Epoxy Amine-Cured

Figure 1. Three main epoxy - amine curing reactions.

Figure 2. Mechanism and reaction rates for the epoxy - amine cure.

Epoxy (Amine-Cured) Bisphenol A-based epoxy resins used for composite fabrication are commonly cured with multifunctional primary amines. For optimum chemical resistance these generally require a heat cure or postcure. The cured resin has good chemical resistance, particularly to basic environments, and can have good temperature resistance. 

Various isothermal DSC studies on epoxy-amine cure have been reported in which the kinetic data are fitted to a generalised form of Equation (4-10) ... 

Figure 3. Effect of EME 58 (58 wt% mercaptoester units co-polymer) coupling agent concentration on the peel strength of flexible epoxy (amine-cured)/AD = acetone-degreased steel test panels following (a) I day and (b) 3 day exposure to 57°C condensing humidity. See Appendix 4 for epoxy resin and cure description.

Sequential Processes. In many cases (anhydride cured-epoxies, amine-cured epoxies, etc.), thermal degradation curves, for instance gravimetric ones, exhibit two distinct stages (Lehuy et al., 1991). The first one corresponds to a relatively fast, pseudo-first-order process, whereas the sec-... 

Uncoated iron Cellulose acetate butyrate Epon 828/V125 Epoxy amine curing agent Shell/General... 

When time rather than temperature is the variable, the reaction kinetics must be considered. As noted earlier, the epoxy-amine cure is autocatalyzed, and consequently, the maximum rate of reaction occurs at about 30 to 40% conversion. Therefore, the time rate of change of Tg also reaches a maximum at these conversions, as demonstrated by Huguenin and Klein48. Furthermore, as cure proceeds, the difference T — Tg decreases, and the conductivity becomes more sensitive to changes in Tg, as illustrated in Fig. 29. 

The kinetically controlled processes determined by the above sets of differential equation can be simulated by Monte Carlo methods The species characterized by X and a vector 1 for the number of groups differing in reactivity or vectors x and 1 are stored in the computer memory and the random numbers select the reaction partners. It is necessary to examine the dependence of the results on the number of monomer units used in simulation. Recently, the application of this approach was reported also for epoxy-amine curing... 

Asphalt, unmodified Coal tar Coal tar— epoxy Coal tar— urethanes Epoxy phenolic- baked Epoxy amine- cured Epoxy ester Furfuryl alcohol Phenolics, baked Polyesters (unsatu- rated) Polyvinyl chloracetates Vinyl ester Urethanes Vinylidene chloride Chlorinated rubber... 

Bailey, M.A., Cauffman, T. and Costin, R. (1996) New developments in acrylates modified epoxy-amine cure coatings, paper presented at FCST International Coatings Technology Conference, 23 October, 19%. 

Epoxy-Amine Curing System Before Gelation. 179... 

In one of the earliest analyses of cure kinetics by DSC, Horie et al. (1970) derived a kinetic relationship for epoxy-amine cure assuming near-equal reactivity of primary and secondary amines and no other reactions. This was later refined for a stoichiometric epoxyamine system (Sourour and Kamal, 1976) and takes the form... 

Figure 3.19 Crosslinking polymers using epoxy-amine-cured reactions.

Figure 18. Ea dependencies for Figure 19. Effect of a nitro-group in thermal (squares) and thermo- amines on the Ea values for the oxidative (pentagons) degradation of epoxy-amine curing reaction. poly(styrene)...

Theoretical study on mechanisms of the epoxy-amine curing reaction. Macromolecules, VoL40, No.l2, (2007), pp.4370-4377, ISSN0024-9297. 

Vyazovkin, S. Sbirrazuoli, N. (19%). Mechanism and kinetics of epoxy-amine cure studied by differential scanning calorimetry. Macromolecules, Vol.29, No.6, (March 19%), pp. 1867-1873, ISSN 0024-9297. 

Calorimetry Semibatch emulsion polymerization of VAc/BA [66, 67] Epoxy-amine curing polymerization [86] Non-invasive, robust and almost continuous/ Requires state estimators and the values of the reactivity ratios for multimonomer systems All polymerization techniques... 

The amount of vitrified material is raised from 10% to 50% over less than 2°C in the case of the epoxy-amine cured at 0.2°C min a more than 4°C temperature rise is necessary for the epoxy-anhydride cured at... 

Pig. 4. A series of DSC temperature scans at 10°C/min of an epoxy—amine cured isother-mally at 160 0 for different times, showing Tg increasing and the residual exotherm decreasing with increasing cure times. From Ref 40. 

The microwave and thermal cure processes for the epoxy-amine systems (epoxy resin diglycidyl ether of bisphenol A, DGEBA) with 4,4 -diaminodiphenyl sulfone (DDS) and 4,4 -diaminodiphenyl methane (DDM) were investigated for 1 1 stoichiometries by using fiber-optic FT-NIR spectroscopy. The kinetic rate parameters for the consumption of amines were determined by a least squares curve fit to a model for epoxy/amine cure. The activation energies for the polymerization of the DGEB A/DDS system were determined for both cure processes and found to be 66 and 69 kJ/mol for the microwave and thermal cure processes, respectively. No evidence was found for any specific effect of the microwave radiation on the rate parameters, and the systems were both found to be characterized by a negative substitution effect [99]. 

Grob et al. [172] have reported the analysis of polyols in a pilot plant operation using a fibre optic transmission probe. Free epoxide (unreacted) and hydroxyl number were monitored to enable cost and safety control during full-scale production. The feasibility of NIR-ATR spectroscopy for the in situ characterisation of epoxy/amine cure reactions has been demonstrated [173]. 

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