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The inherent brittleness of thermosetting resins limit their further applications in many cutting-edges industries, therefore toughening is the most important subject in the field of investigating thermosetting resins. Although many sophisticated methods have been developed for toughening thermosetting resins, these methods usually sacrifice other good performances of original resins, and thus can not meet the requirements of cutting–edge applications. In fact, how to find a way that can effectively increase the toughness of thermosetting resins on the base of maintaining their other outstanding performances (especially dielectric properties) becomes a hot issue, which also has important values in theory and applications.In this thesis, polyetherimide (PEI) is chosen to modify bismaleimide-diallylbisphenol A (BD) and BD/cyanate ester (CE) owing to its excellent heat resistance, low water absorption and stable dielectric properties. The influence of the content of PEI on the morphology and properties of blends were investigated. In order to improve the compatibility between PEI and BD, 3-aminopropyl(triethoxy)silane (KH550) was introduced to prepare KH550/10PEI/BD blends, of which the key properties were systemically discussed.For PEI/BD resins, the effect of PEI concentration on key properties such as morphology, dielectric properties as well as water resistance were discussed in detail. Results reveal that with the increase of the content of PEI, the morphologies of PEI/BD resins turne from a dispersed phase to completely co-continuous phase and perfect phase inversion, successively. The incorporation of PEI decrease the water absorption of BD resin, moreover, this positive effects increase with the increase of PEI concentration in PEI/BD resins. In addition, the addition of PEI to BD resin not only decreases dielectric constant and loss, but also improves the stability of dielectric properties. The PEI/BD resins with desirable PEI content have better integrated properties than neat BD resin.In order to improve the compatibility between PEI and BD resin, KH550 was used to modify 10PEI/BD resin, and the effects of PEI concentration on key properties such as morphology, mechanical, water resistance and dielectric properties as well as thermal property were discussed in detail. Results show that the addition of KH550 does not change the dispersed phase of 10PEI/BD resin, but is beneficial to improve the compatibility between PEI and BD resin. Moreover, the effect of KH550 on 10PEI/BD resin is closely related with the content of KH550, and there is an optimum stoichiometry between KH550 and 10PEI/BD for obtaining the maximum impact and flexural strengths, the lowest water absorption, the lowest and the best stability dielectric loss.For PEI/BD/CE resins, the effect of the formulations on key properties mainly including mechanical, thermal properties, water resistance and dielectric properties, etc, was emphasized investigated. Results show that with increasing the content of PEI in PEI/BD/CE resins, the impact and flexural strengths increase, and the crosslinking density decreases; while the flexural modulus almost does not change. Moreover, the initial degradation temperature of PEI/BD/CE resins decreases slightly. It is worthy pointing out that PEI/BD/CE resins possess lower water absorption and dielectric loss than BD/CE resin, and PEI/BD/CE resins after stayed in boiling water for 100 h still maintain good dielectric properties.
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