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聚氨酯的FTIR光谱与热分析研究 总被引:8,自引:1,他引:7
采用原位傅里叶变换红外光谱法,研究了聚酯型聚氨酯和聚醚型聚氨酯在空气气氛中从室温到400 ℃之间的热解反应,实时考察了其在不同温度条件下分解残留物的基团特性。利用热分析技术考察了它们在不同气氛下从室温到700 ℃之间的热解反应。探讨了在有氧条件下的热解反应机理。结果表明聚酯型聚氨酯在空气中存在硬段和软段先后分解的两个阶段,而聚醚型聚氨酯则是硬段与软段同时分解。热分解结果也显示,硬段相同的聚氨酯,聚酯型聚氨酯的起始失重温度高于聚醚型聚氨酯,显示聚酯型的热稳定性强于聚醚型。同时聚氨酯在空气中的起始失重温度比在氮气中提前,说明氧气的存在能促进聚氨酯主链上C—C和C—O键的断裂。 相似文献
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采用廉价的无机锆源(无水硝酸锆)通过一步法合成表面含强Lewis酸位的SO42-/Zr-SBA-15,该催化剂材料在废弃食用油和甲醇酯交换制生物柴油过程中表现出良好的催化活性和选择性. 实验考察了酯交换反应的最佳条件为:反应温度160 oC、反应时间12 h、催化剂Zr:Si为0.11、催化剂用量为10%、醇油比30:1. SO42-/Zr-SBA-15在最佳反应条件下可使甘油三酯的转化率达到92.3%,脂肪酸甲酯的产率为91.7%. SO42-/Zr-SBA-15具有高比表面积的介孔结构和表面酸性,且具有良好的反应稳定性和重复性,反应7次后的脂肪酸甲酯的产率仍稳定保持在74 ±1%. 相似文献
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近红外光谱法检测聚醚多元醇伯羟基与仲羟基的相对含量 总被引:4,自引:1,他引:3
文章利用近红外光谱法,采用多元线性回归检测了聚醚多元醇的伯羟基与仲羟基的相对含量,得到了较好的预测结果,对工业在线检测具有重要的参考价值。 相似文献
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以聚醚多元醇、甲苯二异氰酸酯和二羟甲基丙酸为主要原料,丙烯酸单体封端,加入改性剂环氧树脂E-44,制备出稳定的水性聚氨酯分散体.红外光谱分析表明反应得到了水性聚氨酯结构;随着环氧树脂含量的增加,水性聚氨酯树脂粒径,黏度逐渐增大,乳液贮存稳定性下降,低温柔韧性变差,吸水率逐渐减小;甲基丙烷酸羟乙酯(HEMA)作为封端剂水性聚氨酯乳液高温稳定性优于季戊四醇三丙烯酸酯(PETA)封端剂乳液;环氧树脂改性增加了水性聚氨酯树脂的热稳定性. 相似文献
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采用多元醇法,在不同温度,不同PVP滴加速度和加入量的条件下合成了银纳米线。利用XRD, UV-Vis, SEM和TEM对银纳米线及其侧向生长过程进行了观察和分析。UV-Vis表明银纳米线在纵向生长的同时发生了侧向生长。而且表示银纳米线侧向生长的紫外吸收光谱峰在银纳米线合成后期发生了明显的红移,由384 nm红移至约388 nm处,表明银纳米线合成后期直径迅速增长,银纳米线发生了快速的侧向生长。SEM研究表明银纳米线直径在反应前期(15~23 min)只增加了20 nm,而在反应后期(23~30 min)银纳米线直径增加了近150 nm,SEM观察结果与UV-Vis分析结论一致。同时还发现银纳米线直径不仅与晶种大小有关而且与银线外覆盖的银层厚度有关,银源以吸附在银线侧面的小银颗粒为附着点沿其侧面多点沉积导致了银纳米线的侧向生长;降低反应液温度(165 ℃降至155 ℃),降低PVP滴加速度(67 mL·h-1减小到49 mL·h-1)以及减少银纳米线合成后期PVP加入量可抑制银纳米线的侧向生长,显著提高银纳米线长径比,银纳米线直径由200 nm减小至100 nm左右,长度仍保持在100 μm以上。 相似文献
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红外光谱法测定聚醚硅油中含氢硅油的含量 总被引:1,自引:0,他引:1
以烷基酚聚氧乙烯醚(OP-10)和含氢硅油为原料,以辛酸亚锡为催化剂,甲苯作溶剂,采用溶液聚合的方法合成了一种新型聚醚硅油。用红外光谱法对合成样品中残留的含氢硅油进行定量分析,利用含氢硅油中Si—H键在2 167 cm-1处的吸收峰,选择司班-60作为内标物,以朗伯-比尔定律为理论依据,推导出样品和内标物的吸光度比(Y)与质量比(X)的线性关系式为Y=kX(k为常数),从而建立了直接红外光谱法测定聚醚硅油中含氢硅油含量的方法。实验测定内标工作曲线为Y=2.072 1X+0.296 3,相关系数r2=0.998 9,通过对方法重现性和回收率的测定,得到了较为满意的结果。该法是确定合成聚醚硅油产品的反应程度和控制产品质量的一种必要手段,同时为调整聚醚硅油的性能提供了依据;从而确定了最佳合成工艺路线及工艺条件。将合成的聚合物经处理后进行了应用实验,该聚合物对醇系和苯系化合物的萃取效果很好,具有广泛的应用前景。 相似文献
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Li-Hui Wang Zhihua Huang Tienxie Hong Roger S. Porter 《Journal of Macromolecular Science: Physics》2013,52(2-3):155-169
A study has been made of the influence of transesterification on the miscibility in binary blends of poly(ethylene terephthalate) and poly(bisphenol-A carbonate). The blends were melt mixed in the range 260–300°C and studied by differential scanning calorimetry, dynamic mechanic analysis, and by Fourier transform infrared spectrometry. It was found that copolymer produced by a transesterification reaction can enhance the miscibility of this system. The new compositions were uniquely identified by FTIR. Gel permeation chromatography showed that molecular weight decreases were not the origin of miscibility. The ester exchange reaction itself was found to be initiated by the residual catalyst in the commercial polymers selected for study. This has been shown by the absence of reaction after polymer purification by solution and reprecipitation prior to melt mixing. 相似文献
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The heterogeneous isotopic exchange reaction of precipitated barium oxalate in barium chloride solution has been studied using Ba-133 as tracer. The effect of barium chloride concentration on the rate of isotopic exchange reaction has been studied. It was found that the rate was controlled by surface mass reaction and particle diffusion process in the solid particle. The result also indicate that the effect of recrystallization can be neglected. 相似文献
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Bishwajit Ganguly Marija Matković Nikola Basarić Kata Mlinarić‐Majerski 《Journal of Physical Organic Chemistry》2011,24(7):578-587
The hydrolysis of ethyl threo‐2‐(1‐adamantyl)‐3‐hydroxybutyrate ( 1 ) and the parent ester ethyl 3‐hydroxybutyrate ( 4 ) has been studied experimentally and computationally. In the hydrolysis of threo‐ester 1 with 2 M NaOH, predominantly retro‐aldol product was observed, whereas the hydrolyzed product was present in a minor amount. When the reaction is carried out under the same conditions with the parent ester ethyl 3‐hydroxybutyrate ( 4 ), hydrolyzed product is exclusively observed. The competitive pathways, namely hydrolysis and the retro‐aldol reaction for 1 and 4 were investigated using DFT calculations in the both gas and solvent phase. The calculated results in the solvent phase at B3LYP/6–31 + G* level revealed that the formation of retro‐aldol products is kinetically preferred over the hydrolysis of threo‐ester 1 in the presence of a base. However, the parent ester 4 showed that the retro‐aldol process is less favored than the hydrolysis process under similar conditions. The steric effect imposed by the bulky adamantyl group to enhance the activation barriers for the hydrolysis of the ethyl threo‐2‐(1‐adamantyl)‐3‐hydroxybutyrate ( 1 ) was further supported by the calculations performed with tert‐butyl group at the α‐carbon atom of ethyl 3‐hydroxybutyrate ( 7 ). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Li-Hui Wang Minglan Lu Xuan Yang Roger S. Porter 《Journal of Macromolecular Science: Physics》2013,52(2-3):171-183
Copolymers made by ester exchange reaction have been obtained from poly(ethylene terephthalate) (PET)/poly(bis-phenol-A carbonate) (PC) blends during melt mixing. The copolyesters were isolated by thin-layer chromatography (TLC) and identified by infrared spectroscopy. It was found that the quantity of copolymer formed was increased by the temperature and duration of melt mixing. The PET/PC blend was found to react at 270°C within 10 min, as detected by TLC. After 60 min, the pure PC had disappeared. The miscibility of PET/PC blends was found to be markedly aided by the addition of as little as 2% of the copolymer isolated by TLC. 相似文献
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利用含时波包方法对D+HS交换和抽取通道进行量子动力学研究,动力学计算中所采用的势能面由高精度从头算能量点构建.在平动能0.0~2.0 eV区间内计算了反应物初始振转基态时的总反应几率和积分反应截面,并且计算了初始振动激发态对积分反应截面的影响.所有动力学计算均考虑了科里奥利耦合效应.在低平动能时抽取通道在反应中占主导地位,而交换通道在高平动能时占主导地位.在整个所研究的平能能区间内,反应物HS的振动激发对抽取和交换通道反应都有增强作用. 相似文献
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Cephalexin, cefixime, ceftriaxone and cefotaxime were determined spectrophotometrically in the pure form and in pharmaceutical formulations by using ferrihydroxamate method. Reaction optimization with respect to reaction time and temperature has been investigated. Influence of the presence of ester functional group on the determination of cephalosporins as ß-lactams under conditions optimized was evaluated. Using cefotaxime sodiume as model drug with ester functional group, it was shown that proposed method gives equally acurate and precise results even in the presence of ester functional group. 相似文献
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The time-dependent wave packet method is used to study the exchange and abstraction processes for the H+H2O reaction with both OH bonds in the H2O reactant treated as reactive bonds in full dimension. The calculation clearly shows that it is necessary to treat both OH bonds in this way in order to accurately investigate the exchange process. However, for the abstraction process, the spectator model works very well. Nonreactive treatment of one OH bond by using a few vibrational basis functions or even freezing the bond can yield very accurate abstraction reaction probability. 相似文献
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Pravin U. Singare 《Ionics》2014,20(6):867-874
Radiotracer isotopic technique as an effective analytical tool was used to study the kinetics of ion-isotopic exchange reactions in the nuclear- and nonnuclear-grade anion exchange resins Duolite ARA-9366B and Indion-AGR. On the basis of kinetic data, specific reaction rate (per minute), amount of ion exchanged (millimoles), initial rate of iodide ion exchange (millimoles per minute), and log K d values were calculated for the two resins. It was observed that under identical experimental conditions of 35.0 °C, 1.000 g of ion exchange resins, and 0.002 mol/L of labeled iodide ion solution, the values calculated were 0.200 min?1, 0.278 mmol, 0.056 mmol/min, and 9.6, respectively, for Duolite ARA-9366B resin, which were higher than 0.102 min?1, 0.216 mmol, 0.022 mmol/min, and 5.7, respectively, for Indion-AGR resins. An identical trend was observed for the two resins during bromide ion-isotopic exchange reaction. The overall results indicate that under identical experimental conditions, Duolite ARA-9366B resins show superior performance than Indion-AGR resins. The results of the present experimental work have demonstrated that the radioanalytical technique used here can be successfully applied for the characterization of different ion exchange resins so as to evaluate their performance under various process parameters. 相似文献