Physical aging of partially crosslinked RTM6 epoxy resin



The aging behavior of partially and completely crosslinked RTM6 epoxy resin samples in the glassy state is investigated by thermophysical and mechanical analyses. Curing degree, glass transition temperature, density, and micromechanical modulus are investigated as function of aging period, initial curing degree or depth below the sample surface. A clear increase of density and modulus with aging period as well as an enhanced surface stiffness is detected for all curing degrees. Also, the aging period necessary to achieve the steady state modulus is independent from the curing degree. In contrast, the degree of physical aging induced modulus changes shows a significant dependence on the curing degree. A discontinuity is detected in the so-called transition region, which is related to the transition from rubber to glassy state during crosslinking. This emphasizes the importance of curing history for physical aging processes and the high potential of partial curing for the development of new processing routes, in particular for production of samples with low sensitivity to physical aging. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41121.