Epoxy-amine Reaction Research Articles

Synergetic catalytic effect of carbon nanotubes and polyethersulfone on polymerization of glassy epoxy-based systems – isothermal kinetic modelling

The effect of multiwalled carbon nanotubes (MWCNTs) and polyethersulfone (PES) on the polymerization kinetics of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenyl-methane epoxy resin (TGMDA) and 4,4diaminodiphenyl-methane-methylenebis(2,6-diethylaniline) hardener (MDEA) was studied by means of isothermal differential scanning calorimetry. The autocatalytic (Kamal–Sourour) model was applied to fit the experimental values of epoxy conversion and the total reaction order of 3 with partial orders m and n both equal to 1.5 were found. PES alone did not have any significant effect on epoxy crosslinking kinetics due to its phase separation at the beginning of the epoxy–amine reaction. The presence of MWCNTs substantially increases the epoxy reaction rate but lowers the final epoxy conversion. The important synergetic catalytic effect of MWCNTs and PES on the epoxy kinetics was observed.

New reversed-phase/anion-exchange/hydrophilic interaction mixed-mode stationary phase based on dendritic polymer-modified porous silica

A novel dendritic polymer-modified silica (DPS) stationary phase was prepared by a divergent synthesis scheme starting from propylamine on silica by consecutive amine-epoxy reactions with 1,4-butanedioldiglycidyl ether and aniline. Both elemental analysis and infrared spectra data shows the successful growth of dendritic polymer on silica particles. The carbon and nitrogen contents increased with an increasing number of reaction cycles and achieved 25.2% and 2.1% (w/w) after 11 reaction cycles. The combination of a phenyl ring with a quaternary ammonium, or a tertiary amine at the branch point along with embedded polar functionalities (including ether and hydroxyl groups) in the branch, generated hydrophobic, electrostatic, as well as hydrophilic interactive domains. Depending on solute structure and mobile phase composition, the DPS stationary phase provided multiple retention mechanisms, including reversed phase (RP), anion-exchange (AEX), and hydrophilic interactions. The RP capability achieved separation of polycyclic aromatic hydrocarbons. Basic, neutral and acidic molecules were well separated under RP/AEX mixed mode. Effective separation of small polar compounds (such as nucleobases and nucleosides) was also obtained under hydrophilic interaction liquid chromatography (HILIC) mode.

Cure kinetics of several epoxy–amine systems at ambient and high temperatures

Epoxy-crosslinker curing reactions and the extent of the reactions are critical parameters that influence the performance of each epoxy system. The curing of an epoxy prepolymer with an amine functional group may be accompanied by side reactions such as etherification. Commercial epoxy prepolymers were cured with different commercial amines at ambient as well as at elevated temperatures. Singularly, only epoxy–amine reactions were observed with diglycidyl ether of bisphenol-A (DGEBA)-based epoxides in our research even upon post-curing at 200°C. Etherification side reaction was found to occur at a cure temperature of 200°C in epoxides possessing a tertiary amine moiety. A combined goal of our research was to understand the effect of tougheners on the cure of epoxy–amine blend. To discern the effect of tougheners on the cure, core–shell rubber (CSR) particles were incorporated into the epoxy–amine blend. It was observed that CSR particles did not restrict the system from proceeding to complete reaction of epoxy moieties. Besides, CSR particles were found to accelerate the epoxy-amine reaction at a lower level of epoxy conversion. The lower activation energy of epoxy–amine reaction of CSR incorporated system compared to control supported the catalytic effect of CSR particles on the epoxy-amine reaction of epoxy prepolymer and amine blends.

New prospects for the synthesis of N-alkyl phosphonate/phosphonic acid-bearing oligo-chitosan

Water-soluble oligo-chitosan were functionalized with N-alkyl phosphonate/phosphonic acid groups via Kabachnik-Fields and epoxy-amine reactions.

Parallel synthesis of polymers from epoxy-amine reaction for gene delivery

Parallel synthesis of polymers from epoxy-amine reaction for gene delivery

Preparation and Characterization of Bio-Hydrogels for Biomedical Engineering

In this work, a new crystalline PEO cross-linked CD films combining PEO and CDs (α-CD and β-CD) was prepared, and their compositions (CD/PEO; wt/wt) ranging from 1/99 to 6/94. The hydroxyl groups of PEO withMnof 20,000 were converted to chlorine groups through reaction with thionyl chloride. PEO cross-linked CD films with various compositions were successfully prepared via the epoxy-amine reaction between amino-CD and PEO-epoxy. The thermal and swelling behavior were studied for the PEO cross-linked CD films. It was found that the cross-linked PEO films form hydrogel in water, achieving a swelling ratio higher than 20 times of original weight. The swelling properties of these cross-linked films depend on the fraction of CDs. The crystallinity of these films was very high, and crystallization rate of PEO was accelerated by cross-linking with CDs.

Solution processable silica thin film coating on microporous substrate with high tortuosity: application to a battery separator

A novel approach to incorporate a conformal inorganic thin layer inside 3D microporous polyolefin film is realized from a versatile solution process and applied to the preparation of a Li-ion battery separator with enhanced thermal and dimensional stability. Inorganic thin film thickness of around several tens of nanometers inside 3D micropores of a polyolefin could be systematically controlled by employing a mixed system of the silanization and epoxy–amine reaction of the UV-curable polymer and the plasma/UV ozone surface treatments. The surface-modified commercialized polyolefin separators with silica layers from the solution process show greatly improved thermal and dimensional stability compared to neat polyolefin separators, while maintaining charging/discharging performances of neat polyolefin separators, such as ionic conductivity, C-rate, and cycle life. Because of the conformal coating of the inorganic thin film inside the 3D polyolefin separator, the polyolefin separator maintains its initial dimension at high temperature, even above its melting point, which will result in improved safety of the Li-ion battery.

Interpretation of Gel Points of an Epoxy-Amine System Including Ring Formation and Unequal Reactivity: Measurements of Gel Points and Analyses on Ring Structures.

Gel points are investigated as the critical extent of reaction at gelation by FT-IR and viscoelastic measurements for the network formed by the epoxy–amine system. The reaction systems examined are comprised of diglycidyl ether of bisphenol A (DGEBA) and polyoxypropylene (POP) diamine of different chain lengths with various degrees of dilution. The experimental results are obtained as the delay of gel point, that is the delay from the gel point expressed by the Flory–Stockmayer formula, and interpreted in terms of ring formation caused by intramolecular reaction which is characterized by the ring forming parameter of λ0. This parameter relates with the internal concentration (in mol L–1) of reactive groups Pab, for RAfa + R′Bfb type polymerization. The analyses of the conversion curve (p vs t curve, where p denotes the extent of reaction) obtained by FT-IR measurement are carried out on the basis of the kinetic model of the epoxy-amine reaction to find the ratio of rate constant. For all the reaction syst...

Synthesis and Characterization of Thermally and Chemically Gelling Injectable Hydrogels for Tissue Engineering

Novel, injectable hydrogels were developed that solidify through a physical and chemical dual-gelation mechanism upon preparation and elevation of temperature to 37 °C. A thermogelling, poly(N-isopropylacrylamide)-based macromer with pendant epoxy rings and a hydrolytically degradable polyamidoamine-based diamine cross-linker were synthesized, characterized, and combined to produce in situ forming hydrogel constructs. Network formation through the epoxy-amine reaction was shown to be rapid and facile, and the progressive incorporation of the hydrophilic polyamidoamine cross-linker into the hydrogel was shown to mitigate the often problematic tendency of thermogelling materials to undergo significant postformation gel syneresis. The results suggest that this novel class of injectable hydrogels may be attractive substrates for tissue engineering applications due to the synthetic versatility of the component materials and beneficial hydrogel gelation kinetics and stability.

Curing Characterization of the Bis-salicylaldehyde-triethylenetetramine Nickel (II)/Epoxy System

The curing reaction of epoxy resin and bis-salicylaldehyde-triethylenetetramine nickel (II) (Ni(sal)2trien) was investigated using differential scanning calorimetry (DSC), UV-vis spectrometer and FT-IR. DSC measurement showed two distinct exothermic peaks on the curing curves, indicating that the reaction consisted of two reactive species. The first peak at low temperature corresponded to the amine-epoxy reaction with the activation energy of 46.85 kJ · mol−1 and the second peak corresponded to the hydroxyl-epoxy reaction with the activation energy of 74.23 kJ · mol−1. As the concentration of Ni(sal)2trien increased, the amine–epoxy reaction was favored, and the temperature of the hydroxyl-epoxy reaction decreased at the same time.

Effects of octa(3-chloroammoniumpropyl)octasilsesquioxane on the epoxy self-polymerisation and epoxy–amine curing

The effect of quaternary ammonium functionalised polyhedral oligomeric silsesquioxane (POSS) on the self-polymerisation of the diglycidyl ether of bisphenol A (DGEBA) and on the DGEBA–Jeffamine-T403 curing was investigated by differential scanning calorimetry. The acidic ammonium groups of POSS were found to catalyze the self-polymerisation of DGEBA but termination reactions severely compete with the propagation and only low conversions in epoxy groups are attained (<20%). A reaction between POSS and DGEBA was revealed at the POSS–matrix boundary suggesting the release of amino functionality of POSS during thermal cure. The catalytic effect of POSS over the epoxy–amine reaction was also demonstrated. The efficiency of this catalytic effect was found to be significantly dependent on the processing conditions. Finally, two competitive effects were found to affect the glass transition temperature of POSS modified epoxy networks cured under dynamic conditions. It is proposed that the inclusion of POSS at the nanometer scale is responsible for the increase in free volume of the system which results in the depression of T g's while a restriction effect of POSS cages on polymer chain motions (enhanced T g's) is associated to the development of POSS aggregates in the networks with high POSS loadings.

Rate equations in the study of the DSC kinetics of epoxy-amine reactions in an excess of epoxy

We show in this work that the heat flow signal as acquired applying DSC to systems in an excess of epoxy must be proportional to the rate of consumption of the excess component but not to the rate of reaction. The rate equations reasoning from this finding have been analysed. According to the model, a DSC data set monitoring the reaction progress of an epoxy excess system must be identical to that exhibiting the reaction advance of the formulation at stoichiometry. Experimental data confirming the proposed methodology have been presented. Both non-isothermal and isothermal DSC experiments support adequately the model. The non-linear transform from the excess component measurement into the reaction rate expression has been also commented in the study from the point of view of the kinetics.

Characterization and modelling of diffusion and reaction of low molecular weight reactants in molten polymer

A model reactive system was defined for studying experimentally and by simulation the competition between reaction and diffusion of two low molecular weight reactants, 2,3-epoxypropyl-phenylether (EPPE) and dipentylamine (DPA). Both reactants are miscible in a high-viscous molten polymer, poly(ethylene-co-vinyl acetate) (EVA). The comparison of the experimental rates of reaction for initially homogeneous samples and bi-layer unpremixed samples proved that the reaction was diffusion controlled. A kinetic model of the epoxy–amine reaction was coupled to mutual diffusion coefficients of reacting species in a transport model and the simulations were compared with experimental results. The diffusion/reaction process was finally related to typical mixing conditions encountered in reactive polymer processes. For the model reactive system, the simulations have established that actual mixing conditions with shear rate values encountered in polymer processing machines, were able to homogenize the system in less than 10s. In other words, the reaction should no longer be controlled by molecular diffusion as soon as a relatively low intensity mixing is applied (shear rate>10s−1).

Kinetic Analysis of Isothermal and Nonisothermal Epoxy‐Amine Cures by Model‐Free Isoconversional Methods

AbstractModel‐free and model‐fitting kinetic approaches were applied to isothermal and nonisothermal DSC data on epoxy cure. The dependence of the effective activation energy on the extent of cure was determined using integral and differential isoconversional methods. A different shape of the dependence in the kinetically controlled regime (α &lt; 0.4) was found when compared to the dependence typically reported for epoxy‐amine systems. This result was shown to arise from the presence of low amounts of bisphenol A in the present epoxy that are efficient catalysts for epoxy amine reaction. A model‐free method prediction of isothermal cure from isothermal data has also been considered.magnified image

On the effect of montmorillonite in the curing reaction of epoxy nanocomposites

The procedure for the fabrication of epoxy-based polymer layered silicate nanocomposites is important in respect of the nanostructure that is developed. To further our understanding of this, the influence of an organically modified clay (montmorillonite, MMT) on the curing kinetics of an epoxy resin has been studied by differential scanning calorimetry. Clay loadings of 10 and 20 mass% are used, and isothermal as well as dynamic cures have been investigated. For both cure schedules the effect of the MMT is to advance the reaction. Kinetic analysis yields values for the activation energy, but shows that the reaction cannot be described simply by the usual autocatalytic equation. The glass transition of the cured nanocomposites is lower than that for the cured neat resin, a result that is attributed to homopolymerisation taking place in addition to the epoxy–amine reaction.

Investigation of the microwave curing of the PR500 epoxy resin system

Microwave heating has been used to cure a resin system, PR500 (3M). The same resin has been cured using a conventional oven. The cured resins have been compared using a number of techniques including modulated differential scanning calorimetry (MDSC), dynamic thermal analysis, infrared spectroscopy (IR) and solid-state NMR spectroscopy. The reaction path appears to be slightly different depending upon the nature of the heating. The epoxy-amine reaction occurs to a greater extent than the epoxy-hydroxyl reaction in the microwave cured resin compared to the thermally cured resin. The dielectric properties for the thermally and microwave cured materials were measured for degrees of cure greater than 75% and over this range are similar for materials cured by the two techniques and thus not sensitive to this change. Broadening of the glass transition for microwave-cured epoxy resins was observed. Since the IR and solid-state NMR results show small differences as does the DMA behaviour of materials cured using the two routes the broadening is attributed to a difference in network structure.

Kinetic method by using calorimetry to mechanism of epoxy-amine cure reaction

Four epoxy-amine reactions differing a number of the functional groups are compared. It has been shown that the main features of kinetics are similar for a whole family of model reactions. In series of epoxy-amine reactions analyzed, the reaction between resorcinol diglycidyl ether and m-phenylenediamine is one where increasing the viscosity of the reaction mixture leads to its vitrification during the reaction. This reaction proceeds very rapid compared with the model reactions. We demonstrate that application of kinetic techniques to analytical problems is facilitated by an understanding of the reaction mechanism involved. We report that thermokinetic method can be used for finding the activation energy in similar epoxy-amine systems through the use of times to point of the maximum in the experimental curve of the heat release rate vs. time. Our results indicate that independent of the initial reagent ratio, the conversion at the peak rate in the total curve the heat release ranges from 47 to 49%.

Isoconversional kinetic analysis of stoichiometric and off-stoichiometric epoxy-amine cures

The curing reaction of stoichiometric and off-stoichiometric diglycidyl ether of bisphenol A (DGEBA) and 1,3-phenylene diamine ( m-PDA) mixtures was studied by differential scanning calorimetry, thermogravimetric analysis and rheological measurements. In order to highlight the side reactions such as etherification and homopolymerization, the neat DGEBA and DGEBA/DMBA ( N, N-dimethylbenzylamine) mixture were examined. The classical model-fitting and the advanced isoconversional methods were used to determine the activation energy of the different reactions. The advanced isoconversional method leads to a good agreement between isothermal, nonisothermal and rheological results. The effective activation energies of primary amine epoxy reaction, etherification and homopolymerization were estimated to about 55–60, 104 and 170 kJ mol −1, respectively.

Kinetic method by using calorimetry to mechanism of epoxy-amine cure reaction

A combination of kinetic method and DSC measurements was used to examine the system of resorcinol diglycidylether-aniline. The purpose of this study is to obtain information about linear polycondensation in epoxy-amine system. The reaction of resorcinol diglycidylether (RDGE) with aniline falls into the family of epoxy-amine reaction mixtures, within of which the functional groups varies only. The molar heats and the rate constants for the three pathways were evaluated by nonlinear regression analysis of the data assuming that reaction mechanism proposed for simple molecular epoxy-amine system such as phenylglycidylether-aniline would be operative in the reaction between resorcinol diglycidylether and aniline. A feature of the present reaction system is that it proceed through the structural changes occurred with the heat effect. The loss of catalytic activity by the molecules of the reaction product was used as indicator for the structure forming in the reaction medium.

Formation and structure of epoxy network interphases at the contact to native metal surfaces

Abstract Films (20 nm d EP For the films , IR spectroscopy reveals the chemistry as a function of d EP . Curing is based on amine-epoxy reactions only. Compared to the bulk, the gross reaction rate slows down for the RT-curing. A metal-specific ‘chemical interphase’ with reduced epoxy group consumption extends over some 100 nm. Post-curing (393 K, 1 h) is not sufficient to consume all epoxy groups. Brillouin spectroscopy and microscopy provide local mechanical stiffness data ( c 11 ) with better than 10-μm resolution. The RT-cured films possess mechanical heterogeneities on the sub-mm scale. Their glass temperature is well below RT for most films while T G bulk = 326 K. In the adhesive joints , ‘mechanical interphases’ are detected on the metal side with an unexpected width of up to some 100 μm and with a c 11 -maximum inside the epoxy. Its shape, height and position depend on the metal and the epoxy curing state. It is interpreted as the result of competing influences from epoxy structure and internal stresses. During polymerisation, a ‘morphological interphase’ should form with a 3-dimensional heterogeneous structure that is specific for the metal and the route of compound formation. Hence, the properties of thin films are not generally equivalent to the situation in thick adhesive bonds. To cite this article: W. Possart et al., C. R. Chimie 9 (2006) .