Phase-separation process in a poly(methyl methacrylate)-modified epoxy system: A novel approach to understanding the effect of the curing temperature on the final morphology

摘要

In this study, the physical and chemical changes of a poly(methyl methacrylate) (PMMA)-modified epoxy system were examined to understand the effect of the curing conditions on its final morphology. The curing process of the PMMA-epoxy reactive system was complementarily analyzed by Fourier transform infrared spectroscopy in the near range (FT-NIR) and fluorescence spectroscopy. The relationships among (1) the chemical conversion of the curing reaction, (2) the first moment of the fluorescence emission band (hmi) arising from a chromophore chemically bonded to the epoxy reactive system, (3) the phase-separation process, and (4) the dynamics of the epoxy thermoset during its curing process are discussed. From a chemical point of view, FT-NIR did not reveal any significant change in the curing reaction with the presence of 2 wt % PMMA. However, in terms of physical changes, the analysis of the fluorescence response clearly showed variations in the curing reaction due to the presence of the thermoplastic polymer. Also, fluorescence allowed the estimation of the glass-transition temperature of the system with curing when the reaction was diffusioncontrolled, whereas Fourier transform infrared spectroscopy was not sensible enough. In the second part of this study, scanning electron microscopy images of the PMMAmodified epoxy system were analyzed to understand the effect of the temperature on the final morphology when the amount of thermoplastic was below the critical volume fraction. A linear dependence between the inverse of the mean area of the thermoplastic-rich domains and the inverse of the absolute temperature was obtained.