Synthesis,characterization, and properties of low viscosity tetra‐functional epoxy resin N,N,N′,N′‐ tetraglycidyl‐3,3′‐diethyl‐4,4′‐diaminodiphenylmethane

Tetra‐functional epoxy resin N,N,N′,N′‐tetraglycidyl‐3,3′‐diethyl‐4,4′‐diaminodiphenylmethane (TGDEDDM) was synthesized and characterized. The viscosity of TGDEDDM at 25°C was 7.2 Pa·s, much lower than that of N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM). DSC analysis revealed that the reactivity of TGDEDDM with curing agent 4,4′‐diamino diphenylsulfone (DDS) was significantly lower than that of TGDDM. Owing to its lower viscosity and reactivity, TGDEDDM/DDS exhibited a much wider processing temperature window compared to TGDDM/DDS. Trifluoroborane ethylamine complex (BF₃‐MEA) was used to promote the curing of TGDEDDM/DDS to achieve a full cure, and the thermal and mechanical properties of the cured TGDEDDM were investigated and compared with those of the cured TGDDM. It transpired that, due to the introduction of ethyl groups, the heat resistance and flexural strength were reduced, while the modulus was enhanced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40009.     

Thermal characterization of carbon‐nanofiber‐reinforced tetraglycidyl‐4,4′‐diaminodiphenylmethane/4,4′‐diaminodiphenylsulfone epoxy composites

The thermal properties of carbon nanofibers (CNF)/epoxy composites, composed of tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) resin and 4,4′‐diaminodiphenylsulfone (DDS) as a curing agent, were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis, and dynamic mechanical thermal analysis. DSC results showed that the presence of CNF had no pronounced influence on the heat of the cure reaction. However, the incorporation of CNF slightly improved the thermal stability of the epoxy. Furthermore, the storage modulus of the TGDDM/DDS epoxy was significantly enhanced, whereas the glass‐transition temperature was not significantly affected, upon the incorporation of CNFs. The storage modulus of 5 wt % CNF/epoxy composites at 25°C was increased by 35% in comparison with that of the pure epoxy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 295–298, 2006     

Effect of chlorine substitution in 4,4′‐diaminodiphenylmethane hardener on shelf life and mechanical properties of epoxies

Curing of N,N,N′,N′‐tetraglycidyldiaminodiphenylmethane with new curing agents like 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane and 2,2′‐dichloro‐4,4′‐diaminodiphenylmethane in comparison with diaminodiphenylmethane and 4,4′‐diaminodiphenylsulphone (DDS) was carried out using dynamic differential scanning calorimetry. The shelf life of various epoxy formulations was evaluated by the residual cure exotherm method. The glass‐transition temperatures of cured epoxy formulations were determined using dynamic mechanical analysis. The mechanical properties such as the tensile strength, tensile modulus, flexural strength, and Izod impact strength were also evaluated and compared. The activation energy, frequency factor, and shelf life of chloro‐substituted hardener formulations were high as compared to those of unsubstituted hardener formulations. The marginal differences in the glass‐transition temperature, tensile strength, tensile modulus, and flexural strength and the small decrement in the Izod impact strength values were interpreted in terms of chlorine substitution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3082–3088, 2002; DOI 10.1002/app.2337     

Tertiary‐amine‐free,non‐planar,sulfone‐containing,tetrafunctional epoxy and its application as a high temperature matrix

Non‐amine‐derived tetrafunctional epoxies have several advantages over the amine‐derived N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) in high temperature applications. Although two non‐amine‐derived tetrafunctional epoxies were developed in our laboratory, further improvements in toughness using less loading amount is still desirable. Thus, a tertiary‐amine‐free, non‐planar and triphenylmethane‐containing tetrafunctional epoxy (STFE) with a sulfone spacer was synthesized. When it was mixed with diglycidyl ether of bisphenol A (DGEBA) and cured with 4,4′‐diaminodiphenylsulfone (DDS), both thermal and mechanical performances outperformed TGDDM. Moreover, STFE modified system shows the highest toughness (35.7 kJ m^–2) among three amine‐free and triphenylmethane‐containing epoxies at merely 5 wt% loading. Molecular simulation and thermomechanical analysis results suggest that the improved mechanical properties could be related to the geometry of the molecule and larger free volume. Despite a marginal drop in T_g, the thermal degradation temperature is better than that of TGDDM/DDS. In addition, the moisture resistance of STFE/DGEBA/DDS is much better than that of TGDDM/DDS. Thus, STFE modified DGEBA could be a potential replacement for TGDDM in some high temperature applications. © 2020 Society of Chemical Industry     

An investigation of cure and thermal stability of poly(amide‐amidic acid) modified tetraglycidyl 4,4′‐diaminodiphenylmethane/4,4′‐diaminodiphenylsulfone

In this work, poly(amide‐amidic acid) (PAA) was used to modify tetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM)/4,4′‐diaminodiphenylsulfone (DDS) system. Results of non‐isothermal differential scanning calorimetry analysis indicated that PAA played a role of catalyst during the process of the curing reaction. The curing mechanism was studied by Fourier transform infrared spectroscopy, showing that the PAA acted as a co‐curing agent in the system. The glass transition temperature decreased firstly and then increased with the increase of the PAA content. PAA equally rendered TGDDM more fire resistant with higher char yield. On examining the fracture surface morphology using scanning electron microscopy, it was observed that there was no obvious phase separation when the content of PAA was less than 20 phr (per hundred weight of TGDDM/DDS resin), however, phase separation was observed when the content of PAA was 25 and 30 phr. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Isothermal Cure of an Epoxy System Containing Tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM), a Multifunctional Novolac Glycidyl Ether and 4,4′-Diaminodiphenylsulphone (DDS): Vitrification and Gelation

Times to gelation and vitrification have been determined at different isothermal curing temperatures between 200 and 240°C for an epoxy/amine system containing both tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) and a multifunctional Novolac glycidyl ether with 4,4′-diaminodiphenylsulphone (DDS). The mixture was rich in epoxy, with an amine/epoxide ratio of 0·64. Gelation occurred around 44% conversion. Vitrification was determined from data curves of glass transition temperature, T_g, versus curing time obtained from differential scanning calorimetry experiments. The minimum and maximum values T_g determined for this epoxy system were T_g0=12°C and T_gmax=242°C. Values of activation energy for the cure reaction were obtained from T_g versus time shift factors, a_T, and gel time measurements. These values were, respectively, 76·2kJmol^-1 and 61·0kJmol^-1. The isothermal time–temperature–transformation (TTT) diagram for this system has been established. Vitrification and gelation curves cross at a cure temperature of 102°C, which corresponds to glass transition temperature of the gel. © of SCI.     

Fibre reinforced composites of multifunctional epoxy resins

Glass and carbon fibre reinforced epoxy composites were fabricated for N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) and its formulated systems with tri- and di-functional reactive epoxy diluents using 30% diaminodiphenyl sulphone (DDS) as a curing agent. The epoxy laminates were evaluated for their physical, chemical and mechanical properties [at room (26°C) and high (100°C) temperatures]. A marginal increase (<20%) in the mechanical properties of CFRP was found compared with GFRP laminates. Incorporation of epoxy diluents altered the mechanical properties of the composites significantly. The incorporation of triglycidyl-4-aminophenol diluent to TGDDM systems resulted in an improvement in mechanical properties of about 2–6%.     

New tetrafunctional epoxy resin system with increased shelf life

Chlorine‐ and methyl‐substituted aromatic diamines based on diaminodiphenylmethane were epoxidized and characterized. The effect of different substituents on epoxidation was studied. The cure studies of the two new tetrafunctional resins in comparison with unsubstituted resin N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) was carried out by DSC with 3,3′‐dichloro‐4,4′diaminodiphenylmethane (o‐DCDDM; 30% w/w) as a common curing agent. The mechanical properties such as flexural, Izod impact, heat distortion temperature (HDT), of such cured neat resins were also studied. The results of the cure studies indicate that the substitution of the α‐hydrogen of the resin by chlorine or methyl group decreases the reactivity of the resin leading to an increase in the shelf life. This study also indicates that the functionality of the resin plays a pivotal role in the reactivity and thus the shelf life of an epoxy resin system. The results of the mechanical properties of the neat resin casts obtained by subjecting to a common cure schedule when compared with the unsubstituted resin showed a decrease in impact strength, which is obvious because of the presence of a bulky pendant group but the impact strength was higher than that of the TGOS30 resin system. Results of flexural strength of the different substituted neat resin casts did not show much of a deviation from that of the unsubstituted resin system. The HDT results indicate no significant difference in the values of the unsubstituted resin vis‐a‐vis with substituted resin systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2790–2801, 2004     

Epoxy resins based on aromatic glycidylamines. V. Shelf life of TGDDM-based epoxy resins

The effect of aging on resin composition was investigated as a part of a study concerned with the evaluation of epoxies containing N, N, N′, N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM). Long-term stability of three different epoxy resins based on TGDDM and their mixtures with 4,4′-diaminodiphenylsulfone (DDS) was followed at 23 ± 2°C at a relative humidity ranging from 45% to 55%, by means of GPC and HPLC; short-term stability of the resins was evaluated at 125°C.     

Curing kinetics and reaction‐induced homogeneity in networks of poly(4‐vinyl phenol) and diglycidylether epoxide cured with amine

Mixtures of diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin with poly(4‐vinyl phenol) (PVPh) of various compositions were examined with a differential scanning calorimeter (DSC), using the curing agent 4,4′‐diaminodiphenylsulfone (DDS). The phase morphology of the cured epoxy blends and their curing mechanisms depended on the reactive additive, PVPh. Cured epoxy/PVPh blends exhibited network homogeneity based on a single glass transition temperature (T_g) over the whole composition range. Additionally, the morphology of these cured PVPh/epoxy blends exhibited a homogeneous network when observed by optical microscopy. Furthermore, the DDS‐cure of the epoxy blends with PVPh exhibited an autocatalytic mechanism. This was similar to the neat epoxy system, but the reaction rate of the epoxy/polymer blends exceeded that of neat epoxy. These results are mainly attributable to the chemical reactions between the epoxy and PVPh, and the regular reactions between DDS and epoxy. Polym. Eng. Sci. 45:1–10, 2005. © 2004 Society of Plastics Engineers.     

Isothermal curing by dynamic mechanical analysis of three epoxy resin systems: Gelation and vitrification

Times to gelation (t_gel) and times to vitrification (t_vit) during isothermal curing for the epoxy systems diglycidyl ether of bisphenol A (DGEBA)/1,3‐bisaminomethylcyclohexane (1,3‐BAC), tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM)/4‐4′‐diaminodiphenylsulfone (DDS), and TGDDM/epoxy novolac (EPN)/DDS were measured at different curing temperatures. This article reports on a method to determine t_gel and t_vit by dynamic mechanical analysis (DMA). Gelation was determined at the onset of the storage modulus or by the peak of the loss factor. Vitrification was defined as the curve of the storage modulus as the curve reached a constant level (endset) in DMA tests. The experimental values obtained for t_gel and t_vit were compared with values obtained by other experimental methods and with theoretical values (t_gel's) or indirect determinations (t_vit's). From kinetic analysis by differential scanning calorimetry, conversions corresponding to gelation were obtained for the three systems; this yielded a constant value for each system that was higher than theoretical value. Values of the apparent activation energies of the DGEBA/1,3‐BAC, TGDDM/DDS, and TGDDM/EPN/DDS epoxy systems were obtained from plots of t_gel's against reciprocal temperatures. They were 53.2, 58.2, and 46.5 kJ/mol, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 78–85, 2002     

Cure kinetics and catalyzed effect of hydroxyl group of LC diglycidyl ether of bisphenol‐S with aromatic diamines

The curing reactions of liquid crystalline 4,4′‐bis‐(2,3‐epoxypropyloxy)‐sulfonyl‐bis(1,4‐phenylene) (p‐BEPSBP) with 4,4′‐diaminodiphenylmethane (DDM) and 4,4′‐diaminodiphenylsulfone (DDS) were investigated by nonisothermal differential scanning calorimeter (DSC). The relationships of E_a with the conversion α in the curing process were determined. The catalyzed activation of hydroxyl group for curing reaction of epoxy resins with amine in DSC experiment was discussed. The results show that these curing reactions can be described by the autocatalytic ?esták‐Berggren model. The curing technical temperature and parameters were obtained, and the even reaction orders m, n, and ΔS for p‐BEPSBP/DDM and p‐BEPSBP/DDS are 0.35, 0.92, ?81.94 and 0.13, 1.32, ?24.45, respectively. The hydroxyl group has catalyzed activation for the epoxy–amine curing system in the DSC experiment. The average E_a of p‐BEPSBP/DDM is 67.19 kJ mol^?1 and is 105.55 kJ mol^?1 for the p‐BEPSBP/DDS system, but it is different for the two systems; when benzalcohol as hydroxyl group was added to the curing system, the average E_a of p‐BEPSBP/DDM decreases and increases for p‐BEPSBP/DDS. The crystalline phase had formed in the curing process and was fixed in the system. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and curing properties of a novel curing agent based on N‐(4‐hydroxyphenyl) maleimide and dicyclopentadiene moieties

A new type of epoxy resin curing agent, containing pendant phenol functions, was synthesized by the free‐radical copolymerization of N‐(4‐hydroxyphenyl) maleimide with dicyclopentadiene (DCPD) monomer in the presence of a radical initiator. The chemical structure was characterized with Fourier transform infrared spectroscopy and nuclear magnetic resonance. The molecular weight of the new curing agent was determined by gel permeation chromatography. The activity and activation energy of this new curing agent with o‐cresol formaldehyde novolac epoxy (CNE) was investigated with a nonisothermal differential scanning calorimetry technique at different heating rates. The thermal properties of the cured polymers were evaluated with thermogravimetric analysis, and the results exhibit good thermal stability. In addition, this new curing agent with CNE showed low moisture absorption because of the hydrophobic nature of the DCPD structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reaction kinetics and thermal properties of epoxidised cresol novolac/4,4′‐diglycidyl (3,3′,5,5′‐tetramethylbiphenyl) epoxy resin composite cured with aromatic diamine

A series of novel composites based on different ratios of epoxidised cresol novolac (ECN) and 4,4′‐diglycidyl(3,3′,5,5′‐tetramethylbiphenyl) epoxy resin (TMBP) have been prepared with the curing agent 4,4′‐methylenediamine (DDM) and 4,4′‐diaminodiphenylsulfone (DDS), respectively. The investigation of cure kinetics was performed by differential scanning calorimetry using an isoconversional method. The high thermal stabilities of the cured samples were also studied by thermogravimetric analysis. In addition, no phase separation was observed for cured ECN/DDM and ECN/DDS blending with different amounts of TMBP by dynamic mechanical analysis and scanning electron microscopy. Moreover, the cured systems also exhibited excellent impact properties and low moisture absorption. All the results indicate that the ECN/TMBP/DDM and ECN/TMBP/DDS systems are promising materials in electronic packaging. Copyright © 2011 Society of Chemical Industry     

Curing behavior,thermal, and mechanical properties of epoxy resins cured with a novel liquid crystalline dicarboxylic acid curing agent

A novel di‐carboxylic acid curing agent (DACA) was successfully synthesized and cured with three different epoxy resins: glycidyl end‐capped poly(bisphenol‐A‐co‐epichlorohydrin) (pDGEBA, M_n = 377), N,N‐diglycidyl‐4‐glycidyloxyaniline (TGAP), and 4,4′‐methylenebis(N,N‐diglycidylaniline) (TGDDM). The cured epoxy exhibited excellent thermal stability, which was indicated by high initial degradation temperature (T_id) and char yield. The T_id values of cured epoxy were in the range of 327–338°C, and the char yields increased with increasing epoxy functionality. The char yields of cured DACA/pDGEPA, DACA/TGAP, and DACA/TGDDM samples were 21.1, 60.4, and 66.9%, respectively. In addition, the cured epoxy samples also showed low coefficients of thermal expansion and high storage moduli (E′), which were around 60 ppm/°C and 2800 MPa, respectively. The failure surfaces were ductile and rough, so the cured epoxy samples are expected to have high fracture toughness and impact strength. POLYM. ENG. SCI., 54:695–703, 2014. © 2013 Society of Plastics Engineers     

Curing behavior and thermal and mechanical properties enhancement of tetraglycidyl‐4,4′‐diaminodiphenylmethane/4,4′‐diaminodiphenylsulfone using a liquid crystalline epoxy

A thermosetting resin system, based on tetraglycidyl‐4,4′‐diaminodiphenylmethane, has been developed via copolymerization with 4,4′‐diaminodiphenylsulfone in the presence of a newly synthesized liquid crystalline epoxy (LCE). The curing behavior of LCE‐containing resin system was evaluated using curing kinetics method and Fourier transform infrared spectroscopy. The effect of LCE on the thermal and mechanical properties of modified epoxy systems was studied. Thermogravimetric analysis indicated that the modified resin systems displayed a high T_0.05 and char yield at lower concentrations of LCE (≤5 wt%), suggesting an improved thermal stability. As determined using dynamic mechanical analysis and differential scanning calorimetry, the glass transition value increased by 9.7% compared to that of the neat resin when the LCE content was 5 wt%. Meanwhile, the addition of 5 wt% of LCE maximized the toughness with a 175% increase in impact strength. The analysis of fracture surfaces revealed a possible effect of LCE as a toughener and showed no phase separation in the modified resin system, which was also confirmed by dynamic mechanical analysis. © 2016 Society of Chemical Industry     

Effect of type of substitution in 4,4′‐bis‐(diaminodiphenyl) methane hardener on cure kinetics,mechanical, and flame retardant properties of tetrafunctional epoxy resins

The nature of the substituent in 4,4′‐bis‐(diaminodiphenyl) methane (DDM) hardener on the cure kinetics, mechanical, and flame retardant properties of N,N,N′,N′‐tetraglycidyl diaminodiphenyl methane (TGDDM) resin is investigated in comparison with unsubstituted DDM and widely used 4,4′‐bis‐(diaminodiphenyl) sulfone hardeners. Dynamic differential scanning calorimetry (DSC) and cure rheology studies showed that the substitution decreased the reactivity of the amine. An electron‐withdrawing chlorine substituent was found to be more effective than an electron‐releasing methyl group in reducing the amine reactivity. Substituted and unsubstituted DDM hardeners showed two peaks in their DSC thermograms that were due to steric hindrance in the former and deficiency of amine in the latter. Substitution showed its effect on the mechanical properties and glass‐transition temperature. The flexural modulus was increased; however, the Izod impact and glass‐transition temperature were decreased in substituted amine systems. The limiting oxygen index results showed higher flame retardancy in the chlorine substituted hardener system compared to other hardener systems that were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 480–491, 2006     

Curing kinetics and thermal property characterization of an o‐cresol formaldehyde epoxy resin and 4,4′‐diaminodiphenyl ether system

The kinetics of the curing reaction for a system of o‐cresol formaldehyde epoxy resin (o‐CFER) with 4,4′‐diaminodiphenyl ether (DDE) as a curing agent were investigated with differential scanning calorimetry (DSC). An analysis of the DSC data indicated that an autocatalytic behavior appeared in the first stages of the cure for the system, and this could be well described by the model proposed by Kamal, which includes two rate constants and two reaction orders (m and n). The overall reaction order (m + n) was 2.7–3.1, and the activation energies were 66.79 and 49.29 kJ mol^?1, respectively. In the later stages, a crosslinked network was formed, and the reaction was mainly controlled by diffusion. For a more precise consideration of the diffusion effect, a diffusion factor was added to Kamal's equation. In this way, the curing kinetics were predicted well over the entire range of conversions, covering both the previtrification and postvitrification stages. The glass‐transition temperatures of the o‐CFER/DDE samples were determined via torsional braid analysis. The results showed that the glass‐transition temperatures increased with the curing temperature and conversion up to a constant value of approximately 370 K. The thermal degradation kinetics of the system were investigated with thermogravimetric analysis, which revealed two decomposition steps. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 182–188, 2004     

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.     

Synthesis and characterization of novel polyaspartimides derived from 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl and various diamines

A novel bismaleimide, 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl, containing noncoplanar 2,2′‐dimethylbiphenylene and flexible ether units in the polymer backbone was synthesized from 2,2′‐dimethyl‐4,4′‐bis(4‐aminophenoxy)biphenyl with maleic anhydride. The bismaleimide was reacted with 11 diamines using m‐cresol as a solvent and glacial acetic acid as a catalyst to produce novel polyaspartimides. Polymers were identified by elemental analysis and infrared spectroscopy, and characterized by solubility test, X‐ray diffraction, and thermal analysis (differential scanning calorimetry and thermogravimetric analysis). The inherent viscosities of the polymers varied from 0.22 to 0.48 dL g⁻¹ in concentration of 1.0 g dL⁻¹ of N,N‐dimethylformamide. All polymers are soluble in N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethylsulfoxide, pyridine, m‐cresol, and tetrahydrofuran. The polymers, except PASI‐4, had moderate glass transition temperature in the range of 188°–226°C and good thermo‐oxidative stability, losing 10% mass in the range of 375°–426°C in air and 357°–415°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 279–286, 1999