Urea-formaldehyde Research Articles

Preparation, characterization and mechanism of SiO2@SiO2 core-shell microspheres through polymerization-induced colloid aggregation for fast separation using ultra performance liquid chromatography

The polymerization-induced colloid aggregation (PICA) method is commonly used to create SiO2@SiO2 core–shell silica microspheres (CSSMs), but it often encounters challenges such as incomplete shell coating and poor reproducibility. In this paper, the formation mechanism of the silica shell layer during the preparation of SiO2@SiO2 CSSMs using the PICA method was investigated. It was found that ureido modification can reduce the Zeta potential of the silica core surface, facilitating the deposition of coacervates formed by urea-formaldehyde resin (UF) and silica nanoparticles on the silica core surface to form the SiO2 shell layer when the Zeta potential of the surface is in the range of −20.1 mV to −4.8 mV. By controlling the interfacial state and surface potential of the SiO2 core, the issue of inconsistent reproducibility in preparing SiO2@SiO2 CSSMs can be overcome. Furthermore, optimization of experimental parameters such as pH, reaction temperature, water content, and reaction time can enhance the formation process. The thickness of the shell and pore size of CSSMs can be successfully adjusted by varying the reaction time and the particle size of colloidal silica sol, respectively. With optimal conditions, the semi-scale production yield of SiO2@SiO2 CSSMs can be increased to 50 g. The SiO2@SiO2 CSSMs were modified with octadecyltrichlorosilane (ODS) to be used as stationary phases in reversed phase liquid chromatography (RPLC) for fast separation of small solutes, peptides, and proteins. The superior separation efficiency indicates that the improved PICA method has the potential to be utilized as an alternative to the layer-by-layer method for large-scale production of SiO2@SiO2 CSSMs.

Cleaning of Water Surface from Oil and Oil Products in Arctic Conditions

The results of obtaining and studying the properties of the composite for elimination of oil and petroleum products on water areas at low temperatures on the basis of oligomer obtained from urea resin and treated with polymer solution in organic solvent are presented. It is concluded that the proposed composite has a high degree of purification from oil and petroleum products, which does not change when the temperature drops to -40 °С.

A Comparative Study of the Physio-Mechanical Properties of Iron Fillings and Mild Steel Chips in Reinforced Particleboard

This study compared the physio-mechanical characteristics of mild steel chips and iron fillings on sawdust-produced particleboard to regular particleboard made from sawdust alone, using identical production conditions. Particle board was made using 1.18mm sawdust, 3mm mild steel chips, and iron filler with diameters of 0.15mm, 0.425mm, 0.6mm, 1.18mm, and 2.0mm. 70g of sawdust, 40g of iron fillings, and 40g of mild steel chips were used in the production process. 50ml urea formaldehyde was used as a binder. The atomic absorption spectroscopy was determined for iron fillings and mild steel chips. Particleboards were produced at a temperature of 160°C and a pressure of 20 tons for 15 minutes. Mechanical property tested indicates that particleboard containing iron filings has a lower Modulus of rupture (MOR) because the size of the iron filings in the particleboard reduces as the MOR increases. The particle size of iron filling with the value of 2.0mm had the least MOR of 3.99mpa/m2 in iron filling samples. The MOR of Mild steel chips was higher compared to all the samples analyzed. Modulus of Elasticity (MOE) of particleboard produced from iron filings increases as the particle sizes of iron filings increases. The samples containing iron filings alone showed the highest MOE of 244.89 MPa/m2 for 2.0 mm particle board, while the ones containing mild steel chips had the highest MOE of 282.82 MPa/m2 across all samples, suggesting their strength as reinforcement. The rate of water absorption and thickness of swell of particleboard produced from iron filings increases as the size of the iron fillings increase.

Sustainable Panels from Cocoa (Theobroma cacao) Wood Wastes Bonded with Cassava starch and Urea–Formaldehyde

Sustainable Panels from Cocoa (Theobroma cacao) Wood Wastes Bonded with Cassava starch and Urea–Formaldehyde

Green transforming black liquors as a new HCHO scavenger in production eco urea formaldehyde-agro composites

Innovative formaldehyde (HCHO)-scavenger based on black liquor is being developed to achieve eco-friendly low toxic urea formaldehyde (UF) adhesive. This scavenger will enhance the UF adhesive in production of agro-composites, complying with the environmental requirements. The HCHO-scavenger is synthesized from black liquor-based aerogels of various types of black liquors. The performance of the prepared scavengers is assessed via adsorption of HCHO; as well as its beneficial effect on properties of UF adhesive and UF-Palm fiber-composite. In order to produce a composite with mechanical properties and free-HCHO compliance with the standard specifications, the UF-scavenger system is optimized from its behavior. The data evidence the effective behavior of all investigated scavenger to improve bond strength of UF adhesive system (from 8.4 MPa to ∼ 18 MPa); and properties of UF-palm-composites, where the enhancement in modulus of rupture (MOR) and internal bond strength (IB), water repellent, reach to 50 %, 83 % and 7.7 %, respectively. In addition to success in producing eco-composites through reducing the free-HCHO of wood sample from 30.77 to 3.0–12.7 mg/100g with reduction percentages (58.7–90.3 %) exceeded those reported in the literature when carbon and silicon scavengers were used.

Green Pathway of Urea Synthesis Through Plasma–Ice Interaction: Optimization and Mechanistic Insights With N2 + CO2 and NH3 + CO2 Gas Mixtures

ABSTRACTThis study presents a green approach for urea synthesis using plasma–ice interaction with N₂ + CO₂ and NH₃ + CO₂ gas mixtures. Plasma characterization via electrical and optical emission spectroscopy revealed that urea formation involves complex reactions driven by high‐energy species, producing reactive nitrogen and carbon intermediates. Plasma‐treated ice exhibited increased pH, electrical conductivity (EC), and reduced oxidation–reduction potential (ORP). Optimization of parameters, especially treatment time, significantly influenced urea formation. The NH₃ + CO₂ plasma produced a higher urea concentration (7.7 mg L−1) compared to the N₂ + CO₂ plasma (0.55 mg L−1) due to ammonia's greater reactivity. This method offers a sustainable, energy‐efficient alternative to traditional urea synthesis processes.

A Strongly Coupled Metal/Hydroxide Heterostructure Cascades Carbon Dioxide and Nitrate Reduction Reactions toward Efficient Urea Electrosynthesis.

The direct coupling of nitrate ions and carbon dioxide for urea synthesis presents an appealing alternative to the Bosch-Meiser process in industry. The simultaneous activation of carbon dioxide and nitrate, however, as well as efficient C-N coupling on single active site, poses significant challenges. Here, we propose a novel metal/hydroxide heterostructure strategy based on synthesizing an Ag-CuNi(OH)2 composite to cascade carbon dioxide and nitrate reduction reactions for urea electrosynthesis. The strongly coupled metal/hydroxide heterostructure interface integrates two distinct sites for carbon dioxide and nitrate activation, and facilitates the coupling of *CO (on silver, where * denotes an active site) and *NH2 (on hydroxide) for urea formation. Moreover, the strongly coupled interface optimizes the water splitting process and facilitates the supply of active hydrogen atoms, thereby expediting the deoxyreduction processes essential for urea formation. Consequently, our Ag-CuNi(OH)2 composite delivers a high urea yield rate of 25.6 mmol gcat. -1 h-1 and high urea Faradaic efficiency of 46.1 %, as well as excellent cycling stability. This work provides new insights into the design of dual-site catalysts for C-N coupling, considering their role on the interface.

Leveraging Spruce Bark Particle Morphology for Enhanced Internal Bonding in Particleboard Production

The continuous rise in global demand for wood products has led to an increase in prices and a surge in research into alternative resources. As a byproduct of the timber industry, bark has emerged as a promising supplement in particleboard (PB) production. However, its anatomical structure, the presence of extractives, and its inferior mechanical properties complicate the production process, which have not yet been fully overcome at a commercial scale. This study proposes a paradigm shift, advocating for separate and specialized bark constituent processing in a wet state. Three bark-based raw materials—namely, outer bark particles, bark fiber clumps, and bark fibers—were investigated under varying wood content scenarios. PBs with a target density of 0.7 g/cm3 and a thickness of 16 mm were produced using mixtures of these bark-based materials and wood particles in different ratios bonded with a urea–formaldehyde adhesive. The results demonstrated that these bark constituents exhibit distinct properties that can be optimized through tailored processing techniques. Compared to bark fibers, outer bark particles displayed about 40% lower water absorption and thickness swelling. However, bark fibers improved the internal bond by about 50% due to their favorable morphology compared to outer bark. These findings highlight the potential of bark as a valuable resource for particleboard production and pave the way for its efficient utilization through specialized processing strategies.

Industrial boiler ash as an alternative for reducing formaldehyde emissions in medium-density fiberboards

ABSTRACT The study aimed to determine the feasibility of utilizing industrial boiler ash in the production of medium-density fiberboard, to reduce formaldehyde emissions without compromising physical and mechanical properties. Panels were manufactured with a density of 750 kg.m−³, employing 12% urea-formaldehyde resin and 1% paraffin emulsion, both with and without an ammonium sulfate-based catalyst. The production process involved cold pre-pressing followed by hot pressing at 180 °C and 40 kgf.cm−² for 10 min. The experimental plan varied in terms of the percentages of ash added to the adhesive (0%, 1%, 3%, and 5%) and the application of the catalyst. Both the properties of the adhesives and the panels were assessed. It became evident that both the catalyst and ash altered the adhesive properties. Regarding panel properties, the ash reduced formaldehyde emissions, but the catalyst had a more pronounced effect. The catalyst's impact on moisture content, bending strength (MOR), and modulus of elasticity (MOE) was observed, whereas ash positively influenced dimensional stability at 5% levels but adversely affected internal bond.

Effect of Resin Content on the Properties of Roofing Tile for Building Materials

The production process of roofing tile materials uses among other materials thermosetting adhesive resins normally urea formaldehyde (UF), phenol formaldehyde (PF), di-isocyanate (PMDI) at various content mixtures, 3wt%, 5wt%, 7wt%, 9w% and 11wt% with a usual thickness of 6 mm. The fibers, adhesives, and other materials are then placed into a steel mold with the standard dimensions of 400 mm x 400 mm, to be then hydraulically pressed at high pressure and the required temperature. Overall, PMDI synthetic adhesives have better physical and mechanical properties than PF synthetic adhesives, however the thermal properties of UF and PF synthetic adhesives are better than PMDI. The physical properties testing were density, humidity content, absorption of water, thickness inflated and water permeability. The mechanical properties such as modulus of rupture (MOR) and modulus of elasticity (MOE), impact strength and tensile strength are all measured according to JIS A 5908-2003, ASTM D 256-2006a,TIS 535-2556 and ASTM D1037-12.The testing for the thermal conductivity, thermal resistivity and solar reflectance were done according to ASTM C177-2010 and ASTM E 891-87. The type of resin content and adhesive used had a significant impact on the physical, mechanical and thermal properties of the roofing tile materials of showed in the results of the analysis of variance (p >0.05). The produced roofing tile has an improved thermal conductivity and heat insulation which can be a substitute for hazardous asbestos based roofing materials.

Relay Catalysis of Isolated Rhodium-Alloyed Copper Boosts Urea Electrosynthesis from Nitrate and CO2.

Urea electrosynthesis from the coelectrolysis of NO3- and CO2 (UENC) presents a fascinating approach for simultaneously migrating NO3- pollutants and producing valuable urea. In this study, isolated Rh-alloyed copper (Rh1Cu) is explored as a highly active and selective catalyst toward the UENC. Combined in situ spectroscopic analysis and theoretical calculations reveal the relay catalysis of the Rh1 site and Cu site to promote the UENC energetics, in which the Rh1 site activates NO3- to form *NH2 while the Cu site activates CO2 to form *CO. The formed *CO is then migrated from the Cu substrate to the nearby Rh1 site, which promotes the C-N coupling of *NH2 and *CO toward the urea formation. Prominently, Rh1Cu achieves an exceptional UENC performance in the flow cell, exhibiting the highest urea-Faradaic efficiency of 67.10% and urea yield rate of 50.36 mmol h-1 g-1 at -0.6 V versus RHE.

The influence of tannin on the improvement of adhesive properties of urea-formaldehyde resin

This study aimed to examine the properties of urea-formaldehyde (UF) adhesive with the addition of tannin, to determine whether it is possible to obtain so-called, bio-adhesives for wood with better mechanical properties compared to commercial UF. Tannin-based UF resins, with four different concentrations of tannin (5, 10, 15, and 20%), were prepared, and adhesive properties were tested and compared with properties of pure UF. Testing of tensile shear strength showed that the addition of tannin in UF adhesive formulation significantly increases its performance compared to pure UF adhesive. It was found that tensile shear strength increased with increasing concentration of tannin, while UF-tannin adhesives with tannin concentrations of 15% and 20% showed higher tensile shear strength than the corresponding pure UF adhesive. Therefore, it can be concluded that tannin-based UF adhesive can be a good candidate for application as an environmentally-friendly wood adhesive due to improvement in terms of adhesive and mechanical properties.

Some physical and mechanical properties of particle boards produced with hazelnut husk and astragalus (Astragalus membranaceus) plant

In this study, under laboratory conditions, hazelnut husk and astragalus plant were mixed separately into black pine wood chips, and multi-purpose boards were produced from the obtained chips with urea formaldehyde glue. After the hazelnut husk and astragalus plant were dried and ground, they were added to the chip and glue mixture in certain proportions. Hazelnut husk mixture ratios were applied as 100 %; 0 %, 75 %; 25 %, 50 %; 50 %, 25 %; 75 %, 0 %; 100 % to black pine wood chip in the particle board mixture. These ratios were made in the same way for the astragalus plant. From these mixtures, chipboard blanks of 16 mm thickness and densities between 0,68 g/cm3 and 0,72 g/cm3 were produced. Density, moisture content, thickness increase, water intake, bending strength, modulus of elasticity in bending and tensile strength perpendicular to the surface were tested in physical and mechanical experiments. According to the results obtained, as the participation rate of hazelnut shells and astragalus increased, the durability properties of the panels decreased. At the same time, it shows that the technological properties of the panels produced by adding up to 25 % astragalus plant and hazelnut shells to the mixture comply with the standards.

The effect of urea-formaldehyde adhesive modification with diisocyanate-functionalized nanocellulose on the properties of particleboard

In this paper, a nanocrystalline cellulose (NCC) functionalized with 4,4′-diphenylmethane diisocyanate (MDI) was used as a modifier for urea-formaldehyde (UF) adhesive in particleboard production. The applied method of NCC functionalization with diisocyanate has not been previously studied in research on wood-based materials. Chemical structure of MDI-NCC evaluated with Fourier transform infrared spectroscopy (FTIR) demonstrated some significant changes indicating that the functionalization was effective. No change in crystallinity caused by the modification was noted based on the lateral order index and total crystallinity index. Hydrophilicity of NCC was reduced due to the functionalization with MDI. Based on the differential scanning calorimetry (DSC) results, it was found that the reactivity of the resin was improved by the addition of NCC, and moreover, the effect was even more noticeable when the MDI-NCC was introduced. Properties of manufactured particleboards such as density, water absorption and formaldehyde content were not affected by the resin reinforcement. In turn, the modification of NCC with MDI allowed to increase the strength and reduce swelling of the particleboards more significantly than in the case of a neat NCC. It indicates that application of diisocyanate-functionalized NCC has great potential for the use as the UF resin modifier in particleboard production.

Effect of pH Value on the Structure and Properties of n-Eicosane@Melamine Urea-Formaldehyde Phase Change Microcapsules

In this article, n-eicosane@MUF phase change microcapsules were prepared by in-situ polymerization with n-eicosane as the core material and melamine urea-formaldehyde (MUF) resin as the shell material. The effects of pH values from 3.5 to 6.0 on the surface morphology, particle size distribution, latent heat of phase transformation, encapsulation degree, thermal stability, and permeability resistance of the microcapsules were investigated. The results showed that the surfaces of the microcapsules gradually became smooth with the increase of pH value, and their encapsulation degree and impermeability also increased roughly. When the pH = 5.5, the particle size of the microcapsule samples ranged from 1.5 to 9.7 μm, the melting enthalpy was 178.8 J/g, and the encapsulation degree was 86.6%, which had the best thermal stability and impermeability. However, when the pH = 6.0, the phenomenon of microcapsule shell rupture occurred and the above performance no longer occurred.

Investigation on the restoration properties of wood oil microcapsules in wood coatings

Wood coatings endure wear and tear and may experience reduced service life. Therefore, the self-healing feature is crucial for practical application in wood protection. The study involved preparing a self-healing microcapsule through in-situ polymerization. Wood oil was utilized as the core material and urea-formaldehyde resin (UF) as the wall structure, forming a “core-shell” structure. The average particle size of the microcapsules is approximately 2.8 μm. Wood oil Microcapsules of varying content are added to water-based coatings and applied to form a self-healing wood coating. When external forces damaged the wood coating, the microcapsules ruptured and released the inner core to repair the coating. The study results indicated that adding microcapsules at a 6 % level significantly increased the coating's repair rate to over 30 %, enhancing its mechanical properties. This microcapsule type in wood oil can protect wood coatings and guide future wood coating repair methods.

Structural Properties of Globulin: A Critical Parameter for Sunflower Meal as Wood Panel Adhesives.

Alternative biobased adhesive formulations are currently being investigated to replace urea-formaldehyde (UF) as wood panel adhesives. In this regard, oilseed meals are valuable alternatives, as it is anticipated that the sticky potential of these meals is linked to their protein content. This work focuses on the protein parameters (primary and/or secondary structures) that could impact the adhesiveness of sunflower meals. The proteins contained in these meals were first separated from the other components and identified using electrophoresis. Oilseed meals contain several families of proteins: globulins, albumins, prolamins, and oleosins. Sunflower meal is mainly composed of globulin (53%) and albumin (45%). The protein structures have then been either oxidized with H2O2 (in the presence or not of NaOH) or physically treated by microwave (MW). The oxidation treatment cleaves the protein backbone and creates smaller peptides, while the MW process converts α-helices into random coils. The adhesive potential of these treated proteins was evaluated by using shear tests onto wood panels. The results demonstrate that the primary and secondary structures of globulins are key parameters toward the sunflower protein meal adhesivity.

Stabilization of Cuδ+ Sites Within MnO2 for Superior Urea Electro-Synthesis.

Electrocatalytic C-N coupling between NO3 - and CO2 has emerged as a sustainable route for urea production. However, identifying catalytic active sites and designing efficient electrocatalysts remain significant challenges. Herein, the synthesis of Cu-doped MnO2 nanotube (denoted as Cu-MnO2) with stable Cuδ+-oxygen vacancies (Ovs)-Mn3+ dual sites is reported. Compared with pure MnO2, Cuδ+ doping can effectively enhance urea production performance in the co-reduction of CO2 and NO3 -. Thus, Cu-MnO2 catalyst exhibits a maximum Faradaic efficiency (FE) of 54.7% and the highest yield rate of 116.7mmolh-1gcat. -1 in a flow cell. Remarkably, the urea yield rate remains over 78mmolh-1gcat. -1 across a wide potential range. Further experimental and theoretical results elucidate the unique role of Cu-MnO2 solid-solution for stabilizing Cuδ+ sites in Cuδ+-Ovs-Mn3+, endowing the catalyst with superior structural and electrochemical stabilities. This thermodynamically promotes urea formation and kinetically lowers the energy barrier of C-N coupling.

Hybrid panels produced with particles and veneers of pine wood in different compositions

Hybrid wood panels can be produced with different particle or veneer sizes, forest species or even mixtures of synthetic materials, with the aim of reusing wood particles and generating new products. The present study aimed to verify the production process of hybrid panels formed with particles and veneers of Pinus taeda wood and urea‒formaldehyde resin. The panels were produced in four different compositions, with a nominal density of 0.65 g/cm³, and their quality was evaluated through their physical and mechanical properties. The addition of veneers in the traditional particleboard system increased the density of the hybrid panels and improved the mechanical properties. The properties of the MOR and MOE in static bending and screw withdrawal were favored using veneers on the panel faces. The internal bonding of the panels was not affected by their composition. The addition of veneers to the particleboard improved the dimensional stability of the panel.

PRODUCTION OF MDP PANELS WITH YERBA MATE HARVEST RESIDUES

The quality of MDP panels produced with Pinus taeda wood particles mixed with yerba mate harvest residues was evaluated. Monolayer panels were produced with the addition of 0. 20. 40. 60. 80 and 100% proportion of yerba mate waste, with a nominal specific gravity of 0.65 g.cm-³, using 12% urea-formaldehyde resin, 0.5% paraffin and 2% ammonium sulfate catalyst. The panels were pressed for 10 minutes at a temperature of 140°C and pressure of 40 kgf/cm². The physical properties of apparent density, moisture content, water absorption and thickness swelling (2 and 24 hours) were evaluated, as well as the mechanical properties of static bending (MOR and MOE), internal bonding, screw withdrawal on the face and Janka hardness. There was a trend towards an increase in internal bonding with an increase in the proportion of yerba mate residue in the panels, but the opposite occurred for the other mechanical properties studied. Some physical properties such as water absorption and thickness swelling resulted in better performance when yerba mate particles were added. In view of this, it can be concluded that it is possible to produce panels with the addition of yerba mate up to 40% in the composition with yerba mate particles, without affecting the quality of the properties.