Effect of various epoxy fortifiers on the reactivity in curing of epoxy resins

Diglycidyl ether of ethylene glycol was prepared and used as a reactive diluent in the curing of an epoxy resin, based on diglycidyl ether of bisphenol A. Effect of different fortifiers on the curing reaction of the resin-diluent system has been investigated using differential scanning calorimetry. The dynamic scans were analyzed using four different relations to evaluate the kinetic parameters, the activation energy and the order of the reaction. The reactions are found to follow first order kinetics with an activation energy in the range of 36 – 84 kJ mol^-1.     

环己二醇二缩水甘油醚/环氧树脂固化动力学

对E-44环氧树脂,1,2-环己二醇二缩水甘油醚与E-44环氧树脂的混合物,1,2-环己二醇二缩水甘油醚分别与二氨基二苯基甲烷的固化反应应用示差扫描量热仪(DSC)进行了研究。在E-44环氧树脂中加入1,2-环己二醇二缩水甘油醚后,不但对环氧树脂有较好的稀释作用,降低了环氧体系固化反应的表观活化能,增加了环氧树脂的固化反应活性和固化反应速度,还提高了环氧固化物的力学性能。测定了反应热焓,计算出固化反应的表观活化能分别为46.08 kJ/mol,39.50 kJ/mol,35.58 kJ/mol,相应的固化反应级数分别为0.86,0.84,0.83。     

Synthesis and characterization of a high refractive diglycidyl ether of thiodibenzenethiol epoxy resin

High refractive index of epoxy resins used as encapsulant in light-emitting diode (LED) is essential in improving the light extraction efficiency, reducing heat and prolonging the service life of LED packages. In this study, diglycidyl ether of thiodibenzenethiol (DGETDBT), an epoxy resin with high refractive index, was synthesized via a novel method and its chemical structure was characterized with Fourier-transform infrared (FTIR) spectrometer and ¹H NMR spectrometer. Using m-xylylenediamine (MXDA) as curing agent, the curing behavior of DGETDBT was studied by differential scanning calorimetry (DSC) and was compared with that of diglycidyl ether of bisphenol A (DGEBA), a generally used encapsulant in LED. The thermal behavior and optical performance of these two resins were investigated with thermogravimetric analyses, UV?CVis scanning spectrophotometer, and Abbe refractometer, respectively. The results showed that DGETDBT/MXDA resin demonstrated similar curing and thermal behavior to DGEBA/MXDA resin. But its refractive index reaches 1.698, which is significantly higher than that of DGEBA/MXDA resin (1.604). Comparatively, DGETDBT resin can be expected to be a more effective encapsulant of LED.     

新型脂环环氧树脂/胺体系固化动力学及性能研究

采用DSC研究了脂环环氧树脂稀释剂1,4-环己烷二甲醇二缩水甘油醚(CHDMDGE)与异佛尔酮二胺及聚醚胺D230的固化行为,得出其固化反应的活化能、指前因子和反应级数等动力学参数。通过外推法计算出了固化工艺的特征温度,以此为依据制定了固化工艺并对固化后体系的力学性能进行了测试。结果表明,与线形脂肪族环氧稀释剂1,4-丁二醇二缩水甘油醚和1,6-己二醇二缩水甘油醚相比,CHDMDGE的拉伸强度分别提高了0.4倍和2.7倍,断裂伸长率则提高了1.9倍和5.0倍。     

光固化ADGDE齐聚物的合成及特性

一缩二乙二醇二缩水甘油醚 (DGDE)与丙烯酸为原料 ,合成紫外光固化环氧丙烯酸(ADGDE)齐聚物。研究了催化剂用量、阻聚剂种类以及反应温度对反应速度和产物性能的影响 ,确定了合成工艺条件 ;用 FTIR表征了结构 ,并与通用双酚 A型环氧丙烯酸酯 (双酚 A型 AEP)比较了颜色、粘度和光固化特性。结果表明 ,ADGDE颜色浅、粘度仅为双酚 A型 AEP的 1 /1 0 0 0、光固化速度快     

Curing of epoxy resin contaminated with water

Epoxy resins used for reinforcement of bridges and buildings are explored in the light of both curing rates and mechanical properties when resins are contaminated with water in outdoor construction. The developed resin is composed of a conventional resin of bisphenol A diglycidyl ether and a hardener with a polyoxipropyldiamine base. Curing rates were obtained by time variation of the near infrared absorbance of amine groups in the hardener at various water contents. They obeyed the second‐order reaction law with respect to the hardener, of which the activation energy was 70 kJ mol⁻¹. Water increased the reaction rate. Mechanical properties such as ultimate tensile strength, adhesive shear stress, and flexural strength were measured at various water contents for the developed epoxy resin and the commercially available low‐temperature epoxy resin. The developed cured resin shows not only higher mechanical strengths but also much less deterioration by water than the conventional cured resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 214–220, 2001     

Cure kinetics, morphological and dynamic mechanical analysis of diglycidyl ether of bisphenol-A epoxy resin modified with hydroxyl terminated poly(ether ether ketone) containing pendent tertiary butyl groups

Hydroxyl terminated poly(ether ether ketone) based on tert-butyl hydroquinone (PEEKTOH) was used to modify a diglycidyl ether of bisphenol-A epoxy resin. A diamine, 4,4′-diaminodiphenylsulfone was used as the curing agent. Isothermal differential scanning calorimetric measurements of the blends were carried out at 180, 165 and 150 °C. The extent of reaction was found to decrease with the addition of PEEKTOH. The phenomenological model developed by Kamal was used for kinetic analysis of curing reaction. The curing reaction followed autocatalytic mechanism regardless of the presence and amount of oligomer present in the epoxy resin. The experimental and theoretical reaction rates were in good agreement during the initial stages of the reaction. The experimental values were lower than theoretical rate during the final stages of reaction due to increase in the viscosity of the system. A semiemperical model was used to explain diffusion control during final stages of reaction. The cured blends exhibited two phase morphology at all the curing temperatures. A uniform particle size distribution was observed at all compositions. The domain size decreased slightly with increase in oligomer content and with decrease in curing temperature. Finally, the viscoelastic properties were analysed using dynamic mechanical thermal analysis. Two T_gs corresponding to epoxy rich and thermoplastic rich phases were evident from the dynamic mechanical spectrum.     

Study on Curing Kinetics and Thermal Degradation Kinetics of Hyperbranched Poly(Trimellitic Anhydride Ethylene Glycol) Epoxy (HTME)/Diglycidyl Ether of Bisphenol-A Epoxy Hybrid Resin

Hyperbranched poly(trimellitic anhydride ethylene glycol) epoxy (HTME) not only has relatively low viscosity and high molecular weight but also is a functional additive of enhancement and toughness and is used in the thermosetting resin field widely. The curing kinetics and thermal degradation kinetics of HTME/diglycidyl ether of bisphenol-A epoxy hybrid resin were studied in detail using differential scanning calorimetry and thermogravimetric analysis technique, respectively, by the Coats-Redfern model. The effect of molecular weight or generation and content of HTME on activation energy, reaction order, curing time, and curing reaction were discussed and analyzed, and the results indicated that HTME could accelerate curing reaction and reduce activation energy and reaction order of the curing reaction.     

Study on Novel Epoxy Based Poly(schiff reagent)s

Abstract

Novel poly(schiff reagent)s (PSs) from diketo derivative of epoxy resin were synthesised and characterised. A series of epoxy resin based poly(schiff reagent)s were synthesised by reacting an epoxy resin, diglycidyl ether of bisphenol-A (DGEBA) with 4-amino acetophenone (4-AAP) in a 1:2 mole ratio to afford the corresponding diketo derivative, and subsequent reaction with various aliphatic diamines in the presence of a triethyl amine as a catalyst The resultant poly(schiff reagent)s were characterised by infrared spectroscopy (IR) and number average molecular weight (Mn) of PSs were estimated by non-aqueous conductometric titration. As produced, PSs having amine groups may act for curing of epoxy resins. Differential scanning calorimetric (DSC) curing kinetics of the epoxy resins viz., diglycidyl ether of bisphenol-A(DGEBA) and triglycidyl-p-amino phenol (TGPAP) have been investigated using PSs as a curing agent and triethyl amine as a catalyst. Thermal stability of the cured epoxy systems was studied by thermo-gravimetric analysis (TGA). The glass fiber reinforced composites of the produced PSs-epoxy system have been fabricated and were characterised by their mechanical properties and chemical resistance.     

Study on Novel Epoxy Based Poly (Schiff Reagent)s

Abstract

Novel poly(schiff reagent)s from diketo derivative of epoxy resin were synthesised and characterised. A series of epoxy resin based poly(schiff reagent)s were synthesised by reacting an epoxy resin, diglycidyl ether of bisphenol-A (DGEBA) with 4-amino acetophenone (4-AAP) in a 1:2 mole ratio to afford the corresponding diketo derivative, and subsequent reaction with various aliphatic diamines in a presence of a triethyl amino as a catalyst. The resultant poly(schiff reagent)s were characterised by infrared spectroscopy (IR) and number average molecular weight (Mn) of PSs were estimated by non-aqueous conductometric titration. As produced, PSs having amine groups may act for curing of epoxy resins. Differential scanning calorimetric (DSC) curing kinetics of the epoxy resins viz. diglycidyl ether of bisphenol-A(DGEBA) and triglytidyl-p-amino phenol (TGPAP) have been investigated using PSs as a curing agent and triethyl amine as a catalyst. Thermal stability of the cured epoxy systems were studied by thermogravimetric analysis (TGA). The glass fiber reinforced composites of the produced PSs-epoxy system have been fabricated and were characterised by their mechanical properties and chemical resistance.     

New biobased carboxylic acid hardeners for epoxy resins

Soybean oil was modified into a novel biobased polyacid hardener by thiol‐ene coupling with thioglycolic acid. The structure of the initial soybean oil and polyacid triglyceride was carefully analyzed using ¹H NMR and titration. The thermal crosslinking reaction between acid hardener and epoxidized resin was studied by differential scanning calorimetry (DSC) and rheology. Then, the synthesized biobased acid hardener was employed as a novel curing agent for bisphenol A diglycidyl ether to elaborate new partially biobased materials. These materials, formulated in stoichiometry ratio, were characterized by DSC, thermogravimetry analyses, dynamic mechanical analyses and exhibit interesting properties for coatings. Practical applications: The products of the chemistry described in this contribution, i.e., polyacid from soybean oil and thioglycolic acid, provide biobased building blocks for further epoxy resin syntheses by reaction with epoxy groups. The obtained epoxy resins are partially biobased and may be applied as binders and coatings.     

Curing of diglycidyl ether of bisphenol‐A epoxy resin using a poly(aryl ether ketone) bearing pendant carboxyl groups as macromolecular curing agent

BACKGROUND: Reactive thermoplastics have received increasing attention in the field of epoxy resin toughening. This paper presents the first report of using a novel polyaryletherketone bearing one pendant carboxyl group per repeat unit to cure the diglycidyl ether of bisphenol‐A epoxy resin (DGEBA). The curing reactions of DGEBA/PEK‐L mixtures of various molar ratios and with different catalysts were investigated by means of dynamic differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy methods. RESULTS: FTIR results for the DGEBA/PEK‐L system before curing and after curing at 135 °C for different times demonstrated that the carboxyl groups of PEK‐L were indeed involved in the curing reaction to form a crosslinked network, as evidenced by the marked decreased peak intensities of the carboxyl group at 1705 cm^?1 and the epoxy group at 915 cm^?1 as well as the newly emerged strong absorptions of ester bonds at 1721 cm^?1 and hydroxyl groups at 3447 cm^?1. Curing kinetic analysis showed that the value of the activation energy (E_a) was the highest at the beginning of curing, followed by a decrease with increasing conversion (α), which was attributed to the autocatalytic effect of hydroxyls generated in the curing reaction. CONCLUSION: The pendant carboxyl groups in PEK‐L can react with epoxy groups of DGEBA during thermal curing, and covalently participate in the crosslinking network. PEK‐L is thus expected to significantly improve the fracture toughness of DGEBA epoxy resin. Copyright © 2009 Society of Chemical Industry     

Kinetic study of polymerization/curing of filament-wound composite epoxy resin sytems with aromatic diamines

The kinetics of the polymerization/curing of an 80/20 blend of a diglycidyl ether of bisphenol A (DGEBA) and a diglycidyl ether of 1,4-butanediol (DGEBD) with a commercial mixture of methylene dianiline and m-phenylene diamine (Tonox 60/40) was studied, at amine/epoxy ratios ranging from 1.1 to 4.4. Fourier transform infrared (FT-IR) measurements were used to follow the extent of epoxy conversion at 18–122°C, and bulk viscosity measurements were used to define the working range of the resin. For an amine/epoxy ratio of 1.1, the activation energy for the polymerization/curing reaction (based on time to 50% epoxy conversion in the S-shaped conversion-time plots) was 11.9 kcal/mole by FT-IR. This value compared favorably with the corresponding value of 12.7 kcal/mole obtained by Moroni and co-workers in a complementary differential scanning calorimetry (DSC) study of the same system. The FT-IR conversion-time plots were fitted to a kinetic expression that can be accommodated by an autocatalytic mechanism; the expression contains two rate constants with activation energies of 13.7 and 10.0 kcal/mole, respectively. The viscosity of the curing epoxy resin was found to obey the Williams-Landel-Ferry equation, with a Di Benedetto expression for the glass transition temperature.     

Synthesis of a novel lignin-based epoxy resin curing agent and study of cure kinetics,thermal, and mechanical properties

In this contribution, first of all, the methoxy groups of organic solvent lignin (OSL) was converted to phenolic hydroxyl groups through demethylation reaction for the purpose of fabricating demethylated organic solvent lignin (DOSL). In addition, the resulting DOSL was utilized as a renewable material to synthesize a novel esterified lignin (EDOSL) by reacting with isobutyryl chloride for curing of epoxy resin. Finally, commercial liquid diglycidyl ether of bisphenol A was cured by EDOSL in the presence of 4-dimethylaminopyridine (DMAP) used as a catalyst based on dual-curing mechanism. Dual curing is a processing methodology based upon the alliance of two diverse and compatible polymerization reactions occurring sequentially or simultaneously. According to the FTIR spectra and ¹H-NMR analyses, the demethylation of OSL, esterification of DOSL, and the curing reaction of epoxy resin with EDOSL were successfully conducted. The value of the phenolic hydrogen in the DOSL was approximately 4.89 mmol/g, which increased by 12.64% after demethylation. The thermal and mechanical performances of these cured epoxy samples were measured by DSC, DMA, TGA, and tensile testing. The epoxy system cured by 10%wt esterified lignin with 1%wt DMAP possessed the tensile strength of 71.54 ± 7.50 MPa and the initial degradation temperature (T_5%) of 370°C, which can compete fairly with commercial aromatic curing agents or other lignin-based agents studied currently for the curing of epoxy systems.     

潜伏型非离子自乳化环氧固化剂的合成与性能

采用十八胺与乙二醇缩水甘油醚为原料,制得了一种两端为环氧基、中间氮原子上接有长疏水烷基侧链的双环氧基化合物,再用酮亚胺上剩余的仲胺对该化合物进行封端,制备了潜伏型的非离子自乳化环氧固化剂;并用红外光谱验证了每一步的产物。该固化剂在水环境下,释放出具有亲水功能的氨基,再加上分子本身具有亲水功能的羟基、醚键和疏水功能的长烷基侧链,该固化剂兼具固化功能和乳化功能。所制备的水性环氧树脂涂料具有良好的柔韧性能、铅笔硬度、附着力、透明性和耐水性。     

Epoxy resin containing the poly(sily ether): Preparation,morphology, and mechanical properties

The poly(sily ether) with pendant chloromethyl groups (PSE) was synthesized by the polyaddition of dichloromethylsilane (DCM) and diglycidylether of bisphenol A (DGEBA) with tetrabutylammonium chloride (TBAC) as a catalyst. This polymer was miscible with diglycidyl ether of bisphenol A (DGEBA), the precursor of epoxy resin. The miscibility is considered to be due mainly to entropy contribution because the molecular weight of DGEBA is quite low. The blends of epoxy resin with PSE were prepared through in situ curing reaction of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM) in the presence of PSE. The DDM‐cured epoxy resin/PSE blends with PSE content up to 40 wt % were obtained. The reaction started from the initial homogeneous ternary mixture of DGEBA/DDM/PSE. With curing proceeding, phase separation induced by polymerization occurred. PSE was immiscible with the 4,4′‐diaminodiphenylmethane‐cured epoxy resin (ER) because the blends exhibited two separate glass transition temperatures (T_gs) as revealed by the means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). SEM showed that all the ER/PSE blends are heterogeneous. Depending on blend composition, the blends can display PSE‐ or epoxy‐dispersed morphologies, respectively. The mechanical test showed that the DDM‐cured ER/PSE blend containing 25 wt % PSE displayed a substantial improvement in Izod impact strength, i.e., epoxy resin was significantly toughened. The improvement in impact toughness corresponded to the formation of PSE‐dispersed phase structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 505–512, 2003     

Differential scanning calorimetric study of curing of acrylated epoxy resin with benzoyl peroxide

The curing reaction of the acrylated diglycidyl ether of bisphenol-A (DGEBA) with benzoyl peroxide has been investigated by differential scanning calorimetry at three different heating rates. The overall cure kinetics were found to be first-order, with Arrhenius parameters E=83 kJ mol^?1 and In A = 16.5 min^?1, independent of the scan rate, up to at least 90% conversion.     

新型非离子型水性环氧固化剂的合成及性能研究

为提高水性环氧涂料的固化性能和适用期,以自制聚酰胺和生物基戊二胺为起始原料,聚乙二醇二缩水甘油醚（ PEGGE）为亲水链段,双酚 A型环氧树脂（ E-51）为疏水链段,邻甲苯缩水甘油醚（ CGE）为封端剂制备了非离子型低温水性环氧固化剂,并与自制水性环氧乳液复配制得双组分水性环氧涂料。考察了环氧固化剂合成工艺参数及涂膜各项性能。结果表明：该固化剂含有较长的柔性脂肪烃碳链和聚醚链段能够提高涂膜的柔韧性;双酚 A型环氧树脂参与扩链反应能够解决与乳液不兼容等问题;苯环结构增加了涂膜的硬度;涂膜室温固化后性能优异,具有良好的物理机械性能、耐水性、耐酸碱性和耐盐雾性。     

Characterization of cure reactions of anhydride/epoxy/polyetherimide blends

The cure kinetics of blends of epoxy (diglycidyl ether of bisphenol A)/anhydride (nadic methyl anhydride) resin with polyetherimide (PEI) were studied using differential scanning calorimetry under isothermal conditions to determine the reaction parameters such as activation energy and reaction constants. By increasing the amount of PEI in the blends, the final cure conversion was decreased. Lower values of final cure conversions in the epoxy/PEI blends indicate that PEI hinders the cure reaction between the epoxy and the curing agent. The value of the reaction order, m, for the initial autocatalytic reaction was not affected by blending PEI with epoxy resin, and the value was approximately 1.0. The value of n for the nth order component in the autocatalytic analysis was increased by increasing the amount of PEI in the blends, and the value increased from 1.6 to 4.0. A diffusion‐controlled reaction was observed as the cure conversion increased and the rate equation was successfully analyzed by incorporating the diffusion control term for the epoxy/anhydride/PEI blends. Complete miscibility was observed in the uncured blends of epoxy/PEI at elevated temperatures up to 120 °C, but phase separations occurred in the early stages of the curing process. © 2002 Society of Chemical Industry     

Studies on the properties of glass fiber reinforced epoxy composites of DGEBA / epoxidized polyhydric alcohols with or without fortifier

Differential scanning calorimetry (DSC) technique was used to study the curing reaction of diglycidyl ether of bisphenol A (DGEBA) resin and different di- and trifunctional polyhydric alcohols with phthalic anhydride as curing agent and triethylamine as catalyst with or without fortifier. The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fiber reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied as well. Activation energies of curing reactions range within 75.1 to 88.3 kJ mol^?1. The cured products have good thermal stability; the composites have good mechanical strength, electrical insulation properties and chemical resistance. 36 to 53% improvement in flexural strength has been observed when fortifier was added to the DGEBA-diluent systems.