In situ detection of the onset of phase separation and gelation in epoxy/anhydride/thermoplastic blends

Abstract

The isothermal cure reactions of blends of epoxy (DGEBA, diglycidyl ether of bisphenol A)/anhydride resin with polyamide copolymer (poly(dimmer acid-co-alkyl polyamine)) or PEI were studied using differential scanning calorimetry (DSC). Rheological measurements have been made to investigate the viscosity and mechanical relaxation behavior of the blends. The reaction rate and the final cure conversion were decreased with increasing the amount of thermoplastics in the blends. Lower values of final cure conversions in the epoxy/thermoplastic blends indicate that thermoplastics hinder the cure reaction between the epoxy and the curing agent. Complete miscibility was observed in the uncured blends of epoxy/thermoplastics up to 120 o C but phase separations occurred in the early stages of the curing process at higher temperatures than 120 o C. According to the rheological measurement results, a rise of G' and G'' at the onset of phase separation is seen. A rise of G' and G'' is not observed for neat epoxy system since no phase separation is seen during cure reaction. At the onset of phase separation the rheological behavior was influenced by the amount of thermoplastics in the epoxy/thermoplastic blends, and the onset of phase separation can be detected by rheological measurements.

Evaluación de la adherencia de uniones adhesivas metálicas con adhesivos epoxídicos modificados

“…Esto parece estar relacionado a una mayor solubilidad de los modo a partir de los análisis reológicos a 40 °C, donde fue incluido el tiempo de gelación de los adhesivos puros para fines comparativos. El procedimiento utilizado para la determinación del tiempo de separación de fases fue utilizando un procedimiento publicado en la literatura [42,43] . El procedimiento consiste en considerar que, la separación de fases ocurre en el momento donde en la curva viscosimétrica construida por la relación del valor de viscosidad dinámica compleja, (η*) y un valor arbitrario de viscosidad (η o , viscosidad de referencia) colocadas en función del tiempo, es observado un ligero aumento de la viscosidad ("on set").…”

Polymerization‐induced phase separation and resulting thermomechanical properties of thermosetting/reactive nonlinear polymer blends: A review

“…The microstructural evolution of the PIPS process can be successfully monitored and has been studied extensively by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), optical microscopy (OM), rheological dynamic analysis, small-angle laser light scattering, and the combination of the aforementioned analyses. [23][24][25][26][27][28][29] In addition to these methods, cloud-point, dielectric relaxation spectroscopy, and temperature-jump light-scattering and rheometry measurements have also been widely used to investigate PIPS in thermosets. [30][31][32][33][34] Jyotishkumar et al 24 traced the dynamics of phase separation and the final morphologies of a poly(acrylonitrile-butadiene-styrene) (ABS) modified diglycidyl ether of bisphenol A (DGEBA) epoxy system in situ with OM, DSC, rheometry, and small-angle laser light scattering.…”

“…In addition, at the onset of phase separation, the rheological behavior is influenced by the amount of thermoplastics in the epoxy/thermoplastic blends. 92 Gan et al 93 discussed the viscoelastic effect on the phase separation of a methyltetrahydrophthalic anhydride/poly(ether imide) (PEI)/epoxy system. The phase separation in thermoplasticmodified ER took place according to the spinodal decomposition mechanism.…”

Effect of substituted trifluoromethyl groups on thermal and mechanical properties of fluorine-containing epoxy resin

“…[1][2][3] However, with the rapid development of advanced electronic material technology, these epoxy resins should have improved their physical, mechanical, thermal, and electronic properties, including 1) good thermal properties, 2) high mechanical properties, 3) low water absorption, and 4) a low dielectronic constant. Therefore, much effect, such as the development of a new type of epoxy resins, have been made to satisfy such requirements.…”