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1.
Miaw-Ling Lin Kuo-Hui Chang Feng-Chih Chang Ming-Shiu Li Chen-Chi M. Ma 《Journal of Polymer Science.Polymer Physics》1997,35(13):2169-2181
Reaction mechanism of the PC–epoxy blends cured by aliphatic amine has been investigated by varying PC contents in the blends. The transamidation reaction tends to convert nearly all the carbonates into N-aliphatic aromatic carbamates even at ambient temperature before normal curing. The remaining amine proceeds the normal curing with epoxy at a higher temperature (80°C). For the PC–epoxy/aliphatic amine blend containing 6 wt % PC, the yielded N-aliphatic aromatic carbamate further reacts with amine to produce the urea structure. The urea undergoes substitution reaction with the hydroxyl formed from the normal curing to give the N-aliphatic aliphatic carbamate. For the blend containing 12 wt % PC, the N-aliphatic aromatic carbamate converts into the N-aliphatic aliphatic carbamate via two different routes. For the blend containing lower molecular weight of the aliphatic amine, the N-aliphatic aromatic carbamate reacts with hydroxyl to form the N-aliphatic aliphatic carbamate directly. For the blend containing higher molecular weight of aliphatic amine, the N-aliphatic aromatic carbamate decomposes into the aliphatic isocyanate accelerated by the presence of the residual oxirane. The isocyanate formed then reacts with hydroxyl to yield the N-aliphatic aliphatic carbamate. The activation energy (Ea) and preexponential factor (A) of the PC–epoxy/POPDA blends decrease with the increase of the PC content. Kinetic study by thermal analysis by the method of autocatalyzed model is able to correctly predict oxirane conversion vs. time relationship for the neat epoxy/aliphatic amine and the PC–epoxy/aromatic amine systems because the dominant reaction is the normal curing reaction between amine and oxirane. The model fails to predict the PC–epoxy/aliphatic amine system because the system is complicated by several other reactions besides the normal curing reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2169–2181, 1997 相似文献
2.
Trong-Ming Don J. P. Bell 《Journal of polymer science. Part A, Polymer chemistry》1996,34(11):2103-2116
An epoxy resin based upon the diglycidyl ether of bisphenol-A was modified with poly(bisphenol A carbonate) (PC). Prior to aromatic amine cure, the possible reactions in the epoxy resin/PC blend were investigated using GPC and FTIR techniques. It was shown that at 150°C, the epoxy resin acted as a plasticizer and promoted the crystallization of PC. In addition, a transesterification between the secondary hydroxyl groups in the epoxy resin with the carbonate groups in PC occurred. This reaction resulted in degraded PC chains with phenolic hydroxyl end groups. There was no evidence of reaction of epoxide groups at 150°C in this blend. At 200°C, the secondary hydroxyl groups acted as a catalyst converting most of the aromatic–aromatic carbonates to the aromaticndash;liphatic and aliphaticndash;aliphatic carbonates through transesterification. At this elevated temperature, the secondary hydroxyl groups were regenerated by the addition reaction between the epoxide groups and the phenolic hydroxyl end groups, either from the transesterification or the hydrolysis of PC. This addition reaction combining the PC chains and epoxy chains eventually resulted in a crosslinked polymer if the extent of reaction was high. Thus, by using a melt blending process at high temperature, e.g., 200°C, a copolymer network structure of PC-modified epoxy could be formed. The fracture toughness should be increased by increasing the capability for plastic deformation due to the incorporation of PC chains into the network; results will be reported in a future study. © 1996 John Wiley & Sons, Inc. 相似文献
3.
Competition between phase separation and transesterification in immiscible polymer blends of polycarbonate (PC) and a copolyester (PET) is studied as a function of time and temperature by differential scanning calorimetry (DSC) and small-angle neutron scattering (SANS). We found that (1) Global structure coarsens at T ≤ 200°C due to the dominance of phase separation over transesterification and melts at T ≤ 220°C due to the dominance of transesterification at the domain interface. However, transesterification is slow but still significant even at T ≤ 200°C. (2) An intricate balance of transesterification and phase separation rates controls global and interfacial structures. (3) Interfacial structures become measurable under certain conditions, and the interfacial thickness between PC or PET and the copolymers generated by transesterification increases with time. (4) DSC results are consistent with results obtained by SANS, but the latter is more sensitive than the former and differentiates the structural change at different length scales caused by phase separation and transesterification. © 1994 John Wiley & Sons, Inc. 相似文献
4.
Dimethyl carbonate synthesis via transesterification catalyzed by quaternary ammonium salt functionalized chitosan 总被引:2,自引:0,他引:2
Yuan Zhao~ 《中国化学快报》2008,19(3):286-290
A quaternary ammonium salt covalently linked to chitosan was first used as a catalyst for dimethyl carbonate (DMC) synthesis by the transesterification of propylene carbonate (PC) with methanol. The effects of various reaction variables like reaction time, temperature and pressure on the catalytic performance were also investigated. 54% DMC yield and 71% PC conversion were obtained under the optimal reaction conditions. Notably, the catalyst was able to be reused with retention of high catalytic activity and selectivity. Consequently, the process presented here has great potential for industrial application due to its advantages such as stability, easy preparation from renewable biopolymer, and simple separation from products. 相似文献
5.
M. Abbate E. Martuscelli P. Musto G. Ragosta G. Scarinzi 《Journal of Polymer Science.Polymer Physics》1994,32(3):395-408
A highly cross-linked thermosetting epoxy resin was modified by a reactive blending process carried out in the presence of bisphenol A polycarbonate (PC). Prior to the curing process the PC component was dissolved at high temperature in the uncured epoxy matrix. FTIR investigation of this reactive mixture demonstrated the occurrence of physical and chemical interactions among the blend components. Isothermal kinetic measurements performed by FTIR spectroscopy showed that the presence of PC does not affect the overall curing mechanism but decreases both the initial reaction rate and the final conversion of reactants. © 1994 John Wiley & Sons, Inc. 相似文献
6.
V. Di Liello E. Martuscelli P. Musto G. Ragosta G. Scarinzi 《Journal of Polymer Science.Polymer Physics》1994,32(3):409-419
The yield and fracture behavior of highly crosslinked epoxy resin modified by a reactive blending process carried out in the presence of bisphenol A polycarbonate has been studied. It was found that the fracture toughness of this blend system increases markedly with increasing PC content in the blend. Scanning electron microscopy of the fractured surfaces indicated a crack blunting mechanism as the main source of energy dissipation in the various investigated blend compositions. No evidence of phase separation of the minor component during the curing and postcuring steps was observed. The yield data were correlated with the fracture toughness data to evaluate the extent of crack-tip blunting. © 1994 John Wiley & Sons, Inc. 相似文献
7.
WANG LiPing XIAO Bin WANG GongYing & WU JiQian Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu China Changzhou Key Laboratory of Green Technology Changzhou Institute of Chemistry Changzhou China Graduate School of Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2011,(9)
The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy.It was then used as the catalyst for the preparation of polycarbonate diol(PCDL) via the transesterification between diphenyl carbonate(DPC) and 1,6-hexandiol(1,6-HD).Its catalytic activity in the transesterification process is evaluated by the yield ... 相似文献
8.
Wan Xuan Zhang Kang Ye 《中国化学快报》2008,19(2):146-148
Macroporous resin (D201)-supported quartemary ammonium bisulfate (D201-HSO4) was prepared and effectively used in catalyzing the hydrolysis of epoxides or aziridines under mild and non-metal conditions to give the corresponding 1,2-diols and β-amino alcohols in high yields. The catalyst was facilely prepared and recyclable. 相似文献
9.
R. E. Jensen E. O'Brien J. Wang J. Bryant T. C. Ward L. T. James D. A. Lewis 《Journal of Polymer Science.Polymer Physics》1998,36(15):2781-2792
We have investigated epoxies based on the diglycidyl ether of bisphenol A (DGEBA) cured with 2-ethyl-4-methylimidazole (EMI-24) in the presence of the nonionic surfactant Triton X-100. A goal was to determine if the viscoelastic properties of the epoxy–surfactant system differed when prepared in bulk form, as opposed to being cast as a thin film on the surface of E-glass cloth. Such a combination of materials has generated great interest for potential use in the construction of laminated circuit boards. Using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and atomic force microscopy (AFM), it was determined that the surfactant acts as a plasticizer and is miscible with the epoxy system in concentrations up to 15% by weight. The glass transition temperature (Tg) depression of the epoxy due to the surfactant was accurately described by the Fox equation. DMA master curves were constructed in the frequency domain. The temperature dependence of the shift factors was used to determine the fragility of each of the samples studied. It was found that the fragility (cooperativity) of the epoxy decreased as the concentration of surfactant increased, presumably due to a reduction of intermolecular constraints. The fragility of the combined epoxy–surfactant system increased when cast on the surface of the E-glass cloth. Results for our model epoxy–surfactant resin were in excellent agreement with those obtained using a commercially available aqueous waterborne epoxy resin. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2781–2792, 1998 相似文献
10.
Dezhu Ma Guoying Zhang Yiyong He Jingwen Ma Xiaolie Luo 《Journal of Polymer Science.Polymer Physics》1999,37(21):2960-2972
The compatibilizing effect of a random copolymer, which is the transesterification product, on its corresponding blend system of bisphenol-A polycarbonate/poly(ethylene terephthalate) (PC/PET) has been studied using a Differential Scanning Calorimeter and a Phase Contrast Microscope. It was found that after a long time of transesterification between PET and PC (50/50, wt %), the obtained product, that is, TCET random copolymer, is miscible with individual homopolymers of PC and PET. The addition of the TCET copolymer into the immiscible PC/PET blend can make the glass transitions of the PC-rich phase and PET-rich phase approach each other, and eventually merge into a single glass transition when the content of TCET in the ternary mixture reaches 60 wt %. Meanwhile, the phase structure images showed that with the increasing content of the TCET copolymer in the ternary blends, the size of the phase domains decreases and the phase domains further diminish at 60 wt % TCET. All these results proved the compatibilizing effect of TCET copolymer on the PC/PET blends in their ternary mixture. The mechanism of the compatibilizing effect is directly related to the reduction of the interfacial tension between PC-rich and PET-rich phase domains in the presence of increasing amounts of TCET copolymer in the ternary blends. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2960–2972, 1999 相似文献
11.
Differential scanning calorimetry (DSC) has been applied to characterize the glass transition behavior of the blends formed by bisphenol-A polycarbonate (PC) with a tetrafunctional epoxy (tetraglycidyl-4,4′-diaminodiphenyl methane, TGDDM) cured with 4,4′-diaminodiphenylsulphone (DDS). A rare miscibility in the complete composition range has been demonstrated in these blends. Additionally, the blend morphology was examined using scanning electron microscopy (SEM) and a homogeneous single-phase PC/epoxy network has been observed in the blends of all compositions. Moreover, polycarbonate incorporation has been found to exert a distinct effect on the cure behavior of the epoxy blends. The cure reaction rates for the epoxy-PC blends were significantly higher due to the presence of PC. In addition, the cure mechanism of the epoxy blends was no longer autocatalytic. An n-th order reaction mechanism with n = 1.2 to 1.5 has been observed for the blends of DDS-cured epoxy with PC of various compositions studied using DSC. The proposed n-th order kinetic model has been found to describe well the cure behavior of the epoxy/PC blends up to the vitrification point. © 1995 John Wiley & Sons, Inc. 相似文献
12.
13.
IRMOF-1是一种最经典的IRMOF系列材料,通过直接在空气中不同温度下热处理IRMOF-1得到三种ZnO催化剂,并采用XRD、SEM、BET、CO_2-TPD等分析技术对所得样品的晶体结构、表观形貌、孔结构、表面碱性进行了表征。结果显示,ZnO为球状结构,是一种典型的介孔材料,BET比表面积和孔径分别为49.7~62.2 m2/g和2.18~2.92 nm。研究了ZnO微球在碳酸二苯酯(DPC)与新戊二醇(NPG)酯交换合成低聚碳酸酯二醇(PCDL)反应中的催化性能。结果表明,500℃下得到的ZnO微球在DPC与NPG酯交换反应中表现出良好的催化活性。 相似文献
14.
C. I. Vallo P. M. Frontini R. J. J. Williams 《Journal of Polymer Science.Polymer Physics》1991,29(12):1503-1511
Glass transition temperatures (Tg) of nonstoichiometric epoxy-amine networks based on the diglycidylether of bisphenol A (DGEBA), are analyzed in terms of the network structure. In most cases reasonable predictions of Tg can be made using an empirical equation reported by L. E. Nielsen together with the experimental Tg value of the stoichiometric network and statistical calculations of the concentration of elastic chains. It is stated that in these rigid networks the concentration of elastic chains is the main structural factor associated to the variations of Tg with stoichiometry. For flexible networks based on the diglycidylether of butanediol (DGEBD), the effect of elastic chains on the Tg value is much less significant. 相似文献
15.
新型碱性离子液体催化酯交换合成生物柴油 总被引:5,自引:0,他引:5
两步法合成了吗啉阴离子型碱性离子液体1-丁基-3-甲基吗啉盐Im,经 1H-NMR和FT-IR分析确认了离子液体中间体的结构,并通过阴离子交换得到碱性离子液体,对该离子液体在酯交换制备生物柴油反应中的催化性能进行了研究。结果表明,该碱性离子液体Im具有较高的酯交换催化活性,在60 ℃、催化剂用量为3%、醇油物质的量比为6.5:1.0、反应2 h的条件下,产物脂肪酸甲酯(FAME)含量可达95.80%。而且该离子液体的催化稳定性较好,重复使用5次后仍有较高的催化活性。 相似文献
16.
Eun-Seon Jeong Kyung-Hoon Kim Dae-Won Park Sang-Wook Park Jae-Wook Lee 《Reaction Kinetics and Catalysis Letters》2005,86(2):241-248
Summary The synthesis of dimethyl carbonate (DMC) was investigated through the transesterification of propylene carbonate (PC) with
methanol using quaternary ammonium salt catalysts. The reaction was carried out in an autoclave at 120-140 oC under carbon
dioxide pressure of 250-400 psig. The main by-product was propylene glycol. The quaternary salts of larger alkyl group and
more nucleophilic counter anion exhibited higher catalytic activity. Kinetic studies were also performed to better understand
the reaction mechanism. Quaternary ammonium chlorides immobilized on polystyrene supports were also tested for their possible
uses as heterogeneous catalysts. 相似文献
17.
18.
Hiroshi Sugimoto Hiroaki Ohtsuka Shohei Inoue 《Journal of polymer science. Part A, Polymer chemistry》2005,43(18):4172-4186
The alternating copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated. A typical example is the copolymerization of CO2 and CHO with the (Salophen)AlMe ( 1a )–tetraethylammonium acetate (Et4NOAc) system. When a mixture of the 1a –Et4NOAc system and CHO was pressurized by CO2 (50 atm) at 80 °C in CH2Cl2, the copolymerization of CO2 and CHO took place smoothly and produced a high polymer yield in 24 h. From the IR and NMR spectra, the product was characterized to be a copolymer of CO2 and CHO with an almost perfect alternating structure. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis indicated that an unfavorable reaction between Et4NOAc and CH2Cl2 and a possible chain‐transfer reaction with concomitant water occurred, and this resulted in the bimodal distribution of the obtained copolymer. With carefully predried reagents and apparatus, the alternating copolymerization in toluene gave a copolymer with a unimodal and narrower molecular weight distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4172–4186, 2005 相似文献
19.
Blends of poly(oxybenzoate-p-ethylene terephthalate) (POB-PET) and polyarylate were confirmed to be a partially miscible system by differential scanning calorimetry. When 60/40 POB-PET/PAr blend was annealed at high temperature (above 270°C) for several minutes, the ester–ester interchange (transesterification) in the blend took place immediately, as evidenced by Fourier Transformed infrared analyses. The analysis of the blend annealed at 290°C by 1H-13C nuclear magnetic resonance disclosed that there were four new diads appearing in 15 min and an additional one produced in 60 min during the heat treatment. The miscibility between POB-PET and polyarylate increased with the mol concentration of these new diads judging from differential scanning calorimetry. The evolution of the concentration of the diad ethylene glycol-isophthalate during the annealing can be described by a second-order reaction. The activation energy of forming the diad ethylene glycol-isophthalate was 26.5 kcal/mol, and the preexponential factor for the transesterification reaction is 3.7 × 108 min−1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1959–1969, 1998 相似文献
20.
Jinhuang Wu Chaodong Xiao Albert F. Yee Christopher A. Klug Jacob Schaefer 《Journal of Polymer Science.Polymer Physics》2001,39(15):1730-1740
To control molecular mobility and study its effects on mechanical properties, we synthesized two series of poly(ester carbonate) and polycarbonate copolymers with different linkages: (Bxt)n (x = 3, 5, 7, 9) and (BxT)n (x = 1, 3, 5, 7, 9), where t represents the terephthalate, T represents the tetramethyl bisphenol A carbonate linkages, and B is the conventional bisphenol‐A (BPA) carbonate. These two series of materials have distinct differences in their relaxation behaviors and chain mobility, as indicated by the π‐flip motion of the phenylene rings in the Bx blocks. Uniaxial tensile tests of the copolymers indicate that the brittle–ductile transition (BDT) temperatures of the copolymers are correlated to whether the γ‐relaxation peaks due to the Bx sequence is fully established. The materials possessing more fully established low‐temperature γ peaks give rise to a lower BDT. Also, the locations of the γ peaks are correlated to the ring flips of the Bx blocks of polymer chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1730–1740, 2001 相似文献