超临界正丁醇对回收碳纤维复合材料的降解及表征

采用响应面分析方法设计超临界正丁醇降解废弃的碳纤维/环氧树脂(CF/EP)复合材料降解实验,用以回收碳纤维.通过Design-Expert V8.0建立环氧树脂降解率和工艺参数之间的数学模型,获得了最优工艺参数;通过图形优化研究了工艺参数对环氧树脂基体降解率的影响规律;通过场发射电子扫描显微镜、原子力显微镜、X射线光电子能谱仪、显微共焦激光拉曼光谱仪及单丝拉伸等分析最优工艺参数下回收的碳纤维的表面形貌、表面化学、石墨化程度及力学性能.结果表明,建立的数学模型拟合误差范围为±5.5%,实现了回收工艺参数的预估;单因素对环氧树脂基体降解率的影响程度为:反应温度保温时间添加剂浓度正丁醇含量;最优工艺参数为:反应温度330℃,保温时间60 min,添加剂浓度0.0538 mol/L,投料比0.024g/mL.回收的碳纤维表面无残留树脂,没有发生明显的石墨化,且表面平均粗糙度与原碳纤维相近;与原始碳纤维相比,回收的碳纤维的拉伸强度约为原碳纤维的93.58%,杨氏模量约为原碳纤维的94.87%.     

亚临界水介质回收酸酐固化环氧树脂/碳纤维复合材料

研究了不同添加剂对碳纤维增强酸酐固化环氧树脂复合材料在亚临界水中降解的影响,通过IR、GC-MS等分析,确定了环氧树脂的分解机理主要为酯键的断裂。 结果表明,KOH与苯酚对酸酐固化环氧树脂的分解没有协同效应,碱性物质更有利于酯键的断裂。 甲基四氢邻苯二甲酸酐固化的环氧树脂增强碳纤维复合材料在反应温度为250 ℃、反应时间为60 min、KOH浓度为0.2 mol/L时可完全分解,回收碳纤维的拉伸强度和表面形貌未受影响。     

四甲基氢氧化铵降解苯酐固化双酚A型环氧树脂的研究

将四甲基氢氧化铵(TMAH)降解聚酯的方法移植用于降解苯酐(PA)固化双酚A型环氧树脂(DGEBA),降解生成的邻苯二甲酸二甲酯(DMP)可被气相色谱―质谱(GC-MS)快速检测到,同时通过内标法考察了TMAH用量对降解率的影响,结果表明TMAH降解苯酐固化环氧树脂效率较高,甲酯化率在95%以上。此项研究为剖析毫克级酸酐固化环氧树脂中的固化剂提供了一种快速且有效的方法。     

磷系阻燃环氧电子封装材料研究进展

磷系阻燃环氧树脂具有阻燃效率高、制备成本低、环境危害小等显著优点,成为5G通讯、智能电子和半导体等领域的重要封装材料。基于高效磷系阻燃环氧封装材料的性能要求,介绍了磷系阻燃环氧树脂的种类和阻燃机理,总结了当前磷系阻燃环氧树脂在电子封装领域的应用研究进展并对其未来发展趋势进行了展望,指出本征型(反应型)磷系阻燃环氧树脂存在制备困难、有效磷含量低等问题,需要进一步优化工艺并提升封装体系中的磷含量。相比之下,填充型磷系阻燃环氧树脂的制备工艺简单、阻燃剂种类多、磷含量较高,在电子封装领域应用最为广泛。     

聚氨酯改性环氧树脂的研究进展

环氧树脂具有优异的粘接性能和力学性能因而被广泛应用,但其耐热性差、脆性大等缺陷限制了其在高性能领域中的应用。聚氨酯具有高弹性、耐磨、抗撕裂等特点,且与环氧树脂相容性好。因此,利用聚氨酯改性环氧树脂能显著提高其力学性能,实现环氧树脂在众多领域的应用。本文综述了不同类型的聚氨酯改性环氧树脂的进展,指出了不同类型的聚氨酯改性环氧树脂的机理、改性效果及影响因素,并对其发展前景进行展望。     

含磷/氮/硫环交联磷腈微纳米管的合成及对环氧树脂的阻燃作用

采用原位模板法,以六氯环三磷腈(HCCP)和二羟基二苯砜(BPS)为原料合成了一种环状交联型不溶不熔的磷腈大分子——聚环三磷腈-二羟基二苯砜(PZS)微纳米管,研究了PZS对环氧树脂(EP)的阻燃作用及阻燃机理.利用红外光谱(FTIR)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)对PZS微纳米管进行了表征;采用热重分析(TG)考察了EP/PZS阻燃材料的热稳定性,并通过极限氧指数(LOI)和微型量热分析(MCC)测试了EP/PZS的阻燃性能.热降解实验结果表明,PZS微纳米管的加入使环氧树脂热降解温度降低,但残炭率显著提高.PZS微纳米管可以显著提高环氧树脂的阻燃性能,当阻燃剂添加量为5%时,环氧树脂的残炭率提高了46%,热释放速率峰值降低了约40%;LOI值从纯环氧树脂的26.0%提高到了30.6%.PZS微纳米管的加入还增强了环氧树脂的力学强度.阻燃性能的显著提高和力学性能的改善归因于PZS微纳米管在环氧树脂基体中的良好分散,以及燃烧炭化过程中生成的石墨化程度较高的类石墨烯结构的残炭,具有较高的抗氧化能力.研究结果表明,PZS微纳米管是一种优良、高效的具有潜在应用价值的阻燃剂.     

热可逆自修复环氧树脂的合成与修复行为

采用环氧氯丙烷与糠醇反应合成了含二烯体结构的环氧单体,并与含亲二烯体结构的双马来酰亚胺反应,制备得到基于热可逆Diels-Alder反应的自修复环氧树脂(EP-DA).分别利用FTIR、DSC以及gel-sol转变对EP-DA的化学结构、热性能以及热可逆性进行了分析表征.结果表明,向EP-DA中引入了热可逆DA键,从而赋予环氧树脂良好的热可逆性和再加工性能,使环氧树脂实现自修复,并可使废弃环氧树脂能够得以回收再利用.模拟环氧树脂实际使用中受冲击破坏情况,采用宏观定性观察和弯曲载荷恢复定量测定相结合,对环氧树脂的修复行为和多次修复能力进行了考察,证实这种材料具有良好的自修复性能和多次重复修复能力,其一次修复效率达到了77.1%,同一试样经由3次冲击破坏—热处理后,其修复效率仍然高达53.9%.     

咪唑固化不同类型环氧树脂的固化特征、固化动力学及其反应活性

以咪唑为固化剂,对缩水甘油醚型、缩水甘油酯型环氧树脂(简称链型环氧树脂)及脂环环氧树脂的固化特征、固化动力学及反应活性进行了研究.DSC实验结果表明,固化过程均分两阶段进行,链型环氧树脂固化反应表观活化能低于脂环环氧树脂.各树脂第一阶段的表观反应活化能均低于第二阶段活化能.当脂环环氧树脂中混入不同比例的链型环氧树脂后,固化反应速率均较脂环环氧树脂单独固化时快,当链型环氧树脂量大于50％时,更为明显.     

热可逆自修复环氧树脂的合成与修复行为

采用环氧氯丙烷与糠醇反应合成了含二烯体结构的环氧单体,并与含亲二烯体结构的双马来酰亚胺反应,制备得到基于热可逆Diels-Alder反应的自修复环氧树脂(EP-DA).分别利用FTIR、DSC以及gel-sol转变对EP-DA的化学结构、热性能以及热可逆性进行了分析表征.结果表明,向EP-DA中引入了热可逆DA键,从而赋予环氧树脂良好的热可逆性和再加工性能,使环氧树脂实现自修复,并可使废弃环氧树脂能够得以回收再利用.模拟环氧树脂实际使用中受冲击破坏情况,采用宏观定性观察和弯曲载荷恢复定量测定相结合,对环氧树脂的修复行为和多次修复能力进行了考察,证实这种材料具有良好的自修复性能和多次重复修复能力,其一次修复效率达到了77.1%,同一试样经由3次冲击破坏—热处理后,其修复效率仍然高达53.9%.     

高性能可回收环氧树脂及其复合材料的制备与性能研究

采用戊二酸酐为固化剂,乙酰丙酮锌为催化剂制备了一种综合性能优异的高性能可回收环氧树脂.系统研究了固化剂及催化剂含量对树脂结构、热学及动态性能的影响,实现了树脂组成的优化设计.基于酯交换反应的热可逆性,制备的vitrimer树脂通过物理热压方法可实现良好回收,力学强度保持率可达80%.采用RTM工艺制备的碳纤维织物增强vitrimer树脂复合材料表现出与传统热固性树脂基复合材料相当的力学性能,并且通过醇类溶剂热降解树脂的方法,可实现复合材料中碳纤维的高效无损回收,回收率近100%.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.