Thermal and mechanical properties of a dendritic hydroxyl‐functional hyperbranched polymer and tetrafunctional epoxy resin blends

Blends of a tetrafunctional epoxy resin, tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), and a hydroxyl‐functionalized hyperbranched polymer (HBP), aliphatic hyperbranched polyester Boltorn H40, were prepared using 3,3′‐diaminodiphenyl sulfone (DDS) as curing agent. The phase behavior and morphology of the DDS‐cured epoxy/HBP blends with HBP content up to 30 phr were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The phase behavior and morphology of the DDS‐cured epoxy/HBP blends were observed to be dependent on the blend composition. Blends with HBP content from 10 to 30 phr, show a particulate morphology where discrete HBP‐rich particles are dispersed in the continuous cured epoxy‐rich matrix. The cured blends with 15 and 20 phr exhibit a bimodal particle size distribution whereas the cured blend with 30 phr HBP demonstrates a monomodal particle size distribution. Mechanical measurements show that at a concentration range of 0–30 phr addition, the HBP is able to almost double the fracture toughness of the unmodified TGDDM epoxy resin. FTIR displays the formation of hydrogen bonding between the epoxy network and the HBP modifier. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 417–424, 2010     

气相生长碳纤维对环氧树脂固化反应的影响及其复合物固化动力学研究

用示差扫描量热方法研究了气相生长碳纤维作为填料对4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)等温固化反应的影响.与纯环氧树脂一样,气相生长碳纤维复合物的固化反应也属于自催化反应类型.气相生长碳纤维对环氧树脂的固化反应动力学影响很小.固化反应的过程可以用一种修正过的自催化动力学模型来描述,在整个固化反应过程中纯TGDDM/DDS环氧树脂及其气相生长碳纤维复合物模型拟合得到的结果和实验数据相当一致.     

环氧树脂/氧化石墨纳米复合物的等温固化行为研究

用示差扫描分析仪(DSC)研究了氧化石墨(GO)对N,N,N',N'-四缩水甘油基-4,4'-二氨基二苯基甲烷环氧树脂(TGDDM)/4,4'-二氨基二苯基砜(DDS)体系的等温固化反应的影响,用X射线光电子能谱仪(XPS)和傅里叶变换红外光谱仪(FTIR)研究了GO上存在的官能团及其对TGDDM/DDS体系固化行为的影响,用热失重分析仪(TGA)研究了天然石墨和GO的热力学稳定性.XPS、FTIR和TGA结果表明,GO上存在的大量羟基、羧基、环氧基等官能团能够影响环氧树脂的固化行为.DSC研究发现,环氧树脂/氧化石墨纳米复合物的固化反应属于自催化类型,随着GO含量的增加,达到最大反应速率的时间不断减小,初始反应速率不断增大,这说明GO对环氧树脂的固化反应有促进作用.Kamal模型计算得到的结果表明,随着GO含量的增加自催化反应初期阶段表观活化能E1先减小再增大,而自催化反应结束后表观活化能E2略微减小.经Kamal模型扩散控制函数修正后,整个固化过程中拟合得到的结果与实验数据相当吻合.以上结果说明,少量的GO对TGDDM/DDS体系的固化反应起着催化作用.     

Novel phthalazinone‐bearing tetrafunctional epoxy: Synthesis,characterization, and their toughening application for TGDDM system

A novel tetrafunctional epoxy (TEPZ) was synthesized by “one spot two steps” method, and the effects of solvents, reaction temperature, and mole ratios of reactants on the reaction conversion were systematically investigated. The results demonstrated that the solvents participating in the reaction were the most crucial factor for high conversions. After curing, TEPZ/4,4′‐diaminodiphenyl sulfone (DDS) system exhibited better thermal stability compared with famous N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM)/DDS analog. When TEPZ is blended with TGDDM/DDS, the initial decomposition temperature of TGDDM/TEPZ/DDS hybrid elevated from 348°C to 362°C. The storage modulus and the glass transition temperature were sensitive to curing procedure and concentration of DDS. While the system consisted of 100 phr TGDDM, 30 phr TEPZ, and 40 phr DDS, the storage modulus and glass transition temperature increased significantly compared with those of TGDDM/DDS, and the impact strength increased by 31.6% simultaneously. Such enhancement could be ascribed to the structural feature of phthalazinone in TEPZ, which formed stable interpenetrating networks during thermal cure procedure.     

Interfacial and wetting properties of carbon fiber reinforced epoxy composites with different hardeners by electrical resistance measurement

In this research, interfacial and wetting properties of N,N,N,N-tetraglycidyl-4,4-diaminodiphenylmethane (TGDDM) epoxy resin with two hardeners with different chemical structure were evaluated by electrical resistance (ER) measurement. The heat of reaction of TGDDM epoxy with the two different hardeners, 33 and 44 di-amino di-phenyl sulphone (DDS), was analyzed by differential scanning calorimetry (DSC). The TGDDM epoxy exhibited different mechanical properties with the two different DDS hardeners. Combined ER, wetting measurements and the microdroplet test were used for evaluating the spreading effect and interfacial shear strength (IFSS) of carbon fiber (CF) reinforced TGDDM epoxy composites with these different hardeners. The heat of reaction and mechanical properties of TGDDM/DDS were influenced by the chemical structure and different free volumes of the epoxy resins. The relationships between the ER-wetting results and the IFSS were internally consistent. Ultimately it was demonstrated that ER measurements makes it possible to estimate the interfacial and wetting properties of CF reinforced epoxy composites.     

Epoxy resin toughened with thermoplastic

Highly crosslinked, brittle epoxy resin based on tètraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) cured with 4,4′-diaminodiphenyl sulphone (DDS) is widely used as a matrix material for aerospace composite applications. This work describes how inclusion of a polyetherimide (PEI) thermoplastic rich phase can significantly toughen the resin without a fall in apparent stiffness, which accompanies the more traditional method of rubber toughening. Dynamic mechanical analysis and scanning electron microscopy are used to characterize morphology, while fracture toughness and flexural modulus measurements are also performed on the cured resins. The extent of toughening is found to be dependent upon PEI concentration and test temperature. It is observed that the PEI rich phase toughens through ductile drawing across the faces of the advancing crack tip, and that this is the dominant toughening mechanism in the material.     

高性能环氧树脂/碳纳米管复合物的热分析研究

用差示扫描量热仪(DSC)、热失重分析仪(TGA)和动态力学热分析仪(DMTA)研究了多壁碳纳米管(MWNTs)/高性能4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)复合物的热性能.Kissinger和Flynn-Wall-Ozawa的非等温固化动力学研究发现,随着MWNTs含量的增加,复合物固化反应的活化能先减小后增大.TGA研究表明,MWNTs的添加对环氧树脂热稳定性影响很小.碳纳米管填充到TGDDM/DDS体系后,复合物的储存模量随着MWNTs含量的增加而增大,而玻璃化温度却随之减小.     

Cure kinetics of carbon nanotube/tetrafunctional epoxy nanocomposites by isothermal differential scanning calorimetry

The cure kinetics of tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) and 4,4′‐diaminodiphenylsulfone (DDS) as a cure agent in nanocomposites with multiwalled carbon nanotubes (MWNTs) have been studied with an isothermal differential scanning calorimetry (DSC) technique. The experimental data for both the neat TGDDM/DDS system and for epoxy/MWNTs nanocomposites showed an autocatalytic behavior. Kinetic analysis was performed with the phenomenological model of Kamal and a diffusion control function was introduced to describe the cure reaction in the later stage. Activation energies and kinetic parameters were determined by fitting experimental data. For MWNTs/epoxy nanocomposites, the initial reaction rates increased and the time to the maximum rate decreased with increasing MWNTs contents because of the acceleration effect of MWNTs. The values of the activation energies for the epoxy/MWNTs nanocomposites were lower than the values for the neat epoxy in the initial stage of the reaction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3701–3712, 2004     

Thermal Degradation of Tetrafunctional/Phenol Novalac Epoxy Mixture Cured with a Diamine

The effect of thermal degradation on the mechanical behaviour of a system containing both tetraglycidyl-4-4′-diaminodiphenylmethane (TGDDM) and a multifunctional novolac glycidyl ether (EPN) resins, cured with 4,4′-diaminodiphenylsulphone (DDS) has been studied using dynamic mechanical analysis (DMA) and tensile tests. Different curing paths using the isothermal time-temperature-transformation (TTT) diagram for this system were designed, obtaining thermosetting materials with different conversions. The influences of the degree of cure and of the aging temperature were also studied. The results showed different trends in the dynamic mechanical properties and an increase in the stiffness of the material with increasing aging time. Changes were faster and more intense with the higher temperature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Chemical degradation of TGDDM/DDS epoxy resin in supercritical 1-propanol: Promotion effect of hydrogenation on thermolysis

Chemical decomposition of an epoxy system made of tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) and 4,4′-diaminodiphenylsulfone (DDS) in supercritical 1-propanol was investigated under different reaction temperature and time. The GC–MS results suggested that the epoxy system was decomposed to the products including aniline, N-propylbenzenamine, and 4,4′-diaminodiphenylsulfone. The change of the products' yield with time was measured by GC. In addition, the formed chars were characterized by SEM, elemental analysis, Raman and XRD. The results implied the presence of some graphite microcrystals and disordered structure in the solid residue. Upon the addition of KOH, the Guerbet reaction of 1-propanol was promoted to generate more hydrogen. A possible free-radical reaction mechanism was proposed for the depolymerization of TGDDM/DDS epoxy resin. Hydrogenation of radicals had a promotion effect on thermolysis of TGDDM/DDS epoxy resin.     

Influence of substituents on the kinetics of epoxy/aromatic diamine resin systems

Eleven different epoxy/diamine systems, including tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), triglycidyl p‐aminophenol (TGAP), and diglycidyl ether of bisphenol A (DGEBA) with 4,4′‐diaminodiphenylsulfone (DDS), diethyltoluenediamine (DETDA), dimethylthiotoluenediamine (DMTDA), and meta‐phenylenediamine (m‐PDA), were studied with near‐infrared spectroscopy at different temperatures. The reactivities of the epoxies were determined and found to be in the following order when reacted with the same amine: DGEBA > TGAP > TGDDM. When the primary amine was reacted with the same epoxy, the order was DETDA > DDS > DMTDA; for the secondary amine, the order was DETDA > DMTDA > DDS. The relative reaction rates of the secondary amine to the primary amine were compared and discussed in terms of the structural differences and the corresponding substitution effect. It was concluded that the increase in the secondary amine reactivity of DETDA and DMTDA was caused by the deconjugation of the benzene‐ring π electrons from the lone pair on the N atom. The overall order of the secondary amine relative reactivity was DMTDA > DETDA > DDS for the same epoxy and TGDDM > TGAP > DGEBA for the same amine. The m‐PDA systems had no significant positive or negative substitution effects. Molecular orbital calculations were performed, and the results showed the most significant deconjugation effect in the secondary amine of DETDA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3143–3156, 2004     

Mechanistic study of thermal behavior and combustion performance of epoxy resins: I homopolymerized TGDDM

Tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) undergoes homopolymerization on heating. Intramolecular reactions which compete with crosslinking favor the formation of cyclic structures with increasing thermal and fire resistance of the resin, whereas physical mechanical properties tend to decrease. The mechanism of thermal decomposition of TGDDM is studied by thermogravimetry, differential scanning calorimetry and thermal volatilization analysis with characterization of volatiles evolved and residue left. Thermal degradation of poly-(TGDDM) starts at 260°C with elimination of water from secondary alcoholic groups which is a typical pathway for epoxy resin degradation. Resulting unsaturations weaken bonds in the β-position and provoke the first chain breaking at allyl–amine and allyl–either bonds. With increasing temperature, saturated alkyl–ether bonds and alkyl carbon–carbon bonds are broken first, followed by the most stable alkyl–aryl bonds at T>365°C. The combustion performance of TGDDM is discussed on the basis of the thermal degradation behavior.     

Cure behavior and thermal stability of an epoxy: new bismaleimide blends for composite matrices

A new bismaleimide (BMI) resin was synthesized to formulate epoxy(tetraglycidyl diaminodiphenyl methane; TGDDM) – bismaleimide thermoset blends for composite matrix applications. 4,4′-diaminodiphenyl methane (DDM) was used as an amine curing agent for the TGDDM. A Fourier transform infrared (FTIR) spectroscopy was employed to characterize the new BMI resin. Cure behavior of the epoxy–BMI blends was studied using a differential scanning calorimeter (DSC). DSC thermograms of the thermoset blends indicated two exothermic peaks. The glass transition temperature of the thermoset blends decreased with BMI content. Thermogravimetric analysis (TGA) was carried out to investigate thermal degradation behavior of the cured epoxy–BMI thermoset blends. The new BMI resin reacted partially with the DDM and weak intercrosslinking polymer networks were formed during cure of the thermoset blends.     

Properties of tetra-N-glycidyl-4,4′-diamino diphenyl methane (TGDDM) cured thick films

Thick films of tetra-N-glycidyl epoxy resin of p,p′-diaminodiphenyl methane (TGDDM) were prepared using p,p′-diaminodiphenyl methane (DDM), p,p′-diaminodiphenyl sulfone (DDS) and diethylene triamine (DETA) as curing agent with or without the epoxy fortifiers PGEHA and VCDRC (at 20 phr level). These thick films were used to evaluate various physical, mechanical, chemical resistant and dielectric properties.     

Accelerating role of clay in photo-oxidation of polypropylene/clay multifilament yarns

Photo-oxidative degradation of polypropylene/clay multifilament yarns containing different amounts of clay was investigated. These samples and pure polypropylene(PP) multifilametns were exposed to long wavelength radiations(λ 300 nm) under atmospheric condition of constant temperature and relative humidity. The photo-oxidative stability was studied using FTIR spectroscopy, tensile testing and microscopy. The results indicate that the addition of clay particles decreases the stability of PP/clay composites to photo-oxidative degradation according to comparison with pure PP. From FTIR study and tensile properties, it was also found that the multifilaments with higher clay loading reveals a faster loss of mechanical properties, higher photo-oxidative product formation and more reduction in the induction time of photooxidation. Moreover, the crack formation on surface of irradiated filaments corresponds well to the conclusions in tensile properties and FTIR characterization.     

Epoxy resins cured with aminophenylmethylphosphine oxide 1: Combustion performance

The kinetics of curing tetraglycidyl 4,4′-diaminodiphenyl methane (TGDDM) or of the mixture TGDDM/diglycidylether of bisphenol A (DGEBA) by bis(m-aminophenyl)methylphosphine oxide (BAMPO) was studied using differential scanning calorimetry. At low advancement of curing (<50%), the low activation energy interaction between epoxy and amino groups seems to be controlled by diffusion, whereas above 50% the role of homopolymerization tends to increase and the process becomes chemically controlled. BAMPO shows a higher fire-retardant effectiveness in the mixture TGDDM/DGEBA than in TGDDM or DGEBA alone, for which the oxygen and nitrous oxide index tests suggest a condensed phase or a gas phase fire-retardant action depending on phosphorus content. An intumescent char is formed on the surface of burning fire-retarded specimens which tends, however, to be oxidized, thus reducing the fire-proofing effect at high BAMPO content.     

Chemical structure of networks resulting from curing of N,N-diglycidylaniline-type resins with aromatic amines. IV. Characterization of TGDDM/DDS and TGDDM/DDM networks by high-resolution solid-state 13C-NMR

Cured N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) based epoxy resins were investigated by high-resolution solid-state ¹³C-NMR spectroscopy. Associated hardeners were the most commonly used low reactivity 4,4--diaminodiphenylsulphone (DDS), as well as, for comparisons reasons, the higher reactivity 4,4′-diaminodiphenylmethane (DDM) with, in each case, a1 to 1 or 1 to 0.6 epoxy/NH ratio. In order to interpret the spectra, the poorly resolved aliphatic region was decomposed into elementary lines, the structural assignments of which were made using solution ¹³C-NMR data resulting from a previous model compound study. The main structural feature of all investigated systems is the predominance of small cyclic units resulting from intramolecular reactions of N,N-diglycidylaniline groups. The resins are therefore far less crosslinked that it could be anticipated from the functionality of the reactants. Using the low reactivity DDS still increases this effect, due to a higher proportion of residual non reacted secondary amines. Reducing the initial ratio of hardener could on the contrary lead to a higher proportion of reacted amine function, and thus to a higher crosslinking degree. A qualitative picture of such networks is given at the end.     

Thermogravimetric Study of Tetrafunctional /Phenol Novolac Epoxy Mixtures Cured with a Diamine

The degradation behaviour of an epoxy system containing both tetraglycidyl-4-4′-diami-nodiphenylmethane (TGDDM) and a multifunctional novolac glycidyl ether resins, which are cured with 4,4′-diaminodiphenylsulphone (DDS) has been studied using thermogravimetric technique (TG). Isothermal and non-isothermal (dynamic) methods were used to determine the kinetic parameters of this system. An isothermal method and five dynamic methods reported in the literature were used to determine the activation energies of the system. Kissinger’s method only requires knowledge of the temperature at which the rate of weight loss is at maximum to calculate the activation energy. The Flynn-Wall-Ozawa method provides the activation energy without any assumption about the reaction order while the other three methods (Coats and Redfern, Horowitz and Metzger and Van Krevelen et al.) require a prior knowledge of the mechanism of degradation for this system to calculate the kinetic parameters. The results obtained by applying these different methods agreed well. In fact, the values of the activation energies provided by the six methods have shown excellent agreement when the degradation behaviour of this system was assumed to be of the deceleratory rate type. The kinetic parameters have been used to estimate the half-life of this system in two different ways.     

Miscibility and cure kinetics studies on blends of bisphenol-A polycarbonate and tetraglycidyl-4,4′-diaminodiphenylmethane epoxy cured with an amine

Differential scanning calorimetry (DSC) has been applied to characterize the glass transition behavior of the blends formed by bisphenol-A polycarbonate (PC) with a tetrafunctional epoxy (tetraglycidyl-4,4′-diaminodiphenyl methane, TGDDM) cured with 4,4′-diaminodiphenylsulphone (DDS). A rare miscibility in the complete composition range has been demonstrated in these blends. Additionally, the blend morphology was examined using scanning electron microscopy (SEM) and a homogeneous single-phase PC/epoxy network has been observed in the blends of all compositions. Moreover, polycarbonate incorporation has been found to exert a distinct effect on the cure behavior of the epoxy blends. The cure reaction rates for the epoxy-PC blends were significantly higher due to the presence of PC. In addition, the cure mechanism of the epoxy blends was no longer autocatalytic. An n-th order reaction mechanism with n = 1.2 to 1.5 has been observed for the blends of DDS-cured epoxy with PC of various compositions studied using DSC. The proposed n-th order kinetic model has been found to describe well the cure behavior of the epoxy/PC blends up to the vitrification point. © 1995 John Wiley & Sons, Inc.