Cryogenic fracture behavior of epoxy reinforced by a novel graphene oxide/poly(p-phenylenediamine) hybrid

Epoxy polymers are actively used in high-end technological applications. However, a major drawback of epoxies is their brittle mechanical behavior especially at cryogenic temperatures. Here we report a novel filler (GO-PDA) of poly (p-phenylenediamine) (PDA) nano-sized particles attached to graphene oxide (GO) sheets. Chemical analysis showed the attachment of PDA particles to GO through amidation of carboxylic groups. Transmission electron microscopy showed that PDA particles are uniform and spherical of ≈70 nm in size. Selected area electron diffraction showed that these particles are crystalline. Mechanical properties of epoxy/GO-PDA composite are tested at 25 °C (RT) and −120 °C (CR) temperatures. Young's modulus was not remarkably affected by GO-PDA addition. However, strength, fracture strain and toughness showed improvement at relatively low GO-PDA wt%. Microstructural analysis of fractured surfaces showed that the fracture mechanism is dependent on testing temperature. GO-PDA has a very good strengthening and toughening effects for epoxy without compromising the modulus both at RT and CR.