共查询到16条相似文献,搜索用时 140 毫秒
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尤戎(Uron)树脂及其用法对脲醛树脂性能的影响 总被引:2,自引:0,他引:2
以不同工艺制备了三种含尤戎结构的脲醛树脂(Uron树脂),通过其与普通脲醛树脂的混合制得多种混合脲醛树脂。研究了Uron树脂及其使用方法对降低脲醛树脂胶粘剂游离甲醛含量及胶接胶合板甲醛释放量的作用与效果。结果表明:1)三种不同摩尔比的Uron树脂对脲醛树脂游离甲醛含量及胶接胶合板甲醛释放量都有明显的降低作用,游离甲醛含量最多可降低43%,甲醛释放量最多可降低61%;2)Uron树脂的添加量在10%-20%时对胶合强度的提高有利,强度最大可提高29%;3)低摩尔比Uron树脂对脲醛树脂的改性效果优于高摩尔比Uron树脂。 相似文献
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探讨了低温弱酸性条件下聚乙烯醇改性脲醛树脂的合成,研究了聚乙烯醇加入量、加入的顺序对脲醛树脂胶粘剂的影响。结果表明,甲醛与尿素的摩尔比F/U=1.87,pH=4.5和温度40℃的反应条件下,加入聚乙烯醇量为0.2 g时,脲醛胶质量最好,游离甲醛含量低至0.64%,耐水时间为14 h,且稳定性好。而传统高温工艺的游离甲醛含量为1.14%,耐水时间3.4 h。本工艺节能环保,提高生产效率。 相似文献
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弱酸性条件起始合成脲醛树脂的工艺研究 总被引:3,自引:0,他引:3
对按设计工艺合成的脲醛树脂进行了性能测定,采用化学和红外方法分析了树脂的官能团,并定性分析了几种树脂固化过程中的热行为,结合实验现象分析了从弱酸性起始合成脲醛树脂的工艺特点。证明从弱酸性起始可以合成具有良好工艺性能的脲醛树脂;合成工艺与传统工艺相比有成本优势;通过工艺的完善可以控制制品的甲醛释放;采用该类工艺能够合成出适合冷固化的木材胶粘剂。 相似文献
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脲醛树脂化学构造与胶接性能、甲醛释放量及固化特性关系的研究 总被引:6,自引:4,他引:6
采用3种典型的脲醛(UF)树脂合成方法合成UF树脂,并对合成UF树脂的性能、化学构造、胶接性能、甲醛释放量及其固化历程进行了研究。揭示了UF树脂化学构造与合成方法、胶接性能、固化特性及甲醛释放量之间的相关关系,证明UF树脂的胶接性能、固化历程、甲醛释放量与UF树脂的化学构造直接相关,尤其是树脂中羟甲基含量与结合方式、亚甲基的构造对树脂性能影响最大。 相似文献
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Chenyu Han Zhengmei Luo Xinlong Su Yanhua Chen Zhaojin Yang An Mao Hong Lei Xiaojian Zhou Hui Wan Guanben Du 《应用聚合物科学杂志》2023,140(4):e53378
Based on the difference in the reaction rate of different groups of urea-formaldehyde resins and isocyanate resins, this study designed two different urea-formaldehyde resins: a normal urea-formaldehyde resin (UF) and one with high mono-hydroxymethylurea content (UF*) to react with polymeric methylene diphenyl diisocyanate (pMDI) resin. The difference in mono- and di-hydroxymethyl urea content between UF and UF* resins was analyzed by nuclear magnetic resonance (NMR) spectroscopy, and results showed that the mono-hydroxymethyl urea content of the UF* resin was much higher than that of the conventional UF resin. The fourier transform infrared spectrometer (FTIR) analysis of differences between UF* and UF resin showed that the UF* process did not change the main structure of the conventional urea formaldehyde resin. Differential scanning calorimeter (DSC) analysis showed that the curing temperature of the hybrid UF*-pMDI resin was reduced 27.3°C compared to that of the UF-pMDI resin. When these hybrid resins were used to bond plywood respectively, test results showed that the UF*-pMDI resin improved the dry and wet bonding strength by 2.6% and 3.9%, respectively, compared with the UF-pMDI resin under the condition of hot pressing time (3 min) and temperature (140°C), meeting the requirement of Chinese standard of GB/T 9846–2015 for Class III board. This study provides a new path for further improving the performance and design of hybrid resins based on isocyanate and urea-formaldehyde resin. 相似文献
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采用自制的可溶性三聚氰胺-甲醛低聚物作为脲醛树脂的添加剂,通过DSC及压制胶合板等方法评价该低聚物对脲醛树脂的固化特性、游离甲醛释放量和胶合强度的影响.结果表明,对于nF/nU为1.1的脲醛树脂UF1.随着三聚氰胺-甲醛低聚物加入量的增加,树脂固化活化能和胶合板的甲醛释放量都呈现先降低后增加的趋势,而胶合强度变化趋势不... 相似文献
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Ya-qing Liu Yu Tian Gui-zhe Zhao You-yi Sun Fu-tian Zhu Yang Cao 《Journal of Polymer Research》2008,15(6):501-505
Traditional method of synthesizing urea-formaldehyde (UF) resins is condensation polymerization with formaldehyde and urea
in aqueous solution, which leads to the low resistance of UF resins against the influence of water and moisture and results
in the high formaldehyde emission. A new method of melt condensation polymerization was used to synthesis UF resin by paraformaldehyde
with urea. Fourier-transform infrared spectroscope and Carbon-13 nuclear magnetic resonance were performed to elucidate the
uron rings structural characteristics of UF resin by the synthetic route. The stability during storage and application were
characterized by measuring concentration of methanol and free formaldehyde, and DSC and TG analysis, respectively. The results
show that UF resin synthesized by melt condensation polymerization has lower content of free formaldehyde, high thermal stability
and better stability during storage. 相似文献
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In this work, the multiepoxy functional glycidyl ether (GE) modified urea‐formaldehyde (UF) resins were synthesized via a traditional alkaline‐acid process under low formaldehyde/urea (F/U) molar ratio. The synthesized resins were characterized by 13C magnetic resonance spectroscopy (13C‐NMR), indicating that GE can effectively react with UF resins via the ring‐opening reaction of epoxy groups. Moreover, the residual epoxy groups of GE could also participate in the curing reaction of UF resins, which was verified by Fourier transform infrared spectroscopy. The storage stability of GE‐modified UF resins and the thermal degradation behavior of the synthesized resins were evaluated by using optical microrheology and thermogravimetric analysis, respectively. Meanwhile, the synthesized resins were further employed to prepare the plywood with the veneers glued. For the modification on bonding strength and formaldehyde emission of the plywood, the influences of addition method, type, and amount of GE were systematically investigated. The performance of UF adhesives were remarkably improved by the modification of GE around 20–30% (weight percentage of total urea) in the acidic condensation stage during the resin synthesis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献