Cure kinetics of multifunctional epoxies with 2,2′‐dichloro‐4,4′‐diaminodiphenylmethane as hardener

Self Cite

ABSTRACT:The nature of the substituent in 4,4Ј-bis-(diaminodiphenyl) methane (DDM) hardener on the cure kinetics, mechanical, and flame retardant properties of N,N,NЈ,NЈ-tetraglycidyl diaminodiphenyl methane (TGDDM) resin is investigated in comparison with unsubstituted DDM and widely used 4,4Ј-bis-(diaminodiphenyl) sulfone hardeners. Dynamic differential scanning calorimetry (DSC) and cure rheology studies showed that the substitution decreased the reactivity of the amine. An electron-withdrawing chlorine substituent was found to be more effective than an electronreleasing methyl group in reducing the amine reactivity. Substituted and unsubstituted DDM hardeners showed two peaks in their DSC thermograms that were due to steric hindrance in the former and deficiency of amine in the latter. Substitution showed its effect on the mechanical properties and glass-transition temperature. The flexural modulus was increased; however, the Izod impact and glass-transition temperature were decreased in substituted amine systems. The limiting oxygen index results showed higher flame retardancy in the chlorine substituted hardener system compared to other hardener systems that were studied.

Section: Resultsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of type of substitution in 4,4′‐bis‐(diaminodiphenyl) methane hardener on cure kinetics, mechanical, and flame retardant properties of tetrafunctional epoxy resins

Jagadeesh

Rao

2006

Self Cite

“…As we know, physical properties of cured epoxy resins are depended on their network structure, curing degree, curing time, and temperatures 8–11. Kinetic parameters relating to network formation can provide substantial information on the final structure of the network, properties, and material processibility.…”

Section: Introductionmentioning

confidence: 99%

Curing kinetics study of an epoxy resin system for T800 carbon fiber filament wound composites by dynamic and isothermal DSC

Chen

et al. 2007

Curing kinetics of DGEAC/DDM/DETDA/ DGEB epoxy resin system was studied using dynamic and isothermal differential scanning calorimetry (DSC) for the preparation of T800 carbon fiber filament wound composites. In dynamic experiment, four kinds of epoxy resin systems were studied. Curing characteristics, such as curing range and curing temperatures of the epoxy resin system with mixed hardeners (DGEAC/DDM/DETDA), were found lying within those of the two epoxy resin systems with a single hardener (DGEAC/DDM, DGEAC/DETDA). The addition of reactive diluter (DGEB) caused increase in curing range and exothermic heat. In addition, the activation energies calculated by the isoconversional method of all four resin systems decreased to the minimum value in the early stage due to the autocatalytic role of hydroxyl groups in the curing reaction and then increased due to the increased viscosity and crosslink of epoxy systems. The addition of reactive diluter led to the decrease in activation energies on the initial stage (conversion 5 0.1-0.3). In isothermal experiment, a series of isothermal DSC runs provided information about the curing kinetics of the DGEAC/DDM/DETDA/ DGEB system over a wide temperature range. The results showed that the isothermal kinetic reaction of the epoxy resin followed an autocatalytic kinetic mechanism. The autocatalytic kinetic expression chosen in this work was suitable to analyze the curing kinetics of this system.

“…On the basis of the resin systems, different models could be used. The first‐order reaction, the n th order reaction, and autocatalytic reaction models have all been used to simulate the dynamic curing process 11, 12, 5. The kinetic parameters, such as the preexponential factor and activation energy, could be determined either by the Kissinger and Ozawa method13, 14 or by the Borchardt and Daniels method 15…”

Section: Introductionmentioning

confidence: 99%

Dynamic modeling of curing process of epoxy prepreg

Sun

Pang

Sterling

et al. 2002

ABSTRACT:The dynamic curing process was studied by using differential scanning calorimetry (DSC) and modeled by two methods. One was based on the Kissinger and Ozawa approach, in which the activation energy was taken as a constant for all the heating rates. The whole curing process was modeled with two cure reactions. Reaction 1 exhibited the behavior of the autocatalytic reaction, whereas Reaction 2 was the nth order reaction. The effect of heating rate on the preexponential factor A 1 of Reaction 1 was apparent. As the heating rate increased, the A 1 decreased. There was no significant effect of heating rate on the preexponential factor A 2 of Reaction 2 and the reaction orders for both reactions. The calculated results showed that the contributions of these two reactions to the total curing process were very different and changed with the heating rate. Except in the early cure stage, the calculated total degree of cure agreed well with the experimental data. Another method was based on the Borchardt and Daniels kinetic approach, where the activation energy of the cure reaction at each heating rate was determined separately. The whole curing process was modeled with one autocatalytic reaction. The fitting results showed that both preexponential factor and activation energy increased with the increment of the heating rate. As in the first method, the effect of heating rate on the orders of reaction was very small. The calculated results agreed well with experimental values in the early cure stage.