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Ethylated Urea - Ether - Modified Urea - Formaldehyde Resins,  [cached]
Mathew Obichukwu EDOGA
Leonardo Electronic Journal of Practices and Technologies , 2006,
Abstract: First, phenol - formaldehyde (PF) and urea - formaldehyde (UFII) resins were separately conventionally prepared in our laboratory. Also, UF resin synthesized from the acid modified synthesis procedure was synthesized in a purely acid medium of pH 1.0, FU molar ratio of 1.0 and at 50oC (one-stage acid modified-synthesis procedure). Subsequently, the UF resin II was modified during synthesis by incorporating ethylated urea-ether (EUER) (i.e. UFIII) and glycerol (GLYC) (i.e. UFV) cured with and without acid curing agent. The structural and physicochemical analyses of the various resin samples were carried out.The results showed that the unmodified UF resin (UF II) synthesized in acid medium of pH 1.0, F/U molar ratio 1.0, and at 50oC, cured in absence of acid curing catalyst, showed features in their spectra which are consistent with a tri-, and/or tetra-substituted urea in the reaction to give a 3 - dimensional network cured UF resin. Modification of the UF resin(UF II) with ethylated urea-ether and glycerol to produce UF resins III and respectively V prominently increased the absorbance of methylene and ether groups in the spectra which are consistent with increased hydrophobicity and improved hydrolytic stability. For the conventional UF resin (UF I), the only clear distinction between spectra for the UF resin II and UF resins (III/V) is the presence of diminished peaks for methylene groups at 2.2 ppm. The relationship between the logarithmic viscosity of cured PF resin with time showed continuos dependence of viscosity with time during cure up to 70 minutes. Similar trends were shown by UF resins (III/V), cured in absence of acid catalyst. In contrast, the conventional UF resins I and UF IV (i.e. UF II cured with NH4CL) showed abrupt discontinuity in viscosity with time just after about 20 minutes of cure.
Setsuo Iwakiri,Alan Sulato de Andrade,Antonio Américo Cardoso Junior,Edielma do Rocio Chipanski
CERNE , 2005,
Abstract: This research was developed aiming to evaluate the effects of board density and melamine-urea-formaldehyde resin onthe properties of particleboard for semi-structural applications. The boards were manufactured with nominal density of 0.65 g/cm3and 0.90 g/cm3 using urea-formaldehyde resin as control and melamine-urea-formaldehyde. The results showed a better dimensionallystability and mechanical properties of the boards manufactured with higher density and MUF resin content. The fine furnish usedfor external layer of particleboard in the industrial process, could be used for high density homogeneous board to semi-strucuturaluses, such as flooring applications.
Factor Affecting Gel Time/Process-Ability of Urea Formaldehyde Resin Based Wood Adhesives  [PDF]
Ravindra V. Gadhave, Prakash A. Mahanwar, Pradeep T. Gadekar
Open Journal of Polymer Chemistry (OJPChem) , 2017, DOI: 10.4236/ojpchem.2017.72003
Abstract: Urea-formaldehyde (UF) resin presents the most utilized adhesive system in the manufacture of plywood, particleboard and fiberboard. At the temperatures above 100°C in the presence of hardener, this resin undergoes cross-linking reaction and the formation of three dimensional cross linked structures takes place and bonding of wood particles in a hot press [1]. UF powder resins show high reactivity and good performance in the production and by their low price; however they lack in water resistance of the hardened resin [2]. Urea-formaldehyde (UF) resins are the most important type of adhesive resins for the production of wood based panels but process-ability and curing behavior of urea formaldehyde resin depended on various factors related to resin properties, types of wood and their properties, amount & type of catalyst, types and amount of polymers addition and environmental conditions [3]. This factor decides the process-ability of UF resin based composite during manufacturing of plywood, particle board and fiberboard. In this review paper, various factors affecting gel time and process-ability of UF resin based wood composite are reviewed.
Some characteristics of urea-formaldehyde powder adhesives  [PDF]
Miljkovi? Jovan,Gavrilovi?-Grmu?a Ivana,?iporovi?-Mom?ilovi? Milanka,Popovi? Mla?an
Glasnik ?umarskog Fakulteta , 2006, DOI: 10.2298/gsf0694223m
Abstract: Urea-formaldehyde (UF) glue resins were the most important type of adhesives in the wood industry last 60 years, especially for the production of wood based panels. More convenient spray dried UF powders went into use last two decades. Small and medium private wood processing plants in Serbia prefer to use such powder adhesives, since they are more convenient for small capacity production. There is no production of UF powder resin in Serbia so necessary quantities are imported from abroad including producers from Asia. However, their characteristics are variable, dependent on syntheses steps and not well known among users. Objective of this research was to determine conveniences and lacks in application of two imported UF powder resins in comparison to domestic UF emulsion.
Amar S. Singha,Vijay Kumar Thakur
BioResources , 2009,
Abstract: Lignocellulosic fibers have received much more attention than ever before from the research community all over the world during the past few years because of their enormous advantages. A study on the preparation of new series of polymer composites using Pine Needles as a reinforcing material in Urea - Formaldehyde resin has been made. Mechanical properties of intimately mixed particle reinforced (Pine Needles) composites have been studied. Effects of different loading of reinforcement in terms of weight % on static mechanical properties such as tensile, compressive, flexural and wear properties have also been evaluated. The Urea-Formaldehyde resin prepared was subjected to evaluation of its optimum mechanical properties. The reinforcing of the resin with Pine Needles was accomplished in particle size of 200 micron by employing optimized resin. The present work reveals that mechanical properties of the Urea- Formaldehyde resin increases to a considerable extent when reinforced with Pine Needle Particles. Thermal (TGA/ DTA/DTG) and morphological studies (SEM) of the resin and polymer composites thus synthesized have also been studied. The results obtained suggest that Pine Needles can be a premium candidate for the reinforcement of high-performance polymer composites.
Comparative Study of Synthesis Procedures for Urea - Formaldehyde Resins (Part I)  [cached]
Mathew Obichukwu EDOGA
Leonardo Electronic Journal of Practices and Technologies , 2006,
Abstract: This paper presents initial results from modifying the conventional synthesis procedure of UF resins, that is reacting urea and formaldehyde first in alkaline medium and subsequently in mild acid medium at reflux (conventional two - stage alkaline - acid synthesis), by conducting the reaction only in purely acid medium at 50oC (modified one - stage acid synthesis).In another attempt, the reaction was carried out in a neutral environment and at atmospheric temperature (modified one - stage neutral synthesis). The structural analysis of the various UF resin samples was carried out. The results showed that the UF resins (II) synthesized in acidic media, particularly that of pH 1.0, showed features in their spectra which are consistent with a tri -, and/or tetra - substituted urea in the reaction to give a 3 - dimensional network UF resin. A 3 - dimensional network resin is characterized by little or no hydroxyl groups with increased cross-link-density and hydrophobicity and hence improved hydrolytic stability. For the resin (III) obtained from the conventional method, the only clear distinction between spectra for the resins (II) synthesized in acid media is the presence of diminished peaks for methylene groups at 2.2 ppm. The resins (I) synthesized in neutral medium exhibited almost the same structural characteristics as those of the resin samples (III) prepared conventionally. The result also showed that UF resin samples (I and III) possessed 5 - 17 percent of free formaldehyde; the UF resin sample (II) had approximately zero formaldehyde percentage.
Effect of Jatropha Seed Oil Meal and Rubber Seed Oil Meal as Melamine Urea Formaldehyde Adhesive Extender on the Bonding Strength of Plywood
Huei Ruey Ong,D.M. Reddy Prasad,Maksudur R. Khan,D. Subba Rao
Journal of Applied Sciences , 2012,
Abstract: Extenders are added to adhesive formulations to reduce resin utilization leading to cost savings. In this work, Melamine Urea Formaldehyde (MUF) resin was synthesized in the laboratory and Jatropha seed oil meal (JM) with Rubber seed oil meal (RM) were added to the Melamine Urea Formaldehyde (MUF) resin in adhesive mix formulations for interior plywood manufacturing using a laboratory press. These formulations were compared with commercialize industry wheat flour (IF). Response Surface Methodology (RSM) was used for identification of the optimum temperature and pressing time for wood adhesive performance. The experiments were conducted with temperature range from 100 to 150°C and pressing time from 50 to 250 sec. The result indicates that the effect of the extender type on plywood bonding strength was significant. The extender with high protein content has greater bonding strength performance.
Optimization of tensile strength for new type acetone-urea-formaldehyde furan resin using uniform design  [PDF]
Lin Shengjun,Zhao Ya,Li Yuancai
China Foundry , 2011,
Abstract: In this study, the 24 h tensile strength of new type acetone-urea-formaldehyde furan resin (nitrogen content 3%) was investigated by uniform design optimization. Four independent variables such as acetone : formaldehyde molar ratio (mol/mol), solution pH value, reaction temperature (℃) and reaction time (min) were considered in the experiments. U*13(134) uniform design was employed and the equation of 24 h tensile strength model was obtained after 13 experimentations. The 24 h tensile strength was optimized by applying single factor experiments and stepwise non-linear regression analysis. Minitab (Minitab 15 trial version) and MATLAB (R2010a trial version) were used for data analysis. The t-value and p-value indicate that the major impact factors include the interaction effect of solution pH value and reaction temperature (X2X3), the linear terms of acetone : formaldehyde molar ratio (X1), reaction time (X4) followed by the square effects of acetone/formaldehyde molar ratio (X1X1). The optimized results were achieved with the acetone: formaldehyde molar ratio (mol/mol) at 3:1, solution pH value at 6.0, reaction temperature at 70 ℃, and reaction time at 140 min, respectively. This method can not only significantly reduce the number and cost of the tests, but also provide a good experimental design strategy for the development of furan resin. The investigation shows that the predicted results of 24 h tensile strength are consistent well with the experimental ones.
Penetration of urea-formaldehyde adhesives in wood tissue, part I: Radial penetration of UF adhesives into beech
Gavrilovi?-Grmu?a Ivana,Miljkovi? Jovan,?iporovi?-Mom?ilovi? Milanka,Rado?evi? Gordana
Glasnik ?umarskog Fakulteta , 2008, DOI: 10.2298/gsf0898039g
Abstract: Adhesive penetration plays an important role in wood adhesion, since wood is a porous material. The degree of penetration mostly depends on the wood factors, resin type and formulation and processing parameters. Tangentially cut 5 mm thick beech wood (Fagus moesiaca) plies, 100 mm long (parallel to grain) and 30 mm wide, were prepared for this study. The urea-formaldehyde (UF) adhesive was applied to the surface of one ply. Two plies were assembled into sample so that the grains of two plies were parallel. Samples were pressed in a hydraulic press at 120°C and 0,7 MPa for 15 min. Microtome test-specimens were cut of each sample. 20 μm thick microtomes were cut by sliding microtome apparatus, exposing a bondline with a cross-sectional surface. The lack of more exhausting research on the penetration of urea-formaldehyde adhesives in wood is evident. Since ureaformaldehyde (UF) glue resins were the most important type of adhesives in the wood industry in the last 60 years (Dunky, 2000), the objective of this research was microscopic detection of UF adhesive penetration in wood tissue. Four types of UF resins with different levels of polycondensation were used in this research. Safranin was added in resins, since epi-fluorescence microscope was used in this research for measuring the adhesive penetration.
G. N. Onyeagoro
Academic Research International , 2012,
Abstract: Surface lignin plays an essential role in the surface characteristics of fibre and the interfacial behaviour of composites prepared with cellulosic fibres. The influence of surface lignin concentration on fibre surface characteristics and tensile properties of oil palm fibre/urea-formaldehyde resin composite was studied by Scanning Electron Microscope (SEM), tensile testing, and internal bonding strength measurements. Fibre surface lignin was removed by chlorine dioxide (Cl02) treatment. The results show that surface lignin concentration was 49.5% for the untreated fibre, and then decreased dramatically to 14.1% for the fibre treated with 1.0% Cl02. Thereafter, it decreased slowly to 9.6% and 7.6% for the fibres treated with 1.5% and 2.0% Cl02, respectively. While fibre/resin interaction was found to be poor for composites prepared with treated fibres, it decreased progressively with composites made with treated fibres due to reduction in surface lignin as revealed by the tensile properties and internal bonding strength of the composites. The SEM micrographs of the fibres reveal an increase in the surface roughness and specific surface area of fibres with reduction in surface lignin, which is believed to have promoted better fibre/resin interaction. These results indicate that the surface properties of single oil palm fibres can be tailored to improve the fibre/resin interface by chlorine dioxide treatment.
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