Structural characteristics of p‐t‐Octylphenol formaldehyde resole resins using molecular simulation

p‐t‐Octylphenol formaldehyde resole resins have two linkage types of methylene‐ and dimethylene ether‐linkages and have three terminal types of hydrogen, methylol, and o‐methylene quinone. Variation of structural characteristics of the resins due to different types of linkages and terminals were studied using molecular dynamics and molecular mechanics. The structural characteristics of the methylene‐bridged resins were intramolecular hydrogen bonds between hydroxyl groups of the adjacent p‐t‐octylphenols. In the dimethylene ether‐bridged resin, the intramolecular hydrogen bonds between oxygen atoms of the dimethylene ether‐linkages and hydroxyl groups of the neighboring phenolic units were found. For the resins with both methylol terminals, one of both terminals of the resins was hidden at the center of the molecule when the resin size is large. The number of hydrogen bonds in the resins with the methylol terminal was larger than for the resins with the o‐methylene quinone terminal. Variation of the structural characteristics of the resins by dehydration of the terminal methylol was discussed. Using the calculated results, dissociation of the dimethylene ether linkage and crosslinking reaction of rubber chains by the resin were explained. Copyright © 2002 John Wiley & Sons, Ltd.     

苯基二氨三嗪-甲醛树脂高温固化过程的红外光谱研究

本文通过不同平均加成度的A阶苯基二是三嗉甲醛树脂的红外光谱分析,对其红外吸收峰的归属进行了讨论。应用高温红外光谱和差谱技术对两种树脂样品的交联行为进行跟踪观察,由的红外吸收变化和反应体系中甲醛的检测推论了树脂的热固化反应。     

On the structure and cure acceleration of phenol-urea-formaldehyde resins with different catalysts

Phenol-urea-formaldehyde (PUF) resins with different catalysts [calcium oxide (CaO), sodium carbonate (Na₂CO₃), zinc oxide (ZnO), and magnesium oxide (MgO)] were prepared to accelerate the cure of the resin at low temperature. The cure-acceleration effects of catalysts on chemical structure and cure characteristics of PUF resins were investigated by using both liquid ¹³C nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). The liquid ¹³C NMR analysis indicated that the catalyst such as CaO seemed to present a retarded effect on the polycondensation reaction of phenolic components with urea units, while the Na₂CO₃ appeared to promote the self-condensation reaction of phenolic methylol groups at para position toward the formation of para-para methylene linkage. Both ZnO and MgO in PUF resins promoted self-condensation reaction of para methylol groups and condensation reaction of ortho methylol groups with para methylol groups. The catalysts such as Na₂CO₃, ZnO, and MgO can make PUF resins cure at a low temperature. Among these catalysts, the MgO had the most significant accelerating effect on polycondensation and cure reaction of PUF resin.     

LaHY分子筛的羟基及其酸性的红外分析

在原位红外光谱装置上, 通过氨的吸,脱附, 对脱水(320 ℃)LaHY分子筛上形成的羟基峰作了归属, 对酸性质作了进一步的分析. 其结果是: 除强酸性羟基3638 cm~(-1) (HY), 3631 cm~(-1)(LaHY)和3536 cm~(-1)(HY)、3556 cm~(-1)(LaHY)外, 还有二种直接与镧离子联结的羟基, 3520 cm~(-1)归属为弱酸性, 3531 cm~(-1)归属为非酸性. 从红外和固体核磁谱来说明, 超笼中高频羟基的酸强度是非均一的。     

Melamine–formaldehyde resins: Constitutional characterization by fourier transform 13C-NMR spectroscopy

The random chemical structures of melamine–formaldehyde resins, including methylated melamine–formaldehyde resins and urea–melamine formaldehyde resins, were investigated by ¹³C-NMR spectroscopy (Fourier transform). All the combined formaldehydes, methylol and methyl ether groups, methylene structures, and dimethylene ether structures were assigned. A ¹³C chemical shift of methylene carbon occurred by substitution of other constituents of the methylene group for a proton of the adjacent monosubstituted nitrogen atom, as shown in a ¹³C-NMR spectrum of urea–formaldehyde resins. It was found that the chemical shift of each corresponding carbon of both melamine resins and urea–melamine resins was almost superimposed with that of urea resins.     

用红外光谱法对热固性酚醛树脂固化过程的研究

用红外光谱法研究了四种热固性酚醛树脂在固化过程中的化学变化。结果表明热固性酚醛树脂的固化过程,首先是羟甲基发生缩合反应,缩合反应形成醚键是主要的。热固性酚醛树脂在进一步固化时(150—200°)出现了羰基,它的出现不是亚甲基氧化所致,而是部分醚键断裂形成了醛羰基。对热固性酚醛树脂的固化过程的机理进行了讨论。     

不同尺度和分散状态的钯纳米粒子红外光学性能研究

运用CO分子探针红外光谱研究不同尺度和分散状态的钯纳米粒子的红外光学性能.结果表明,粒子尺度为6.6nm分散的球型钯纳米粒子(Pdn)和粒子尺度为100～150nm分散的立方体型钯纳米粒子(Pdncube)均给出两个不同吸附方式的桥式CO红外谱峰,其吸收峰位置约在1970cm-1和1910cm-1.将Pdn引入到电极表面后,通过界面电化学诱导使之形成团聚体(Pdnag),其红外光学性能发生显著变化,表现为随着界面电化学诱导时间的增加,其1970cm-1处的谱峰方向从正常转为异常.本研究进一步证明红外谱峰方向的倒反是由于粒子间的相互作用引起的.     

A 13C NMR study of the methylol derivatives of 2,4′‐ and 4,4′‐dihydroxydiphenylmethanes found in resol phenol–formaldehyde resins

A total of 13 of the 16 possible methylol derivatives of 2,4′‐ and 4,4′‐dihydroxydiphenylmethane have been synthesized, isolated, and identified. These compounds are found as intermediates in the cure process of resol phenol–formaldehyde (PF) resins. Analysis of the ¹³C NMR spectra (in acetone‐d₆) of these compounds provided a way to evaluate the seven methylolphenol ring types (methylol derivatives of 2‐hydroxyphenyl and 4‐hydroxyphenyl rings) found in typical resol PF resins using the ipso carbon region from 150 to 160 ppm. A simple diagnostic test was developed using the chemical shift values of the methylol methylene carbon atoms to identify the presence of intermediates containing either a 2‐hydroxyphenyl or a 4‐hydroxyphenyl ring. Using these data it is now possible to analyze the major components in extracted prepreg PF resins. Copyright © 2002 John Wiley & Sons, Ltd.     

铜电极上CN-、SCN-电化学行为的现场红外反射吸收光谱研究

本文用循环伏安法和现场红外光谱方法研究了铜电极上CN~-和SCN~-的电化学行为。对于0.5mol~(-1)L~(-1)NaCN+0.5 mol L~(-1)NaF/Cu体系, 电极电势在-1.60至0.30 V(相对SCE)范围内, 2030—2230 cm~(-1)范围内可得到三个吸收峰, 位置分别为2076, 2094和2170 cm~(-1)。2076和2170 cm~(-1)峰分别对应于溶液中CN~-和表面沉积难溶化合物CuCN。2094 cm~(-1)峰是吸附态CN~-和溶液中配合物Cu(CN)_3~2二物种的红外吸收叠加。对于0.5 molL~(-1)NaSCN+0.5 molL~(-1)NaF/Cu体系, 在上述电势范围内可得到2060, 2177和2170 cm~(-1)三个红外吸收峰, 分别对应于溶液中的SCN~-, 吸附态的SCN~-和表面难溶化合物CuNCS。     

ZSM-5沸石上Brönsted酸的红外光谱测定法及改性ZSM-5沸石的表面酸性研究

研究各种 ZSM-5沸石样品的红外光谱发现: 在1875和2000 cm~(-1)附近有两个强红外吸收谱带, 两个谱带吸光度的比值是个特征值。本文提出了以2000 cm~(-1)谱带为“内标”, 用相对吸光度的办法处理ZSM-5沸石的红外光谱, 测定了各种改性ZSM-5样品的Brönsted酸, 并同电位滴定法所测得的Brönsted 酸浓度和异丙苯裂解活性分别关联, 都有较好的对应关系。文中以实验为依据讨论了1875和2000 cm~(-1)谱带的归属, 并根据Beer-Lambert定律, 推导出了相对吸光度与浓度的关系, 从而确立了ZSM-5沸石上红外光谱定量处理方法的理论基础。