三元乙丙橡胶/蒙脱土纳米复合材料制备中硫化体系的比较

采用了熔融插层和两种硫化体系硫磺 促进剂和过氧化物体系制备了三元乙丙橡胶 蒙脱土纳米复合材料 ,并将这两种体系形成的纳米复合材料进行了形态、力学性能和光学性能的比较 ,同时采用Flory Rehner方程对它们的硫化行为进行了评价 .X射线衍射 (XRD)、透射电镜 (TEM)、力学性能和光学性能的测试结果表明 ,由硫磺硫化体系制备的纳米复合材料为不透明和剥离型 .其原有的d0 0 1 衍射峰消失 ,有序层被剥离成 10 0～ 2 0 0nm的片层均匀分散在EPDM基体中 ,其力学性能有了极大的提高 ;而过氧化物体系制备的纳米复合材料为半透明和插层型 .对两种体系的硫化行为的评价结果表明 ,随着有机蒙脱土加入量的增加 ,硫磺 促进剂硫化体系的t90 延长 ,交联密度减小 ,最大 最小转矩也变小 ;而过氧化物硫化体系的相应值却变化不大     

Phase structure and thermomechanical properties of primary and tertiary amine‐cured epoxy/silica hybrids

Several kinds of organic–inorganic hybrids were synthesized from an epoxy resin and a silane alkoxide with a primary amine‐type curing agent or tertiary amine curing catalyst. In the hybrid systems cured with the primary amine‐type curing agent, the storage modulus in the high‐temperature region increased, and the peak area of the tan δ curve decreased. Moreover, the mechanical properties were improved by the hybridization of small amounts of the silica network. However, these phenomena were not observed in the hybrid systems cured with the tertiary amine catalyst. The differences in the network structures of the hybrid materials with the different curing processes were characterized with Fourier transform infrared (FTIR). In the hybrid systems cured with the primary amine‐type curing agent, FTIR results showed the formation of a covalent bond between silanol and hydroxyl groups that were generated by the reaction of an epoxy group with an active hydrogen of the primary amine. However, this phenomenon was not observed in the hybrids cured with the tertiary amine. The hybrids with the primary amine showed a homogeneous microstructure in transmission electron microscopy observations, although the hybrids cured with the tertiary amine showed a heterogeneous structure. These results mean that the differences in the interactions between the organic and inorganic phases significantly affect the properties and microstructures of the resultant composites. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1071–1084, 2001     

A STUDY ON THE TOUGHENING OF EPOXY RESIN BY HTBN-EPOXY RESIN PRECOPOLYMER

A novet toughened epoxy resin was obtained by using aprecopotymer of epoxy resin and hydroxy-terminated butadiene-acrylonitrilecopolymer(HTBN)and amine curing agent.The cured toughened resin hasexcellent mechanical properties due to the two-phase structure,which has beenobserved from SEM and TEM.     

Evolution of structure and properties of a liquid crystalline epoxy during curing

The evolution of structure, and thermal and dynamic mechanical properties of a liquid crystalline epoxy during curing has been studied with differential scanning calorimetry (DSC), polarized optical microscopy, x-ray scattering, and dynamic mechanical analysis. The liquid crystalline epoxy was the diglycidyl ether of 4,4′-dihydroxy-α-methylstilbene (DGEDHMS). Two curing agents were used in this study: a di-functional amine, the aniline adduct of DGEDHMS, and a tetra-functional sulfonamido amine, sulfanilamide. The effects of curing agent, cure time, and cure temperature have been investigated. Isothermal curing of the liquid crystalline epoxy with the di-functional amine and the tetra-functional sulfonamido amine causes an increase in the mesophase stability of the liquid crystalline epoxy resin. The curing also leads to various liquid crystalline textures, depending on the curing agent and cure temperature. These textures coarsen during the isothermal curing. Moreover, curing with both curing agents results in a layered structure with mesogenic units aligned perpendicular to the layer surfaces. The layer thickness decreases with cure temperature for the systems cured with the tetra-functional curing agent. The glass transition temperature of the cured networks rises with increasing cure temperature due to the increased crosslink density. The shear modulus of the cured networks shows a strong temperature dependence. However, it does not change appreciably with cure temperature. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2363–2378, 1997     

Synthesis and curing kinetics of cardanol‐based curing agents for epoxy resin by in situ depolymerization of paraformaldehyde

Three novel cardanol‐based phenalkamines with good stability have been successfully prepared by Mannich reaction using phenolic compounds with paraformaldehyde and hexamethylenediamine (or its mixture with other amines). The structure of the prepared phenalkamines has been analyzed using liquid chromatography‐mass spectrometry, nuclear magnetic resonance, and Fourier transform infrared spectroscopy. The curing kinetics of the prepared epoxy resin/phenalkamine systems has been investigated using differential scanning calorimetry (DSC), and determined by Kissinger, Flynn–Wall–Ozawa, and Crane methods. Furthermore, the thermal properties of the cured materials have been evaluated using DSC and thermogravimetric analysis, and the mechanical properties of the cured materials have been analyzed systematically. The results demonstrate that the phenalkamine 1 (PAA1) had a lower reactivity and better toughness than phenalkamine 2 (PAA2) and phenalkamine 3 (PAA3). In addition, PAA1 is a solid curing agent, while PAA2 and PAA3 are liquid curing agents, which were more convenient for practical usage. Results indicate that the properties of the prepared phenalkamines strongly depend on the structures. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 472–480     

端噁唑啉聚醚对环氧树脂的固化与增韧作用的研究

用IR、DSC等分析方法研究了端2-噁唑啉聚环氧丙烷(活性聚醚)与环氧树脂的固化反应,对固化机理作了讨论。并考察了不同分子量活性聚醚对环氧树脂的增韧作用。结果表明,此活性聚醚对环氧树脂增韧效果明显,固化树脂综合性能较好。     

Relationship between fracture toughness and domain size of liquid‐crystalline epoxy resins having polydomain structure

A liquid‐crystalline (LC) epoxy resin was cured at different temperatures and some types of curing systems having different phase structures (isotropic or polydomain, which have a microscopically ordered LC network structure) were obtained. The diameters of each domain in the polydomain system changed from the small to the larger size. The diameters of the LC domains were evaluated using a polarized optical microscope and the polarized microscopy FTIR mapping method. These systems were used to investigate the relationship between the network arrangement and mechanical properties. The fracture toughness of the cured systems was related to the enlargement of the ordered area in the network structures. With the toughness improvement, the meandering cracks were observed at the fracture surfaces. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 156–165, 2009     

Synthesis and characterization of novel polythiourethane hardeners for epoxy resins

A novel thiol-terminated polythiourethanes were synthesized from low-molecular-weight di- and multifunctional mercaptans and diisocyanates and employed as curing agent of epoxy resin. The curing reaction of epoxy resin and thermal properties of cured products were investigated with differential scanning calorimetry. Evaluation of climatic ageing resistance was made by the change in mechanical properties. Mechanical studies indicated that the application of polythiourethane has toughening effect and significantly increases ageing resistance of the cured resins. The results of this study indicate that molecular structure and functionality of polythiourethane oligomers are of critical importance in governing the curing mechanism, structure of the network and final properties of epoxy compositions.     

Effects of tertiary amine accelerators on curing of epoxide resins

The effects of seven tertiary amine accelerators on curing of bisphenol-type epoxide resins using azelaic acid as a curing agent have been investigated. The structure of the cured resins is characterized and reaction and structure schemes are proposed. The reaction mechanism and the resulting structure of the resin depend on the basicity of the accelerator. With increasing accelerator basicity crosslinking in the cured resin increases. Characterization results indicate that the network structure consists of ether bonds or a mixture of ether and ester bonds; the linear structure consists of only ester bonds. The structure and, therefore, the properties of the cured epoxide resin may thus be regulated by selection of the amine basicity.     

Comparative curing kinetics of 1,4-bis (4-diaminobenzene-1-oxygen) n-butane and 4,4′-bis-(diaminodiphenyl) methane with tetraglycidyl methylene dianiline systems

Aromatic amine curing agent with flexible unit in backbone, 1,4-bis (4-diaminobenzene-1-oxygen) n-butane (DDBE), was synthesized, and the structure was confirmed by FT-IR and ¹H NMR. The curing kinetics of tetraglycidyl methylene dianiline (TGDDM, or AG80) using DDBE and 4,4′-bis-(diaminodiphenyl) methane (DDM) as curing agents, respectively, were comparatively studied by non-isothermal DSC with a model-fitting Málek approach and a model-free advanced isoconversional method of Vyazovkin. The dynamic mechanical properties and thermal stabilities of the cured materials were investigated by DMTA and TG, respectively. The results showed that the activation energy of AG80/DDBE system was slightly higher than that of AG80/DDM system. ?esták-Berggren model can generally simulate well the reaction rates of these two systems. DMTA measurements showed that the storage modulus of cured AG80/DDBE is similar to that of cured AG80/DDM at the temperature below glass transition temperature (T _g) and lower than that of cured AG80/DDM at the temperature above glass transition temperature, while T _g of cured AG80/DDBE is lower than that of cured AG80/DDM. TG showed that the thermal stabilities of these two cured systems are similar.     

Hydrothermal ageing of radiation cured epoxy resin-polyether sulfone blends as matrices for structural composites

The hydrothermal ageing of epoxy-thermoplastic blends, used as matrices for carbon fibre composites, cured by electron beam, has been studied. Two different thermoplastic percentages have been adopted. A suitable choice of both curing process and formulation parameters allows to carry out irradiation at mild temperature with several advantages, coming from a “non thermal” process, for both the final properties of the materials and the environment. Nevertheless the occurring of vitrification phenomena needs the use of a short thermal treatment after irradiation on the already solid materials, in order to complete the cure reactions. Radiation cured epoxy based matrices have been subjected to a thermal and moisture absorption ageing treatment and its influence on the thermal and mechanical properties has been investigated through dynamic mechanical thermal analysis and fracture toughness tests. The results have been interpreted on the basis of the different curing degree reached by the investigated systems and in the light of their morphological structures. Plasticization, thermal curing and degradation reactions occur in different extent depending on the kind of the material. In particular, for fracture properties, a better resistance to ageing is shown by the system at higher thermoplastic concentration.     

混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响

采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能     

Influence of Reactive Diluent on UV-curing of Acrylate Terminated Hyperbranched Polymers

A Aeries of hydroxylic hyperbranched polymers were derived from 2,2-bis (methylol) propionic acid and tris (methylol) propane reacted with acrylic acid to various extents. The obtained acrylated hyperbranched polymers alone or with a monofunctional diluent, isobornylene acrylate(IBOA) were further cured by UV radiation. The cured films based on the modified polymers alone all demonstrated poor mechanical properties due to their high network densities and low moving ability of polymer chains. For the composite systems, the cured films demonstrated improved mechanical properties due to the low network densities and high chain moving ability. With more IBOA included in the systems, acrylate groups can react to a higher extent during the curing process.     

Curing behavior and kinetics of epoxy resins cured with liquid crystalline curing agent

This article describes the synthesis of a liquid crystalline curing agent 4,4′-bis-(4-amine-butyloxy)-biphenyl (BABB), and its application as a curing agent for the epoxy resin (DGEBA) in comparison with normal curing agent, 4,4′-diaminobiphenyl (DABP). BABB was investigated with polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scatting, and the results showed that BABB displayed smectic liquid crystalline phase. The curing behaviors of DGEBA cured with BABB and DABP were studied by using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and dynamic mechanical analysis (DMA). The results indicated that BABB showed a higher chemical reactivity than DABP. The kinetics was studied under isothermal conditions using an isoconversional method, and the isothermal DSC data can be fitted reasonably by an autocatalytic curing model. The nematic droplet texture was observed for the resulting polymer network of DGEBA/BABB system, while the DGEBA/DABP system showed an isotropic state. The storage modulus of DGEBA/BABB system was enhanced in comparison with DGEBA/DABP system because of the formation of LC phase, whereas the glass transition temperatures decreased because of the introduction of flexible spacer group.     

Mechanical relaxation mechanism of epoxide resins cured with acid anhydrides

The mechanism of low-temperature mechanical relaxation in epoxide resins cured with various acid anhydrides has been investigated by comparing dynamic mechanical properties and chemical structures of these networks. One mechanical relaxation, denoted as the β relaxation, is observed at about ?70°C. The β relaxation is affected by the chemical structure of the curing agents, but not by that of the epoxide resins. In addition, the strength of the relaxation increases linearly with increasing concentration of diester linkage introduced in the network by reaction with acid anhydrides. From these results, it is concluded that the β relaxation mechanism of the anhydride-cured systems involves the motion of diester segments included in the network structures.     

Synthesis,characterization, and thermal properties of ladderlike polyepoxysiloxanes

Starting from trichlorosilanes and using 1,4‐phenylenediamine as a template, we have synthesized some ladderlike poly(glycidyl‐co‐alkyl/aryl)siloxanes (polyepoxysiloxanes or polyepoxies for short). The structures of copolymers were confirmed through IR, ¹H NMR, elemental analyses, and gel permeation chromatography. Curing behaviors of these polyepoxies in the absence and presence of a curing agent have been studied with DSC. It was shown that these epoxies could be cured without any curing agent. Copolymers having aromatic groups showed higher curing reactivity than those having alkyl groups. The experimental results also demonstrate that the curing reaction occurred solely via epoxy functionality, not via the condensation reaction of the hydroxy groups located at the end of polymer main chains. The thermal stability of the cured polymers was examined by thermogravimetric analysis. The results confirm that polyepoxies with aromatic groups had better thermal stability than those with alkyl groups. It was also found that polyepoxies cured with a diamine have a higher thermal stability than those cured in the absence of a curing agent. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2215–2222, 2001     

EB/UV treatment of protective coatings for porous materials

A method for improving surface properties of porous inorganic materials is presented. The method is particularly tailored to cement-based materials in order to obtain properties suitable for mechanical applications such as dies manufacturing, where hardness, abrasion resistance and low friction are requested. The coating system is based upon using two coatings of different characteristics. The underlying base coating layer is infiltrated in air on three different formulations of hardened cement composite. Two different bi-component resins, one relatively soft and the other relatively hard, were tested as underlying surface coating. The outer surface coating, based upon a bi-component resin characterized by high hardness, is added after hardening and curing of the first layer. Both coatings were chemically hardened and then cured with EB. UV curing is also suitable for the outer surface coating. An experimental campaign was carried out in order to evaluate the influence of radiation processing as curing treatment with reference to particular investigated materials. Hardness and resistance to peeling of coating systems have been measured and are presented.     

Thermoset modified with polyethersulfone: Characterization and control of the morphology

Thermoset (TS) epoxy resins can be toughened with a thermoplastic (TP) for high-performance applications. The final structure morphology has to be controlled to achieve high mechanical properties and high impact resistance. Four polyethersulfone-modified epoxy resins are considered. They consist of different epoxy monomer structure (TGAP, triglycidyl-p-aminophenol and TGDDM, tetraglycidyl diaminodiphenylmethane) and a fixed amount of thermoplastic, and they are cured with two different amounts of curing agent. A reaction-induced phase separation occurs for all formulations generating morphologies, different in shapes and scales. The aim is to control the final morphology and in particular its dominant length scale. This morphology depends on the phase separation process, from the initiation to its final stage. The initiation relies on the relative miscibility of the components and on the stoichiometry between epoxy and curing agent. The kinetics depends on the viscosity of the systems. The different morphologies are characterized by electron microscopy or neutron scattering. Dynamic mechanical analysis allows confirming the presence of a phase separation even when it is not observable by electron microscopy. Vermicular morphologies with few hundreds nanometer width are obtained for the systems containing the TGAP as epoxy monomer. Systems formulated with TGDDM presents morphologies on much smaller scale of order a few tens of nanometers. We interpret the different sizes of the morphologies as a consequence of a larger viscosity for the TGDDM systems as compared to the TGAP ones rather than by a latter initiation of phase separation.     

Synthesis and properties of phosphorus-containing bio-based epoxy resin from itaconic acid

A phosphorus-containing bio-based epoxy resin (EADI) was synthesized from itaconic acid (IA) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO). As a matrix, its cured epoxy network with methyl hexahydrophthalic anhydride (MHHPA) as the curing agent showed comparable glass-transition temperature and mechanical properties to diglycidyl ether in a bisphenol A (DGEBA) system as well as good flame retardancy with UL94 V-0 grade during a vertical burning test. As a reactive flame retardant, its flame-resistant effect on DGEBA/MHHPA system as well as its influence on the curing behavior and the thermal and mechanical properties of the modified epoxy resin were investigated. Results showed that after the introduction of EADI, not only were the flame retardancy determined by vertical burning test, LOI measurement, and thermogravimetric analysis significantly improved, but also the curing reactivity, glass transition temperature (T _g), initial degradation temperature for 5% weight loss (T _d(5%)), and flexural modulus of the cured system improved as well. EADI has great potential to be used as a green flame retardant in epoxy resin systems.     

Mechanical relaxations in episulfide network polymers

A variety of condensation network polymers have been prepared by the reaction between amine, episulfide, and epoxide monomers. The mechanical relaxations occurring in these systems have been examined using a torsion pendulum and the role of hydrogen bonding in the mechanism of the β relaxation is shown to be insignificant. The chemical reaction between amine and episulfide groups has been investigated by IR spectroscopy and is shown to parallel the reaction between amine and epoxide groups. However, steric and electronic factors are suggested to decrease the extent of reaction when aromatic amines are involved. In the case of networks prepared from blends of episulfide and epoxide monomers, measurements of the gel time, together with the mechanical behavior around the glass transition, indicate that either interpenetrating or two-phase networks are formed. This is postulated to be a consequence of the high reactivity of the episulfide ring compared to the epoxide ring. The blending of small amounts of episulfide monomer with the epoxide monomer prior to curing may provide an effective method for lowering gel times without reducing the crosslink density and its dependent physical properties.