Kinetics of Epoxy–Amine Curing Accompanied by the Formation of Liquid Crystalline Structure

Abstract

The curing of a mesomorphic epoxy has been studied by polarized light microscopy (PLM) and differential scanning calorimetry. PLM in combination with wide‐angle X‐ray diffraction proves the formation of a liquid crystalline (LC) structure. An advanced isoconversional method reveals that the formation of the LC structure is accompanied by a dramatic decrease in the effective activation from ∼60 to ∼10 kJ · mol−1. A kinetic model of the phenomenon has been discussed.The dependence of the activation energy on the extent of conversion for isothermal curing of the diglycidyl ether of 4,4′‐dihydroxybiphenyl/2,6‐diaminopyridine (diamonds) and DGEBA/2,6‐diaminopyridine (circles) systems.magnified imageThe dependence of the activation energy on the extent of conversion for isothermal curing of the diglycidyl ether of 4,4′‐dihydroxybiphenyl/2,6‐diaminopyridine (diamonds) and DGEBA/2,6‐diaminopyridine (circles) systems.

Isoconversional kinetic study of alachlor and metolachlor vaporization by thermal analysis

“…The activation energy values obtained for both alachlor and metolachlor at the end of the vaporization are in close agreement with the enthalpies of vaporization calculated from DSC measurements. This result was also confirmed by several authors [25,26]. Additional XRD and FTIR measurements performed before and after the heating cycle show that metolachlor follows vaporization without decomposition, while a different behavior was observed for alachlor.…”

“…Isoconversional methods have recently been used with success to describe the kinetics of physical transformations [23], and of chemical reactions complicated by physical transformations [24][25][26].…”

Use of isoconversional methods to analyze the cure kinetics of isocyanate‐ended quasi‐prepolymers with water

“…Similar behaviour was observed for isothermal curing of epoxy-amine 29 0.07 1.93 Figure 5 Determination of E a for isothermal DSC cure of quasi-prepolymer and water, by applying the method of Friedman (a) and the integral method (b).…”

Synthesis and Curing of Liquid‐Crystalline Epoxy Resins Containing a Biphenyl Mesogen

“…[20] Also the curing rates of DEPBP/DDM show an abnormal increase under medium conversion at 120 and 130 8C. The interesting phenomenon of this increase of curing rate was reported by most researchers in isothermal [1,11,15,21] or dynamic investigations. [19] However some researchers reported curing rate-conversion curves without abnormity from that of a cure of epoxy without mesogenic groups, which can be described by the Kamal 2228 G. Liu, J. Gao, L. Song, W. Hou, L. Zhang Figure 6.…”

“…[8][9][10] Even then, most studies showed that a liquid crystalline phase develops during curing despite the fact that the epoxy monomer or its mixture with hardener shows no mesophase. [3,[8][9][10][11][12] Thus, a mesophase may appear, independent of the properties of the dioxide monomer, if it has a mesogenic structure.…”