Novel trifluoromethylated epoxy based thermosets: synthesis and characterization

Two series of trifluoromethylated crosslinked epoxy‐based polymers with different molecular architectures and fluorine contents (from 1 to 5 wt%) have been investigated. The epoxy monomer was a diglycidyl ether of bisphenol A, and the curing agents were 3‐(trifluoromethyl)aniline and 4,4′‐methylenebis(3‐chloro‐2,6‐diethylaniline). The structural parameters of networks such as gelation and vitrification and the properties of the resulting fluorinated materials were investigated and compared. Final materials showed high transparency with an ultraviolet‐visible absorption cut‐off between 350 and 380 nm, low moisture (0.60 wt%) and a decrease in dielectric constant from 6.3 to 5.2 with increasing fluorine content. Copyright © 2012 Society of Chemical Industry     

Glass fiber-reinforced epoxy composites

Glass fiber-reinforced epoxy composites were prepared from the matrix resins tetraglycidyl diaminodiphenylmethane

1 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-diaminodiphenylmethane.

(TGDDM) and tetraglycidyl bis(o-toluidino)-methane

2 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-bis(o-toluidino)methane.

(TGMBT) using various amines like 4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylsulfone (DDS) and diethylene triamine (DETA) as curing agents. The fabricated laminates were evaluated for their mechanical and dielectrical properties and chemical resistance. The composites prepared using an epoxy fortifier (20 phr) showed significant improvement in the mechanical properties.     

Epoxy resins based on aromatic glycidylamines. IV. Preparation of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane from aniline and analysis of the product by GPC and HPLC

Epoxy resins containing N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) were prepared from aniline and epichlorohydrin and analyzed by GPC and HPLC. The product composition was compared with that of resins prepared from 4,4′-diaminodiphenylmethane (DDM) and epichlorohydrin, which had been analyzed in our previous work. A new byproduct designated Y4 was isolated by semipreparative HPLC and identified by NMR and mass spectroscopy. The course of formaldehyde condensation with N,N-dichlorohydrin of aniline (DCHA) was followed by GPC and HPLC and the mechanism of formation of Y4 was proposed on the basis of obtained results. Attention was also paid to the differences in reactivity of DCHA diastereoisomers.     

Low-temperature fast curable behavior and properties of bio-based carbon fiber composites based on resveratrol

Environmentally friendly materials are an integral part of sustainable chemistry, and bio-based polymer composites are an important class of materials. The manufacture of composites is expected to reduce or even eliminate the use of adjuvants, considering the importance of reducing energy consumption and avoiding health and environmental risks. In this study, a phenyl-containing, polyfunctional, bio-based epoxy resin (TGER) was synthesized, and carbon fiber-reinforced, bio-based epoxy resin composites were fabricated by vacuum-assisted resin infusion using two aromatic amine curing agents, 4,4′-diaminodiphenylmethane (DDM) and 3,3′-diethyl-4,4′-diaminodiphenylmethane (DEDDM). Curing reactions and rheological behavior studies showed that TGER had higher curing reactivity toward DDM and DEDDM than to diglycidyl ether of bisphenol A (DGEBA) and possessed good processability. The results indicated that the resveratrol-based epoxy resin displayed low-temperature fast curing properties. The evaluation of the mechanical properties of the carbon fiber composites showed that the flexural strengths of CF/TGER/DDM and CF/TGER/DEDDM were 520 and 628 MPa, respectively. The initial decomposition temperature of CF/TGER composites is above 200°C. Furthermore, the carbon fiber–reinforced biopolymers possess excellent heat resistance. Therefore, carbon fiber-reinforced, resveratrol-based epoxy resin composites are promising candidates as alternatives to petroleum-based high-performance carbon fiber composites.     

Properties of Epon 828 resin cured by cyclic phosphine oxide tetra acid

A new phosphorylated epoxy polymer was obtained using Epon 828 resin cured with a phosphorus-containing curing agent, 10-phenylphenoxaphosphine-2,3,7,8-tetracarboxylic acid-10-oxide (PDAC). In addition, compositions of Epon 828 with common curing agents, for example, 4,4′-diaminodiphenylmethane (DDM) and 4,4′-diaminodiphenylsulfone (DDS), were used for making a comparison of its curing reactivity, heat, and flame retardation with that of PDAC. The reactivites of the three curing agents toward Epon 828, as measured by differential scanning calorimetry (DSC), was in the following order: DDM > PDAC > DDS. Through thermal gravimetric analysis evaluation (TGA), the thermal and flame resistance of epoxy polymers were confirmed in this study as capable of being improved through introduction of the cyclic phosphine oxide group into the carboxyl curing agent structure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1877–1885, 1998     

Fracture toughness of epoxy resins modified with polyethersulfone: Influence of stoichiometry on the morphology of the mixtures

Toughened mixtures containing 15 wt % polyethersulfone were made with diglycicdyl ether of bisphenol-A resin and 4,4′-diaminodiphenylmethane curing agent, with amine/epoxy group stoichiometric ratios varying from 0.6 to 1.5. Fracture behavior of the modified mixtures has been investigated as a function of the stoichiometry in the matrix. Morphology has been analyzed by transmission and scanning electron microscopy. The increase of amine content in the matrix results in a further increased fracture toughness. This behavior has been related to the changes on the ductility of the matrix upon stoichiometric ratio, but also to the changes on microstructural features of the modified mixtures as stoichiometric amine/epoxy group ratio increased. These morphological changes have been interpreted in terms of spinodal decomposition during curing of the epoxy matrix. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 183–191, 1998     

Influence of Multiwalled Carbon Nanotubes on Mechanical,Thermal and Electrical Behavior of Polybenzoxazine-Epoxy Nanocomposites

Multiwalled carbon nanotubes (MWCNT)-reinforced polybenzoxazine-epoxy nanocomposites were prepared via the solvent method and were investigated for their thermal, thermo-mechanical, mechanical, electrical and morphological properties. Epoxy resin (DGEBA) was modified with 5, 10 and 15 wt.% of benzoxazines using 4,4′-diaminodiphenylmethane as a curing agent at appropriate conditions. Epoxy and benzoxazines-modified epoxy systems were further reinforced with 0.25, 0.50 and 0.75 wt.% of surface-modified MWCNT. MWCNT-reinforced polybenzoxazine-epoxy nanocomposites exhibited better thermal, mechanical and dielectric properties. Dispersion of MWCNT in benzoxazine-epoxy resins and nanostructure of the composites was confirmed by transmission electron microscopy analysis.     

Epoxy resin based on 4,4′-dihydroxydiphenysulfone. I. Synthesis and reaction kinetics with 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenylsulfone

Epoxy resins based on 4,4′-dihydroxydiphenylsulfone (DGEBS) and diglycidyl ether of bisphenol A (DGEBA) were prepared by alkaline condensation of 4,4′-dihydroxydiphenylsulfone (bisphenol S) with epichlorohydrin and by recrystallization of liquid, commercial bisphenol A-type epoxy resin, respectively. Curing kinetics of the two epoxy compounds with 4,4′-diaminodiphenylmethane (DDM) and with 4,4′-diaminodiphenylsulfone (DDS) as well as T_g values of the cured materials were determined by the DSC method. It was found that the ? SO₂? group both in the epoxy resin and in the harener increases T_g values of the cured materials. DGEBS reacts with the used hardeners faster than does DGEBA and the curing reaction of DGEBS begins at lower temperature than does the curing reaction of DGEBA when the same amine is used. © 1994 John Wiley & Sons, Inc.     

Effects of moisture and stoichiometry on the dynamic mechanical properties of a high-performance structural epoxy

Dynamic mechanical measurements have been made on a 4,4′-diaminodiphenyl sulfone-cured tetraglycidyl 4,4′-diaminodiphenylmethane epoxy (TGDDM-DDS). There are basically three transitions on the mechanical spectra that have been identified, and the effects of moisture uptake and amount of DDS on these transitions were examined. The dynamic mechanical behavior of the same epoxy with 60% carbon fiber loading was also studied, providing further elucidation on the nature of the transitions observed with this system.     

Structure characterization,reactivity, and thermal properties of new cyclic phosphine oxide epoxy resin containing tetra-oxirane rings

A new type of epoxy resin, which contained cyclic phosphine oxide and tetra-oxirane rings in the main chain, was synthesized. The structure of the new type of epoxy resin was confirmed by elemental analyses (EA), infrared (IR) spectroscopy, and ¹H nuclear magnetic resonance (NMR) and ¹³C-NMR spectroscopies. In addition, compositions of the new synthesized cyclic phosphine oxide epoxy resin (TGCAO) with three curing agents, for example, bis(3-aminophenyl)ethylphosphine oxide (BEMP), 4,4′-diaminodiphenylmethane (DDM), and 4,4′-diaminodiphenylsulfone (DDS) were used for making a comparison of its curing reactivity, heat, and flame retardancy with those of Epon 828 and DEN438. The reactivities were measured by differential scanning calorimetry. Through the evaluation of thermal gravimetric analysis, those polymers, which were obtained through the curing reactions between the new epoxy resin and three curing agents (BEMP, DDM, and DDS), also demonstrated adequate thermal propeties, as well as a high char yield. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1397–1409, 1998     

Amine-terminated oligoimides for epoxy curing

Oligoimides of N,N′,-4,4′-bismaleimidodiphenyl ether (DDEBM) and 4,4′-diaminodiphenylmethane (DDM) were prepared by the Michael addition reaction. The synthesized oligoimides (DDEBM–DDM) were characterized for their molecular structure by elemental analysis and IR spectroscopy. The number-average molecular weight (M _n) was determined by nonaqueous conductometric titration. Thermal characteristics were studied by thermogravimetry. Use of DDEBM–DDM oligomers as a curing agent for epoxy resin was studied by differential scanning calorimetry (DSC). The resin curing of the epoxy was monitored by the change in oxirane spectral band in the IR spectrum. Glass fiber reinforced composites of DDEBM–DDM-epoxy were prepared and evaluated for their physical and chemical properties. © 1996 John Wiley & Sons, Inc.     

新型环氧树脂固化剂的合成及其环氧胶粘剂

以4,4’-二氨基二苯甲烷为原料,经乙酰化、硝化、酸解、还原、中和5步反应合成得到了一种新型环氧树脂固化剂,即3,3’,4,4’-四氨基二苯甲烷,并通过FT—IR分析及熔点测定对其进行了表征。此外,对改性环氧树脂／3,3’,4,4’-四氨基二苯甲烷体系也作了性能研究。     

Epoxy resins based on aromatic glycidylamines. VI. Toughening of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane by reactive additives

Mechanical properties of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane and its mixtures with liquid bisphenol A-type epoxy resins, bisphenol A and ε-caprolactone have been studied. 4,4′-Diaminodiphenylsulfone was used as hardener. Materials with improved fracture toughness and good mechanical strength in the temperature range 20–200°C have been formulated.     

A simple imide compound as a curing agent for epoxy resin. I. Synthesis and properties

A simple imide compound, 4‐amino‐phthalimide (APH), was synthesized as a curing agent for epoxy resin. APH was prepared from the hydration of 4‐nitro‐phthalimide, which was prepared from the nitration of phthalimide. The chemical structure of APH was verified by IR and ¹H‐NMR spectra. The thermal properties and dielectric constant (ε) of a phosphorus‐containing novolac epoxy resin cured by APH were determined and compared with those of epoxy resins cured by either 4,4′‐diamino diphenyl methane (DDM) or 4,4′‐diamino diphenyl sulfone (DDS). The results indicate that the epoxy resin cured by APH showed better thermal stability and a lower ε than the polymer cured by either DDM or DDS. This was due to the introduction of the imide group of APH into the polymer structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

室温固化改性芳胺固化剂的研制

研究了改性芳香胺环氧树脂室温固化剂。通过甲醛与苯胺缩合所生成的缩聚多元伯胺能获得良好的固化性能。着重研究了胺醛物质的量比、催化剂对缩合物的影响。     

Epoxy–imide resins based on bis (carboxyphthalimide)s

Epoxy–imide resins have been obtained through the reaction of Araldite GY 250 (diglycidylether of bisphenol-A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac-epoxy resin; polyfunctional) with bis(carboxyphthalimide)s derived from 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenylmethane and trimellitic anhydride. For each epoxy-imide resin system, epoxy equivalent to carboxy equivalent ratio has been optimised to obtain the maximum tensile lap shear adhesive strength on stainless steel substrates at room temperature. The lap shear strength at 100, 150, and 175°C has been determined for the optimum ratio. Araldite EPN-1138-based systems give the lap shear strength of 141–182 kg/cm² at room temperature for the optimum compositions and retain about 84–100% of the lap shear strength at 150°C. Araldite GY-250-based systems have lap shear strength of 183–193 kg/cm² and retain 76–84% of the lap shear strength at 150°C except for the one cured with bis (carboxyphthalimide) prepared from 4,4′-diaminodiphenylmethane, which retains only 17% of the lap shear strength. Among the systems studied, Araldite GY 250 cured with bis (carboxyphalimide) synthesized from 3,3′-diaminodiphenylsulfone appears to be the best, retaining 75% (138 kg/cm²) of the lap shear strength at 175°C.     

Polyester/lignosulfonate blends with enhanced properties

The compatibility of poly(ethylene terephthalate) and its copolymer containing isophthalate units with epoxy-modified lignin has been studied. The following methods have been used: DSC, thermogravimetry, IR spectroscopy, contact angle measurements and dielectric properties determination. The optimum compatibility ratios and the necessity of a partial crosslinking with 4,4′-diaminodiphenylmethane to obtain a stable morphology have been established.     

Synthesis,characterization, thermal and flame-retardant properties of silicon-based epoxy resins

A new silicon-containing oxirane triglycidyl phenyl silane oxide (TGPSO) and its corresponding silicon-containing epoxy resins are synthesized and characterized. The activation energies of TGPSO curing reaction with various curing agents, including 4,4-diaminodiphenylmethane, 4,4-diaminodiphenylsulfone, and dicyanodiaminde, are found to be 180, 196.5, and 154 kJ/mol. The curing reaction of TGPSO with diamines is determined to be a first-order reaction through means of Arrhenius plots. The introduction of the silicon-containing group results in higher curing reactivity. This silicon-containing resin possesses higher char yield as well as higher limiting oxygen index (LOI = 35) than the commercial epoxy resins, confirming the usefulness of these silicon-containing epoxy resins as flame retardants. Char yields and LOI measurements demonstrate that incorporating silicon into epoxy resins is able to improve their flame retardancy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1231–1238, 1999     

Phosphorus containing epoxy for flame retardant II: Curing reaction of bis-(3-glycidyloxy) phenylphosphine oxide

The curing reaction of a phosphorus containing epoxide, bis-(3-glycidyloxy) phenylphosphine oxide (BGPPO), was studied by differential scanning calorimeter (DSC) using dynamic and isothermal methods. Kinetic parameters and activation energy of the BGPPO cured with diamine or dianhydride curing agents were determined. The dynamic activation energies were significantly larger than the isothermal ones. Via isothermal analysis technique, the activation energies of BGPPO cured with 4,4′-diaminodiphenylmethane, dicyanodiamide, methyl tetrahydrogen phthalic anhydride, and phthalic anhydride were found to be 69.5, 83.5, 93.6, and 90.6 kJ/mol, respectively. These values were comparable with those of other commercial epoxy curing system. © 1996 John Wiley & Sons, Inc.