Curing and characterization of oxazolidone-isocyanurate-ether networks

Oxazolidone-isocyanurate-ether networks were prepared by copolymerization of mixtures of DGEBA and toluene-2,4-diisocyanate (TDI) in presence of benzyldimethylamine (BDMA) as catalyst. Changes during curing and final properties of the cured materials were investigated by using DSC, FTIR/ATR, TMA, DMTA, TGA, and densitometry. The influence of the molar ratio of isocyanate to epoxide groups on the properties and curing were studied. The kinetics of curing was analyzed by means of an integral isoconversional nonisothermal procedure. The fractions of oxazolidone, isocyanurate, and ether groups present in the final network were evaluated and were found to be dependent on the initial isocyanate/epoxy ratio and curing conditions. By increasing the initial proportion of isocyanate the glass transition temperature, the thermal stability, the shrinkage, and the amount of isocyanurate rings increase, whereas the fraction of ether linkages and oxazolidones decreases. It was observed that the gelation is controlled by the formation of isocyanurate rings at the beginning of the curing. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

含二氮杂萘酮结构环氧树脂胶粘剂的研制

以双氰胺 (DCDA)为固化剂 ,以咪唑 (MZ)为固化促进剂 ,研制了一种含二氮杂萘酮结构的环氧树脂 (ER)胶粘剂 ,其成分为ER∶DCDA∶MZ∶SiO2 ∶Al=10 0∶7∶1∶3∶60 ,固化工艺为 12 0℃下固化 40min时 ,拉伸剪切强度为 17.8MPa ,有良好耐热性     

有机酸改性咪唑环氧树脂固化促进剂的研究

二氰二胺作为环氧树脂的潜伏性固化剂,其固化物机械性能和介电性能优异。但由于二氰二胺与环氧树脂相溶性差,得不到均匀的组成物,且环氧树脂/二氰二胺体系的固化过程需在高于160℃的温度中进行。利用不同含量的有机酸与咪唑3位氮原子中和,改性生成的盐作为环氧树脂/二氰二胺体系固化促进剂,对该体系进行了改进,使其能够在中温(90～120℃)条件下固化。利用IR对改性产物进行了表征,并对未加促进剂的环氧树脂/双氰胺体系和以咪唑及有机酸改性咪唑为促进剂三种体系分别进行了差热分析。结果表明,有机酸改性咪唑促进剂可以使环氧树脂/二氰二胺体系的固化温度降低近50℃,并且适用期显著增加,长达141d,耐水性和耐热老化性能增加。     

光固化粉末涂料涂膜性能研究

以不饱和聚酯和丙烯酸环氧树脂为光固化粉末涂料的基体树脂,研究了两种基体树脂的结构、配比对光固化涂膜固化度及其性能的影响。结果表明固化度是影响耐溶剂性能、附着力、涂膜硬度和冲击强度的关键,适宜的n(UP)/n(EA)为1∶1;固化度应大于95%,可以达到99%。     

异氰酸酯/环氧树脂的固化机理

详细研究了异氰酸酯/环氧树脂体系的固化反应和固化机理。采用差示扫描量热法（DSC）和红外光谱法（FTIR）跟踪了异氰酸酯/环氧树脂固化反应过程,定量分析了异氰酸酯、环氧基团和新生成的异氰脲酸酯和口恶唑烷酮的变化。DSC分析结果表明,DSC曲线上出现3个放热峰,说明固化过程中存在至少3种反应;FTIR分析结果表明,在140℃以下固化体系主要发生异氰酸酯的三聚反应生成三嗪环（异氰脲酸酯）;在200℃下,异氰酸酯-NCO基团与环氧基团开环反应生成口恶唑烷酮;在230℃ 下,三嗪环（异氰脲酸酯）进一步与环氧基团开环反应生成口恶唑烷酮。研究了不同温度下环氧基团、异氰酸酯基团、异氰脲酸酯基团、口恶唑烷酮基团随反应时间的变化规律。     

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.     

Epoxy resin cured with diamine bearing azobenzene group

The epoxy resin: N,N-diglycidyl-4-glycidyloxyaniline (DGOA) is cured with the new diamine-chromophore: 2,4-diamino-4′-methylazobenzene (DMAB). The spectral characterization of infrared spectroscopy (FTIR), ¹H NMR spectroscopy and of elemental analysis (EA), confirm the chromophore structure. The curing kinetics of aminophenol epoxy resin/2,4-diamino-4′-methylazobenzene system is studied in isothermal experiments by means of differential scanning calorimetry (DSC). The structural changes occurring during the cure reaction are investigated by Fourier transform infrared spectroscopy (FTIR). Thermal stability characterized by the temperature of 5 and 10% weight loss and residue at 1000 °C of the cured product is studied by thermogravimetric analysis (TGA). Amorphous character of the cured material is determined using X-ray spectroscopy. The preliminary investigations of optical grating recording are carried out.     

A study in the formation and characterisation of oxazolidone-isocyanurate polymers using differential scanning calorimetry and infrared spectroscopy

Epoxy resins of functionality 2–4 were reacted with 4,4′-diisocyanato diphenyl methane within the range of isocyanate to epoxide ratios of 0.5–1-5 in the presence of 2-ethyl-4-methyl imidazole to form oxazolidone-isocyanurate polymers. The state and extent of cure of the resins were followed by infrared spectroscopy in conjunction with differential scanning calorimetry. The ratios of isocyanurate to oxazolidone linkages in the cured resins were determined quantitatively by an infrared method and the glass transition temperatures of the corresponding structures were measured by differential scanning calorimetry and dynamic mechanical thermal analysis.     

Liquid-rubber-modified epoxy adhesives cured with dicyandiamide. I. Preparation and characterization

n-Butylacrylate/acrylic acid (nBA/AA) copolymers were synthesized and used to modify epoxy resin (DGEBA) cured with dicyandiamide (DICY). The precuring reaction between nBA/AA copolymer and DGEBA, the curing cycle of DGEBA, and the effects of DICY and aluminum powder upon the adhesive strengths of modified DGEBA were studied. It was found that the optimum DICY/DGEBA ratio was 6 g/100 g, and lap shear strength and T-peel strength increased with increasing amount of aluminum powder. The curing cycle for modified DGEBA was determined to be 1 h at 177°C.     

Structural Adhesive Bonds to Primers Electrodeposited on Steel

Adhesive bond strength and durability were investigated for steel substrates which had been cathodically electroprimed before bonding. Lap shear and torsional impact strengths of two model epoxy adhesives were evaluated. Very poor strengths and durability were found for one adhesive, which was cured with a mixture of three amine curing agents. Scanning electron microscopy and analysis of primer susceptibility to interaction with the curing agents suggested that, for the high concentrations of curing agent in the amine-cured adhesive, chemical and physical degradation of the primer occurred during cure at elevated temperature.

For the second adhesive, which was cured with a single imidazole catalyst, excellent strength and durability were obtained, with no evidence of primer degradation. Surprisingly, for this adhesive, strengths to primed steel were up to 88% higher than to cleaned (i.e., degreased) bare steel. The concurrent improvements in environmental durability over bare steel, as assessed by water immersion and salt spray accelerated exposures, were attributed to the more favourable surface energetics of the adhesive/primer interface.     

端异氰酸酯聚醚的合成及对环氧树脂的改性作用

合成端异氰酸酯聚醚 (ITPE) ,使其在不同条件下与环氧树脂 (ER)进行反应 ,得到分子链中含氨基甲酸酯和口恶唑烷酮结构的环氧树脂预反应物 ,考察了聚醚种类、相对分子质量和用量及固化条件对改性环氧胶胶接件拉伸剪切强度和浇铸件断裂韧性的影响 ,并以扫描电镜观察断面形貌     

Analysis of the cure kinetics of epoxy/imidazole resin systems

The reaction kinetics for the cure of epoxy resins with imidazoles were determined from Fourier transform infrared spectroscopy and differential scanning calorimetry studies. The diglycidyl ether of bisphenol A and phenyl glycidyl ether were cured with various concentrations of 2-ethyl-4-methyl-imidazole ranging from 4.0 to 100.0 mol %. The first step in the curing process is the formation of epoxide/imidazole adducts. These adducts initiate the etherification reaction which crosslinks the resin. The kinetics were determined and confirmed for both the adduct and the etherification reactions as a function of the imidazole concentration. A model was developed and used to predict the concentrations of the unreacted epoxide groups and the reaction products for a wide range of imidazole concentrations and cure temperatures.     

Toughening epoxy resin with blocked isocyanate containing soft chain

A series of imidazole (MI) blocked 2,4‐toluene diisocyanate (TDI) with polyethylene glycol (PEG‐400) as soft segment (PEG‐MI‐b‐TDI) were synthesized for toughening and curing the bisphenol A type epoxy resin (E‐44). Fourier transform infrared (FTIR) spectrum indicates that the NCO groups of the isocyanate molecule are blocked with MI. For curing epoxy systems, elimination of epoxy group and the formation of urethane bonds were studied by FTIR spectroscopy. The results of mechanical property were shown that the tensile shear and impact strengths of neat MI and MI‐b‐TDI cured E‐44 are lower than those of PEG‐MI‐b‐TDI cured E‐44. Based on the scanning electron microscope studies, microstructure evolutions of the E‐44 cured by different curing agents were imaged. The mechanical, thermal, and dynamic mechanical properties were measured by universal testing machine, differential scanning calorimeter and dynamic mechanical analyzer (DMA). The toughness of E‐44 cured by PEG‐MI‐b‐TDI was effectively improved without sacrificing the tensile shear strength. Based on the DMA studies, the long soft chain of PEG brought in a noticeable lowering in the glass transition temperature (T_g). The glass transition temperature is near 165°C for the neat MI cured E‐44, which is higher than the T_gs of the other curing agents cured epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41345.     

Thermally curable adhesive tapes with complex catalyst system for fabricating semiconductor packages

Thermal curing of adhesive films was investigated to facilitate the fabrication of a reliable bonding for semiconductors. The formulated adhesive films contained acrylic polymer, epoxy resins, phenol resin, and an imidazole derivative that was the catalyst for curing the epoxy resins with phenol resin. The solubility, thermally latent characteristics, mechanical and adhesive properties of 2‐methylimidazole/boron trifluoride (2MZ/BF3), and 2MZ/aluminum trisacetylacetonate (AlAC) were investigated. It was found that 2MZ/BF3 and 2MZ/AlAC had excellent solubility in adhesive materials and they had excellent latent characteristics as thermal curing catalysts for epoxy resins, whereas conventional catalysts (2MZ and 2‐phenyl‐4, 5‐dihydroxymethylimidazole (2PHZ)) could not achieve both excellent solubility and thermally latent characteristics. The mechanical and adhesive properties of the post‐thermal‐cured adhesive film that contained 2MZ/BF3 or 2MZ/AlAC were comparable to those of the post‐thermal‐cured adhesive films that contained conventional catalysts. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Glycidyl amine adducts as accelerators for the curing of unsaturated polyester resin

The behavior of the adducts of aromatic amines with epoxide compounds as accelerators in curing of an unsaturated polyester resin was studied. To determine their usefulness, the gelation times, peak exotherm temperatures, and chromatographic and gravimetric analyses of the products extracted from the cured resin samples were investigated. The effectiveness of the adducts was compared with that for N,N-dimethylaniline. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1525–1531, 1997     

快速固化酚醛树脂胶黏剂的研制

以缩短酚醛树脂固化时间为目的,使用纳米氧化铝为催化剂,丁腈橡胶为增韧剂,AlCl3络合物为固化促进剂,制备了一种能够快速固化的酚醛树脂胶黏剂。通过固化时间、DSC、TG和力学性能等测试,结果表明,当加入15%丁腈橡胶和2%AlCl3络合物时,酚醛树脂胶黏剂的增韧效果和固化速度均为最佳,可在180℃下20min内实现快速固化,同时具有优异的耐热性能和力学性能。     

Production of bio-epoxide and bio-adhesive from non-edible oil

Epoxidation of Nahor oil was performed by H₂O₂ in the presence of acid catalyst at 50 °C. It was possible to obtain around 70% epoxide yield within 8 hrs of reaction. Amberlite IR 120H showed better epoxide yield compared to H₂SO₄ and Dowex 50 WX8. The performance of carboxylic acids was found to be in the order of formic acid>acetic acid>propanoic acid. The curing of epoxidized nahor oil involved using ethylenediamine (EDA) and diethylenetriamine (DETA). The adhesive property of the cured resins was tested and compared with commercially available glue. The force required to detach the cardboard joint was about 36.3 N for DETA-cured resin.     

Carboxyl-terminated poly(propylene glycol) adipate-modified room temperature curing epoxy adhesive for elevated temperature service environment

An investigation was carried out into the effect of modification of an epoxy resin with carboxyl-terminated poly(propylene glycol) adipate (CTPPGA) liquid rubber, on room temperature and elevated temperature adhesive joint strengths, after curing at room temperature (25°C) with tris-2,4,6-(N,N-dimethyl amino methyl) phenol hardner. CTPPGA prepared by the esterification of poly(propylene glycol) (PPG) and molar excess of adipic acid was incorporated into the epoxy resin by the prereact method. CTPPGA modification showed significant enhancement of adhesive joint strengths over the unmodified epoxy and the joint strengths were found to depend on the molecular weight of CTPPGA and its content in the epoxy resin. The elevated temperature lap shear strength measurement made for the CTPPGA-modified epoxy adhesive showed that the adhesive formulation has a temperature service capability up to 120°C. The results are discussed in terms of the data obtained from the tensile tests, DSC analysis, and SEM observations of the fractured surfaces.     

Solute separation by the amidoxime of poly(4-vinylpyridine-co-acrylonitrile)

The quantitatively amidoximated poly(4-vinylpyridine-co-acrylonitrile) (4VNX) could be cast with divinyl sulfone as a crosslinking agent to form membranes for reverse osmosis. They were stronger than a cellulose acetate membrane when dried for more then 45 min at 80°C, most balanced in their performance when 4VNX was composed of about 60 mol % acrylonitrile amidoxime, and highly rejected NaCl, CoCl₂, NiCl₂, and phenol as well at pH 12. They were superior in the performance to the membranes prepared from the amidoximes of poly(2,4-diamino-6-vinyl-s-triazine-co-acrylonitrile) and polyacrylonitrile. 4VNX membranes prepared by drying for about 30 min were capable of separating NaCl and transition metals under lower pressures because of great differences in rejections between NaCl and those metals. Potential use of 4VNX membranes in ultrafiltration was demonstrated, particularly to the effect that flux was enhanced while the rejection differences were hardly changed. It was also demonstrated that the isolation of transition metals of considerably different uptake from their mixture could be achieved by breakthrough of the column packed with divinylbenzene-crosslinked 4VNX resin.     

壬基酚改性胺固化剂的合成及性能研究

壬基酚改性胺固化剂是由壬基酚、甲醛、胺经过曼尼希反应制成的环氧树脂固化剂。本文介绍了采用不同胺,不同反应配比进行的合成反应,并通过TAG-DTA研究了不同胺制成的固化剂与环氧树脂固化反应过程的热效应。表明采用壬基酚合成曼尼希碱,反应比较温和,易于控制,产品可用作环氧树脂固化剂。