An interpenetrated system based on a tetrafunctional epoxy resin and a thermosetting bismaleimide: Structure–properties correlation

Thermal-Oxidative Degradation of Epoxy and Epoxy-Bismaleimide Networks: Kinetics and Mechanism

“…From this it can be inferred that, in the ternary system, the TGDDM-DDS and the BMI networks undergo thermal-oxidative degradation independently of each other; there is no evidence, in fact, of alternative mechanistic pathways introduced in the ternary mixture due to the presence of the BMI component. This conclusion indirectly supports the IPN molecular structure which has been hypothesized in previous work [7,8] on the basis of spectroscopic and dynamic-mechanical results.…”

“…It was found that, in all cases, the first order model (n = 1) gave a satisfactory fit. The curves simulated by the model Equation (6) (or (7), where appropriate) through a non-linear leastsquares regression of the experimental data, are reported, as continuous lines, in Figure 8 and 9. In Table 3 are reported the kinetic constants and the final conversions, where appropriate, for the different reactive groups whose degradation was monitored spectroscopically.…”

“…Details about the preparation procedures for the TGDDM/ DDS resin and the ternary TGDDM/DDS/BMI mixtures are reported elsewhere. [7,8] In order to obtain infrared spectra suitable for quantitative analysis according to the Beer-Lambert relationship, the absorbance of the peaks of interest must not exceed values in the region 1.3-1.5 units. Films for these studies (5 to 10 lm of thickness) were prepared by dissolving TGDDM, DDS and BMI in the appropriate amounts in acetone (total concentration 10 wt.-%), followed by casting on KBr disks.…”

“…The epoxy resin crosslinks through reaction with its hardener, DDS, while BMI polymerizes via a thermally initiated radical process. [7,8] Dynamic mechanical analysis, on the other hand, has Full Paper: The thermal oxidative stability of an epoxide/ diamine network (TGDDM/DDS) and of an epoxide/diamine/bismaleimide IPN system (TGDDM/DDS/BMI) have been investigated by thermogravimetric analysis (TGA), dynamic-mechanical thermal analysis (DMTA) and isothermal, time-resolved FTIR spectroscopy. Both TGA and DMTA data revealed a considerable enhancement of the stability of the material as the bismaleimide content in the system is increased.…”

“…The presence of the BMI network, which is more "rigid" than that produced by TGDDM has been found to increase such properties as the T g , the modulus and the yield stress. [7] These improvements have been achieved, however, at the expenses of a slight reduction in fracture toughness, i. e. K c and G c . [7,8] The presence of the BMI network in such systems has, furthermore, been found to lower the equilibrium water uptake and to increase the sorption rate (hence, the diffusion coefficient, D), with respect to the unmodified TGDDM/DDS resin system.…”