Comparative study of the physical aging of the epoxy systems BADGEn = 0/m-XDA and BADGEn = 0/m-XDA/PEI (original) (raw)
Related papers
Physical aging for an epoxy network diglycidyl ether of bisphenol A/m-xylylenediamine
Polymer, 2003
The physical aging of the epoxy network consisting of a diglycidyl ether of bisphenol A (BADGE n ¼ 0) and m-xylylenediamine (m-XDA) were studied by differential scanning calorimetry. The following aging temperatures have been used in this work: 60, 70, 80, 90, 100 and 110 8C. The glass transition temperature and the variation of the specific heat capacities have been calculated using the method based on the intersection of both enthalpy-temperature lines for glassy and liquid states. The endothermic aging peak, relaxation enthalpy and fictive temperature were also calculated for each aging temperature and aging time.
Study of the physical aging of the epoxy system BADGE n = 0/ m -XDA/CaCO 3
Journal of Applied Polymer Science, 2009
The physical aging of the epoxy network consisting of a diglycidyl ether of bisphenol A (BADGE n ¼ 0), m-xylylenediamine (m-XDA), and calcium carbonate was studied by differential scanning calorimetry. The glass transition temperature and the variation of the specific heat capacities were calculated using the method based on the intersection of both enthalpy-temperature lines for glassy and liquid states. The apparent activation energy was calculated using a single method that involved separate temperature and excess enthalpy dependency. All calorimetric data were compared with those obtained for the epoxy network without filled calcium carbonate.
Journal of Applied Polymer Science, 2002
Lifetime of the epoxy system diglycidil ether of Bisphenol A (BADGE nϭ0)/ m-xylylenediamine (m-XDA) was calculated by thermogravimetric analysis. The Flynn-Wall-Ozawa method is used to determine the activation energy of the reaction. Experimental lifetimes in the range of 60-300°C vary from 1.41 10 9 (2682 years) to 3.35 10 Ϫ4 min. This isoconversional method is not appropiate to calculate lifetime prediction because of high errors. Scaling factors were determined using the ratio of two reaction rates.
Physical aging of linear and network epoxy resins
Polymer Engineering and Science, 1981
Network and linear epoxy resins principally based on the diglycidyl ether of bisphenol-A and its oligomers have been prepared and studied. Both diamine and anhydride crosslinking agents were utilized. In addition, some rubber modified epoxies and a carbon fiber reinforced composite was investigated. All of these materials display time-dependent changes in many of their properties when they are stored (following quenching) at temperatures below their glass transition temperature (sub-T,/ annealing). For example, the degree of stress relaxation for a given time period is observed to decrease in a linear fashion with the logarithm of time during sub-T, annealing. Young's modulus and yield stress were also found to increase in physical aging. Solvent sorption experiments initiated after different sub-T,) annealing times have demonstrated that the rate of solvent uptake can be indirectly related to the free volume of the epoxy resins. The effect of water on the physical aging of these epoxy resins was not found to be a significant variable, Residual thermal stresses were also found to have little effect on the physical aging process, although this variable was not studied in detail. Finally, the physical aging process also affected the sub-T, properties of uniaxial carbon fiber reinforced epoxy material and the effects were as expected. The importance of the recovery or physical aging phenomenon, which affects the durability of epoxy glasses, is considered in view of the widespread applications for these resins as structural materials.
The physical aging of a n epoxy resin based on diglycidyl ether of bisphenol-A cured by a hardener derived from phthalic anhydride has been studied by differential scanning calorimetry. The isothermal curing of the epoxy resin was carried out in one step a t 130°C for 8 h, obtaining a fully cured resin whose glass transition was at 98.9"C. Samples were aged a t temperatures between 50 and 100°C for periods of time from 15 min to a maximum of 1680 h. The extent of physical aging has been measured by the area of the endothermic peak which appears below and within the glass transition region. The enthalpy relaxation was found to increase gradually with aging time to a limiting value where structural equilibrium is reached. However, this structural equilibrium was reached experimentally only a t an aging temperature of Tg -10°C. The kinetics of enthalpy relaxation was analysed in terms of the effective relaxation time 7,ff. The rate of relaxation of the system given by 1 / T ,~ decreases as the system approaches equilibrium, as the enthalpy relaxation tends to its limiting value. Single phenomenological approaches were applied to enthalpy relaxation data. Assuming a separate dependence of temperature and structure on 7, three characteristic parameters of the enthalpic relaxation process were obtained (In A = -333, EH = 1020 kJ/ mol, C = 2.1 g/ J ) . Comparisons with experimental data show some discrepancies at aging temperatures of 50 and 60"C, where sub-T, peaks appears. These discrepancies probably arise from the fact that the model assumes a single relaxation time. A better fit to aging data was obtained when a Williams-Watts function was applied. The values of the nonexponential parameter p were slightly dependent on temperature, and the characteristic time was found to decrease with temperature.
J Appl Polym Sci, 2001
Master plots were used to corroborate R n-type mechanisms calculated in a previous study, using the method proposed by Criado et al. (Thermochim Acta 1989, 147, 377). Analysis of experimental data seems to belong to the family of decelerated curves (R n) in the range of conversion studied. The lifetime of the system diglycidil ether of bisphenol A (BADGE n ϭ 0)/m-xylylenediamine (m-XDA) for different decelerated mechanisms was calculated using thermogravimetric analysis. From the experimental data it was found that the optimum temperature range of use for this material is 60-100°C for all R n-type mechanisms, at which corresponding lifetimes range between 190 years and 1 year.
Thermo-oxidative aging of epoxy coating systems
Progress in Organic Coatings, 2014
The thermo-oxidative behavior of unformulated (unfilled) samples of epoxy coatings has been studied at five temperatures ranging from 70 • C to 150 • C. Two epoxy networks based on diglycidyl ether of bisphenol A (DGEBA), respectively, cured by jeffamine (POPA) or polyamidoamine (PAA) were compared. Infrared spectrophotometry (IR), differential scanning (DSC) and sol-gel analysis (SGA) were used to monitor structural changes. Thermal oxidation leads to carbonyl and amide formation in both systems. POPA systems appear more sensitive to oxidation than PAA ones. Thermal oxidation leads to predominant chain scission as evidenced by the decrease of glass transition temperatures (T g) and increase of sol fraction.
Cure kinetics of a diglycidyl ether of bisphenol a epoxy network ( n = 0) with isophorone diamine
Journal of Applied Polymer Science, 2007
The study of the cure reaction of a diglycidyl ether of bisphenol A epoxy network with isophorone diamine is interesting for evaluating the industrial behavior of this material. The total enthalpy of reaction, the glass-transition temperature, and the partial enthalpies at different curing temperatures have been determined with differential scanning calorimetry in dynamic and isothermal modes. With these experimental data, the degree of conversion and the reaction rate have been obtained. A kinetic model introduces the mechanisms occurring during an epoxy chemical cure reaction. A modification of the kinetic model accounting for the influence of the diffusion of the reactive groups at high conversions is used. A thermodynamic study has allowed the calculation of the enthalpy, entropy, and Gibbs free energy.
Thermodegradation kinetics of a hybrid inorganic–organic epoxy system
European Polymer Journal, 2005
Lifetime of the epoxy system formed by diglycidyl ether of bisphenol A, DGEBA/4,4 0 -diaminediphenylmethane, DDM, modified with the silsesquioxane, glycidylisobutyl-POSS, was calculated from thermogravimetric analysis. The activation energy of the decomposition of this system was evaluated by the integral method developed by Flynn-Wall-Ozawa (E = 88.9 ± 2.1 kJ mol À1 ) and by Coats and Redfern method (E = 85.2 ± 1.5 kJ mol À1 ). The kinetic parameters have been used to estimate the lifetime of the system POSS/DGEBA/DDM. The obtained results by two different ways are similar.
Journal of Applied Polymer Science, 1984
The cure behavior and thermal degradation of high Tg epoxy systems have been investigated by comparing their isothermal time-temperature-transformation (TIT) diagrams. The formulations were prepared from di-and trifunctional epoxy resins, and their mixtures, with stoichiometric amounts of a tetrafunctional aromatic diamine. The maximum glass transition temperatures (TgJ were 229°C and > 324°C for the fully cured di-and trifunctional epoxy materials, respectively. Increasing functionality of the reactants decreases the times to gelation and to vitrification, and increases the difference between Tg after prolonged isothermal cure and the temperature of cure. At high temperatures, there is competition between cure and thermal degradation. The latter was characterized by two main processes which involved devitrification (decrease of modulus and T,) and revitrification (char formation). The experimentally inaccessible Tcm (352T) for the trifunctional epoxy material was obtained by extrapolation from the values of Tgm of the less highly crosslinked systems using a relationship between the glass transition temperature, crosslink density, and chemical structure. This article discusses the competition between cure and thermal degradation for high T, epoxy systems prepared from di-and trifunctional epoxy resins, and their mixtures, cured with stoichiometric amounts of a tetrafunctional aromatic diamine, and the influence of the functionality of the epoxy reactants on cure and the glass transition temperature. The experimentally determined maximum glass transition temperatures (Tgm) were 229°C and > 324°C for the di-and trifunctional epoxy materials, respectively. A general problem in polymer science is to obtain the values of Tgm for high Tg polymers in the absence of degradation. The experimentally inaccessable value of Tgm for the trifunctional epoxy material was obtained by