Epoxy nanocomposites filled with thermotropic liquid crystalline epoxy grafted graphene oxide

Abstract

Thermotropic liquid crystalline with epoxy groups grafted graphene oxide (LCE-g-GO) was synthesized by graphene oxide (GO), hexamethylene diisocyanate (HDI), and 4,4′-bis-(2-hydroxyhexoxy) biphenyl (BP₂) by using pyridine and dibutyltin dilaurate as catalyst and dimethylformamide (DMF) as solvent. In this work, the LCE-g-GO nanosheets were characterized by Fourier transform infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and polarizing optical microscopy (POM). The epoxy nanocomposites were fabricated by incorporating different LCE-g-GO loading using cast molding method. The results revealed that the incorporation of the LCE-g-GO resulted in a significant improvement in thermal and mechanical properties. The epoxy nanocomposite with 5 wt% LCE-g-GO produced an increase in the temperature for 5 wt% weight loss (T_5%) by 47 °C and glass transition temperature (T_g) by 14 °C when compared with the neat epoxy. Moreover, at the addition of 5 wt% LCE-g-GO, the impact strength of the epoxy nanocomposite is 35.06 kJ m⁻², which is 2 times higher than that of the neat epoxy resin (17.49 kJ m⁻²). Meanwhile, the tensile strength of the nanocomposite is significantly increased to 92.5 MPa from 54.3 MPa, while the elongation at break is also increased to 42.9% from 25.7% of the neat epoxy, respectively. Therefore, the presence of the LCE-g-GO in the epoxy matrix could make epoxy not only stronger but also tougher.