Environmentally friendly water-soluble epoxy emulsions nano sphere improved the interfacial performance of high modulus carbon fiber reinforced epoxy composites based on robust van der Waals force

High modulus carbon fibers (CFs) are widely desirable in aerospace, robotics, etc. However, their high degree of graphite microcrystalline structure leads to poor interfacial properties with host matrices, deteriorating the mechanical properties of carbon fiber reinforced polymer composites (CFRPs). Here, to improve interfacial properties of CFRPs, we present to construct a uniform and continuous active sizing nanolayer on the surface of CFs via synthetic water-based epoxy (WEP) emulsion nanospheres with strong van der Waals force. The WEP emulsions were prepared by introducing polar polyethylene glycols into epoxy resin chain. The modified CFRPs showed robust interfacial properties, improving by 25% over the untreated counterparts. Moreover, the proposed method can retain monofilament tensile strength of fibers and protect CFs from being destroyed during processing at industrial scales. This work opens an avenue toward the development of materials with superior interfacial performance for various inert high modulus fibers. • The interfacial properties between high modulus CFs and host matrices are improved by water-soluble epoxy. • Environmentally friendly water-soluble epoxy nano emulsions are prepared by chemically grafting EP with PEG. • Water-soluble epoxy with Mw of 6000 has the best modification effect on high modulus fibers. • The proposed method can protect CFs from being destroyed during processing at industrial scales.