Modification Of Thermosetting Resins By High Performance Liquid Crystalline Epoxy Resin

High performance thermosetting resins occupy very important place in many cutting-edge fields. Big brittleness is the inherent disadvantage of thermosetting resins, so toughening has been one of the most important subjects of developing high performance thermosetting resins. Cyanate ester (CE) resin and Silicone resin are regarded as two typical resins of high performance resins, so which were selected as the model for investigation on modification of thermosetting resins in this thesis through the synthesis of a high performance of liquid crystalline epoxy resin.In this thesis, aromatic polyester liquid crystalline epoxy containing three benzene type-----p-phenylene di{4-[2-(2,3-epoxypropyl) ethoxy] benzoate} (LCE) was synthesized using the process of acryl chlorination and oxidation. Its structure and liquid crystalline behavior were characterized by FTIR,DSC,1H-NMR, polarizing microscope with a hot stage (POM) and X-ray diffractometer (XRD). Results show that LCE is a thermotropic liquid crystalline polymer and has a nematic phase. On the base of successful synthesis of LCE, two modified resins, LCE/CE and LCE/EP/Silicone resins, were developed, and the integrated properties of the two systems were systemically investigated.With regard to LCE/CE resin system, four LCE/CE resins with different contents of LCE were prepared to systemically evaluate the effect of the content of LCE on the key properties such as curing behavior,mechanical, dielectric and thermal properties as well as water resistance. Results reveal that the addition of LCE to CE can not only decrease the curing temperature of CE, but also significantly improve mechanical properties as well as water resistance of cured resin. Moreover, these positive effects increase with the increase of LCE concentration in LCE/CE resins. In addition, with the increase of LCE content in LCE/CE resins, both thermal resistance and dielectric loss decrease, indicating that the LCE/CE resins with desirable content of LCE have better integrated properties than CE resin.For LCE/EP/Silicone resins, the effect of the formulations on key properties including mechanical, dielectric, thermal properties and water resistance was mainly discussed. Results show that 15LCE/EP/Silicone resin has the maximum impact strength, which is about 1.7 times of that of EP/Silicone resin. Comparing with EP/Silicone resin, LCE/EP/Silicone resins have much better water resistance. With increasing the content of LCE in LCE/EP/Silicone resins, thermal resistance has no change, while the dielectric constant and loss decrease. LCE/EP/Silicone resins with desirable content of LCE have outstanding thermal and dielectric properties as well as water resistance. These changes of properties are proved to be attributed to the liquid crystalline feature of LCE, and the alteration of chemistry in the network.