Synthesis of tri‐aryl ketone amine isomers and their cure with epoxy resins

Isomeric tri‐aryl ketone amines, 1,3‐bis(3‐aminobenzoyl)benzene (133 BABB), 1,3‐bis(4‐aminobenzoyl)benzene (134 BABB), and 1,4‐bis(4‐aminobenzoyl)benzene (144 BABB) are synthesized and cured with diglycidyl ether of bisphenol A and diglycidyl ether of bisphenol F in this work. Differential scanning calorimetry and near‐infrared spectroscopy reveal higher rate constants and enhanced secondary amine conversion with increasing para substitution attributed to resonance effects and the electron withdrawing nature of the carbonyl linkages. Glass transition temperatures increase from 133 BABB to 134 BABB, but decrease modestly for the 144 BABB hardener. With increasing para substitution, the flexural modulus and strength both decrease while the strain to failure increases but all BABB amines displaying higher mechanical properties than the corresponding 4,4‐diaminodiphenyl sulfone (44 DDS) networks. The thermal stability of the BABB networks is found to be modestly lower than 44 DDS, but char yields are significantly higher. Changes in thermal and mechanical properties are described in terms of molecular structure and equilibrium packing density.     

Effect of the network structure on thermal and mechanical properties of mesogenic epoxy resin cured with aromatic amine

The epoxy resin containing a typical mesogenic group such as biphenol was cured with catechol novolak and aromatic diamines which have neighboring active hydrogens. In the biphenol-type epoxy resin cured with catechol novolak, 4,4′ diaminodiphenylmethane, and p-phenylenediamine (PPD), the glass-rubber transition almost disappeared, and thus a very high elastic modulus was obtained in the high temperature region. It is clear that the thermal motion of the network chains is significantly suppressed in these cured systems. In addition, in the PPD-cured system, a characteristic pattern like a schlieren texture was clearly observed under the crossed polarized optical microscope. Thus we conclude that the mesogenic group contained in the epoxy molecule is oriented in the networks when the mesogenic epoxy resin is cured with phenols and diamines which have neighboring active hydrogens. On the other hand, the biphenol-type resin cured with 3,3′,5,5′-tetraethyl-4,4′-diamino diphenylmethane (TEDDM) showed a well-defined glass-rubber transition and, thus, a low rubbery modulus. In this cured system, no characteristic pattern was observed under the crossed polarized light. These results show that the large branches, such as ethyl groups on the network chains, prevent the orientation of network chains which contain the mesogenic group. © 1997 John Wiley & Sons, Inc.     

Influence of the type of epoxy hardener on the structure and properties of interpenetrated vinyl ester/epoxy resins

The morphology–toughness relationship of vinyl ester/cycloaliphatic epoxy hybrid resins of interpenetrating network (IPN) structures was studied as a function of the epoxy hardening. The epoxy was crosslinked via polyaddition reactions (with aliphatic and cycloaliphatic diamines), cationic homopolymerization (via a boron trifluoride complex), and maleic anhydride. Maleic anhydride worked as a dual‐phase crosslinking agent by favoring the formation of a grafted IPN structure between the vinyl ester and epoxy. The type of epoxy hardener strongly affected the IPN morphology and toughness. The toughness was assessed by linear elastic fracture mechanics, which determined the fracture toughness and energy. The more compact the IPN structure was, the lower the fracture energy was of the interpenetrated vinyl ester/epoxy formulations. This resulted in the following toughness ranking: aliphatic diamine > cycloaliphatic diamine ≥ boron trifluoride complex > maleic anhydride. For IPN characterization, the width of the entangling bands and the surface roughness parameters were considered. Their values were deduced from atomic force microscopy scans taken on ion‐etched surfaces. More compact, less rough IPN‐structured resins possessed lower toughness parameters than less compact, rougher structured ones. The latter were less compatible according to dynamic mechanical thermal and thermogravimetric analyses. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5471–5481, 2004     

胺固化环氧酚醛树脂对Hg~(2+)的吸附性能

螯合树脂能与金属离子形成稳定的配合物,在无机、冶金、分析药物、催化、海洋化学、放射化学、环境保护各领域都有非常重要的应用[1-3]。我们曾以酚醛树脂为大分子骨架与多胺反应制备了一系列螯合树脂并对其结构及对多种金属离子的吸附性能进行了探讨[4,5]。本文则以线型环氧酚醛树脂为大分子骨架、多乙烯多胺为固化剂,制备了五种不同氮含量的氨基环氧酚醛螯合树脂,并考察其对金属离子Ｈｇ2+的吸附性能。1　实验部分1.1　仪器与试剂ＮｉｃｏｌｅｔＭＡＧＮＡ ＩＲ550(ＳｅｒｉｅｓＩＩ)红外分光光度计,ＳＨＡ-Ｃ水浴恒温振荡器,ＰＥ2000…     

Mechanical properties and inhomogeneous nanostructures of dicyandiamide-cured epoxy resins

Dicyandiamide (DICY)-cured epoxy resins are important materials for structural adhesives and matrix resins for fiber reinforced prepregs. The objective of this study was to examine the mechanical and physical properties as well as the gel structures of the cured resins and discuss the relationships among them. Diglycidyl ether of bisphenol-A (DGEBA) oligomers were chosen as the common chemical structure of the epoxy resins. Four kinds of resin mixtures were formulated using the seven types of DGEBA oligomers having different molecular weight distributions. Three resin formulations having bimodal-type molecular weight distributions were designed to have almost identical rubbery plateau values of the storage modulus in dynamic mechanical analyses after curing, means that they had almost equivalent average crosslink density and basic chemical structure. However, the toughness, ductility, and environmental (heat and solvent) resistance of these three formulations were different. Atomic force microscopy revealed the existence of inhomogeneous nanoscale gel structures in these cured resins. The morphological differences in the gel structures in terms of their size, the connectivity, and the relative magnitude of the heterogeneity would cause the difference in several properties of the DICY-cured epoxy resins. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1425–1434, 2007     

Flame retardant epoxy resins based on diglycidyl ether of (2,5-dihydroxyphenyl)diphenyl phosphine oxide

Phosphine oxide-containing epoxy resins were prepared from diglycidyl ether of (2,5-dihydroxyphenyl)diphenyl phosphine oxide and diglycidyl ether of bisphenol A by crosslinking with 4,4′-diaminodiphenylmethane. Several (2,5-dihydroxyphenyl)diphenyl phosphine oxide/diglycidyl ether of bisphenol A molar ratios were used to obtain materials with different phosphorus content. The properties of the thermosetting materials were evaluated by differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, and limiting oxygen index and related to the phosphorus content. Thermal and thermooxidative degradation was studied by GC/MS, ³¹P MAS NMR spectroscopy, and scanning electron microscopy. Limiting oxygen index values indicate good flame retardant properties that are related to the formation of a protective phosphorus-rich layer that slowed down the degradation and prevented it from being total. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2142–2151, 2007     

Curing reaction characteristics and phase behaviors of biphenol type epoxy resins with phenol novolac resins

Diglycidyl ether of 4,4′-dihydroxybiphenol (BPDGE) is a liquid crystalline epoxy. The biphenyl epoxy (diglycidyl ether of 3,3′,5,5′-tetramethyl-4,4′-biphenyl, TMBPDGE) has found great applications in plastic encapsulated semiconductor packaging. Phenol novolac (PN) was used as curing agent. The reaction kinetics of BPDGE/PN and TMBPDGE/PN systems in the presence of triphenylphosphine (TPP) were characterized by an isoconversional method under dynamic conditions using differential scanning calorimetry (DSC) measurements. The results showed that the curing of epoxy resins involves different reaction stages and the values of activation energy are dependent on the degree of conversion. The effects of curing temperature on their phase structure have been investigated with polarized optical microscopy and Wide-angle X-ray diffraction. With proper curing process, BPDGE showed a nematic phase when cured with PN.     

Syntheses,structure, reactivity,and thermal properties of new cyclic phosphine oxide epoxy resins cured by diamines

A new type of epoxy resin which contained cyclic phosphine oxide group in the main chain was synthesized. The structure of the new type of epoxy resin was confirmed by elemental analyses (EA), infrared spectroscopy (IR), and ¹H-NMR and ¹³C-NMR spectroscopies. In addition, compositions of the new synthesized cyclic phosphine oxide epoxy resin (EPCAO) with three curing agents, e.g., bis(3-aminophenyl)methylphosphine oxide (BAMP), 4,4′-diamino-diphenylmethane (DDM), and 4,4′-diaminodiphenylsulfone (DDS), were used for making a comparison of its curing reactivity, heat, and flame retardancy with that of Epon828 and DEN438. The reactivities were measured by differential scanning calorimetry (DSC). Through the evaluation of thermal gravimetric analysis (TGA), those polymers which were obtained through the curing reactions between the new epoxy resin and three curing agents (BAMP, DDM, DDS) also demonstrated excellent thermal properties as well as a high char yield. © 1996 John Wiley & Sons, Inc.     

Study of the structure and the mechanical properties of dynamically cured PP/MAH-g-SEBS/epoxy blends

A new method concerning with the simultaneous reinforcing and toughening of polypropylene(PP) was reported.Dynamical cure of the epoxy resin was successfully applied in the PP/maleic anhydride-grafted styrene-ethylene-butylene-styrene(SEBS) triblock copolymer,and the obtained blends named as dynamically cured PP/MAH-g-SEBS/epoxy blends.The stiffness and toughness of the blends are in a good balance,and MAH-g-SEBS was acted as not only an impact modifier but also a compatibilizer. The structure of the dyn...     

In situ FTIR and DSC investigation on cure reaction of liquid aromatic dicyanate ester with different types of epoxy resin

Cure reactions of a liquid aromatic dicyanate ester [1,1′‐bis(4‐cyanatophenyl) ethane, DiCy] associated with a liquid cycloaliphatic epoxy ester (3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexane‐carboxylate, EPC) and with liquid bisphenol A epoxide [2,2‐bis(4‐glycidyloxyphenyl)propane, EPA] were studied through a cross‐reference between in situ FTIR and DSC dynamic scanning. DiCy can act here as a latent catalyst to cure EPC and EPA resins. Reaction mechanisms were found to be different for both curing systems (EPC/DiCy and EPA/DiCy). Two significantly separated exotherms were observed in the DSC thermograms in each system. The reaction mechanism of the EPA/DiCy system was found to follow mainly Bauer pathways. We postulate a new sequence of the mechanism in this system due to the presence of an oxazoline structure during the progression of the curing process. In the curing system of EPC/DiCy, however, another five principle reaction paths, rather than Bauer pathways, are suggested: (1) polycyclotrimerization of DiCy, (2) formation of oxazoline, (3) insertion of EPC into cyanurate, (4) formation of tetrahydro–oxazolo–oxazole, and (5) ring cleavage and reformation of oxazoline to form the insertion structure of cyanurate. The lower temperature peak in the DSC thermogram is primarily contributed by the former three reaction paths, whereas the higher temperature peak can mainly be attributed to the reaction paths 4 and 5. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2934–2944, 2000     

Influence of curing conditions on the morphology and physical properties of epoxy resins modified with a liquid polyamine

A diglycidyl ether of bisphenol-A (DGEBA) epoxy resin has been stoichiometrically cured with cycloaliphatic amine 4,4′-diamino-3,3′-dimethylcyclohexylmethane (3DCM) and modified with an amine terminated oligomer polyoxypropylenetriamine (POPTA) at a concentration of 15 wt %. Mixtures, postcured at the same temperature, have been precured at different temperatures. Phase separation takes place before gelation at all precure temperatures used. The variation in the glass transition region of the mixtures has been analyzed by dynamic mechanical measurements. Mechanical properties and fracture toughness of the modified mixtures have been related to their microstructural spherical features. Results are compared to those for the unmodified mixtures cured with different precure temperatures. © 1997 John Wiley & Sons, Inc.     

Nonaqueous synthesis of nanosilica in epoxy resin matrix and thermal properties of their cured nanocomposites

Nonaqueous synthesis of nanosilica in diglycidyl ether of bisphenol‐A epoxy (DGEBA) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly with DGEBA epoxy matrix, at 80 °C for 4 h under the catalysis of boron trifluoride monoethylamine (BF₃MEA). BF₃MEA was proved to be an effective catalyst for the formation of nanosilica in DGEBA epoxy under thermal heating process. FTIR and ²⁹Si NMR spectra have been used to characterize the structures of nanosilica obtained from this direct thermal synthetic process. The morphology of the nanosilica synthesized in epoxy matrix has also been analyzed by TEM and SEM studies. The effects of both the concentration of BF₃MEA catalyst and amount of TEOS on the diameters of nanosilica in the DGEBA epoxy resin have been discussed in this study. From the DSC analysis, it was found that the nanosilica containing epoxy exhibited the same curing profile as pure epoxy resin, during the curing reaction with 4,4′‐diaminodiphenysulfone (DDS). The thermal‐cured epoxy–nanosilica composites from 40% of TEOS exhibited high glass transition temperature of 221 °C, which was almost 50 °C higher than that of pure DGEBA–DDS–BF₃MEA‐cured resin network. Almost 60 °C increase in thermal degradation temperature has been observed during the TGA of the DDS‐cured epoxy–nanosilica composites containing 40% of TEOS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 757–768, 2006     

Synthesis, characterization, and cure properties of phosphorus-containing epoxy resins for flame retardance

An organophosphorus compound, 10-(2,5-dihydroxyl phenyl)-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DHPDOPO), was synthesized through the reaction of 9,10-dihydro-9-oxa-10-phosphaphnanthrene-10-oxide (DOPO) and p-benzoquinone, and characterized by elemental analysis, Fourier transform infrared spectrum (FTIR), and ¹H-NMR and ³¹P-NMR spectroscopes. Consequently, the phosphorus-containing epoxy resins with phosphorus content of 1 and 2 wt.% were prepared via the reaction of diglycidyl ether of bisphenol-A with DHPDOPO and bisphenol-A, and confirmed with FTIR and gel permeation chromatography (GPC). Phenolic melamine, novolak, and dicyanodiamide (DICY) were used as curing agents to prepare the thermosetted resins with the control and the phosphorus-containing epoxy resins. Thermal properties and thermal degradation behaviors of these the thermosetted resins were investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Phenolic melamine-cured resins exhibited higher glass transition temperatures than the other cured resins due to the high rigidity of their molecular chain. TGA studies demonstrated that the decomposition temperatures of the novolak-cured resins were higher than those of the others. A synergistic effect from the combination of the phosphorus-containing epoxy resin and the nitrogen-containing curing agent can result in a great improvement of the flame retardance for their thermosetted resins.     

Synergistic effect of bismuth oxide and mono‐component intumescent flame retardant on the flammability and smoke suppression properties of epoxy resins

A novel mono‐component intumescent flame retardant named pentaerythritol phosphate melamine salt (PPMS)‐hybrid bismuth oxide (PPMS‐Bi₂O₃) was synthesized and carefully characterized by FTIR, ¹H NMR, ³¹P NMR, SEM‐EDS, and TG analyses. Then, PPMS‐Bi₂O₃ was utilized as flame retardant for epoxy resins (EPs), and the thermal stability, flame retardancy, and smoke suppression properties of EP composites were investigated. TG results show that PPMS‐Bi₂O₃ is more conducive to enhance the thermal stability and char forming ability of EP composites compared with the same addition of PPMS or the mixture of PPMS and Bi₂O₃, and this positive effect is enhanced with the increasing Bi₂O₃ content. Cone calorimeter test reveals that the PPMS‐Bi₂O₃ can effectively reduce the heat release and smoke production in comparison with PPMS or the mixture of PPMS and Bi₂O₃ due to the formation of a more compact and intumescent char against fire, as judged by digital photographs and SEM images. EDS analysis indicates that the combination PPMS and Bi₂O₃ by hydrogen bonds promotes to generate more phosphorus‐rich and aromatization structures in the condensed phase that enhance the barrier effect and anti‐oxidation ability of the char, thus imparting higher flame retardant and smoke suppression efficiencies to EP composites.     

Mechanical properties and curing kinetics of epoxy resins cured by various amino-terminated polyethers

<正>A high performance thermosetting epoxy resin crosslinkable at room temperature was obtained via directly moulding diglycidyl ether of bisphenol A(DGEBA) and flexibleα,ω-bisamino(n-alkylene)phenyl terminated poly(ethylene glycol).The influences of the n-alkylene inserted in aminophenyl of flexible amino-terminated polythers(ATPE) on the mechanical properties,fractographs and curing kinetics of the ATPE-DGEBA cured products were studied.The results show that the insertion of n-alkylene group into the aminophenyl group of the ATPE,on one hand,can significantly increase the strain relaxation rate and decrease glass transition temperature of the ATPE-DGEBA cured products,resulting in slight decrease of the Young's modulus and tensile strength,and significant increase of the toughness and elongation of the ATPE-DGEBA cured products.On the other hand,it can remarkably enhance the reactivity of amine with epoxy,much accelerating the curing rate of the ATPE-DGEBA systems.The activation energy of DGEBA cured by BAPTPE,BAMPTPE and BAEPTPE was 53.1,28.5 and 25.4 kJ·mol~(-1),respectively.The as-obtained ATPE-DGEBA cured products are homogeneous, transparent,and show excellent mechanical properties including tensile strength and toughness.Thus they are promising to have important applications in structure adhesives,casting bulk materials,functional coatings,cryogenic engineering, damping and sound absorbing materials.     

Syntheses and properties of cured epoxy resins containing the perfluorobutenyloxy group. I. Epoxy resin cured with perfluorobutenyloxyphthalic anhydride

Perfluorobutenyloxyphthalic anhydride (PFPA) has been synthesized as a new curing agent for epoxy resins, and the properties of epoxy resin cured with PFPA have been investigated. Good PFPA synthesis yields were realized by a dehydrating ring closure of perfluorobutenyloxyphthalic acid, which was obtained through the reaction of hexafluoropropene trimers with 4-hydroxyphthalic acid. Epoxy resin cured with PFPA was found to have several excellent properties. Its boilding water absorption was 0.45%, which is about a one-fourth that for conventionally cured epoxy resin. Its heat resistance was excellent, and its critical surface tension was almost the same as for PTFE.     

Effect of a novel green modification of alumina nanoparticles on the curing kinetics and electrical insulation properties of epoxy composites

A novel green surface modification was successfully implemented on alumina nanoparticles using chitosan (CS) to prevent nanoparticles' aggregation. To evaluate the surface changes of nanoparticles, FTIR, TGA, TEM, and SEM analyses were used. The cure kinetics of the uncured samples was analyzed by DSC. Different methods such as KAS, Friedman, Starink, and FWO were applied to measure the activation energy. The activation energy of epoxy reinforced with chitosan-functionalized alumina (epoxy/[CS-EPO-alumina]) was less than that of epoxy reinforced with alumina (epoxy/alumina), which was a confirmation of the positive effect of CS on curing reaction kinetics. Using the Malek method, the Sestak-Berggren autocatalytic equation was chosen to investigate the cure kinetics of the epoxy. It was found that the Sestak-Berggren equation is well matched with the experimental data and the model was suitable to predict the epoxy curing reaction reliably. Moreover, the glass transition temperatures of all samples were approximately the same. The effect of surface modification of alumina on the electrical insulating behavior of epoxy was also studied. It was found that CS functionalized alumina (CS-EPO-alumina) increased volume resistivity of epoxy at a temperature range of 30 to 80°C more than that of alumina. Electric stability and breakdown strength of epoxy/alumina and epoxy/(CS-EPO-alumina) also enhanced, where epoxy/(CS-EPO-alumina) experienced a further increase compared to epoxy.     

Miscibility and cure kinetics studies on blends of bisphenol-A polycarbonate and tetraglycidyl-4,4′-diaminodiphenylmethane epoxy cured with an amine

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.     

Effect of structure on thermal behaviour of epoxy resins

The paper deals with the curing behaviour of diglycidyl ether of bisphenol-A (DGEBA) using three novel multifunctional aromatic amines having phosphine oxide and amide-acid linkages. The amines were prepared by reacting tris(3-aminophenyl)phosphine oxide (TAP) with 1,2,4,5-benzenetetracarboxylic acid anhydride (P)/4,4^′-(hexafluoroisopropylidene)diphthalic acid anhydride (F)/3,3^′,4,4^′-benzophenonetetracarboxylic acid dianhydride (B). Amide-acid linkage in these amines is converted to thermally stable imide linkage during curing reaction. Curing temperatures of DGEBA were higher with phosphorylated amines than the conventional amine 4,4^′-diamino diphenyl sulphone (D). A decrease in initial decomposition temperature and higher char yields were observed when phosphorus containing amide-acid amines were used as curing agents for DGEBA.     

Control of reaction mechanisms in cationically polymerized epoxy resins facilitates the adjustment of morphology and mechanical properties

Structure–property relations of cationically polymerized epoxy thermosets with different morphologies are examined. The morphology adjustment of amorphous epoxy based copolymers and partially crystalline polymer alloys is carried out with star‐shaped poly(ε‐caprolactone) (SPCL) bearing various numbers of hydroxyl end groups. These hydroxyl groups are known for their reactivity toward epoxides following the activated monomer (AM) mechanism. For this reason, four‐armed SPCL was synthesized with four hydroxyl end groups (SPCL‐tetraol) and, in addition, with successively esterified ones down to a SPCL with four ester end groups (SPCL‐tetraester). SPCL species bearing fewer or no hydroxyl end groups segregate into needle‐like nanodomains within the epoxy networks and, if the concentration is high enough, also into crystalline domains. The stronger phase separation of SPCL‐tetraester within the epoxy network compared with SPCL‐tetraol is due to a reduction of the AM mechanism. The mechanical properties resulting from different morphologies lead to a trade‐off between higher storage moduli and T_g values in the case of the more phase separated (and partially crystalline) polymer alloys and higher strain at break in the case of the amorphous copolymers. Nevertheless, in both cases toughness is improved or at least kept on the same level as for the pure epoxy resin. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2188–2199