Thermosetting epoxy resins have been widely used as impregnating materials, adhesives or matrices for advanced composites applied in cryogenic engineering fields such as spacecraft and superconducting technologies. However, as a kind of thermosetting resins, the intercrossed molecular chains make epoxy resins rigid and brittle, thus micro-cracking and even fracture of epoxy resins might happen when their thermal-stress induced stress intensity factor exceeded their fracture toughness as temperature decreased down from room temperature to cryogenic temperature (e.g. liquid nitrogen temperature 77 K). In order to obtain epoxy nanocomposites with excellent mechanical properties at cryogenic temperature, an efficient method to functionalize graphene nanoplatelets (GNPs) has been proposed. Through a simple dip-coating procedure, the GNPs were first functionalized with deposition of polydopamine coating (PDA@GNPs). Furthermore, using polydopamine as a bridge, the PDA@GNPs were modified with amine groups after following polyetheramine T403 grafting (T403-PDA@GNPs). Adding 0.1 wt% T403-PDA@GNPs significantly improved the cryogenic tensile strength and impact strength of the epoxy nanocomposites by 34.5% and 64.5%, which showed greater reinforcing effect than the pristine GNPs (12.6% and 19.1%) and PDA@GNPs (26.3% and 50.1%). The results of dynamic mechanical analysis and scanning electron microscopy observations indicated that the PDA and further polyetheramine T403 functionalization improved the interfacial interactions between GNPs and matrix, which ensured the much improved mechanical properties.

Reinforcing effect of polydopamine functionalized graphene nanoplatelets on the mechanical properties of epoxy resins at cryogenic temperature

254th National Meeting (2017)

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