Research Articles

Waste Tetra Pak containers, from the same brand of milk, were crushed into fibers. They were formed into composites with 40-mesh bamboo fibers with phenolic resin and hot pressed with different parameters. The effects of hot-pressing temperature, hot-pressing time, hot-pressing pressure, phenolic resin amount, and the ratio of Tetra Pak and bamboo on the elastic modulus, static bending strength, internal adhesive bonding strength, and 24 h thickness swelling rate of the composites were investigated by orthogonal testing. The results showed that during the hot-pressing process, hot-pressing temperature was the most important factor for the elastic modulus and static bending strength of the composites and the hot-pressing pressure was the most important factor for the 24 h thickness swelling of the composites. Optimal hot-pressing parameters of TP/bamboo composites were a hot-pressing temperature of 180 °C, hot-pressing time of 16 min, hot-pressing pressure of 1.0 MPa, phenolic resin amount of 12%, and ratio of Tetra Pak/bamboo of 9:1, in which the least phenolic resin and the most Tetra Pak materials were added. Moreover, the elastic modulus was 7670 MPa, the bending strength was 40 MPa, the internal adhesive bonding strength was 0.86 MPa, and 24 h thickness swelling rate was 10.6%, meeting the requirements for MDF in different states.

A gyroid structure is a commonly used energy-absorbing infill structure for packaging that can be prepared by fused deposition modeling (FDM) 3D printing. In this paper, square specimens based on gyroid infill structure were designed, and the energy-absorbing performances of the square specimens were analysed by quasi-static compression testing under different printing parameters (layer height, extrusion rate, and extrusion temperature). A gourd ornament carved from rosewood was selected as the design object, and a packaging liner that highly fits the curved shape of the gourd ornament was designed through the process of reverse scanning and forward modelling. The prototype of the packaging liner was fabricated by using FDM 3D printing technology and thermoplastic polyurethane (TPU) filament. With decreased layer height, the energy absorption (E_A) value of the gyroid infill structure increased, while the specific energy absorption (S_EA) value first increased and then decreased. With the increased extrusion rate, the E_A value of the gyroid infill structure increased, and the S_EA value increased. With increased extrusion temperature, the E_A and S_EA values of the gyroid infill structure increased. The packaging liner developed based on the gyroid infill structure and the optimised printing parameters exhibited strong energy-absorbing performance.

The high extractives content in rice straw inhibits the reactivity of castor oil-based polyurethane (CPUR) resin and hinders its bonding. This study employed steam treatment to pretreat rice straw to decrease the extractives content before using it for particleboard production. The effects of steam pressure and time on the chemical composition of the rice straw were investigated. Variable parameters tested were steam pretreatment time (5, 10 min) and steam temperature (110, 120, 130, and 140 °C). In addition, the mechanical properties and water resistance of particleboard manufactured from rice straw bonded with CPUR resin were evaluated. A three-phase hot press schedule at 110 °C was adopted. Other production parameters, such as resin content (20 wt%), hot press time (5 mm/s), and board density (800 kg/m³) were held constant. The resulting particleboards were tested for their mechanical properties in terms of modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB). Further, the physical properties including water absorption (WA) and thickness swelling (TS) were analyzed. The results showed that steam pretreatment significantly decreased the hemicellulose and extractives contents of the rice straws. Furthermore, steam pretreatment improved the mechanical properties and water resistance of the rice straw particleboards.

Selected fire properties of oak wood (mass loss, burning rate, and charring rate) and its chemical composition (extraction substances, lignin, cellulose, hemicellulose) were assessed. Oak wood samples with dimensions of 50 × 40 × 50 mm (l × w × t) were thermally loaded by a heat flux of 15, 20, 25, and 30 kW·m^-2, using a ceramic infrared heater with a power of 1000 W. At the given thermal loading, the mass loss ranged from 26% to 47%, whereas the burning rate ranged from 0.0365 to 0.0584%·s^-1. The maximum thickness of charred layer was 20 mm, and the charring rate reached values from 0.65 to 0.87 mm·min^-1, in a time interval of 1800 s. With increasing thermal loading, the content of extraction substances increased by 30% and the content of lignin increased slightly as well. In contrast, the content of hemicelluloses decreased by 10.3%. This indicates that hemicelluloses are the least thermally resistant wood component. The obtained results can be used as basic data for future testing using medium-sized tests. Subsequently, they can be compared with the input parameters for calculating the fire resistance of wooden constructions elements, which will be the subject of further research.

Camellia formosensis is a significant under the forest canopy crop in Taiwan. This study investigated the composition and yield variations of native Camellia formosensis tea leaves across different relative light intensities levels and seasons. Increasing the relative intensity of natural light resulted in a corresponding increase in the dry weight of C. formosensis leaves. At a relative light intensity of 70%, the dry weight of the leaves per unit area was 15.8 g. However, the yield of C. formosensis was lower at relative light intensities of 40% or 20%. A positive correlation was observed between relative light intensities and the contents of catechin gallate (CG), epicatechin gallate (ECG), and gallocatechin gallate (GCG) and relative light intensity. At 20% relative light intensity, the mean CG, ECG, and GCG contents were 4.97, 0.57, and 4.43 mg/g, respectively. These values surged to 6.93, 2.23, and 7.53 mg/g, respectively, at 70% relative light intensity. Caffeine content exhibited an inverse relationship with relative light intensity, declining notably after surpassing 70%. Moreover, C. formosensis leaves harvested in summer under 70% relative light intensity boasted higher contents of CG, epicatechin (EC), ECG, epigallocatechin gallate (EGCG), and caffeine than those harvested in spring. Ester catechin content surpassed non-ester catechins, with the former consistently higher at 100% relative light intensity, irrespective of the season.

To identify suitable pigments for the precoating of paperboard, the rheological properties of coating colors and their effects on the surface and printing properties of coated paperboard were evaluated with respect to the type and combination of coating pigments. The investigation included porous precipitated calcium carbonate (PCC) and four types of coarse ground calcium carbonate (GCC) of different sizes. As the GCC particle size increased, the viscosity of the coating color decreased in the low-shear region, and the degree of dehydration increased. Coatings containing PCC, which comprised relatively small and highly porous particles, were found to be less dehydrated than coatings containing only GCC. The surface roughness of the coated paperboard increased as the GCC particle size increased, leading to reduced paper gloss. However, increasing the GCC particle size decreased the binder usage and increased surface strength. In conclusion, it is believed that the use of 55-grade GCC rather than the smaller size of 60-grade GCC can reduce costs and enhance surface strength by reducing binder and energy.

Some traditional building materials, such as concrete and steel, have a negative impact on the environment. With the in-depth implementation of sustainable development, green materials are gradually being considered, and bamboo is a green high-energy building material. However, there have been few studies on the prediction of mechanical properties of bamboo. In order to predict the longitudinal compressive properties of bamboo, tests were carried out on the longitudinal compressive tests of bamboo. The failure mode was explored, as well as the relationship between the physical and mechanical properties of bamboo. Prediction formulas were developed for the longitudinal compressive properties of bamboo. The results showed that the failure mode of the longitudinal compressive test of bamboo was ductile failure. The wall thickness and diameter of bamboo were found to be positively correlated with height. The longitudinal compressive strength and elastic modulus were positively correlated with height and negatively correlated with wall thickness and diameter. The longitudinal compressive strength and elastic modulus were positively correlated with height. The linear model can be used to fit the relationship between mechanical properties and height. This research provides a reference for the prediction of bamboo properties.

The production of edge-glued boards is one of the possibilities of using European beech wood for products with higher added value. European beech is highly abundant in the forests of Central Europe, but it is a wood species that has specific characteristics that affect the efficiency of processing. The dimensions and quality of the raw material are determined by the standard. This study analyzes the influence of the quality of European beech raw material on the quantitative and qualitative yield during the production of cross-sections used to produce edge-glued boards. Results show that the effect of class (raw material quality) on the quantity of timber produced is not remarkable. For classes III.B and III.C, the most prevalent factors diminishing yield were the quality and extent of red false heartwood, as well as cracks. This study confirmed that superior raw material quality has a positive impact on the yield of blanks with the highest quality.

Thermomechanical pulp (TMP) was bleached with an ozone–hydrogen peroxide system, with the addition of hydrogen peroxide and ethylene glycol to enhance bleaching efficacy. The ISO brightness of TMP increased proportionally with higher concentrations of hydrogen peroxide across all sequences. Notably, TMP treated with the ozone and hydrogen peroxide sequence (ZP sequence) exhibited ISO brightness levels comparable to those of TMP bleached with hydrogen peroxide alone. However, the addition of hydrogen peroxide during the Z stage of the pZP sequence resulted in a 2.4% increase in ISO brightness and enhanced lignin solubility. A brief alkaline extraction step in the pZEP sequence led to a significant 4.3% increase in ISO brightness, though this improvement was accompanied by a yield loss due to removal of lignin in the E stage. Furthermore, the addition of polyethylene glycol alleviated yield loss by enhancing the selectivity of ozone bleaching, while effectively maintaining a stable ISO brightness.

The objective of this study was to investigate the sound absorption efficiency of plywood-carbon fiber composite materials and evaluate their potential as acoustic panels. In this work, plywood and plywood-carbon fiber composite materials were produced using Uludağ fir (Abies nordmanniana subsp. bornmülleriana Mattf.) peeling veneer, woven carbon fiber, and polyvinyl acetate (PVAc) adhesive. Three experimental groups and a control group were created. The materials from plywood-carbon fiber composite were manufactured in three different designs to form experimental groups. The sound absorption coefficients of the plywood and the composite materials were tested via the impedance tube method, according to ASTM standard E1050-98 (2006). Attention was paid to the acoustic behavior at low (bass) frequencies (63 Hz to 250 Hz), mid frequencies (315 Hz to 1600 Hz), and high (treble) frequencies (2000 Hz to 6300 Hz). It was determined that the plywood-carbon fiber composite materials could reflect or transmit sound waves at low (bass) frequencies, while significantly absorbing sound waves at high (treble) frequencies. It can be suggested that plywood-carbon fiber composite materials could be used as sound absorbing acoustic panels.