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Study on curing of novolac epoxy resin

Polyamide hardener systems

Journal of Thermal Analysis and Calorimetry
Authors: J. P. Agrawal, N. M. Bhide, and S. R. Naidu

The optimization of proportions of novolac epoxy resin, Dobeckot E4 and polyamide hardener, EH411 has been established by DSC and the data indicates that resin-polyamide, 100∶40 and 100∶50, appear to be optimum where ‘extent of cure’ is maximum. The kinetic parameters for these formulations have been evaluated using isothermal and dynamic modes by employing DSC.

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The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict the gel time t g and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation time t gand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent activation energy of the cure reaction after gelation point. There is no special curing process required for the formation of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite.

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Summary A kinetic study of cure kinetics of epoxy resin based on a diglycidyl ether of bisphenol A (DGEBA), with poly(oxypropylene) diamine (Jeffamine D230) as a curing agent, was performed by means of differential scanning calorimetry (DSC). Isothermal and dynamic DSC characterizations of stoichiometric and sub-stoichiometric mixtures were performed. The kinetics of cure was described successfully by empirical models in wide temperature range. System with sub-stoichiometric content of amine showed evidence of two separate reactions, second of which was presumed to be etherification reaction. Catalytic influence of hydroxyl groups formed by epoxy-amine addition was determined.

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In order to expand the industrial usefulness of an isothermal time-temperature-transformation (TTT) cure diagram, a method to make it applicable to a solid-state sample involving only resins and a catalyst was studied by using dynamic DSC (DDSC) and cone plate dynamic mechanical analysis (DMA). To estimate how much curing occurred for an industrially used epoxy resin molding compound manufactured in a production process was also studied, together with its position in the TTT cure diagram. The TTT cure diagram proved to be useful for determining the differences between compounds without their dissolution in a solvent, and for estimating their heat history during the production process.

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With the aid of thermal analysis, epoxy (EP) resins have been characterized from the curing of the components all the way to disposal. The methods employed for the investigations were DSC, TMA, DMA, TG and TG-QMS. The experimental results obtained will be used here to demonstrate the typical possibilities offered by these methods for characterization of an epoxy resin from cradle to grave.

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Three types of commercially available organophilic Montmorillonite (Cloisite 30B, 25A and 15A) were used to prepare VARTM epoxy resin nanocomposites in order to study the effect of the nanoclay organophilic modification on the epoxy matrix. The morphology of the dispersions was investigated through XRD and TEM analyses. The thermal stability of the nanocomposites was studied by means of HI-RES TG measurements and the influence of the nanoclay on the viscosity of the resin was investigated through rheological measurements. It was found that the nanoclay modification had no significant influence on the dispersion and on the thermal properties of the nanocomposites. Areas of exfoliated and intercalated morphology were observed. The viscosity of the resin furthermore did not exceed the critical value of the infusion process.

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Introduction Epoxy resins are an important class of polymeric materials, characterised by the presence of more than one three-membered ring known as the epoxy (“epoxy” is derived from the Greek prefix “ep,” which means over and

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Introduction Epoxy resins are extensively used in surface coatings, adhesives, laminating, castings, matrices for advanced composites, electronic encapsulation materials, sealants, etc., due to their vast formulation

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Introduction Epoxy resin is one of the most important polymeric materials widely used in the polymer industry as coatings, structural adhesives, insulating materials, and polymeric composite materials, etc. [ 1 – 3 ]. The

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Introduction Epoxy resin is one of the most used thermosetting polymer matrix for its good mechanical strength and corrosion resistance. It plays an important role in industry. As a matrix of composites, the curing course of

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