Nadic Methyl Anhydride Research Articles

Curing Kinetics of Octaepoxysilsesquioxane/MNA System

Polyhedral oligomeric silsesquioxane (POSS) can be added to polymers to prepare the organic/inorganic hybrid materials. Octaepoxysilsesquioxane (E-POSS) containing eight reactive epoxy groups in a molecule is one of the important POSSs. E-POSS was cured with methylnadic anhydride (MNA) in this study. The curing kinetics of the E-POSS/MNA system was studied by using differential scanning calorimetry (DSC). Two different kinds of methods, Kinssinger and Flynn-Wall-Ozawa, were used to calculate the activation energy and pre-exponential factor of the curing reaction.

Thermal cure kinetics of epoxidized linseed oil with anhydride hardener

The thermal cure kinetics of an epoxidized linseed oil with methyl nadic anhydride as curing agent and 1-methyl imidazole as catalyst was studied by differential scanning calorimetry (DSC). The curing process was evaluated by non-isothermal DSC measurements; three iso-conversional methods for kinetic analysis of the original thermo-chemical data were applied to calculate the changes in apparent activation energy in dependence of conversion during the cross-linking reaction. All three iso-conversional methods provided consistent activation energy versus time profiles for the complex curing process. The accuracy and predictive power of the kinetic methods were evaluated by isothermal DSC measurements performed at temperatures above the glass transition temperature of the completely cured mixture (T g∞ ). It was found that the predictions obtained from the iso-conversional method by Vyazovkin yielded the best agreement with the experimental values. The corresponding activation energy (E a) regime showed an increase in E a at the beginning of the curing which was followed by a continuous decrease as the cross-linking proceeded. This decrease in E a is explained by a diffusion controlled reaction kinetics which is caused by two phenomena, gelation and vitrification. Gelation during curing of the epoxidized linseed/methyl nadic anhydride system was characterized by rheological measurements using a plate/plate rheometer and vitrification of the system was confirmed experimentally by detecting a significant decrease in complex heat capacity using alternating differential scanning calorimetry (ADSC) measurements.

Study on Bismaleimide Modified TDE-86 Epoxy Resin

In the study, BMI was modified by Ortho-diallyl Bisphenol A under certain conditions and got performed polymer. Epoxy resin was modified by the performed polymer using nadic methyl anhydride (MNA) as curing agent. The study investigated the manufacturability, thermal and mechanical properties of modified resin. The manufacturability of the modified resin was indicated by viscosity- temperature, viscosity- time and the gel time curves. Thermal properties of modified resin were characterized by means of dynamic mechanical analysis (DMA). According to per GB/T standard, mechanical properties of resin casting body like impact strength and tensile strength were tested. The results demonstrated that the viscosity of modified resin is below 200mPa.s at 60°C and the gel time is 110mins at 120°C. The modified resin can be used in the resin transfer moulding (RTM) process of all kinds of complex structural composites. The incorporation of the performed polymer improves the heat resistance of epoxy resin. The glass transition temperature (Tg) of the modified epoxy resin is 201.2°C and improves 44°C. The impact strength of the modified epoxy resin is 8.061KJ/m2. The tensile strength and tensile modulu of the modified are 60.9MPa and 3.89GPa. The present paper observed electron micrographs of impact fracture cross-section of modified resin systems. The results showed that the fracture of the modified resin is ductile fracture.

Epoxy resin/liquid natural rubber system: secondary phase separation and its impact on mechanical properties

An investigation was carried out to explore the morphology and mechanical properties of diglycidyl ether of bisphenol A epoxy resin (DGEBA) with liquid natural rubber possessing hydroxyl functionality (HLNR). Though modification of epoxies by synthetic rubber has been extensively studied not much attention has been paid to liquid natural rubber. Photo depolymerisation of natural rubber enables us to synthesise low molecular weight oligomers by varying the experimental parameters. Epoxy resin was cured using nadic methyl anhydride as hardener in presence of N,N-dimethyl benzyl amine accelerator. Hydroxylated natural rubber of different concentrations is used as modifier for epoxy resin. The addition of such chemically modified liquid rubber to an anhydride hardener–epoxy resin mixture has given rise to the formation of a two-phase microstructure in the cured systems, consisting of spherical particles of liquid natural rubber strongly bonded to the surrounding matrix, there by providing the required mechanism for toughness enhancement. Subinclusions of epoxy resin were present in the elastomer domains as secondary particles (particle in particle morphology) as evidenced from the SEM (scanning electron micrograph) photomicrographs. The origin of the so-called secondary phase separation is due to the combined effect of hydrodynamics, viscoelastic effects of rubber phase, diffusion, surface tension, polymerisation reaction and phase separation. In a dynamic asymmetric system, the diffusion of the fast dynamic phase is prevented by the slow dynamic phase, and hence the growth of fast dynamic phase gets retarded due to the slow dynamic phase. In the case of low viscosity blends the growth of fast dynamic phase turns fast and hence diffusion of fast dynamic phase cannot follow geometrical growth and cannot establish local concentration equilibrium and hence double phase separation takes place. The double phase separation is responsible for the enhanced impact and toughness behaviour of the blends. The mechanical behaviour of the liquid rubber-modified epoxy resin was evaluated in terms of tensile and flexural properties.

PF/EP/Nano-SiO2 composite paint for resistor

Phenolic resin(PF) and nano-SiO2 were used to improve the curing property and high humidity resistance of epoxy resin (EP) and methyl nadic anhydride (MNA) resistor paint, respectively. Hydrogen bonds, formed between phenolic resin and nano-SiO2 in alcohol, made nano-SiO2 disperse easily in EP/MNA paint through phenolic resin without being treated by supersonic vibration. When the mass ratio of PF to EP in paint is 3:7, the formed composite paint film can be cured in 2 min at 170 °C. When the mass ratio of nano-SiO2 to PF in paint is 3:100, the property of high humidity resistance of the composite paint is the best, meeting the requirement of varying ratio of resistance less than 0.1% after experiment on high humidity resistance. SEM analysis shows the surface of the composite paint film is smooth, glassy, tight and homogeneous, without acicular air holes.

New Age of Polymer Nanocomposites Containing Dispersed High-Aspect-Ratio Silicate Nanolayers

A new natural mica/epoxy nanocomposite was formed through the exfoliation of a mica layer. The natural mica used was a potassium sericite (K-SE) whose interlayer was saturated with potassium cations. Powdered samples were separated through an air classifier into D50 = 13.6 µm (its median particle diameter), D10 = 7.9 µm, and D90 = 23.7 µm. An organophilic SE was prepared by an ion exchange reaction between the SE powder and alkylammonium solutions of various initial concentrations. As a typical procedure to forming a completely organically modified sample, the K-SE powder was treated with the highest alkylammonium concentration. This corresponded to an alkylammonium+/K+ mole ratio = 10.0 which was kept at 90 °C for four days. The nanocomposites were prepared by dispersing the organophilic SE in an epoxy resin (diglyxidyl ether of bisphenol A, DGEBA) with subsequent curing in the presence of nadic methyl anhydride (NMA) and benzyldimethylamine (BDMA) at 120–180 °C. Considerable exfoliation of the organical...

Cure kinetics, morphology and miscibility of modified DGEBA-based epoxy resin – Effects of a liquid rubber inclusion

Kinetics of the curic reaction and morphology of a diglycidyl ether of bisphenol-A based epoxy resin (DGEBA), using an anhydride hardener (nadic methyl anhydride) at different weight contents of carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) was investigated using a differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM). The aim of the work is to understand the effects of inclusion of the liquid rubber phase in the transition phenomena that occur during the curing reaction. The curic reaction at three different curic temperatures and at varying rubber contents in the range of 5–20 wt% has been studied. The reaction rate and conversions that occurred at the curic temperatures were analyzed. The increase in the rate with the curic temperature showed this as a thermally catalyzed reaction. The rate of the reaction was found to decrease in liquid rubber-modified epoxies due to the effect of dilution and viscosity increase as obtained from the gelation times. The experimental data showed an autocatalytic behavior of the reaction, which is explained by the model predicted by Kamal. This model includes two reaction constants k 1 and k 2 and two reaction orders m and n. The order of the overall reaction was found to be approximately 2. The activation energies Ea 1 and Ea 2 were estimated at all curic temperatures for neat and all modified epoxies. The results obtained from the DSC data were also applied to diffusion controlled kinetic models. A schematic model to represent the curic reaction and phase separation was introduced and the molecular mechanism of this curing reaction was discussed. During the curic reaction, phase separation of the liquid rubber from the epoxy matrix took place and the modified epoxies showed phase separated morphology. The dispersed phase showed a homogenous particle size distribution. The size of the phase separated domains increased with increasing concentration of the CTBN and decreased with rise in curing temperature. The glass transition temperature ( T g) of the modified epoxies decreased with increase in curic temperature as studied from dynamic mechanical thermal analysis. Addition of the liquid rubber lowered the T g of the network. This became prominent in the modification of the matrix with 15 and 20 wt% of the elastomer. This is attributed to flexibilization of the matrix. The dissolved rubber plasticizes the epoxy network. The T g of the neat rubber in the low-temperature region was shifted to higher temperature upon addition of the elastomer. A higher shift was noted for 15 and 20 phr inclusion. This was due to dissolved epoxy in the rubber-rich phase that increased the modulus of the rubbery phase. The inclusion of a large wt% of carboxyl-terminated butadiene- co-acrylonitrile (CTBN) decreased the cross-linking density of the thermoset matrix.

Characterization of the curing agents used in epoxy resins with TG/FT-IR technique

Samples of epoxy resin (EP) based on the diglycidyl ether of bisphenol A (DGEBA), cured with nadic methyl anhydride (NMA) and mercaptan (CAPCURE 3-800), or amine-phenol (CAPCURE EH-30), respectively, SE 4 and SE 5, were prepared in the stoichiometric ratio determined by the supplier. The curing behaviour of the epoxy systems SE 4 and SE 5 was followed by DSC (Differential Scanning Calorimetry). These SE and their ingredients were analyzed using FT-IR transmission techniques (KBr pellets, pyrolysis without control and controlled pyrolysis-FT-IR, the CONTROLPIR/ FT-IR) for characterizing the curing agents (CA). The temperature range used for samples pyrolysis was found from TG (thermogravimetry). Thus, the FT-IR bands of liquid pyrolysate obtained by CONTROLPIR/FT-IR were evaluated, in comparison to the reference spectrum of CA. The characterization of CA was also possible, by the analysis of such SE with the TG/FT-IR technique.

Keratocan, a Cornea-specific Keratan Sulfate Proteoglycan, Is Regulatedby Lumican

Lumican is an extracellular matrix glycoprotein widely distributed in mammalian connective tissues. Corneal lumican modified with keratan sulfate constitutes one of the major proteoglycans of the stroma. Lumican-null mice exhibit altered collagen fibril organization and loss of corneal transparency. A closely related protein, keratocan, carries the remaining keratan sulfate of the cornea, but keratocan-null mice exhibit a less severe corneal phenotype. In the current study, we examined the effect of lumican overexpression in corneas of wild type mice. These mice showed no alteration in collagen organization or transparency but had increased keratocan expression at both protein and mRNA levels. Corneas of lumican-null mice showed decreased keratocan. This coupling of keratocan expression with lumican also was observed after intrastromal injection of a lumican expression minigene into the corneal stroma of Lum-/- mice. Small interfering RNA knockdown of lumican in vitro reduced keratocan expression, whereas co-injection of a lumican-expressing minigene with a beta-galactosidase reporter driven by the keratocan promoter demonstrated an increase of keratocan transcriptional activity in response to lumican expression in Lum-/- corneas in vivo. These observations demonstrate that lumican has a novel regulatory role in keratocan expression at the transcriptional level. Such results help provide an explanation for the differences in severity of corneal manifestation found in Lum-/- and Kera-/- mice. The results also suggest a critical level of small proteoglycans to be essential for collagen organization but that overabundance is not detrimental to extracellular matrix morphogenesis.

Sulforaphane-induced Cell Death in Human Prostate Cancer Cells Is Initiated by Reactive Oxygen Species

We have shown previously that sulforaphane (SFN), a constituent of many edible cruciferous vegetables including broccoli, suppresses growth of prostate cancer cells in culture as well as in vivo by causing apoptosis, but the sequence of events leading to cell death is poorly defined. Using PC-3 and DU145 human prostate cancer cells as a model, we now demonstrate, for the first time, that the initial signal for SFN-induced apoptosis is derived from reactive oxygen species (ROS). Exposure of PC-3 cells to growth-suppressive concentrations of SFN resulted in ROS generation, which was accompanied by disruption of mitochondrial membrane potential, cytosolic release of cytochrome c, and apoptosis. All these effects were significantly blocked on pretreatment with N-acetylcysteine and overexpression of catalase. The SFN-induced ROS generation was significantly attenuated on pretreatment with mitochondrial respiratory chain complex I inhibitors, including diphenyleneiodonium chloride and rotenone. SFN treatment also caused a rapid and significant depletion of GSH levels. Collectively, these observations indicate that SFN-induced ROS generation is probably mediated by a nonmitochondrial mechanism involving GSH depletion as well as a mitochondrial component. Ectopic expression of Bcl-xL, but not Bcl-2, in PC-3 cells offered significant protection against the cell death caused by SFN. In addition, SFN treatment resulted in an increase in the level of Fas, activation of caspase-8, and cleavage of Bid. Furthermore, SV40-immortalized mouse embryonic fibroblasts (MEFs) derived from Bid knock-out mice displayed significant resistance toward SFN-induced apoptosis compared with wild-type MEFs. In conclusion, the results of the present study indicate that SFN-induced apoptosis in prostate cancer cells is initiated by ROS generation and that both intrinsic and extrinsic caspase cascades contribute to the cell death caused by this highly promising cancer chemopreventive agent.

Study of the Effect of BDMA Catalyst in Epoxy Novolac Curing Process by Isothermal DSC

Epoxy-Novolac/Anhsydride cure kinetics have been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was Epoxy Novolac resin (DEN431), nadic methyl anhydride as hardener and benzyl dimethyl amine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants were investigated. The cure reaction was described with the catalyst concentration and the normalized kinetic model was developed for it. It is shown that, the cure reaction was dependent on the cure temperature and catalyst concentration and proceeded through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained by the Arrhenius kinetic model. The suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetic of Epoxy Novolac resin compositions as a function of the catalyst content and temperature.

Synthesis, characterization and curing behaviour of partial esters of cycloaliphatic epoxy resins

Partial esters of cycloaliphatic epoxy resins C1 and C2, containing glycidyl and epoxy cyclohexane groups, respectively, as their reactive units were synthesized using a 1:0.4 stoichiometric ratio of resin and methacrylic acid in the presence of triphenylphosphine. The reaction was performed as a function of temperature to determine various kinetic and thermodynamic parameters of the reaction. The prepared esters of C1 and C2, designated as C1P and C2P, respectively, were characterized for their structure by FT-IR spectroscopy. The degree of esterification and epoxy content in partial esters were determined by their epoxide equivalent weight. The curing behaviour of the CERs and their esters was studied using DSC. Dynamic DSC scans of cycloaliphatic epoxy resins mixed with nadic methyl anhydride (NMA)/methyl tetrahydrophthalic anhydride (MTHPA) showed that curing of C1 starts earlier than that of C2. DSC thermograms for the curing of C1P and C2P with benzoyl peroxide (BPO) and NMA/MTHPA showed two distinct exothermic peak positions, T p and T p′, due to the curing of esterified fraction and epoxy groups, respectively. The hydroxyl groups formed during partial esterification were found to catalyse the epoxy–anhydride reaction.

Kinetic Reaction Analysis of an Anhydride-Cured Thermoplastic Epoxy: PGE/NMA/BDMA

A comprehensive reaction analysis of a linear epoxy resin cured with an anhydride was performed to evaluate the reaction rate expressions. Monomers included phenyl glycidyl ether and methyl-5-norbornene-2,3-dicarboxylic anhydride or nadic methyl anhydride; the catalyst was N,N-dimethylbenzylamine; the initiator was n-propanol. Emphasis was initially placed on the molar dynamics of monomeric and oligomeric molecules. Molecular fractionations were achieved using reversed phase, high performance liquid chromatography. Chemical reaction rate constants were examined as a function of degree of polymerization. For the chain-initiated polymerization, the initiation rate constant was observed to be approximately 3 times greater than the propagation constant associated with oligomeric molecules. Both Poisson and Gold distributions were used to fit data. Examinations of polymeric fractions obtained by gel permeation chromatography in conjunction with a multiangle laser light scattering photometer revealed a minor si...

Preparation and performance of aluminum borate whisker–reinforced epoxy composites. I. Effect of whiskers on processing, reactivity, and mechanical properties

AbstractAluminum borate (Al18B4O33) whisker–reinforced composites based on a epoxy resin, which was made up of a trifunctional epoxy resin, TDE 85, and methyl nadic anhydride (MNA), were prepared, and the effects of the whiskers on the processing, reactivity, and typical mechanical properties of the composites were investigated. Two coupling agents, aluminate (DL411A) and borate (BE4), were used to surface treat the whiskers. Results show that the addition of the whiskers does not change the reactivity of the matrix, while increasing the viscosity of the resin, but when the whisker content is less than 5 wt %, the increased viscosity does not obviously influence the processing characteristics of the resin. Mechanical properties are greatly dependent on the chemistry and concentration of the coupling agent for treating the whiskers. A good coupling agent, which has good interaction with the whiskers and the matrix, can effectively improve the compatibility between the whiskers and the matrix, and thus result in great improvement of mechanical properties. BE4 proved to be better than DL411A for treating the whiskers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1950–1954, 2004

Modeling of Multi-Autocatalytic Cure Reactions of An Epoxy/Amine Terminated Polyetherimide/NMA System

Amine terminated polyetherimide (ATPEI) as a modifier for epoxy resin was synthesized, then blended with a diglycidyl ether bisphenol A (DGEBA)/nadic methyl anhydride (NMA)/catalyst. A study on cure kinetics and morphology was conducted for a blend of a DGEBA/NMA/Catalyst/ATPEI (5phr) system. In the curing process, two major reactions were observed. Each reaction was identified, and a novel model equation for the cure kinetics is suggested.

Study of the effect of BDMA catalyst in the epoxy novolac curing process by isothermal DSC

AbstractEpoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry

Characterization of cure reactions of anhydride/epoxy/polyetherimide blends

AbstractThe 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

A Syndrome of Joint Laxity and Impaired Tendon Integrity in Lumican- and Fibromodulin-deficient Mice

Lumican and fibromodulin regulate the assembly of collagens into higher order fibrils in connective tissues. Here, we show that mice deficient in both of these proteoglycans manifest several clinical features of Ehlers-Danlos syndrome. The Lum(-/-)Fmod(-/-) mice are smaller than their wild type littermates and display gait abnormality, joint laxity, and age-dependent osteoarthritis. Misaligned knee patella, severe knee dysmorphogenesis, and extreme tendon weakness are the likely causes for joint laxity in the double-nulls. Fibromodulin deficiency alone leads to significant reduction in tendon stiffness in the Lum(+/+)Fmod(-/-) mice, with further loss in stiffness in a Lum gene dose-dependent way. At the protein level, we show marked increase of lumican in Fmod(-/-) tendons, which may partially rescue the tendon phenotype in this genotype. These results establish fibromodulin as a key regulator and lumican as a modulator of tendon strength. A disproportionate increase in small diameter immature collagen fibrils and a lack of progression to mature, large diameter fibrils in the Fmod(-/-) background may constitute the underlying cause of tendon weakness and suggest that fibromodulin aids fibril maturation. This study demonstrates that the collagen fibril-modifying proteoglycans, lumican and fibromodulin, are candidate genes and key players in the pathogenesis of certain types of Ehlers-Danlos syndrome and other connective tissue disorders.

Relationship between viscoelastic properties and gelation in the epoxy/phenol-novolac blend system with N-benzylpyrazinium salt as a latent thermal catalyst

A study of viscoelastic properties and gelation in epoxy/phenol-novolac blend system initiated with 1 wt % of N-benzylpyrazinium hexafluoroantimonate (BPH) as a latent cationic thermal initiator was performed by analysis of rheological properties using a rheometer. Latent behavior was investigated by measuring the conversion as a function of curing temperature using traditional curing agents, such as ethylene diamine (EDA) and nadic methyl anhydride (NMA) in comparison to BPH. In the relationship between viscoelastic properties and gelation of epoxy/phenol-novolac blend system, the time of modulus crossover was dependent on high frequency and cure temperature. The activation energy (Ec) for crosslinking from rheometric analysis increased within the composition range of 20–40 wt % phenol-novolac resin. The 40 wt % phenol-novolac (N40) to epoxy resin showed the highest value in the blend system, due to the three-dimensional crosslinking that can take place between hydroxyl groups within the phenol resin or epoxides within the epoxy resin involving polyaddition of the initiator with BPH. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2299–2308, 2001

Toughening of tetrafunctional (TGDDM) epoxy resins with telechelic extended perfluoroligomers

Telechelic extended perfluoroether oligomers containing carboxylic acid terminal groups were found to be miscible in mixtures of a tetrafunctional epoxy resin (TGDDM) and methyl nadic anhydride. After curing the resin system remained transparent. SAXS examination revealed the presence of a two-phase morphology with domains of the order of 16–17 nm. The glass transition of the cured resin system showed a maximum at perfluoroether concentrations in the region of 5% and remained at about the same level as the unmodified system at concentrations as high as 20 wt %. The critical strain energy release rate (Gc) for these systems was found to increase very rapidly in the region of 5 to 15 wt % fluoroligomer to reach values about 8 times higher than those obtained for the control resin system. This was accompanied by a small reduction in modulus and yield strength. The main reason for the enhanced toughness, however, is attributed to the increased size of the yield zone at the crack tip. The fluoroligomer modified cured resin systems exhibited an unusual change in water diffusion characteristics. At about 15 wt % concentration of fluoroligomer modifier the diffusion coefficient increased by a factor of 70, while the equilibrium water absorption was reduced by more than 10 wt %.