Diglycidyl ether of bisfenol-A (DGEBA)/polybenzyl methacrylate (PBzMA)
blends cured with 4,4’-diaminodiphenylmethane (DDM) were studied. Miscibility,
phase separation, cure kinetics and morphology were investigated through differential
scanning calorimetry (DSC) and scanning electron microscopy (SEM). Non-reactive
DGEBA/PBzMA blends are miscible over the whole composition range. The addition
of PBzMA to the reactive (DGEBA+DDM) mixture slows down the curing rate, although
the reaction mechanism remains autocatalytic. On curing, initially miscible
(DGEBA+DDM)/PBzMA blends phase separate, arising two glass transition temperatures
that correspond to a PBzMA-rich phase and to epoxy network. Cured epoxy/PBzMA
blends present different morphologies as a function of the PBzMA content. 相似文献
The morphology of a quaternary blend containing a diglycidyl ether of bisphenol-A (DGEBA), a thermoplastic modifier (PMMA), a phase-separating curing agent (diaminodiphenylmethane, DDM), and a non-phase-separating curing agent (methylenebis(3-chloro-2,6-diethylaniline, MCDEA) was studied as a function of volume fraction of the thermoplastic modifier and fractional concentration of the curing agents in their mixture. It was found that using mixtures of curing agents a co-continuous morphology could be obtained at PMMA concentrations as low as 2.5 volume percent. Using FTIR spectroscopy it was proved that specific interactions are present between PMMA and individual amine curing agents. On the other hand, there was no detectable specific interaction between PMMA and DGEBA. By analyzing the micro-indentation hardness data of the cryo-fractured samples and putting forward the intrinsic hardness concept, it was proposed that the co-continuous morphology is inherently more effective than the other morphologies in changing the mechanical properties of the above-mentioned multi-component blends. 相似文献
This article describes the synthesis of a liquid crystalline curing agent 4,4′-bis-(4-amine-butyloxy)-biphenyl (BABB), and
its application as a curing agent for the epoxy resin (DGEBA) in comparison with normal curing agent, 4,4′-diaminobiphenyl
(DABP). BABB was investigated with polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray
scatting, and the results showed that BABB displayed smectic liquid crystalline phase. The curing behaviors of DGEBA cured
with BABB and DABP were studied by using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and
dynamic mechanical analysis (DMA). The results indicated that BABB showed a higher chemical reactivity than DABP. The kinetics
was studied under isothermal conditions using an isoconversional method, and the isothermal DSC data can be fitted reasonably
by an autocatalytic curing model. The nematic droplet texture was observed for the resulting polymer network of DGEBA/BABB
system, while the DGEBA/DABP system showed an isotropic state. The storage modulus of DGEBA/BABB system was enhanced in comparison
with DGEBA/DABP system because of the formation of LC phase, whereas the glass transition temperatures decreased because of
the introduction of flexible spacer group. 相似文献
Phosphorus- and silicon-containing epoxy resins were prepared from (2,5-dihydroxyphenyl)diphenyl phosphine oxide (Gly-HPO), diglycidyloxy methylphenyl silane (DGMPS) and 1,4-bis(glycidyloxydimethyl silyl)-benzene (BGDMSB) as epoxy monomers and diaminodiphenylmethane (DDM), bis(3-aminophenyl)methyl phosphine oxide (BAMPO) and bis(4-aminophenoxy)dimethyl silane (APDS) as curing agents. Epoxy resins with different phosphorus and silicon content were obtained. Their thermal, dynamic mechanical and flame retardant properties were evaluated. The high LOI values confirmed that epoxy resins containing hetero-atoms are effective flame retardants, but a synergistic efficiency of phosphorus and silicon on flame retardation was not observed. 相似文献
Octa(aminophenyl)silsesquioxane (OAPS) was used as the curing agent of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin. A study on comparison of DGEBA/OAPS with DGEBA/4,4′-diaminodiphenyl sulfone (DDS) epoxy resins was achieved. Differential scanning calorimetry was used to investigate the curing reaction and its kinetics, and the glass transition of DGEBA/OAPS. Thermogravimetric analysis was used to investigate thermal decomposition of the two kinds of epoxy resins. The reactions between amino groups and epoxy groups were investigated using Fourier transform infrared spectroscopy. Scanning electron microscopy was used to observe morphology of the two epoxy resins. The results indicated that OAPS had very good compatibility with DGEBA in molecular level, and could form a transparent DGEBA/OAPS resin. The curing reaction of the DGEBA/OAPS prepolymer could occur under low temperatures compared with DGEBA/DDS. The DGEBA/OAPS resin didn’t exhibit glass transition, but the DGEBA/DDS did, which meant that the large cage structure of OAPS limited the motion of chains between the cross-linking points. Measurements of the contact angle indicated that the DGEBA/OAPS showed larger angles with water than the DGEBA/DDS resin. Thermogravimetric analysis indicated that the incorporation of OAPS into epoxy system resulted in low mass loss rate and high char yield, but its initial decomposition temperature seemed to be lowered. 相似文献
The curing behaviour of diglycidyl ether of bisphenol-A (DGEBA) was investigated by the dynamic differential scanning calorimetry
using varying molar ratios of aromatic imide-amines and 4,4′-diaminodiphenylsulfone (DDS). The imide-amines were prepared
by reacting 1 mole of naphthalene 1,4,5,8-tetracarboxylic dianhydride (N) and 4,4′-oxodiphthalic anhydride (O) with 2.5 moles
of 4,4′-diaminodiphenyl ether (E) or 4,4′-diaminodiphenyl methane (M) or 4,4′-diaminodiphenylsulfone (S) and designated as
NE/OE or NM/OM or NS/OS. The mixture of the imide-amines and DDS at ratio of 0:1, 0.25:0.75, 0.5:0.5, 0.75:0.25 and 1:0 were
used to investigate the curing behaviour of DGEBA.
A single exotherm was observed on curing with mixture of imide-amines and DDS. This clearly shows that the two amines act
as co-curing agents. Curing temperatures were higher with imide-amines having sulfone linkage irrespective of anhydride. Curing
of DGEBA with mixture of imide-amines and or DDS resulted in a decrease in characteristic curing temperatures. The thermal
stability of the isothermally cured resins was also evaluated using dynamic thermogravimetry in a nitrogen atmosphere. The
char yield was higher in case of resins cured imide-amines based on N and E. The activation energy of decomposition and integral
procedural decomposition temperature were also calculated from the TG data. 相似文献
The kinetic of the curing process in the ethylenediamine (EDA)-poly (bisphenol A-co-epichlorohydrin) glycidyl end-capped (DGEBA) mixture modified with poly(ethylene oxide) (PEO) was studied. The epoxy component was labeled with a fluorescence group (dansyl) treating the DGEBA with the reactive dansyl derivative DNS-EDA. Dynamic DSC experiments were carried out and from their results the effect of the PEO composition on the epoxy curing was discussed. Furthermore, the effect of cure temperature and PEO composition on the morphology and crystallinity of the blend were studied as well. The morphologic study was carried out using complementarily optical transmission (TOM) and epifluorescence (EFM) microscopy. It was observed that: i) the addition of a non-reactive thermoplastic leads to a dilution effect of the reactive groups and therefore a decrease of the epoxy amine reaction rate; ii) the PEO composition does not seem to affect the non catalyzed process of the epoxy curing, while an increase in the PEO fraction within the epoxy/PEO mixture seems to change the mechanism of the cure reaction; iii) dynamic DSC scans, TOM and EFM images and steady state fluorescence spectra of the cured samples suggest that when the curing temperature increases there is an increase in the miscibility between PEO and the epoxy-amine reaction mixture; and iv) a reduction in the PEO/cured epoxy miscibility as the fraction of PEO increases was observed. 相似文献
The sulfonated poly(ether sulfone) (SPES) was successfully prepared using chlorosulfonic acid as a sulfonating agent. Diglycidylether of bisphenol-A (DGEBA) epoxy resins were modified with different contents of SPES, and the thermal and mechanical interfacial properties of DGEBA/SPES blends were investigated. As a result, the surface free energy of the blends was increased by the addition of SPES. DSC measurements revealed that the curing reaction was delayed with the increase of SPES content. Whereas, the thermal stabilities of the blends were slightly decreased as the SPES content increased. Meanwhile, the glass transition temperature and fracture toughness of the blends were increased with increasing SPES content, due to the improved intermolecular interactions, such as hydrogen bonding, between the hydroxyl group of DGEBA and the sulfonic group of SPES in the blends. The agreement could be observed by SEM which revealed phase separated morphology of DGEBA/SPES blends. 相似文献
Curing kinetics of diglycidyl ether of bisphenol-A (DGEBA) in the presence of varying molar ratios of aromatic imide-amines
and 4,4′-diaminodiphenylsulfone (DDS) were investigated by the dynamic differential scanning calorimetry. The imide-amines
were prepared by reacting 1 mole of benzophenone 3,3′,4,4′-tetracarboxylic acid dianhydride (B) with 2.5 moles of 4,4′-diaminodiphenyl
ether (E)/ or 4,4′-diaminodiphenyl methane (M)/ or 4,4′-diaminodiphenylsulfone (S) and designated as BE/ or BM/ or BS. The
mixture of imide-amines and DDS at ratio of 0:1, 0.25:0.75, 0.5:0.5, 0.75:0.25 and 1:0 were used to investigate the curing
behaviour of DGEBA.
The multiple heating rate method (5, 10, 15 and 20°C min−1) was used to study the curing kinetics of epoxy resins. The peak exotherm temperature was found to be dependent on the heating
rate, structure of imide-amines as well as on the ratio of imide-amine: DDS used. A broad exotherm was observed in the temperature
range of 180–230°C on curing with mixture of imide-amines and DDS. Curing of DGEBA with mixture of imide-amines and/or DDS
resulted in a decrease in characteristic curing temperatures. Activation energy of curing reaction as determined in accordance
to the Ozawa’s method was found to be dependent on the structure of amine. The thermal stability of the isothermally cured
resins was also evaluated using dynamic thermogravimetry in a nitrogen atmosphere. The char yield was highest in case of resins
cured using mixture of DDS: BS (0.25:0.75; EBS-3), DDS: BM (0.5: 0.5; EBM-2) and DDS: BE (0.5: 0.5; EBE-2). 相似文献
Summary: Experimental observations of the dynamics of phase behavior for blends of reactive constituents, i.e. diglycidyl ether of bisphenol A (DGEBA), curing agent methylene dianiline (MDA), and a reactive liquid rubber (R45EPI), have been theoretically modeled by coupling system thermodynamics governed by a summation of the free energies of mixing and network elasticity with reaction kinetics and diffusion equations. Snap‐shots of the temporal evolution of ternary phase diagrams have been established based on the self‐condensation reactions of DGEBA‐MDA and R45EPI as well as a cross‐reaction between the two constituents forming a copolymer. Numerical solution of the proposed mean‐field model provides good qualitative agreement with experimental results, namely, the observance of phase separation followed by a phase dissolution and subsequent secondary segregation in a 50/25.4/50 DGEBA/MDA/R45EPI mixture, as well as a single gradual phase separation in a 70/25.4/30 mixture. The phase separation dynamics are explained by a competition between the growth in molecular weights of the reactive species rendering the systems towards instability, and the formation of copolymer acting to compatibilize the mixtures.
Theoretical phase diagram for a DGEBA/MDA/R45EPI system. 相似文献
Mixtures of diglycidylether of bisphenol A (DGEBA) resin and commercially available hyperbranched polyester (HBP) Boltorn H30 were cured by anhydride to covalently bond the hydroxyl end groups in HBP with the epoxy resin. The curing mixtures were investigated by Differential Scanning Calorimetry (DSC) to study the curing evolution and to evaluate the kinetic parameters. DSC studies suggested that HBP could increase the curing rate of epoxy/anhydride systems at low conversions, but it produced a decelerative effect in the last stages of the curing. The influence of the HBP content and the proportion of anhydride on the curing conversions were discussed in detail. The addition of a tertiary amine was proved to decrease the curing temperatures. By Fourier Transform Infrared Spectroscopy (FTIR) the reaction of hydroxyl groups during the whole process was confirmed. By the determination of the conversion at the gelation, we could prove that it increased on increasing the proportion of HBP in the reactive mixture. By Thermomechanical Analysis (TMA) we could determine a reduction of the shrinkage after gelation. 相似文献
Cold crystallization and melting of poly(l-lactide) (PLLA) blended with an uncured or with an amino-cured epoxy resin (diglycidyl ether of bisphenol-A [DGEBA]) were
investigated. It was found that the uncured PLLA/DGEBA blends were miscible, as they exhibited a single composition-dependent
glass transition temperature (Tg). Melting point depression measurements indicated the existence of some type of interaction between the blend components,
which was confirmed by Fourier transform infrared spectroscopy. Depending on the crystallization conditions and on the blend
composition, a mixture of α and α′ crystals have been detected in PLLA and in uncured DGEBA/PLLA blends when crystallized
from the glassy state. At high DGEBA contents, preferably imperfect α crystals are formed. On the contrary, at low DGEBA contents,
the α′ form predominates and an exotherm associated to the α′–α transformation appears on the differential scanning calorimetry
(DSC) scan before the main melting peak. Upon curing, the system transforms from a homogeneous mixture with a single refractive
index into an opaque multiphasic one, as revealed by the existence of two Tgs in the DSC scans. These cross-linked immiscible blends displayed a single crystallization exotherm which scarcely changed
with composition, and PLLA cold crystallized mainly into the α′ form from an almost pure PLLA phase; subsequently, the α′
crystals transform into the α form just before melting during the DSC scan. 相似文献
Thermoset (TS) epoxy resins can be toughened with a thermoplastic (TP) for high-performance applications. The final structure morphology has to be controlled to achieve high mechanical properties and high impact resistance. Four polyethersulfone-modified epoxy resins are considered. They consist of different epoxy monomer structure (TGAP, triglycidyl-p-aminophenol and TGDDM, tetraglycidyl diaminodiphenylmethane) and a fixed amount of thermoplastic, and they are cured with two different amounts of curing agent. A reaction-induced phase separation occurs for all formulations generating morphologies, different in shapes and scales. The aim is to control the final morphology and in particular its dominant length scale. This morphology depends on the phase separation process, from the initiation to its final stage. The initiation relies on the relative miscibility of the components and on the stoichiometry between epoxy and curing agent. The kinetics depends on the viscosity of the systems. The different morphologies are characterized by electron microscopy or neutron scattering. Dynamic mechanical analysis allows confirming the presence of a phase separation even when it is not observable by electron microscopy. Vermicular morphologies with few hundreds nanometer width are obtained for the systems containing the TGAP as epoxy monomer. Systems formulated with TGDDM presents morphologies on much smaller scale of order a few tens of nanometers. We interpret the different sizes of the morphologies as a consequence of a larger viscosity for the TGDDM systems as compared to the TGAP ones rather than by a latter initiation of phase separation. 相似文献
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. 相似文献