Synthesis And Properties Of Liquid Crystalline Epoxy Resin Composites

Liquid crystalline epoxy resin (LCER) and its composites have been extensively studied for decades.The curing conditions of the curing system of the LCER, diglycidyl ether of 4,4'-bis(4-hydroxybenzoyloxy)-3,3',5,5'-tetramethyl biphenyl (DGE-BHBTMBP), and the curing agent, diaminodiphenylsulfone (DDS), were studied by means of differential scanning calorimetry (DSC) based on the recent literatures. The LCER was cured by the method of compression molding and measured by dynamic mechanical thermal analyzer, impact tester and universal materials tester.The glass transition temperature, the storage modulus, the thermostability, the impact strength, the bending strength and the elastic modulus of the cured epoxy resins with both DGE-BHBTMBP and a common diglycidyl ether of bisphenol A (epoxy resin E-51) were investigated. The results showed that DGE-BHBTMBP could increase the glass-transition temperature and the initial decomposition temperature of the composites. The impact strength and the bending strength of the composites would be higher with the proper content of LCER. The phase separation caused by the excess LCER made the mechanical properties worse. A reasonable explanation was given based on the features observed by scanning electron microscope (SEM) and other experimental results.The curing system of DGE-BHBTMBP/DDS/carbon nanotubes was prepared and the effects of the content of carbon nanotubes on the physical properties of the composites were intensively investigated. Test of transmission electron microscopy (TEM) showed that the multi-wall carbon nanotubes oxidated by acid (OX-MWNT) performed a better dispersion in the composites than the untreated multi-wall carbon nanotubes (MWNT) did. The impact strength and the bending strength of the composites with the OX-MWNT were higher than that of the same content of MWNT.