Green fabrication of functionalized graphene via one-step method and its reinforcement for polyamide 66 fibers

Graphene has attracted a significant number of attentions due to the extraordinary properties. Development of a method to obtain graphene with high yield and quality is crucial for the investigations and applications of graphene. However, the large-scale fabrication of mono- and few-layer graphene sheets still remains challenges. This paper demonstrates a green and scalable one-step fabrication of single- and few-layer graphene by graphite delamination in water/tannic acid (TA) dispersion using a high-pressure homogenizer. The effect of TA concentration, homogenization pressure, and homogenization cycles on the quality and concentration of graphene dispersions were systematically investigated. The concentration of the graphene sheets (GS-TA) in TA aqueous solution reaches up to 1.16 mg/mL, with about 84% of them are fewer than five layers. Significantly, the exfoliated GS-TA is highly stable for more than 5 months. Next, for a potential application, the GS-TA/polyamide 66 composite fibers were melt-spun. The non-covalent functionalization of graphene compatibilized the interface between graphene and PA66 matrix, and increased the filler's dispersibility in the PA66 matrix. The results show similar to 118% enhancement in tensile strength of polyamide 66 nanocomposite fibers when the loading of GS-TA is 0.1 wt%. It is believed that this new green protocol for graphene production will pave the way for relatively simple industrial-scale fabrication of high-performance graphene-based nanocomposites.