paid to the blending ratio > 50%. CM and coal co-firing affected by the furnace temperature had a close association with its characteristics. Inhibition was found in most conditions, and the trend of interaction between CM and coal under the non-isothermal and isothermal condition was consistent. These experiments provided information for the utilization of livestock and poultry manure and pulverized coal blends in the oxy-fuel atmosphere.

Polyester/kenaf composites reinforced with zinc oxide nanoparticles (ZnO NPs) were fabricated. The nanoparticle treatment had a noticeable effect on the mechanical properties of the composites. Kenaf treatments with five different concentrations 1%, 2%, 3%, 4%, and 5% were performed. The mechanical analysis showed an increased flexural strength stability and break elongation in the functionalized ZnO NPs-treated kenaf polyester resin composites. The polymer nanocomposites with 2% ZnO NPs had stable mechanical properties with moderate elastic properties compared with the remaining ZnO NPs systems. The mechanical properties of the composites that contained different layers of kenaf mat demonstrated positive influence on the polymer nanocomposites. The material increased in stiffness with an increase in layers from 1 to 5. The results of weathering confirmed the stability of the polymer nanocomposites with increased stability. The 2% nanoparticle coating with a 5-layer kenaf layer revealed no remarkable changes in the mechanical degradation throughout the 6-month weathering period. The results of the mechanical properties tests suggested that a 2% ZnO NPs concentration with five kenaf layers had the highest moisture resistance, thus; the ZnO NPs acted as a water repellent agent.

The management of variables with uncertainties in stochastic cash flow models related to capital investments in energy crops projects allows, in addition to risk measurement, the adoption of proactive measures that can assure the generation of value to the project. This study analyzes the economic feasibility of sugarcane cultivation for bioethanol production from sugar cane molasses, under technical and economic uncertainty. The analysis characterizes sugarcane productivity, capital investment, production costs, and costs of cutting, loading, and transport, considered as stochastic variables. For this, the uncertainty was propagated through Latin hypercube sampling. Sensitivity analysis was also performed to assess the impact of these variables. The results indicated that the productivity of the crop and the sugarcane price in the conveyor belt are determinant to guarantee the economic value of the investment project. There is a high probability of achieving positive NPV (net present value), in addition, MIRR (modified internal rate of return) is 5% higher than MARR (minimum acceptable rate of return).

To investigate the feasibility of replacing eucalyptus fiber with lignin, ternary composites (Lignin/Eucalyptus fiber/Polyvinyl chloride) were prepared by extrusion molding, and the effect of the lignin content on the wood-plastic composites was studied. The microstructure, functional groups, creep behavior, and thermal behavior of the ternary composites were analyzed. The results showed that the tensile strength, flexural strength, and impact strength decreased with an increasing lignin content, whereas, the water absorption, creep resistance, hardness, and heat resistance of the ternary composites improved.

The association between natural mold resistance and the wood’s chemical components was studied for nine wood species. The mold resistance of the different wood species was tested by artificially accelerated tests and scanning electron microscopy (SEM). The chemical components were analyzed by gas chromatography-mass spectrometry (GC-MS). The results indicated that the sequence of mold resistance of different wood flours was as follows, from greatest to least resistance: spruce, Mongolian pine and camphor, toon and teak, eucalyptus (E. urophylla and E. grandis × E. urophylla), sweetgum, and castor straw fiber. GC-MS analysis indicated that the total contents of the antifungal compounds present in all wood flour extractives were consistent with the sequence of mold resistance of wood flour. This suggested that the natural durability of wood flour against molds was affected by its chemical components.

The effects of the tensile elastic properties of fabrics used as cushion covers, foam thicknesses of cushion cores, seat bases as the support of an upholstered wooden furniture seat foundation, and sitting areas of subjects were studied relative to the load-deformation behavior of cushions situated on wooden seat base frames when subjected to human sitting forces. The experimental results indicated that the sitting area of a subject, fabric tensile elastic constant, and foam thickness had significant effects on the cushion stiffness, but the seat base type did not. The sitting area of a subject had the greatest effect on the cushion stiffness constants, followed by the fabric tensile elastic constant and foam thickness. A regression technique was proposed to derive a power equation for the estimation of the cushion stiffness using the parameters investigated in this study.