B. Rial

thermal stability of epoxy systems badge (n=0)/1,2-dch and badge (n=0)/ 1,2-dch/vinylcyclohexene dioxide

The thermal degradation of the epoxy system diglycidyl ether of bisphenol A (BADGE n=0)/1,2-diamine cyclohexane (DCH) containing different concentrations of an epoxy reactive diluent was studied by thermogravimetric analysis in order to determine the reaction mechanism of the degradation process and to compare it with the results for the same system without diluent. The value of the activation energy, necessary for this study, was calculated using various integral and differential methods. Values obtained using the different methods were compared to the value obtained by the Flynn-Wall-Ozawas method (between 193-240 kJ mol-1 depending on the diluent concentration) with does not require a knowledge of the nth order reaction mechanism. All the experimental results were compared to master curves in the range of Doyles approximation (20-35% of conversion). Analysis of the results suggests that the reaction mechanism could be F2, F3, or A2 type.

Kinetic study of an epoxy system badge (n=0)/1, 2 dch modified with an epoxy reactive diluent

The curing reaction of an epoxy system consisting of a diglycidyl ether of bisphenol A (n=0) and 1, 2 diaminecyclohexane (DCH) with an epoxy reactive diluent vinylcyclohexane dioxide was studied by temperature modulated differential scanning calorimetry (TMDSC). The models proposed by Kamal and by Horie et al. were employed in the kinetic study. From these studies reaction orders, rate constants, and activation energies were determined. The technique of TMDSC allows to include in the kinetic study the effect of diffusion by means of the mobility factor, calculated from the curves of the complex heat capacity registered during the curing isothermal experiments. The results were compared to those obtained for the same system employing the reaction rate data.

Comparative study of the thermal stability of the epoxy systems badge n=0/1, 2 dch and badge n=0/1, 2 DCH/CaCO3

The thermal degradation of the epoxy systems diglycidyl ether of bisphenol A (BADGE n=0)/1, 2 diamine cyclohexane (DCH) and diglycidyl ether of bisphenol A (BADGE n=0)/1, 2 diaminecyclohexane (DCH) containing calcium carbonate filler immersed and not immersed in hydrochloric acid have been studied by thermogravimetric analysis in order to compare their decomposition processes and to determine the reaction mechanism of the degradation processes. The value of the activation energies, necessary for this study, were calculated using various integral and differential methods. Analysis of the results suggests that hydrochloric acid does not affect the decomposition of the epoxy network and that the reaction mechanisms produce sigmoidal-type curves for the systems not immersed in HCl and deceleration curves for the same systems immersed.

TTT Cure Diagram

Curing reactions of the epoxy system consisting of a diglycidyl ether of bisphenol A (BADGE n=0) and m-xylylenediamine (m-XDA) were studied to calculate time-temperature-transformation (TTT) isothermal cure diagram for this system. Gel times were measured as a function of temperature using solubility test. Differential scanning calorimetry (DSC) was used to calculate the vitrification times. DSC data show a one-to-one relationship between Tg and fractional conversion, a independent of cure temperature. As a consequence, Tg can be used as a measure of conversion. The activation energy for the polymerization overall reaction was calculated from the gel times obtained using the solubility test (41.5 kJ mol-1). This value is similar to the results obtained for other similar epoxy systems. Isoconversion contours were calculated by numerical integration of the best fitting kinetic model.

Enviromental utility materials

The influence of agents originated in a municipal landfill on the thermal degradation of a polymeric system composed of a diglycidyl ether of bisphenol A (n=0) and 1,2-diaminecyclohexane was studied by thermogravimetric analysis (TG) in order to obtain the lifetime of this material before and after being attacked. The different data obtained were analyzed to check the resistance of these materials to chemical attack and the possibility of their use as coating materials in plants where those reagents were present. At the optimum temperature of service for this material, 373.16 K, the lifetimes obtained from the experimental results were 2633 years and 2135 years, respectively.