环氧树脂与氰酸酯共固化产物性能的研究

环氧树脂是一类综合性能优良并获广泛应用的热固性树脂基体 .但是通常的环氧树脂基体中含有大量反应生成的羟基等极性基团 ,吸湿率高 ,使其复合材料在湿热环境下力学性能和介电性能显著下降 .应用氰酸酯改性固化的环氧树脂等热固性树脂 ,将赋予以其为基体的复合材料以优异的耐热性能、力学性能和介电性能[1 ,2 ] .这类复合材料的研究开发对特种电子电气绝缘材料和先进复合材料的发展具有重要意义 .作者曾应用ＦＴ ＩＲ、ＤＳＣ等分析技术对氰酸酯与环氧树脂 (氰酸酯在欠量、适量和过量条件下 )的共固化反应机理和固化物结构特征等进行过深入…     

双氰胺固化环氧树脂的研究

<正> 双氰胺做为环氧树脂的固化剂,其贮存期可以达到一年以上,这种固化物的机械和介电性能优异,因此,广泛用于制造层压等电工材料方面。国外许多人都曾对双氰胺与环氧树脂的固化反应历程和固化物的性能做过研究,指出了在固化过程中化学结构的变化     

Alteration of matrix curing characteristics and its role in extension of hydrodynamic equation for predicting viscoelastic properties of nitrile rubber/silica nanocomposites

Neglecting the alteration of matrix curing characteristics in a filled rubber nanocomposite, as a result of possible interactions between the nano filler and curing agent ingredients, leads to inaccurate properties prediction using conventional hydrodynamic equations. In the current work, we present a new empirical extended version of hydrodynamic equation and examine its capability in predicting the viscoelastic properties of NBR/nanosilica system in which the negative influence of the filler on the curing process of the NBR matrix was confirmed through various analyses such as tensile test, rheometry, swelling experiments, and dynamic mechanical analysis. The results showed that the proposed empirical extended model is able to account the contribution of alteration of matrix curing characteristics in changing the composite properties below the filler percolation threshold. It was demonstrated that the extended model provides more accurate prediction of viscoelastic properties of silica‐filled cured NBR nanocomposites above glass transition temperature.     

3‐Phenylethynyl phthalimide end‐capped imide oligomers and the cured polymers

In the past decades, 4‐phenylethynyl phthalic anhydride (4‐PEPA) has been the most important endcapper used for thermoset polyimide. As the isomer of4‐PEPA, 3‐phenylethynyl phthalic anhydride (3‐PEPA) has attracted our interest. In this article, 3‐PEPA was synthesized and a comparative study with 4‐PEPA on curing temperature, curing rate, thermal and mechanical properties of oligomers and cured polymers was presented. The new phenylethynyl endcapped model compound, N‐phenyl‐3‐phenylethynyl phthalimide, was synthesized and characterized. The molecular structure of model compound was determined via single‐crystal X‐ray diffraction and the thermal curing process was investigated by Fourier transform infrared. Differential scanning calorimetry clearly showed that the model compound from 3‐PEPA had about 20 °C higher curing onset and peak temperature than the 4‐PEPA analog. This result was further proved by the dynamic rheological analysis that the temperature of minimum viscosity for oligomers end‐capped with 3‐PEPA was above 20 °C higher than that of the corresponding 4‐PEPA endcapped oligomers with the same calculated number average molecular weight. The cured polymer from 3‐PEPA displayed slightly higher thermal oxidative stability than those from 4‐PEPA by thermogravimetric analysis. The thermal curing kinetics of 3‐PEPA endcapped oligomer (OI‐5) and 4‐PEPA endcapped oligomer (OI‐6) fitted a first‐order rate law quite well and revealed a similar rate acceleration trend. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4227–4235, 2008     

Free radical photopolymerization process for fiber‐reinforced polymer: Effect on the mechanical properties

Glass–fiber‐reinforced polymers were manufactured either through a room temperature thermal curing or under ultraviolet (UV) light from a LED. The thermal system yields high performances when a post‐curing process at 65°C is applied. The photochemical curing leads to a composite in a faster timescale, albeit at the extent of the mechanical properties. It is found that in this case, impregnation and vacuum steps are too fast to allow a good wetting of the fibers, thereby leading to mechanical weaknesses and larger void volume. However, when applying longer vacuum and impregnation steps, the mechanical properties of the photochemically cured sample match the best thermally cured one. As a conclusion, it is shown that photochemical curing of glass–fiber‐reinforced polymer can lead to high performance composite provided that the preparation steps are well controlled.     

丁腈羟增韧环氧树脂形态与力学性能

研究了丁腈羟增韧环氧树脂的力学性能和形态结构，丁腈羟的用量、丁腈羟中丙烯腈的含量、固化条件对所形成的微区尺寸都有较大影响，并进一步影响固化物的力学性能。     

New approaches to reversible crosslinking in epoxy resins

The objective of the research is to investigate epoxy resins where crosslinks formed in curing reactions can be cleaved and reformed without significant sacrifice in resin properties. Experimental disulfide-containing crosslinking agents have been selected for the study, including dihydrazides of dithiodicarboxylic acids (aliphatic and aromatic) and dithioaromatic diamines. Conditions for curing reactions and for subsequent cleavage of crosslinks by reduction have been determined in model systems and confirmed for a prototype epoxy resin. A comparative evaluation of cure kinetics, crosslink density, and thermal and mechanical properties has been carried out for resin cured with aromatic curing agents (dithiodianiline and methylenedianiline) and with aliphatic compounds (3, 3′-dithiopropionic acid dihydrazide and hexamethylenediamine). It has been shown that in resin fully cured with disulfide-containing crosslinking agents, crosslinks are ruptured by reduction, and re-established by oxidation under mild conditions, or by reaction of thiol groups with bifunctional alkylating agents.     

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.     

Magnetic composites based on natural rubber prepared by using peroxide and sulfur curing system

In this work, rubber magnetic composites were prepared by incorporation of strontium ferrite into elastomeric matrix based on natural rubber. Cross‐linking of the rubber matrix was performed by using sulfur and peroxide curing system. The study was aimed at the investigation of the type of curing system and magnetic filler content on curing process and cross‐link density of prepared materials. Then, the influence of both factors on physical–mechanical and magnetic properties was observed. The obtained results demonstrate that sulfur‐cured composites show better physical–mechanical properties, especially at lower content of strontium ferrite. With increasing amount of ferrite, the differences between the characteristics of both types of composites became less visible, while peroxide‐cured sample with maximum ferrite content showed superior tensile strength in comparison with tensile strength of maximally filled sample cured with sulfur system. The obtained results demonstrate better compatibility between the rubber and the filler when peroxide system was introduced for cross‐linking of the rubber matrix. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of Temperature on Formation of Structure and on Mechanical Properties of Plasticized Polyether-Urethane-Urea

The influence exerted by temperature and time of curing on the strength and deformation properties of plasticized polyether-urethane-urea was examined. Addition of a plasticizer ensures the optimal rheological properties, and the resulting material cured at a low temperature exhibits high mechanical characteristics.     

HEAT-RESISTANT COMPOSITES CURED BY ELECTRON BEAM*

 Electron beam (EB) curing of composites has many advantages. Heat-resistant EB-curing composites could substitute polyimide composites used in aeronautical engines. In this paper, the effects of catalyst and dose on the cured resin were investigated. The heat-resistance of the resin cured by EB was evaluated by dynamic mechanical analysis (DMA). The experimental results show that the mechanical properties of the composites cured by EB could meet the specifications of aeronautical engines at 250℃.     

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     

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.     

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。     

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.     

Studies on Surface Free Energy of an Anhydride-Epoxy Cured System: Effect of Side Alkenyl Chain Length of Hardener on Tensile and Impact Properties

Three kinds of alkenyl succinic anhydrides (ASA) with varying side chain lengths (2-octenyl, 2-dodecyl, and 2-hexadecynyl succinic anhydrides) for hardeners as epoxy curing agents are synthesized by the ene reaction. The curing effect of ASA on the mechanical tensile and impact properties of cured diglycidyl ether of bisphenol-A (DGEBA) epoxy resin is studied. It is observed that increasing the side alkenyl chain length of ASA leads to a decrease of tensile strength of the cured epoxy resin, probably due to the decreasing of cross-linking density. However, it is found that the impact properties of the casting specimens are increased as the side alkenyl chain length of the hardener increases. This is probably due to the effect of the nonpolar or London-dispersive component of the surface free energy of the ASA studied, resulting in improving of the toughness properties of the casting specimens. Copyright 2000 Academic Press.     

Synthesis and characterization of imide ring and siloxane-containing cycloaliphatic epoxy resins

A novel imide ring and siloxane-containing cycloaliphatic epoxy compound 1,3-bis[3-(4,5-epoxy-1,2,3,6-tetrahydrophthalimido)propyl]tetramethyldisiloxane (BISE) was synthesized from 1,3-bis(3-aminopropyl)tetramethyldisiloxane and tetrahydrophthalic anhydride by a two-step procedure, which was then thermally cured with alicyclic anhydrides hexahydro-4-methylphthalic anhydride (HMPA) and hexahydrophthalic anhydride (HHPA), respectively. As comparison, a commercial available cycloaliphatic epoxy 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ERL-4221) cured with the same curing agents was also investigated. The experimental results indicated that the BISE gave the exothermic starting temperature higher than ERL-4221 no mater what kind of curing agents applied, implying the reactivity of the former is lower than the latter. The fully cured BISE epoxy resins have good thermal stability with thermal decomposition temperature at 5% weight loss of 346-348 °C in nitrogen, although they gave the relatively low glass transition temperatures due to the presence of flexible propyl and siloxane segments in the epoxy backbone. The BISE epoxy resins exhibited good mechanical and dielectric properties as well as low water absorption. The improved dielectric properties and the reduced water absorption of BISE epoxy resins are attributed to the low polarity as well as the hydrophobic nature of siloxane segment in the epoxy backbone.     

Synthesis and curing of liquid crystalline epoxy resin based on naphthalene mesogen

Aromatic liquid crystalline epoxy resin (LCE) based on naphthalene mesogen was synthesized and cured with aromatic diamines to prepare heat‐resistant LCE networks. Diaminodiphenylester (DDE) and diaminodiphenylsulfone (DDS) were used as curing agents. The curing reaction and liquid crystalline phase of LCE were monitored, and mechanical and thermal properties of cured LCE network were also investigated. Curing and postcuring peaks were observed in dynamic DSC thermogram. LCE network cured with DDE displayed liquid crystalline phase in the curing temperature range between 183 and 260°C, while that cured with DDS formed one between 182 and 230°C. Glass transition temperature of cured LCE network was above 240°C, and crosslinked network was thermally stable up to 330°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 419–425, 1999     

双氨基邻苯二甲腈/环氧树脂固化物的制备及性能研究

本文合成出了一种双氨基邻苯二甲腈(DPN)单体,采用红外和核磁共振表征了DPN及其中间体含双氨基的酚类单体(DHTM)的分子结构,利用差示扫描量热证明了DPN的自催化性能及其对环氧树脂(EP)的固化作用。将DHTM与DPN分别与EP制得共混体系,然后将其固化。热失重和动态热机械性能测试表明,DPN-EP固化物的各项性能都要优于DHTM-EP固化物。其在氮气和空气下的初始分解温度(T_(5%))分别提高了27和68℃,计算得到的极限氧指数达到36.36,提高了9.12,其玻璃化温度为202℃,展现出了良好的耐热和阻燃性能。