PREPARATION OF NEW COMPOSITION ADHESIVES FOR REED-CRAP PLATES BASED ON KFK-85

“INTERNATIONAL CONFERENCE ON INNOVATIVE DEVELOPMENT OF EDUCATION” 2025/1 3 DOI: https://10.5281/zenodo.17268342 PREPARATION OF NEW COMPOSITION ADHESIVES FOR REED-CRAP PLATES BASED ON KFK-85 1Karimova K.B., 2Turaev Kh.Kh., 3Eshmurodov Kh.E., 4Togayev J.B., 5Bobomurodov B.U. 1Tashkent Tashkent State Technical University. Tashkent, Uzbekistan 2,4,5Termez State University, Termez, 190100, Uzbekistan 3Tashkent Research Institute of Chemical Technology. Tashkent, Uzbekistan E-mail: [email protected] ABSTRACT In this study, new adhesives based on urea-formaldehyde concentrate (KFK-85) were synthesized and used in the production of reed-shaving composite panels. The physicochemical properties of the adhesive were optimized, and the physicomechanical properties of the panels were determined on a universal testing machine. The results showed a high bonding ability of the adhesive with reed particles and the possibility of using the panels in construction and furniture manufacturing. The optimal raw material ratio and pressing conditions provided the best mechanical properties. Key words: reed-chipboard, reed, urea-formaldehyde resin, physical and mechanical properties. АННОТАЦИЯ В данном исследовании на основе карбамид-формальдегидного концентрата (КФК-85) были синтезированы клеи нового состава, которые применялись для производства композитных плит из тростниковой щепы. Физико-химические свойства клея были оптимизированы, а физикомеханические характеристики плит определены с использованием “INTERNATIONAL CONFERENCE ON INNOVATIVE DEVELOPMENT OF EDUCATION” 2025/1 4 универсальной испытательной машины. Результаты показали высокую способность клея к связыванию с частицами тростника и возможность применения плит в строительстве и мебельной промышленности. Оптимальное соотношение сырья и условия прессования обеспечили наилучшие механические свойства. Ключевые слова: камыше-стружечная плита, камыш, карбамидоформальдегидная смола, физико-механические свойства. INTRODUCTION Urea-formaldehyde adhesives are widely used in the wood industry for the production of particleboards. In the preparation of these adhesives, formaldehyde is added to urea to form methylolated amines, which are then condensed with additional urea under acidic conditions to create a three-dimensional network. These reactions depend on the molar ratio of formaldehyde to amine and can occur at room temperature or elevated temperatures if a catalyst is present. Ammonium chloride or ammonium sulfate serves as a catalyst, while the addition of calcium phosphate enhances strength and heat resistance [1]. Urea-formaldehyde adhesives, which are condensation products of urea and formaldehyde, consist of a two-component system comprising resin and a hardener. They are also used in the form of dried powders. Curing typically occurs under pressure without heat exposure. For general purposes, curing is performed at 20°C and 0.350.70 MPa pressure for 2-4 hours. Typical conditions include a temperature of 120°C for 5-10 minutes and pressures up to 1.6 MPa. Wood is pressed at 20°C and 0.14 MPa for 15-24 hours. Bonding pressure depends on factors such as wood type, component shape, and similar variables [2]. Adhesives based on urea-formaldehyde resins are nearly colorless, provide strong bonding, have a fast curing time, and are relatively inexpensive. However, these adhesives are not stable in wet or humid environments, which limits their application areas. In some cases, melamine-formaldehyde, either alone or combined with ureaformaldehyde resins, is used to improve moisture resistance. Occasionally, phenol- “INTERNATIONAL CONFERENCE ON INNOVATIVE DEVELOPMENT OF EDUCATION” 2025/1 5 formaldehyde and methyl diisocyanate-based adhesives are used in the production of particleboards and medium-density fiberboard (MDF). These adhesives are more expensive than urea-formaldehyde but offer greater resistance to water and moisture [3]. Globally, over 10 million tons of urea-formaldehyde resin are produced annually. More than 70% of this resin is used in the wood products industry. Urea-formaldehyde resin is utilized in the production of particleboards (61%), medium-density fiberboard (27%), hardwood plywood (5%), and as an adhesive for lamination (7%). Ureaformaldehyde resins are the primary representatives of the amino resin class, accounting for approximately 80% of global amino compound production. Their widespread use in the wood products industry is attributed to advantages such as low cost, ease of use under various curing conditions, low curing temperature, water solubility, resistance to microorganisms, and high hardness [4-6]. Reed (Phragmites australis) is increasingly used in the production of composite boards due to its environmental and economic benefits. The chemical composition of reed typically includes 40-50% cellulose, 20-30% lignin, and 20-25% hemicellulose [7]. This composition makes reed suitable for strong bonding with adhesives, as cellulose provides mechanical strength and lignin contributes to rigidity. For example, urea-formaldehyde resin forms hydrogen bonds with the cellulose in reed [8]. Wood materials, especially softwoods, may contain higher starch content, which reduces moisture resistance. The low starch content in reed enhances its moisture resistance [9]. Reed is a fast-growing, naturally renewable resource, and its harvesting does not contribute to deforestation. In contrast, wood-based material production requires logging, which causes environmental issues [12]. The local availability of reed reduces transportation costs. Reed is an inexpensive raw material, and its processing costs may be lower than those for wood. For instance, reed residues can be obtained for free or at a low cost from agricultural waste [10]. Reed-based boards can be used in furniture manufacturing (e.g., lightweight panels), construction (e.g., interior wall cladding), and packaging materials. Their low “INTERNATIONAL CONFERENCE ON INNOVATIVE DEVELOPMENT OF EDUCATION” 2025/1 6 density and good mechanical properties make them an attractive alternative to particleboards and MDF [11]. Reed-particleboards meet the demand for eco-friendly products [12]. However, reed has some drawbacks, including a SiO₂ content of up to 2-5%, which can lead to rapid wear of processing equipment [7]. In wood-based materials, SiO₂ content typically does not exceed 0.1-0.5%, simplifying the manufacturing process. The chemical composition of reed varies significantly depending on its growing location and season, which poses challenges in ensuring standardized material quality [10]. Wood materials, on the other hand, have a more consistent composition. The screw-holding strength of reed-particleboards (32-42 N/mm) may be lower than that of MDF (40-50 N/mm) and plywood (50-60 N/mm), which can limit their use in certain structural applications [11]. Reed-based boards are not yet as widely adopted in the global market as particleboards and MDF, indicating limitations in their production and marketing infrastructure [13]. MATERIALS AND METHODS Materials. Experiments were conducted with the following chemicals: KFK-85, urea, ammonium chloride, PVA, NaOH. Methods. In this study, new urea-formaldehyde adhesives were synthesized, and samples of reed-scrap boards were prepared based on the obtained adhesive and reed shavings. The physicochemical properties of the adhesive were studied, and the physicomechanical properties of the finished reed-scrap boards were determined using a universal testing machine using the appropriate methodology. EXPERIMENT PART To conduct the experiment, 4150 g of KFK-85 semi-finished resin and 2410 g of water were initially added to the reactor. While the reaction mixture was continuously stirred, 15 g of PVA-24-88 was added. The pH was adjusted to 8 using NaOH. Then, 1250 g of urea was added, the temperature was raised to 90°C, and the mixture was stirred for 60 minutes. Ammonium chloride was added to lower the pH to 3.8, and once the reaction mixture reached sufficient viscosity, the pH was raised to 6.5 using NaOH. Subsequently, 650 g of urea and additional NaOH were added (to achieve pH 7.5). “INTERNATIONAL CONFERENCE ON INNOVATIVE DEVELOPMENT OF EDUCATION” 2025/1 7 Another 610 g of urea was added, and the reaction continued. The temperature was reduced to 70°C, and an additional 610 g of urea was introduced. Once the reaction mass reached a homogeneous state, it was cooled to 30°C. The resulting adhesive was tested for flowability, gelation, density, viscosity, and dry residue content. Using the newly formulated adhesive and two different fractions of ground reed, reedparticleboard samples were produced via thermal pressing. The physical-mechanical properties of the board samples were determined using a universal testing machine and compared with boards made using other adhesive compositions. RESULTS AND DISCUSSION The physicochemical properties of the newly prepared adhesive are given in Table 1. Table 1 Physical and chemical properties of the new adhesive composition № Properties Yelim namunalari Sample 1 Sample 2 Sample 3 1 Flowability, sec 41 42 45 2 Gelatinization, sec 59 62 66 3 Density, gr/dm3 1240 1245 1250 4 Viscosity, mPa 440 430 440 5 Dry residue, % 66,5 66,8 67,7 As shown in Table 1, Sample 1 exhibited a flowability of 41 seconds, gelation time of 59 seconds, density of 1240 g/dm3, viscosity of 440 mPa, and dry residue of 66.5%. Sample 2 had a flowability of 42 seconds, gelation time of 62 seconds, density of 1245 g/dm3, viscosity of 430 mPa, and dry residue of 66.8%. Sample 3 showed a flowability of 45 seconds, gelation time of 66 seconds, density of 1250 g/dm3, viscosity of 440 mPa, and dry residue of 67.7%. These parameters are crucial for ensuring uniform distribution of the adhesive with reed particles. The high viscosity (430-440 mPa) and dry residue (66.5-67.7%) confirm the adhesive’s effectiveness as a bonding agent. The gelation time (59-66 seconds) and flowability (41-45 seconds) indicate good mixing with reed particles and uniform distribution during the pressing process. The three-stage synthesis process (alkaline-acidic-alkaline) optimized the resin’s polycondensation degree and minimized the free formaldehyde content [14]. “INTERNATIONAL CONFERENCE ON INNOVATIVE DEVELOPMENT OF EDUCATION” 2025/1 8 Table 2 Physical and mechanical properties of reed-shaving boards obtained on the basis of a new composition of glue № Sample density (kg/cm3) Bending Strength (Mpa) Resistance to hardening of syrup (N/mm) Resistance to lateral compression (N) Water absorption, %. 12 hours 1 750 12,8 36 642 20 2 650 13,1 42 582 21 3 670 9,6 33 520 23 Based on Table 2, the physical-mechanical properties of reed-particleboards were analyzed. Sample 1 exhibited the highest density (750 kg/m3) and good bending strength (12.8 MPa), which is attributed to the larger fraction size (1200 g) and higher resin content (220 g). The screw-holding resistance was average (36 N/mm), but it showed high resistance when screws were inserted from the side (642 N). Sample 2 demonstrated the highest screw-holding resistance (42 N/mm) and bending strength (13.1 MPa), but had a lower density (650 kg/m³), explained by the use of less raw material (960 g) and resin (166 g). Sample 3 showed the lowest bending strength (9.6 MPa) and side screw-holding resistance (520 N), with a moderate density (670 kg/m3). High temperatures (162-165°C) may have caused excessive resin hardening, potentially leading to reduced strength. Figure 1. Glue preparation process Figure 2. Preparation for pressing Figure 3. Pressed plate Figure 3. Pressed plate The research results demonstrated that urea-formaldehyde resin is an effective adhesive for reed-particleboards. Sample 2 exhibited the best mechanical properties (13.1 MPa bending strength, 42 N/mm screw-holding resistance), which is attributed “INTERNATIONAL CONFERENCE ON INNOVATIVE DEVELOPMENT OF EDUCATION” 2025/1 9 to the optimal ratio of raw material and resin. The reduced density (646 kg/m3) contributes to lighter boards, but long-term durability testing is required. CONCLUSION Urea-formaldehyde resin was successfully synthesized through a three-stage process and used as an adhesive in the production of reed-particleboards. The resulting boards met construction and furniture industry requirements with densities (646-754 kg/m3), bending strength (9.6-13.1 MPa), and screw-holding resistance (32-42 N/mm). Sample 2 exhibited the best mechanical properties, attributed to the optimal raw material ratio and pressing conditions. Further studies on the boards’ water absorption, biodegradability, and long-term durability are recommended. REFERENCES: 1. Chen, J., Zhang, S., & Xu, Y. “Recent advances in urea-formaldehyde resins for wood-based composite materials” Journal of Materials Science, 56(12), 2021, pp. 7612-7630. https://doi.org/10.1007/s10853-021-05755-8. 2. Lee, S. 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