J. Eloundou, M. Feve, J. Gérard
Oct 7, 1996
Citations
0
Influential Citations
60
Citations
Journal
Macromolecules
Abstract
A flexible epoxy−amine system based on the diglycidyl ether of 1,4-butanediol (DGEBD) and 4,9-dioxa-1,12-dodecanediamine (4D) was studied between 40 and 70 °C by rheological and viscosimetric methods near the gel point. This temperature domain is located well above the maximum glass transition temperature of the fully cured network, for which Tg∞ = −12 °C. At the gel point, the theoretical extent of reaction, xgel, is equal to 0.5745, considering the reactivity ratio, n, of the secondary amines to the primary ones equal to 1.1 (equireactivity, n = 1). For the times corresponding to xgel, the rheological curves follow a classical behavior, i.e., (i) divergence of the viscosity in steady flow conditions, (ii) crossover of the tan δ curves measured as a function of time at several frequencies, and (iii) proportionality between G‘ and G‘‘ and the pulsation ωΔ (G‘(ω) and G‘‘(ω) are proportional to ωΔ). Above 50 °C, the exponent, Δ, is constant and equal to the average value of 0.70 ± 0.02. The width of the rel...