Papers by Keyword: Urea-Formaldehyde Resin

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Authors: Zhe Wang, Jing Wen Xue, Wen Xia Liu
Abstract: Liquid mulching film was prepared with technical gramineae lignin from waste pulping liquid via hydroxymethylation and then cross-linking reaction with urea or aromatic ring of lignin. Results showed the amount of lignin added had an influence on the property, viscosity and water resistance of liquid film material. This influence was little when lignin dosage was less than 30%, but turned apparent when lignin dosage was higher than 30%. The optimum lignin quantity was 30%. The growth of plant was accelerated when the concentration of liquid film material was around 1000 mg/L. Both planstic and liquid mulching film could improve soil temperature, the result of liquid film was a little worse than that of plastic film, but was better than the control. The optimum lignin dosage was 30% which had the best heat incubation effect.
Authors: Daria A. Perminova, Victor S. Malkov, Irina Kurzina, Tatiana B. Babushkina, Anton M. Nachkebiya
Abstract: The paper represents the results of research related to the application of urea and glyoxal condensation product to modify the urea-formaldehyde resins (UF resins) aiming to obtain low-toxicity wood plates on the basis thereof. It was stated that the bicyclic polyfunctional compound is an effective modifier which not only does allow reducing the toxicity of wood-composite materials based on UF resins, but also increasing their physical-mechanical characteristics.
Authors: Xiao Ying Liu, Ji Zhi Zhang, Yong Lin Yang, Shi Feng Zhang, Jian Zhang Li
Abstract: The effect of melamine content in melamine modified urea formaldehyde (MUF) resin on durable properties of plywood was investigated using ammonium chloride (NH4Cl) with different melamine/urea (M/U) ratios. The plywood specimens were exposed to laboratory accelerated aging and/or cyclic soak-dry (SD). The experiment results indicated that the melamine contents in MUF resin showed an unobservable effect on the durable properties of MUF resin bonded plywood. The mechanical properties of plywood decreased more severely after accelerated aging test in acidic condition. However, the influence of different curing catalyst contents on mechanical properties and formaldehyde emission of UF resin can be minimized by adding melamine to the resin.
Authors: Hong Xia Shao, Qing Guo Tang, Jin Sheng Liang, Yan Ding
Abstract: Attapulgite mineral powder as raw material, through surface modification and composite of various mineral processing, the effect of modifier dosage, composite powder filler ratio on the mechanical properties and formaldehyde emission of the plywood which is bonded by filled urea-formaldehyde resin were investigated. The results show that under the conditions of the plywood bonding strength to meet the national standard, modified attapulgite make the plywood formaldehyde emission decrease from 4.5 to 2.1 mg/L, the composite material can make the formaldehyde emission decreased to 1.6 mg/L, which can improved the indoor environment and the grade of plywood.
Authors: Jun You Shi, Sheng You Ye
Abstract: This study was carried out to investigated the effect of addition ammonia which concentration is 20 percent modified urea-melamine-formaldehyde resin on the formald-ehyde emission and internal bonding strength, when hotpress temperature, time and pressure for every plywood was coincide.To determine and compare the effect of ammonia content 0, 2.5, 5 percent by weight of formaldehyde were used. To determine the level of formaldehyde emission, we used the desiccator method. The formaldehyde emissions from poplar multi-plywoods were significantly decreased with increased additions of ammonia, at a ammonia ratio of only 2.5%, the formaldehyde emission level of the un-coated samples which is seven-ply plywood can meet the F☆☆☆ grade, and also the samples with 2.5% ammonia modified resin hot-pressed showed good bonding strength.
Authors: Ivaldo D. Valarelli, Rosane A.G. Batistelle, Luiz A. Melgaço N. Branco, Eduardo Chahud, André Luis Christoforo, Francisco Antonio Rocco Lahr, Barbara Stolte Bezerra
Abstract: The bamboo waste can be an alternative material to sustain the crescent demand for particleboards, also bringing ecological benefits as reduction of the pressure for raw materials and landfill space demands. In this context, this research aimed to manufacture and determine some physical and mechanical properties of particleboards with bamboo waste particles (Dendrocalamus giganteus), obtained from different sources, bonded with four different percentages of urea–formaldehyde (UF) based resin (6%, 8%, 10% and 12% related to dry material of particles). Response variables investigated were: density; moisture content; thickness swelling in 2 and 24 hours; water absorption in 2 and 24 hours; internal adhesion (STpe); strength in tension parallel to faces (STpa); modulus of elasticity (MOE) and modulus of rupture (MOR). Results permitted to conclude that particleboards as mentioned showed good performance only in the physical properties requirements imposed by Brazilian Standard NBR 14810, but this was not observed to mechanical properties considered. New researches are needed in order to optimize the producing process parameters.
Authors: Juan Liu, Jing Ya Nan, Chun Peng Wang, Tie Ling Jin, Ri Qing Chen
Abstract: In this paper, the moulding conditions of urea-formaldehyde resin were optimized to prepare moulding plastic with good mechanical properties using orthogonal experimental design method. The effects of moulding temperature, pressure and pressing time on the impact strength and blending strength of urea-formaldehyde resin were studied and analyzed. The results showed that moulding temperature had most noticeable influence on the impact strength and blending strength of urea-formaldehyde moulding compounds. The ratio F of moulding temperature to the impact strength was 2.077; the ratio F of moulding temperature to blending strength was 1.082. The most optimum conditions of preparing samples for testing the impact strength were that moulding temperature was 155 °C, pressure was 30 MPa and pressing time was 12 min; and the optimum moulding temperature of preparing samples with high blending strength was 155 °C, pressure was 25 MPa and pressing time was 5 min.
Authors: Ji Zhi Zhang, Xiao Ying Liu, Ying Ying Qiu, Xiao Mei Wang, Jian Zhang Li, Shi Feng Zhang
Abstract: Urea-formaldehyde resin was modified by a modifier with different synthetic processes labelled as UFM1, UFM2, and UFM3 respectively. As a comparison, normal UF resin with a F/U molar ratio of 1.1 labelled as UF0 was synthesized. The thermal behavior of modified urea-formaldehyde resins was studied by TG-DTA techniques, and the properties of plywood bonded with the UFM resins were investigated. The conclusions were as follows: (1) the modifier used in this study could significantly reduce the free formaldehyde content of urea-formaldehyde resin and the formaldehyde emission of plywood; (2) The exothermic peak temperatures of DTA curve were 129.37, 125.05, 120.98, and 116.11 °C for UF0, UFM1, UFM2, and UFM3 respectively. (3) The plywood manufactured with UFM2 and UFM3 resins have high bonding strength (1.28MPa and 1.59MPa) and low formaldehyde emission value (E1 grade).
Authors: Kun Xu, Shi Rong Liu, Zhong Bin Ni, Ming Qing Chen, Ming Fu Mao
Abstract: A kind of form stable phase change material (PCM) based on expanded perlite, paraffin, urea formaldehyde hybrids is prepared by using vacuum-impregnation process. This kind of form stable PCM is made of paraffin as a dispersed phase change material and expanded perlite as a supporting material, and urea-formaldehyde resins as membrane materials to be applied to the porous surface of expanded perlite(EP). The structure of urea-formaldehyde resins(UF) being prepared is characterized by Fourier Transform Infrared Spectrophotometer(FT-IR). Hybrids’ thermal stability, latentheat and morphology are characterized by the thermogravimetry analysis(TGA), differential scanning calorimeter(DSC) Method and scanning electronic microscope(SEM), respectively. The FT-IR and SEM curves show that urea-formaldehyde resins have already been formed. The TGA analysis indicates that the form-stable phase change material has very good thermostability under working atmosphere. The application of DSC not only studies the appropriate curing time of UF,but also indicates that the form-stable PCM that has been prepared has more stable thermal energy storage performance than the traditional one.
Authors: Zong Rong Ying, Hai Shen Liu, Rui Yan, Tian Yin Yang, Zhi Min Dang
Abstract: Urea-formaldehyde (UF) resins modified by montmorillonite(MMT) were prepared for coating materials of controlled-release fertilizers. The influences of MMT on the mechanical properties and fertilizer-permeation performance of UF resin were studied. The mechanical properties of modified UF resins are enhanced by the addition of MMT. The shear strength of modified UF resin with 3% MMT increases by nearly 20% and reaches the maximum. The urea permeation rate of modified UF resin membranes decreases with the increasing of membrane thickness and increases with the increasing of MMT content.
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