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A maleimido-terminated butadiene-acrylonitrile copolymer was employed as an impact modifier for a commercial thermosetting bismaleimide resin. FTIR spectroscopy was used to monitor in real time the kinetics of the curing process in this blend system at different temperatures. The toughening agent was found to produce strong effects on the kinetics and mechanism of the curing process. The fracture toughness parameters K c and G c showed a substantial enhancement as the rubber content in the blend was increased. Only a modest reduction of the elastic modulus and of the compressive yield stress was brought about by incorporation of the impact modifier.

The photo-oxidative degradation of a highly cross-linked epoxide/diamine network has been investigated by FTIR spectroscopy, dynamic-mechanical thermal analysis (DMTA) and compressive mechanical tests. The FTIR measurements allowed us to monitor the degradation process and to obtain reliable kinetic data. Two dimensional infrared (2D IR) correlation spectroscopy, was employed to analyze the spectra collected as a function of time. This approach effectively enhanced the spectral resolution and revealed details about the reaction mechanism hardly detectable in the one-dimensional, frequency domain. In particular, the sites of initiation of the auto-oxidative sequence were identified, and the main pathways through which the degradation reaction proceeds were proposed. Dynamic-mechanical measurements performed in a multifrequency mode were used to reveal the effect of the photo-oxidative degradation on the relaxation processes of the epoxy network. It was found that the T g decreases with increasing the exposure time. An analogous trend was found for the storage modulus, E′, at temperatures above the glass transition. The overall cross-linking density was found to decrease as a consequence of the chain scission reactions. A marked reduction of the mechanical performances of the material was evidenced at high exposure times, especially in terms of yield-strength and strain.

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