The first part of the research consisted of synthesis of aminomaleimide which was a key ingredient in cross-linking with various epoxy resins. Furthermore, to investigate the effect of maleimide group on thermomechanical properties of the material, three mixtures of aminomaleimide and respective epoxy were produced. The research was further expanded by closely examining not only aromatic but also aliphatic epoxy resins of different molar masses, structures and functionality. As a reference epoxy resins were also cross-linked with diamine and dimaleimide compound, where the kinetics of reaction and their respective thermomechanical properties were studied. While the dimaleimide molecule did not react with epoxy resin, not even at elevated temperatures, the diamine reacted, which agrees with extensive literature on cross-linking phenomena between different epoxy and amine molecules.
Thermal properties of the reaction were studied with differential scanning calorimetry (DSC), which provided data needed for further kinetic analysis. Reaction between aminomaleimide and epoxy was determined to follow the autocatalytic model, additionally proven as Šesták-Berggren model. The autocatalytic nature of the reaction was theoretically verified using Malék analysis and by Friedman method. Kinetic parameters were determined by approximating the theoretical model to experimental data using least square difference method achieving satisfactory agreement. The mechanical properties of cross-linked materials were observed with dynamical mechanical analysis (DMA). The results confirmed that the addition of maleimide group improves mechanical properties. Increase of the glass transition temperature, relatively to the amount of maleimide added, was observed. The higher the amount of maleimide group, the higher the glass transition temperature. Meanwhile, aromatic epoxides exhibit shifts of glass transition temperature to higher values, compared to their aliphatic competitors. It was also determined that cross-linking with aminomaleimide, compared to the reference 4,4-diaminodiphenylmethane, improves thermomechanical properties. TGA surprisingly demonstrated higher temperatures of decomposition of reference mixtures, however char yield did improve relatively to the addition of aminomaleimide. Despite the above, to get absolute values on improvement of materials, a molar mixture 1:1 of all samples should be measured as to determine which mixture provides the best thermomechanical properties and if molar mass and structure of epoxides plays a significant role.
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