Thickness Expansion Rate Research Articles

Preparation of waste Camellia oleifera shell and high‐density polyethylene composites: Effect of pretreatment on fiber and materials properties

AbstractThe preparation of wood‐plastic composites (WPCs) with high filling fibers and excellent physical properties remained a great challenge. This study used Camellia oleifera shell (COS, agroforestry product waste) as raw material, and prepared 60 wt% COS/high‐density polyethylene (HDPE) WPCs using profile extrusion method through pretreating fibers including hot water, hot steam, alkali, acid, extraction, and fine fiber screening. After pretreatments, the relative contents of cellulose and lignin increased, the relative contents of hemicellulose and extract decreased significantly, and the length‐diameter ratio was improved. The flexural strength, tensile strength and impact strength of hot water and steam heat treated composites reached 31.4, 17.1 MPa and 6.9 kJ/m2, 31.8, 16.8 MPa and 6.7 kJ/m2, respectively. Compared with untreated 28.8, 14.7 MPa and 5.5 kJ/m2, the advantages were more obvious. Alkali treatment and acid treatment improved the thermal stability and residue rate of the material. Extraction treatment and alkali treatment significantly reduced the processing torque force, which was conducive to processing, while acid treatment was the opposite. The highest water absorption and thickness expansion rate were 13.75% and 3.60% respectively at 7 days after alkali treatment, which were considerably higher than 5.60% and 0.78% without treatment, while other pretreatments improved the dimensional stability of the material.Highlights High filling Camellia oleifera shell waste/HDPE composites were prepared. Physical and chemical pretreatments improved interfacial adhesion of the composites. Heat treatments significantly improved mechanical performance of the composites.

Preparation of dimensionally stable and strong thin-type bamboo bundle laminated veneer lumber through delignification and phenolic resin synergies

The development of thin-type bamboo bundle laminated veneer lumber (T-BLVL) represents a significant advancement in environmentally friendly and sustainable building materials. However, the application of T-BLVL is still hindered by poor dimensional stability and low mechanical strength. In this study, the delignified thin-type bamboo bundle laminated veneer lumber (D-T-BLVL) was prepared through the partial delignification of bamboo bundles and the synergistic effects of phenolic resin (PF). These effects included gluing, strengthening, and waterproofing. D-T-BLVL exhibited high strength, dimensional stability, and a remarkable thickness of only 5 mm. After the removal of 26 % lignin, the porosity of bamboo bundles increased by 117 % compared with natural bamboo bundles, facilitating enhanced PF infiltration. D-T-BLVL exhibited a bending strength of 281.84 MPa, representing an 83.75 % increase over that of T-BLVL (153.38 MPa). Additionally, the water absorption thickness expansion rate of D-T-BLVL (3.37 %) was only approximately 1/4 times that of T-BLVL (13.30 %). The development of D-T-BLVL provides valuable guidance for developing wind turbines, infrastructures, and other advanced technologies.

Optimizing gypsum particleboard properties: An orthogonal analysis of pennisetum giganteum and phosphogypsum composites

Gypsum particleboard is attracting attention in the construction industry due to its excellent properties. However, the traditional raw materials for gypsum particleboard are facing a shortage of supply. In this study, we innovatively utilized bulk solid waste Phosphogypsum and Pennisetum giganteum for the first time to manufacture gypsum particleboard. This approach not only effectively addresses the issue of insufficient supply of traditional raw materials for gypsum particleboard but also provides a new pathway for the resource utilization of phosphogypsum. Through an orthogonal experimental design, we focused on optimizing the gypsum particleboard formulation, concentrating on factors such as density, the ratio of Pennisetum giganteum to gypsum (grass-plaster ratio), the ratio of water to gypsum (water-plaster ratio), and the size of the particles. The study determined that the optimal formulation parameters were a density of 1.2 g/cm³, a grass-plaster ratio of 0.20, a water-plaster ratio of 0.25, and a particle mesh number of 14. Under these conditions, the gypsum particleboard exhibited excellent performance, characterized by a static flexural strength of 6.5 MPa, a modulus of elasticity of 2010 MPa, an internal bond strength of 0.4 MPa, a 24-hour water-absorption thickness expansion rate of 2.2%, and an equilibrium moisture content of 1.6%, all meeting the American Society for Testing and Materials (ASTM) Standard D1037. These findings indicate that gypsum particleboards made with Pennisetum giganteum and phosphogypsum can perform comparably to those made with conventional materials. Additionally, a performance prediction model was established using Multiple Linear Regression Analysis (MLRA). The analysis revealed a significant linear relationship between the independent and dependent variables in the model, with the Analysis of Variance (ANOVA) significance levels being less than 0.05, demonstrating statistical significance. This result provides a theoretical basis for the future development of high-performance gypsum particleboard.

Synergistic in-situ reinforcement of lignin and adhesive for high-performance aligned bamboo fibers composites

To replace plastics with bamboo, it is necessary to develop renewable, lightweight, high-strength, damping, and vibration-reducing bamboo structural materials that can be applied in buildings, transportation, and mechanical engineering applications. Here, a low-cost and high-efficiency top-down method was designed for processing natural bamboo into a lightweight and high-strength aligned bamboo fiber composite. This composite used oriented bamboo fibers that had their lignin and hemicellulose removed, which were used as continuous reinforcement materials, and phenolic resin was used as the adhesive, followed by hot pressing. A highly-interwoven structure was formed by the penetration of the adhesive and the combination of strong hydrogen bonds and chemical bonds formed during hot pressing. This resulted in the high performance of the composite, which exhibited a tensile strength of 421.5 MPa, a bending strength of 211.19 MPa, and an impact toughness of 26.7 J/cm2, which were respectively 2.50, 2.09, and 5.7 times higher than those of natural bamboo. Due to its low density (1.08 g/cm3) and specific tensile strength of 390 MPa g−1 cm3, it was superior to commonly used engineering structural materials such as aluminum alloy, steel, and titanium alloy. It also exhibited excellent damping and vibration reduction performance (with the first three damping ratios of 0.75 %, 0.68 %, and 1.75 %) and dimensional stability (with a 24-h water absorption thickness expansion rate of 7.75 %). Due to its excellent mechanical properties and dimensional stability under wet and hot conditions, this composite is expected to replace nonrenewable synthetic materials as a green and sustainable engineering structural material. It may find applications in drone wings, wind turbine blades, and automotive manufacturing.

Thermal stratification characteristics during simultaneous charging and discharging for different storage tank geometries with immersed discharging coil

The geometrical shapes of the thermal energy storage and the configurations of immersed discharging coils dictate the efficacy of low-to-medium temperature hot water applications. This study uses a three-dimensional numerical model to investigate the thermal characteristics of three storage configurations for simultaneous charging and discharging. The same tank volume and height, as well as the same coil tube dimensions, are considered for three different configurations - cylindrical tank with a helical discharging coil, as well as circular truncated cone-shaped and paraboloidal tanks with conical discharging coils. The discharging flow rate is varied for a deeper understanding of the realistic interplay between energy demand and supply. Results obtained for the cylindrical tank are found to have good agreement with the observations from the in-house experiments. The energy stored, discharging coil outlet temperature, and the extent of thermal stratification decrease with increasing coil flow rate, whilst discharging efficiency and primary thermocline thickness increase. The paraboloidal tank equipped with a conical discharging coil exhibited the highest cumulative energy stored (8821 kJ) just before the commencement of dynamic dual operation, owing to the minimal thermal losses attributable to the lowest surface-area-to-volume ratio. Thermocline thickness is found to expand with time for all the cases, and the highest thermocline thickness expansion rate of 0.208 mm/s is found for the cylindrical tank indicating a higher degree of energy degradation. The peak values for the cumulative energy discharged (9788 kJ), and average discharging efficiency (0.36) occurred for the paraboloidal tank with the conical discharging coil configuration. Based on the detailed analyses, the paraboloidal storage tank configuration is found to exhibit better system reliability and energy management, leading to more efficient heat dispatch controllability due to the enhanced energy harnessing features.

Bamboo-Inspired Renewable, High-Strength, Vibration-Damping Composites for Structural Applications

Renewable structural materials derived from natural biological materials can potentially replace non-renewable synthetic materials for civil engineering and transportation applications. Here, inspired by the functional gradient structure of bamboo, we propose a simple and efficient two-step preparation strategy to convert natural bamboo into a lightweight, high-strength, damping, and sound-insulating structural engineering material called densified bundle-laminated veneer lumber (DBLVL). DBLVL was prepared by finely grading and thinning three layers of bamboo slices and removing the lignin and hemicelluloses from the surface of bamboo bundles. This was followed by penetrating the phenol formaldehyde resin and then solidifying and densifying it in situ. DBLVL had superior mechanical properties due to its bamboo-like gradient laminated structure, three-dimensional network distribution of adhesive under high temperature and high pressure, in situ curing, and solid interfacial bonding. It had a specific tensile strength of 297 MPa cm3 g–1, which was superior to those of many other construction materials. The tensile strength of DBLVL reached 363 MPa, and the bending strength reached 219 MPa, which were 97.28 and 92.11% higher than those of natural bamboo, respectively. The impact toughness reached 15.4 J/cm2. DBLVL also showed excellent damping and vibration reduction (the first three damping ratios were 2.35, 1.81, and 2.40%) and dimensional stability (the thickness expansion rate after 24 h of water absorption was 4.43%). Because of its excellent mechanical properties and hygrothermal stability, DBLVL is expected to replace non-renewable synthetic materials as a green and sustainable structural material for engineering applications.

Preparation and characterization of birch plywood prepared by hot-pressed peanut meal adhesive

The preparation of birch plywood by hot-pressed peanut meal (HPM) adhesive was studied using response surface methodology. The effects of hot-pressing temperature, hot-pressing time, and hot-pressing pressure on the boiling water strength (BWS) were investigated. The BWS of birch plywood was significantly affected by hot-pressing temperature and hot-pressing time. The optimal preparation conditions for maximizing the BWS were: hot-pressing temperature of 120 °C, hot-pressing time of 80 s mm −1 and hot-pressing pressure of 1.2 MPa. Under these conditions, the BWS was 1.21 ± 0.02 MPa. The thickness expansion rate of water absorption (TS) and the wood compressibility were 6.39% and 15.8% respectively. Characterization of birch plywood showed the chemical reactions between hydroxyl of plywood, and the amino, carboxyl and azacyclobutane structures of peanut protein, forming a dense bonding surface and resulting in the higher BWS of birch plywood. This work provided an important reference for the application of HPM adhesive in the production of wood-based panels. • High value utilization of hot-pressed peanut meal was improved. • Chemical reaction between hot-pressed peanut meal adhesive and birch veneer. • The hot processing has strong universality and birch plywood has no formaldehyde. • The boiling water strength of birch plywood reached the national class I standard.

Surface Characteristics of Thermally Modified Bamboo Fibers and Its Utilization Potential for Bamboo Plastic Composites.

Bamboo fibers are considered as a more attractive option for the reinforcement of wood plastic composites as compared to wood fiber due to its fast growth rate and good toughness. Heat treatment is an environment-friendly method of improving the integrated performance of bamboo materials. This paper highlights the heat treatment of bamboo fiber for suitable properties as reinforcements in bamboo plastic composites. The effects of vacuum heat treatment on the surface characteristics of bamboo fibers and the properties of bamboo plastic composites were analyzed by studying the chemical composition, surface elements and polarity of bamboo fiber before and after treatment, and the physical and mechanical properties of bamboo plastic composite. The results showed that after vacuum heat treatment, the bamboo fibers became darker and experienced a transition from green to red. Moreover, FTIR, XPS and contact angle analysis indicated that the hemicellulose content, the oxygen/carbon ratio and the polar component of the bamboo fiber had a decreasing trend as the treatment temperature increased. In addition, the 24 h water absorption and the 24 h thickness expansion rate of the water absorption showed a trend of first decreasing and then increasing as the treatment temperature increased, while the bending performance of bamboo plastic composite showed a trend of increasing first and then decreasing as a result of increased treatment temperature. Therefore, a combined process of vacuum heat treatment and the addition of MAPE could improve the physical and mechanical properties of bamboo plastic composites to a certain extent.

Improving the Properties of Fast-Growing Chinese Fir by Vacuum Hot Pressing Treatment

Chinese fir was compressed by vacuum hot pressing and conventional hot pressing at different temperatures (180°C, 200°C and 220°C), respectively. The color parameters of the heat-compressed sample were measured, the relative mechanical properties of the material were tested and changes in the chemistry of fir were investigated using Fourier transform infrared spectroscopy (FTIR) and Xray photoelectron spectroscopy (XPS). The results indicated that the color difference between compressed and untreated wood increased gradually with the increase of temperature. Compared with the conventional hot pressing treatment, the color difference (ΔE*) of the Chinese fir treated by vacuum hot pressing decreased by 43.73%, 69.91%, and 77.17%, respectively. The mechanical properties (bending elastic modulus and bending strength) of Chinese fir treated by vacuum hot pressing were significantly improved. The 24-hour water absorption thickness expansion rate of fir treated by vacuum hot pressing is smaller than that of conventional hot pressing. It is implied that vacuum hot pressing treatment is an effective method to produce compressed wood, which can improve the mechanical properties and dimensional stability of wood, and reduce the influence of carbonization on wood color.

In-situ construction of porous Si@C composites with LiCl template to provide silicon anode expansion buffer

Silicon-based anode material is one of the most promising alternative anodes for graphite due to its advantages of abundant reserves, environmental protection and high-energy-density. However, silicon still cannot be directly applied commercially as anode materials owing to the existences of huge volume change during the alloying and dealloying process. Herein, porous Si@C composites are prepared by employment of nano silicon as the active substance particles, lithium chloride as the template and pitch powder as the carbon precursor. Results of electrochemical performance tests show that the cell based on the in-situ prepared porous Si@C composites deliver a reversible good cycle stability. Besides, porous Si@C composites show a lower thickness expansion rate of electrode (15.38%), compared with pure nano silicon (162.46%) and conventional Si@C anodes (40.24%), respectively. It is believed that the improved performance is benefitted from the porous structure, which provides a buffer for the expansion of silicon, reduces the volume expansion of the electrode during the charge and discharge process, and thus inhibits the damage to the solid electrolyte interphase film outside the Si@C composites. This work provides an environmentally friendly method to prepare porous Si@C composite anode materials, which is suitable for large-scale preparation and industrialized production.

Effects of rice husk fibers on the properties of mixed-particle-size fiber-reinforced polyvinyl chloride composites under soil accelerated aging conditions

In this article, rice husk fiber/polyvinyl chloride composites were prepared and analyzed. The optimal composition of mixed-particle-size fiber-reinforced composites was determined through orthogonal experimentation. The physical, mechanical, and thermal properties of the mixed-particle-size fiber-reinforced composites were compared to unprocessed (100 mesh) rice husk fiber/polyvinyl chloride composites. The surface microscopic appearances of the unprocessed and final composites were observed via laser microscope. Long-term accelerated soil aging caused micro-cracks to appear on the surfaces of the composites. Interfacial adhesion was observed via scanning electron microscopy. The results indicated that mixed-particle-size fibers can better fill interfacial gaps, leading to strong interfacial adhesion. Furthermore, the addition of mixed-particle-size fibers improves the soil aging resistance of composites. The hardness, flexural strength, impact strength, and first onset pyrolysis temperature (after 0 days) increase from 50 HRR, 35.2 MPa, 3.19 KJ/m2, and 258.5°C to 55 HRR, 39.4 MPa, 3.86 KJ/m2, and 261.2°C, respectively. However, the mass loss rate and thickness expansion rate (after 21 days) decrease from 2.9% and 0.79% to 2.21% and 0.74%, respectively. In general, the addition of mixed-particle-size fibers improves the ultimate properties of composites under soil aging conditions.

The Effect of Modifier on Properties of Bamboo Powder/High-Density Polyethylene Composites

Abstract The focus of this study was to observe the properties of bamboo plastic composites modified with a self-made modifier, 18 acyl-dopamine (0, 0.25, 0.50, 0.75, 1.00, and 1.25 weight percent [wt%] based on the dry weight of bamboo powder). The effects of the modifier were demonstrated by measures of mechanical properties, water absorption, thermal stability, and scanning electron microscopy (SEM). The results revealed that 18 acyl-dopamine could be used as an effective modifier of bamboo powder/high-density polyethylene composites. When the modifier was increased, the toughness of the composite deteriorated, and the strength and rigidity improved. This indicated that when the dosage became higher, the compatibilization became stronger, and the toughening effect became worse. Based on the experimental data, a small dosage modifier acted as a toughening agent; as the dosage increased to 1.0 wt%, the compatibility began to appear. The modifier reacted with the hydroxyl groups on the surface of the bamboo powder, which caused the bamboo powder to absorb less water, so the thickness expansion rate was lowest at 1.25 wt%. The pyrolysis peak of bamboo powder and plastic showed a tendency to be close to each other, indicating that the interface was improving. Based on the equation of Flynn-Wall-Ozawa, as the dosage of the modifier increased from 0.50 to 1.25 wt%, the apparent activation energy also increased. The SEM analysis showed the binding between bamboo powder and the plastic matrix was strongest when the modifier dosage was 1.25 wt%.

Impact of Hot Pressing Temperature on Medium Density Fiberboard (MDF) Performance

Hot pressing temperature is determined according to the performance of boards, type of glue, and production efficiency of hot press. During hot pressing, the thermal energy has enhanced the plasticity of the fiber and created conditions for the integration of different bonds. The thermal energy will cause the moisture in raw board to vaporize. Temporary heating will expedite the solidification of hot set resin for decreased friction and increased fluidity. The hot pressing temperature usually refers to the temperature of hot pressing plate, but what plays function in actual use is the temperature inside the raw board. This research investigates the performance of MDF with respect to hot pressing temperature. The strength and water resistance of the product are improved with the increase of hot pressing temperature from 140°C to 160°C, the Modulus of Rupture (MOR) is increased by 9.8%, the Internal Bonding (IB) is increased by 33.6%, the water absorption (Wt) is decreased by 38.2%, and the thickness expansion rate (Ts) is decreased by 15.2%.

Research New Waterproof Agent of the Particleboard

Modern society,with the rapid development of economy,people living standard increasing, for the plate demand continues to grow. Because the forest resources dwindling, To make full use of waste bagasse, corn straw and non wood fiber materials to produce an artificial plate material instead of wood man-made board has be imperative.Corn straw shavings can realize the recycling of waste materials, bring the economic value, so this topic with corn straw shavings as raw material, in the laboratory preparation of melamine resin adhesive, pressing flake molded sheet.Melamine plastic using M ( melamine ):U ( urea ) :F ( formaldehyde ) =1∶0.6∶2.5, adhesive solid content is 54%, the sizing, hot pressing temperature, hot pressing time as three factors orthogonal experiment, pressed sheet. On the plate thickness swelling, internal bond strength and surface plate bending strength test, on the analysis and summarization of results, the optimum process parameters: sizing quantity20%, temperature 150 °C, hot pressing time25min. The corresponding optimum mechanical properties: the absorbing water thickness expansion rate (2H ) 9.76%, inner strength, bend strength of17.49Mpa,0.45MPa. Key words: Non wood shavings; Molded sheet; Process parameters; Mechanical properties

Study on the Application of Desulfurization Gypsum for the Gypsum Fiber Board Production

Through semidry process, the wood fiber as reinforced materials and the industrial flue gas desulfurization waste calcinated calcium sulfate hemihydrate as an inorganic adhesive produced the environmental gypsum fiber board. This process is effective on utilization of desulfurization gypsum, which reduced the pollution of the environment and the demand of the natural gypsum, further to protect the natural environment. As green building decoration materials, gypsum fiber board has good prospects for development. The research results show that it is remarkable that the amount of the composite retarder is effective on the static bending strength, internal bond strength, grip screws to impact; the ratio of the wood and plaster is effective on the absorbent thickness expansion rate.

Effects of the Degree of Cure on the Electrical and Mechanical Behavior of Anisotropic Conductive Films

In this work, the effects of the degree of cure on the electrical and mechanical behavior of an anisotropic conductive film (ACF) were investigated. The degree of cure of the ACF as a function of bonding time was quantified by dynamic differential scanning calorimetry (DSC) study and attenuated total reflectance/Fourier-transform infrared (ATR/FT-IR) analysis. According to the results, the thickness expansion rate of the ACF as a function of temperature decreased and the storage modulus increased as the degree of cure increased. In addition, the contraction stress of a partially cured ACF with a degree of cure below 40% was much smaller than that of an ACF with a degree of cure above 90%. The ACF contact resistance decreased and the ACF peel adhesion strength increased as the degree of cure of the ACF increased. In particular, poor electrical contact was observed when the degree of cure was below 40%. The ultimate tensile strength (UTS) increased as the degree of cure increased and was closely related to the peel adhesion strength. Furthermore, ACF joints with a degree of cure below 40% had higher contact resistance than those with a degree of cure above 90% during 85°C/85% relative humidity testing.

Microscopic structure and properties of wood-based foaming composites

In order to reduce the density of wood-based composites without causing a deterioration of their mechanical properties, we studied the process of manufacturing wood-based composites. A combination of polymer foaming technology and flat hot-pressing technology was used. The microscopic structure of the various wood-based composites was analyzed with a scanning electron microscope (SEM). Modulus of rupture (MOR), modulus of elasticity (MOE), impact strength, and thickness expansion rate of water sorption (TS) were all measured. The results showed that fibers loosely interweave, and fibers had been connected by micropore. They also showed that spaces between fibers had big micropore structure. MOR, MOE and impact strength were the highest among three levels of ratio. When the total content of resin and foaming agent were 20% by weight, TS was higher. A hot-pressing temperature of 120°C was optimal. At the low temperatures of 80°C, the foaming process was uncompleted. At a higher temperature, micropores burst at a certain pressure. Based on the variance analysis and maximum difference analysis, a significance test shows that the optimum conditions for the total content of resin and foaming agent is 20% by weight, with a hot pressing temperature of 120°C for 15 min. Under these conditions, the properties of wood-based foaming composites all achieved the industry standard.