Modeling of Curing Reaction Kinetics in Liquid-Crystalline Epoxy Resins

Abstract

The curing kinetics of an epoxy stoichiometrically equivalent mixture of 4,4‘-(diglycidyloxy)-α-methylstilbene and 2,4-diaminotoluene has been determined experimentally. A liquid-crystalline phase has been observed to form during the curing reaction. A phenomenological model of the system is developed, and with parameter values extracted from the data by fitting of separate parts of the DSC curve, the model equations fit the measured data over a wide range of temperatures.

Nanocomposites Based on Liquid Crystalline Resins

“…The curing schedule was: 120 min at T ¼ 130 C for cure; 30 min at T ¼ 180 C for post-cure. These conditions were chosen by taking into account the best compromise between the melting temperature of DOMS and the optimal conditions to make the reacting DOMS-DAT system form liquid crystalline domains upon cure [31]. V. Ambrogi et al…”

Composites based on carbon fibers and liquid crystalline epoxy resins, 1 Monomer synthesis and matrix curing

“…A phenomenological model was proposed in order to explain the curing kinetics. [12,22,27] The results indicate that the activation energies in the liquid crystalline phase are lower than in the isotropic state: this implies that the curing process is favoured in the liquid crystalline state.…”

“…Isotropic to liquid crystalline phase transition is observed when a critical fractional conversion a is reached, i. e. when, after the addition and chemical bonding of several rigid units via short flexible spacers, the liquid crystalline phase is stabilized by geometric constraints, provided that the curing temperature does not exceed the thermodynamic transition temperature to the isotropic phase. [12] Optical microscopy analysis can be used in order to evaluate the times required for the occurrence of the isotropic-LC phase transition at different temperatures. The observed times can then be used to calculate a from the calorimetric data; of course, at different reaction temperatures, the times necessary for the isotropic-LC phase transition to occur are different.…”

“…The curing reaction was monitored by DSC and compared to an analogous liquid crystalline monomer which had previously been investigated by us. [12] The mechanical properties of the cured resin and of the composites will be reported in a subsequent paper.…”

Reaction pathway of liquid crystalline epoxy resin/aromatic diamine curing system

“…[1][2][3][4][5][6][7][8][9][10][11][12] There have been numerous studies on the curing of LC epoxy resins with various curing agents. However, the exact curing mechanism of LC epoxy resins have not been clarified yet because the curing reaction is affected by several curing parameters such as the curing condition, reactivity of epoxide ring and morphology.…”