Synthesis of isocyanurate-based imidazole carboxylate as thermal latent curing accelerator for thermosetting epoxy resins

A novel thermal latent curing accelerator, 1-(2-cyanoethyl)-2-methylimidazole/tris (2-carboxyethyl) isocyanurate adduct (2MICN-T), was successfully synthesized through an acid–base neutralization of tris(2-carboxyethyl)isocyanurate (TCEIC) and 1-(2-cyanoethyl)-2-methylimidazole (2MICN). It was further added into diglycidylether of bisphenol A based epoxy resin/methylhexahydrophthalic anhydride mixture to form one-component curing systems. With the addition of 2 wt% of 2MICN-T, the one-component system could be steadily stored for more than 1 month at room temperature, while the shelf life of 2MICN curing system was only 2 days. Nonisothermal differential scanning calorimeter also demonstrated the excellent thermal latency of 2MICN-T in low-temperature region and rapid initiation of the curing reaction when raising temperature. Compared to the cured resins with original 2MICN as accelerator, the resulted thermosets exhibited enhanced glassy storage modulus, glass transition temperature, and thermal stability when 2 wt% of 2MICN-T was applied. It was attributed to the chemical incorporation of the isocyanurate moieties with multi carboxyl groups and nitrogen-contained heterocyclic ring, effectively increasing the crosslinking density, chain rigidity, and heat resistance of the cured resin. Thus, it is suggested that 2MICN-T can play both roles as latent curing accelerator and modifier for one-component epoxy compounds, and is particularly recommended for application in electronic packaging fields.     

潜伏性环氧树脂固化促进剂M-Cd的合成及其应用

采用间苯二胺和溴化镉合成了一种具有潜伏性的环氧树脂固化促进剂M－Cd它是一种络合物，将它应用于二氰二胺／环氧树脂脂固化体系的高温结构粘剂中，能够显著地降低粘剂的固化温度，缩短固化时间，本文还讨论了合成该促进剂主要成分的投料比，应用于二氰二胺／环氧树脂固化体系的高温结构胶粘剂中该促进剂的使用量以及固化条件对粘剂力学性能的影响，同时还考核了应用该促进剂M的高温结构胶粘剂的综合性能。     

六氢苯酐／环氧树脂体系的固化工艺研究

研究了以双酚A环氧树脂为基体,六氢苯酐(HHPA)为固化剂,MZ-31为固化促进剂组成的六氢苯酐/环氧树脂体系。结合凝胶化实验、动态DSC法和红外跟踪实验法,并借助T-β图外推法,确定了HHPA/EP体系的最佳固化工艺为:100℃/1h 120℃/2h 150℃/4h,再于190℃下后处理3 h。     

含有潜伏性催化剂的环氧树脂/酸酐体系的研究

使用固态聚胺与疏水性微粒子WS-12制备出一种潜伏性催化剂,评价了该催化剂在环氧树脂/甲基六氢苯酐固化体系中的催化固化作用。在25～50℃的范围内本固化体系长时间黏度变化平稳,而在150℃以上时具有高效的催化效果,显示出该催化剂具有优异的潜伏功能。该催化固化体系能适合于各种黏度的环氧树脂,当使用一种低黏度环氧树脂时,即m(环氧树脂6002):m(甲基六氢苯酐):m(潜伏性催化剂)=100:70:3时,其固化物显示出最佳的力学性能。     

后处理对环氧树脂/酸酐固化体系性能的影响

分别以2,4,6-三(二甲氨基甲基)苯酚(DMP-30)、2-乙基-4-甲基咪唑(2,4-EMI)和三乙醇胺(TEA)作为促进剂,探讨了后处理对3种EP(环氧树脂)/酸酐固化体系力学性能和耐热性的影响。研究结果表明:2,4-EMI促进EP/T-80(改性酸酐固化剂)体系具有相对较好的综合力学性能和耐热性;后处理工艺可明显改善固化产物的性能,使得固化物在提高强度的同时,也具有良好的抗变形能力和更好的韧性。     

环氧树脂/酸酐固化剂体系的热性能研究

在使用传统酸酐固化剂Me-THPA(甲基四氢苯酐)的基础上,加入PA(邻苯二甲酸酐)或PMDA(均苯四甲酸酐),通过改变酸酐固化剂比例制备了高温固化EP(环氧树脂),并探讨了不同类型和比例的混合酸酐固化剂对EP固化产物耐热性的影响。研究结果表明:Me-THPA固化EP体系的耐热温度为116.99℃,Me-THPA/PA固化EP体系的耐热温度为134.63℃,Me-THPA/PMDA固化EP体系的耐热温度为283.73℃;Me-THPA/PMDA固化EP体系的耐热性相对最好,其耐热温度比Me-THPA固化EP体系提高了142.53%。     

脂环族环氧树脂/酸酐体系固化促进剂的研究

利用示差扫描量热仪研究了乙酰丙酮铝、三苯基膦、2-乙基-4-甲基咪唑(2E4MZ)等3种促进剂在脂环族环氧树脂(UVR-6103)/甲基六氢邻苯二甲酸酐(MHHPA)体系中的固化行为,通过Ellerstien方程计算得到了UVR-6103/MHHPA体系在3种促进剂作用下的固化动力学参数,其表观活化能分别为48.6,69.2,90.2kJ/mol,反应级数分别为0.96,2.09和1.60。     

新型潜伏性环氧树脂固化剂的研制

采用乙二胺与丙烯酸甲酯在乙醇中反应合成了一种具有潜伏性的环氧树脂固化剂。利用红外光谱和元素分析确定产物的化学结构 ,热失重分析结果表明产物基本达到了作为潜伏性固化剂的要求     

Novel imidazole derivatives with recoverable activity as latent curing agents for epoxy

A series of latent curing agents were developed by replacing the hydrogen atom on secondary amine in imidazole with methoxy polyethylene glycol maleate diesters via Michael addition reaction. Methoxy polyethylene glycol maleate diesters with different molecular weight also restrained the reactivity of tertiary amine in imidazole ring. The curing properties and pot-life of the modified imidazole/epoxy systems were measured by differential scanning calorimeter and rotational rheometer. The modified imidazole/epoxy system could be cured quickly at 175°C. The modified imidazole shows good latency. After stored for more than 1 month, viscosity of modified imidazole/epoxy system remains unchanged. The longer chain polyether had the better thermal latency these curing agents had. Compared with unmodified imidazole, the novel latent curing agents led to better impact strength for cured epoxy. However, the compatibility between epoxy and latent curing agent will get worse if the molecular weight of polyether unite is over 750.     

Aryl phosphinate anhydride curing for flame retardant epoxy networks

An aryl phosphinate anhydride (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-methyl succinic anhydride (DMSA), with a pendent phosphorus group was synthesized and used as a reactive type flame retardant. The structure of DMSA was confirmed by FTIR, mass, elemental analysis, ¹H and ³¹P NMR spectroscopies. The aryl phosphinate anhydride was successfully used to cure some commercial epoxides, such as bisphenol A diglycidyl ether (DGEBA) and epoxy-novolac. The epoxy networks obtained were characterized by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and the limiting oxygen index (LOI) test. Epoxy resins cured with DMSA exhibit higher LOI values and char yields compared with those cured by commercial anhydrides, such as phthalic anhydride (PA) and hexahydrophthalic anhydride (HHPA). Furthermore, the LOI value and the char yield of the epoxy-resin composites increase with increasing phosphorus content. The flame retardancies of the epoxy-resin composites were significantly improved by using aryl phosphinate anhydride. © 1998 Society of Chemical Industry.     

Viscoelastic changes of epoxy resin–acid anhydride system during curing

The changed viscoelastic properties of the epoxy resin-acid anhydride system, Epikote 834-HHPA, are followed to the gel point at 130, 140, and 150°C with a dynamic viscoelastometer. The viscosity increases with curing time through two inflections designated A and B. The point A is interpreted (from the reference to the chemical changes reported in the previous paper) as the termination of the initial stage of this curring reaction, and point B coincides with the gel point determined by the torsion method. The resonance frequency remains constant value up to the point B, followed by a rapid increase. The extents of reaction for epoxide, anhydride, and initial OH are 15, 45.8, and 100% at the point A; 27.8, 63.7, and 100% at the point B, respectively. The apparent activation energies for viscosity are 7.5 kcal/mole for the resin mixture before curing, 10.5 kcal/mole for point A, 48.8 kcal/mole for point B (gel point). The overall apparent activation energies of this curing reaction are obtained from the Arrhenius plots for the curing time required for the resin mixture to reach the state of the points A and B; these values were 8.9 kcal/mole for point A and 16.2 kcal/mole for point B.     

Crown ethers as new curing agents for epoxy resins

Different crown ethers (4‐aminobenzo‐15‐crown‐5 (4‐aminobenzo‐15‐C5), 1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane (diaza‐18‐crown‐6), tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (H₄DOTA) and tetraazacyclododecane‐1,4,7,10‐tetraacetamide (H₂ODDA)) were used as curing agent for bisphenol A diglycidyl ether (BADGE, n = 0). The maximum enthalpy change for all systems except that formed by the epoxy resin with H₄DOTA corresponds to a stoichiometric ratio, since from this value the reaction enthalpies decrease when the proportion of epoxy increases. Heteropolymerization reaction occurs in all the crown ethers. Etherification reactions occur at temperatures much lower (30 °C less) than for the porphyrin systems studied in which a second signal appears at 300 °C. The etherification is evidenced by a slight shoulder in the thermograms for H₄DOTA and H₂ODDA. The systems BADGE (n = 0)/4‐aminobenzo‐15‐C5 and BADGE (n = 0)/diaza‐18‐crown‐6 improve the thermal stability of the epoxy resin by 30 °C approximately while the improvement for BADGE (n = 0)/H₄DOTA and BADGE (n = 0)/H₂ODDA is about 60 °C. © 2017 Society of Chemical Industry     

Citric acid–diethylenetriamine salts as latent curing agents for epoxy resins

Citric acid (CA)–diethylenetriamine (DETA) salts (CADETA) were prepared by using a 4.5 : 1 molar ratio of DETA–CA and removing the DETA excess. The structure of CADETA was analyzed by ¹³C-NMR, IR, and DSC associated with weight loss. One-step formulations consisted on dispersions of CADETA (variable amounts) in an epoxy resin based on diglycidylether of bisphenol A (DGEBA, EEW = 185.5 g/eq). The cure was followed in the pressure cell of a DSC (N₂ at 2.5 MPa), to avoid volatilization of DETA in the temperature range where decomposition of CADETA and beginning of reaction took place (T > 175°C). A very small heat of reaction was observed, (?ΔH) ～ 10 kJ/eq, resulting from the simultaneous endothermic salt decomposition and exothermic network formation. A stoichiometric formulation showed a T_g = 180°C, i.e., some 60°C higher than the one observed for the usual DGEBA/DETA system.     

环氧树脂/苯乙烯-马来酸酐共聚物体系固化动力学研究

用示差扫描量热仪(DSC)对环氧树脂/苯乙烯-马来酸酐共聚物/甲基咪唑体系的固化反应过程进行了分析,并用Kissinger和Ozawa方法分别求得固化反应的表观活化能ΔE为58.27 kJ/mol和64.93 kJ/mol;根据Crane理论计算得到该体系的固化反应级数n=0.85,为该环氧树脂体系的固化工艺确定提供理论依据。     

单组分环氧胶固化剂及促进剂的改性研究

采用间甲苯胺对固化剂双氰胺进行改性,红外表明双氰胺的—C≡N与间甲苯胺的—NH2发生反应,提高了固化剂的反应活性;XRD也证实了改性反应的进行。采用硫酸铜改性咪唑,XRD表明了有新的物质生成。经改性的双氰胺具有较好的活性和贮存稳定性。但单独使用改性双氰胺作固化剂,用量一般较大(为环氧树脂的25%),影响体系的流动性;而复合使用改性双氰胺和咪唑,在保证性能和固化时间的前提下,双氰胺的用量可减少至15%。改性双氰胺与环氧树脂具有较好的相容性,使环氧树脂固化体系的力学性能具有较大幅度的提高。     

潜伏性环氧固化剂研究进展

按固化条件的不同分别介绍了加热型、光固化型、潮湿型潜伏性环氧固化剂,列举了各类固化剂的典型代表及其性质,展望了今后潜伏性固化剂的研究重点和发展趋势。     

桐马酸酐与环氧树脂的非等温固化反应动力学

采用Málek法对桐马酸酐与双酚A环氧树脂E-51体系(含有1%质量分数的DMP-30)的非等温固化反应动力学进行了研究。通过机理函数esták-Berggren方程很好地模拟了真实的固化反应过程。等转化率法求得反应活化能为69.78 kJ/mol。指前因子A的值为4.567×108 min-1,n和m的值分别为1.082和0.456。根据得到的固化动力学方程计算可知,在固化温度为137.05℃时达到98%固化度的固化时间为115 min。     

环氧树脂固化剂的改性研究

以异佛尔酮二胺和1,6-己二胺为原料,加入适量自制的催化剂,在190℃反应2.5 h,即制成新型环氧树脂固化剂(简称YFJA)。将其按不同比例添加到传统固化剂二氨基二苯甲烷(简称DDM)和甲基四氢苯酐(简称Me-THPA)中,通过对固化物的冲击强度、拉伸强度和力学损耗等性能的检测分析,发现当自制固化剂添加量为固化剂总量的50%时,体系的力学性能达到最佳效果,冲击强度最高可提高346.5%,拉伸强度可提高73.0%。     

Preparation and curing behavior of latent 2-PhIm-PS microcapsule curing agent for epoxy resin

A core–shell microcapsule latent epoxy curing agent (2-PhIm-PS) is obtained by solvent evaporation method with 2-phenyl imidazole (2-PhIm) as the core material and polystyrene (PS) as the wall material. The microcapsule parameters, morphology, structure, curing behavior, and the mechanic properties of cured epoxy resin with this microcapsule latent curing agent were characterized through comparing with 2-PhIm. The particle size distribution of the microcapsule is narrow, the average particle size is about 10.56 μm, and the core material content is 23%. The prepared 2-PhIm-PS microcapsule curing agent has excellent latent curing properties. It can completely cure epoxy resin E-51 within 10 min at 130°C, and its latent period can be more than 40 days at room temperature. In addition, the curing kinetics of one-component epoxy resin curing system (E-51/2-PhIm-PS) composed of 2-PhIm-PS microcapsules and epoxy resin E-51 is also studied by using Kissinger equation, Flynn–Wall–Ozawa and Crane formula. The results provide an outline for the evaluation on the applicability of the microcapsule curing agent of 2-PhIm-PS for epoxy resin.     

Novel microencapsulated curing accelerator for prolonging shelf life of epoxy resin composition

A novel micron‐sized microencapsulated curing accelerator, imidazole (Im), particles, was first prepared by an ultrasound‐assisted dispersing and spray‐drying method and can significantly prolong the shelf life of epoxy resin‐based microelectronic packaging material. The shell of the encapsulated particles was made from ladderlike copoly(phenyloctyl silsesquioxane) (Ph‐Oct‐T), which was synthesized by a “stepwise coupling polymerization” method. Its softening or flowing temperature can be adjusted by changing the composition. Carbon tetrachloride (CCl₄) was chosen as both a solvent of the capsular material Ph‐Oct‐T and a suspending/precipitating agent of the fine Im particles. Subsequently, the solution containing Ph‐Oct‐T and suspended Im particles was treated by a spray‐drying process to produce the microencapsulated curing accelerator, Im particles, whose size and appearance was observed by scanning electronic microscopy (SEM). A greatly improved shelf life of the epoxy resin composition containing this microencapsulated curing accelerator was exhibited by curing tests and DSC measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 873–878, 2002