共查询到19条相似文献,搜索用时 78 毫秒
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将不同投料比的OMMT(有机蒙脱土)引入脲醛树脂(UF)合成的3个阶段(加成、缩聚和缩聚后期)中,制备出相应的OMMT改性UF胶粘剂。研究结果表明:该改性UF胶粘剂的耐热性高于未改性UF胶粘剂,其游离甲醛含量随OMMT投料比增加而降低,粘接强度随之增大。加成阶段投入OMMT后,该改性UF胶粘剂的降醛效果明显;缩聚阶段投入OMMT后,该改性UF胶粘剂的补强效果显著。OMMT较佳的投入阶段为缩聚阶段,较佳的投料比为2%~3%(相对于尿素总质量而言)。 相似文献
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为考察氯化铵对蒙脱土改性UF(脲醛树脂)胶粘剂固化性能的影响,先对蒙脱土进行酸化改性,再将一定量的H-MMT(酸化蒙脱土)以原位聚合的方式投入到UF合成的不同阶段,以此制备改性效果不同的UF胶粘剂,并考察氯化铵用量对改性UF胶粘剂固化时间、适用期、胶合强度的影响。研究结果表明:反应第二阶段投入H-MMT改性的UF胶粘剂在3%氯化铵作用下固化性能较好,其固化时间为75.92 s,适用期为325 min,胶合强度为1.09 MPa;H-MMT改性的UF胶粘剂中存在未反应的游离尿素,加入固化剂氯化铵后,体系游离尿素量有所降低。 相似文献
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基于膨润土的脲醛树脂填料的开发与性能研究 总被引:4,自引:2,他引:2
比较了面粉、膨润土及其用量对脲醛(UF)树脂胶粘剂的pH值、固含量、固化时间和胶合强度的影响,探讨了膨润土用作胶粘剂填料的可行性。研究结果表明:随着膨润土用量的增加,UF树脂胶粘剂的pH值、固化时间和固含量呈递增趋势,游离甲醛含量明显下降;随着面粉用量的增加,UF树脂胶粘剂的固含量和固化时间呈递增趋势(但增幅比膨润土体系小),pH值有所降低;用添加膨润土的UF树脂胶粘剂生产的胶合板,当w(膨润土)≤20%、施胶量为280~300 g/m2时,胶合板的湿态胶合强度(1.69 MPa)比面粉体系(1.53 MPa)和纯UF树脂胶粘剂体系(1.09 MPa)的高,其湿态胶合强度能达到GB 9 846-1988的标准,而干态胶合强度则远高于GB 9 846-1988标准。 相似文献
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木质素在脲醛树脂胶粘剂中的应用 总被引:3,自引:3,他引:0
为解决脲醛树脂(UF)胶粘剂中游离甲醛含量偏高等问题,首先确定了n[甲醛(F)]∶n[尿素(U)]的合适比例,然后以羟甲基化木质素作为UF的改性剂,制备木质素改性UF胶粘剂。研究了木质素的种类及用量对UF各项性能的影响。结果表明:UF中游离甲醛含量随n(F)∶n(U)比例增加而增大;在UF改性过程中,硝酸木质素对游离甲醛的捕捉能力优于硫酸木质素,当w(硝酸木质素)=30%(相对于尿素总质量而言)时,游离甲醛含量(0.126%)相对最低;木质素加入的同时还有助于提高改性UF胶粘剂的胶接强度和耐水性。 相似文献
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《中国胶粘剂》2013,(12)
利用不同硅烷偶联剂改性ATP(凹凸棒石)或SiO2-ATP,并制备了相应的UF(脲醛树脂)胶粘剂。探讨了改性ATP或SiO2-ATP的工艺条件及其对UF胶粘剂的甲醛释放量、剪切强度等影响。结果表明:含氨基的硅烷偶联剂(A-1160和KH-792)对ATP/UF或SiO2-ATP/UF胶粘剂的甲醛释放量、剪切强度的影响较大;当w(A-1160或KH-792)=15%(相对于ATP质量而言)、w(改性ATP)=10%(相对于甲醛和尿素总质量而言)时,经60℃、3 h吸附后,相应UF胶粘剂的甲醛释放量分别下降了53.27%或53.04%,剪切强度分别增加了57.27%或46.73%;当w(A-1160或KH-792)=15%、w(改性SiO2-ATP)=10%时,经60℃、2 h吸附后,相应UF胶粘剂的甲醛释放量分别下降了34.84%或48.82%,剪切强度分别增加了68.88%或55.38%。 相似文献
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Hao Zhang Ying She Shuping Song Qian Lang 《Journal of Adhesion Science and Technology》2013,27(9):1023-1031
In this study, nanocrystalline cellulose (NCC) was used for reinforcement and formaldehyde (HCHO) adsorption of urea-formaldehyde (UF) resin adhesive in fiberboard. The original NCC was modified by 3-aminopropyltriethoxysilane for improving the wetting property with UF resin adhesive. The UF resin adhesive with modified NCC was analyzed by X-ray powder diffraction, thermogravimetric analysis, and Fourier transform infrared. The HCHO emission and bending and bonding strength of the UF resin adhesive with modified NCC were tested according to Chinese National Standard GB/T 17657-1999. Compared with the original UF resin adhesive, modified NCC led to limited effects on the crystal structure, thermal stability, and characteristic absorption peaks of UF resin adhesive. The HCHO emission of the UF resin adhesive with 1.0% modified NCC decreased by 13.0%, while the bending and bonding strength increased by 40.5 and 158.3%, respectively. The improvements of modified UF resin adhesive were destroyed by the reunion of NCC when the content was more than 1.5%. 相似文献
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Urea‐formaldehyde (UF) resins are prone to hydrolysis that results in low‐moisture resistance and subsequent formaldehyde emission from UF resin‐bonded wood panels. This study was conducted to investigate hydrolytic stability of modified UF resins as a way of lowering the formaldehyde emission of cured UF resin. Neat UF resins with three different formaldehyde/urea (F/U) mole ratios (1.4, 1.2, and 1.0) were modified, after resin synthesis, by adding four additives such as sodium hydrosulfite, sodium bisulfite, acrylamide, and polymeric 4,4′‐diphenylmethane diisocyanate (pMDI). All additives were added to UF resins with three different F/U mole ratios before curing the resin. The hydrolytic stability of UF resins was determined by measuring the mass loss and liberated formaldehyde concentration of cured and modified UF resins after acid hydrolysis. Modified UF resins of lower F/U mole ratios of 1.0 and 1.2 showed better hydrolytic stability than the one of higher F/U mole ratio of 1.4, except the modified UF resins with pMDI. The hydrolytic stability of modified UF resins by sulfur compounds (sodium bisulfate and sodium hydrosulfite) decreased with an increase in their level. However, both acrylamide and pMDI were much more effective than two sulfur compounds in terms of hydrolytic stability of modified UF resins. These results indicated that modified UF resin of the F/U mole ratio of 1.2 by adding acrylamide was the most effective in improving the hydrolytic stability of UF resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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Three grades of liquid urea-formaldehyde (UF) resin with different formaldehyde emission levels such as super E0 (SE0), E0 and E1 were modified by adding different amounts of microfibrillated cellulose (5 wt% MFC and 95 wt% water) that had been isolated by mechanical disintegration of pulp fibers. Thermal properties of these UF resins were investigated to understand thermal curing and degradation behaviors of the modified UF resins, using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC thermograms showed an exothermic curing reaction, and the curing peak temperature of modified UF resins heavily depended on the emission resin grade with an increasing order from E1, E0 to SE0. The addition of MFC suspension into the UF resins gradually increased curing peak temperature suggesting a decrease in the resin reactivity. TGA results showed three main thermal degradation temperatures for the modified UF resins except the SE0 UF resin, which had four degradation temperatures. 相似文献
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Hydrolytic and thermal stability of urea-formaldehyde resins based on tannin and betaine bio-fillers
Mirjana Ristić Suzana Samaržija-Jovanović Vojislav Jovanović Marija Kostić Tamara Erceg Tijana Jovanović Gordana Marković Milena Marinović-Cincović 《乙烯基与添加剂工艺杂志》2023,29(6):1082-1092
In this work, betaine (trimethyl glycine) and tannin (complex biomolecules of polyphenolic nature) were used as bio-fillers. Urea-formaldehyde (UF) resin with a molar ratio of formaldehyde versus urea (FA/U) of 0.8 was synthesized in situ with tannin and betaine as bio-fillers, to obtain UF resin with reduced free FA content and increased hydrolytic and thermal stability by the principles of sustainability. The samples TUF (with tannin) and BUF (with betaine) were characterized by using X-ray diffraction analysis (XRD), non-isothermal thermogravimetric analysis (TGA), and differential thermal analysis (DTA), supported by data from Fourier Transform Infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The percentage of free FA in modified BUF resin is 0.1%, while the percentage of free FA in tannin-modified resin is 0.8%. The hydrolytic stability of the modified UF resins was determined by measuring the concentration of liberated FA in the modified UF resins, after acid hydrolysis. The modified BUF resin is hydrolytically more stable because the content of released FA is 3.6% compared to the modified TUF resin, where it was 7.4%. Based on the value for T5%, the more thermally stable resin is the modified TUF resin (T5% = 123.1°C), while the value of the T5% for the BUF resin is 83.1°C. This work showed how UF bio-composite with reduced free FA content and increased hydrolytic and thermal stability can be obtained using tannin and betaine as bio-fillers. 相似文献
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Urea–formaldehyde (UF) resins are prone to hydrolytic degradation, which limits their use to indoor applications. This study examined the modification of UF resin with various thermoplastics as a means to increase the moisture resistance of the adhesive. UF adhesives were modified in situ with various hydrophobic and hydrophilic thermoplastic formulations, using either polar or nonpolar initiators. Unmodified and modified UF resins were characterized in terms of viscosity, pH, and gel time in their prepolymer suspension state. Cured solid UF resin plaques were prepared to isolate moisture sorption effects of the cured UF resin from that of the wood component in composites, which dominates their moisture uptake. Relative crosslink density and moisture sorption tests were run on cured UF resin plaques. Results indicated that viscosity increased after modification in most cases, with higher viscosities resulting from formulations using an acidic (polar) initiator. In all cases, activation energies of the curing reactions of thermoplastic‐modified UF suspensions were lower than the unmodified UF. High relative crosslink density compared to the unmodified UF was found for one sample, which correlated well with lower overall moisture sorption. Higher relative crosslink density of cured UF resin plaques appeared to be an indicator of lower moisture uptake. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4222–4229, 2006 相似文献