Abstract: Here we examined an epoxy binder based on the ED-20 resin and the Ethal-M7 hardener of an amine type. This study
was aimed at exploring the rheological, physicomechanical and thermomechanical behavior of Ethal-M7-based binder specimens
cured at different modes. The initial viscosity of the binder and the viscosity variation were measured on a rotation viscometer as per
GOST 25276-82. The glass transition temperature was measured by the TMA technique pursuant to GOST 32618.2-2014; the degree
of polymerization and the glass transition were determined by the DSC technique as per GOST R 57687-2017 and GOST R 55135-
2012, respectively. The tensile strength was measured by GOST 11262-2017. The rheological study results for the binder
demonstrated that it had an initial viscosity of 2.75 Pa∙s, was low active at room temperature, and could be processed for 2.5 h. The
binder had a fairly good tensile strength of 69.5 MPa after 4-h curing at 60 °С, keeping up with other composites in the same class.
The TMA analysis showed that the binder based on curing agent Ethal-M7 had two glass transitions: the first one was basic, ranging
from 52 to 66 °С, and the second one was between 83 and 108 °С. The glass transition temperature after 3-day curing at room
temperature ranged from 56 to 62 °С, and after 12 days, from 53 to 66 °С. Following 2-h curing at 23 °С and then 4-h curing at 60
°С, the temperature transition increased to 73–80 °С; the second peak did not show up. The DSC analysis of the binder cured in the
mode of 2 h at 23 °С + 4 h at 60 °С demonstrated that the first endoeffect corresponded to the glass transition temperature of 79.8 °С,
while the second endoeffect at 120.3 °С pertained to the second glass transition temperature.
Index terms: epoxy binders, amine hardener, Ethal-М7, Ethal-45М, Ethal-23Х, TMA, DSC, strength, tension, glass transition temperature, curing, degree of polymerization.