Reaction-induced phase separation mechanisms in modified thermosets

Control of pore size in epoxy systems.

“…In fact, in many of the previous CIPS studies, such as those by Gan et al [31], Girard-Reydet et al [27], Inoue et al [21,22], and Remiro et al [32], SD is seen at early stages of growth, and often continues to be present, leading to co-continuous morphology even in late stages of growth. In the images obtained here, SD does not manifest at any point (as far as we could observe, there was no intermediate morphology in the transition from nano-sized pores to no pores).…”

“…The former is confirmed by the high fraction of octadecanol that remains in the continuous matrix even after slow cure (10-25 % of the original amount of octadecanol). The relatively large size of the alcohol, while having a negative influence on inter-diffusion rates, is shown to be a minor factor by studies that have shown high-molecular weight polymers to have the capability to phase separate into a co-continuous morphology [32,27,22]. Similar cases to the present, where NG is the only visible morphology throughout the curing process, were found by Okada et al [33], Kiefer et al [26,34], Siddhamalli et al [35], and Inoue [22].…”

“…Also critical in the TIPS of block copolymers is the distinction between spinodal decomposition (SD) or nucleation and growth (NG), where the former is induced by a sudden large change in temperature or composition and leads to a bicontinuous network, and the latter is induced by slow changes and leads to spherical inclusions in a continuous matrix [25]. In CIPS, both SD and NG are accessible [22,26,23,27], and selection between these two routes depends on three factors: phase separation rate (driven by thermodynamics), reaction rate, and chain mobility (rate of interdiffusion). In general, as the ratio of phase separation rate to reaction rate increases, NG is more likely; and as chain mobility decreases relative to phase separation rate, SD is more likely.…”

High Performance Thermoplastic/Thermosetting Composites Microstructure and Processing Design Based on Phase Separation

“…Good combination of TP/TS with proper miscibility and cure cycle can display synergistic toughening effect. Since the mechanical properties of the toughened materials are closely related to their final morphologies, many studies have been focused on the qualitative or pseudo-quantitative thermodynamic and kinetic analysis of the phase separation mechanism (Girard et al, 1998;Gan et al 2003;Zucchi et al,2004) and morphological microstructure control as we will describe in next sections. At the same time, lots of the researches on the CIPS are limited to academic concern, the control of the morphology during cure cycle of commercial application targeting predefined mechanical properties is to be disclosed.…”

“…rheology Zhang et al, 2006;Bonnet et al, 1999), small angle light scattering (SALS) and turbidity (Girard et al, 1998). Rheology can measure certain abrupt mechanical change upon phase separation, while SALS and turbidity trace the change of the optical mismatch between TP and TS rich domains during phase separation.…”