Non-isothermal curing of a diepoxide–cycloaliphatic diamine system by temperature modulated differential scanning calorimetry

Vitrification during the Isothermal Cure of Thermosets: Comparison of Theoretical Simulations with Temperature‐Modulated DSC and Dielectric Analysis

“…The dependence of the devitrification time on frequency is also less pronounced than in the case of vitrification, while, as can be seen in Figure 2, the devitrification temperature is almost independent of the underlying heating rate. to the TTT diagram in the isothermal case, can be constructed, [5][6][7][8] and is shown in MATLAB version 7.0 was used to simulate the non-isothermal cure reaction, taking into account similar considerations as for the isothermal case. [14] In the absence of vitrification, the reaction is chemically controlled and the time (t) dependence of the degree of cure (α, 0 ≤ α ≤ 1) during the reaction can be described by the equation of Kamal: [15] …”

“…As the reaction proceeds, the glass transition temperature increases from its initial value, T g0 , being that of the mixture of monomers of resin and cross-linking agent, and, in the absence of vitrification, will reach a limiting value, T g∞ , corresponding to the fully cured system (α=1). The relationship between the degree of cure and the glass transition temperature of the curing system can be described by the DiBenedetto equation: [16,20] T T (6) where λ is a fit parameter related to the ratio of heat capacities of the fully cured and uncured system. The effect of λ is also investigated in these simulations.…”

“…The values of the constants used in these simulations are summarized in Table 2. Also shown are the ranges of parameter values investigated, namely the underlying heating rate, q, the reaction orders, m and n, in Equation (2), the parameter λ of the DiBenedetto equation, Equation (6), and the reduced activation energy, E f /R, in Equation (7 [18] Equation (3) E c1 (kJ mol -1 ) 51.8 [18] Equation (3) A 2 (s -1 ) 10 3.4 [18] Equation (3) E c2 (kJ·mol -1 ) 41.5 [18] Equation (3) k dg (s -1 ) 0.0051 [14] Equation (4) C 1 40.2 [17] Equation (4) C 2 (K) 51.6 [17] Equation (4) T g0 (ºC) -15 Equation (6) T g∞ (ºC) 80 Equation ( …”

“…[1,2] The subsequent process of devitrification occurs when the continually increasing cure temperature, T c , again exceeds the T g of the vitrified system. The vitrification and devitrification processes which occur during non-isothermal cure have been studied by temperature modulated differential scanning calorimetry (TMDSC) [3][4][5][6] and other dynamic techniques such as dielectric relaxation [7] and torsional braid analysis. [8] The advantage of these dynamic techniques is that they permit the observation of vitrification and devitrification in real time during the experiment, for example through the complex heat capacity in TMDSC.…”

Effects of Surface Treatments of Montmorillonite Nanoclay on Cure Behavior of Diglycidyl Ether of Bisphenol A Epoxy Resin

“…Interactions between nanoclay particles and epoxy molecules affect the viscosity and mobility of reacting species during curing. Consequently this influences rate of cure, reaction time, enthalpy, vitrification, activation energy, viscoelastic properties, and crosslinking density of the final composite [9,12,16,17]. Other factors such as type and amount of clay fillers and organic modifiers and their interaction with the intended host polymer molecules and their curing agents have all shown to influence properties of polymeric composites during processing [12-14, 17, 18].…”