Aspects of reproducibility and stability for partial cure of epoxy matrix resin

Partial cure of thermosets is a promising approach to enhance manufacturing possibilities of reinforced and unreinforced polymers. If partial cure is taken into consideration as a genuine process parameter, novel manufacturing technologies can be developed by exploiting the specific properties of incomplete polymer networks. A main concern in this context is to control the kinetic reaction avoiding inhomogeneous or instable degrees of cure. Based on a combination of numerical simulations and experiments, a methodology is presented that enables a systematic assessment of the reproducibility and stability of partial cure. Special attention is paid to the interaction of thermal boundary conditions and the cure kinetic of thick samples as well as the storability of partially cured resin under different conditions. Guidelines for cure cycle selection, mold design, and storage are derived. The possibility to use complex multistep cure schedules and extended storage periods is demonstrated for an unmodified noninhibited epoxy resin. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48342.