Graphene Oxide coating could improve Surface Modification of Aramid ‘Bulletproof’ Fibres

A team of researchers, Lei Zeng, Xuqing Liu, Xiaogang Chen & Constantinos Soutis, had published their paper in 8 May 2018 /Accepted: 26 June 2018:

Surface Modification of Aramid Fibres with Graphene Oxide

Abstract A novel method of biomimetic surface modification was used for aramid fibres aiming to enhance the interface properties between epoxy resin and the modified aramid fibre.

Inspired by the composition of adhesive proteins in mussels, a thin layer of poly(dopamine) (PDA) was self-polymerized onto the surface of the aramid fibre. The graphene oxide (GO) was then grafted on the surface of PDA-coated aramid fibres. The microstructure and chemical characteristics of the pristine and modified fibres were characterised using Scanning Electron Microscopy (SEM) andX-ray photoelectron spectroscopy (XPS), indicating successful grafting of GO on thePDA-coated aramid fibres.

Single fibre tensile test and microbond test were carried out to evaluate the mechanical properties of the modified fibres. It was found that the fibre surface modification improved the interfacial shear strength by 210% and the fibre tensile strength was protected by GO-PDA coating.

Fibre reinforced composites have been widely used in aerospace, automobile, and military industries, due to their high specific strength, modulus, lightweight and flexible design.

Particularly, aramid fibre is an ideal reinforcement for high-performance composites as it contains high mechanical properties, chemical stability and low density

[1].Appl Compos Materhttps://doi.org/10.1007/s10443-018-9718-9*Xiaogang Chenxiaogang_chen@hotmail.com

1 School of Materials, The University of Manchester, Manchester M13 9PL, UK

2 Aerospace Research Institute, The University of Manchester, Manchester, UK

The surface of aramid fibres is smooth and chemically inert which lead to less strong interface with the matrix. It has been reported that weak bonding can lead tolow load transfer efficiency between the fibre and resin in a fibre composite [2]. To enhance the interfacial adhesion strength of aramid fibre-reinforced composites, effortswere mainly made to modify fibre surface using plasma treatment, γ-ray irradiation,ultrasonic treatment, chemical grafting and etching [3–5]. However, these techniques request multistep procedures and are associated to the use of high cost instrument. Inaddition, these surface treatments are limited with strict reaction condition and in some case the use of toxic materials. Due to the damage caused to the fibre surface, fibre strength reduction is inevitable.

This paper aims to improve the interfacial adhesion between aramid fibres andepoxy resin based on the use of a novel method for fibre surface treatment at ambient temperature. A biopolymer, polydopamine (PDA), is applied to form a coating layer on the surface of fibre via pH-induced oxidative self-polymerization, introducing functional groups such as carboxyl, amine and catechol for bonding enhancing between the fibre and resin to improve the physical properties of the composites [6,7].

Then, graphene oxide (GO) is to be grafted onto the polydopamine-treated aramid fibre to enhance the mechanical property of the aramid fibre and to improve the interfacial bonding between fibre and resin. As a 2D material, GO has high aspect ratio with flexible structure, and it also has extraordinary mechanical properties and superior thermal and electrical conductivity. Graphene oxide is chemically more active with the fibre and resin polymers than graphene, because of the epoxide and hydroxylgroups within the GO sheets and carbonyl and carboxyl at the edges of the GOsheets.

Evaluations of the coated aramid fibre are to be tested for strength and for interface adhesion with the epoxy resin., graphene oxide (GO) is to be grafted onto the polydopamine-treated aramid fibre to enhance the mechanical property of the aramid fibre and to improve the interfacial bonding between fibre and resin. As a 2D material, GO has high aspect ratio with flexible structure, and it also has extraordinary mechanical properties and superior thermal and electrical conductivity.

Graphene oxide is chemically more active with the fibre and resin polymers than graphene, because of the epoxide and hydroxylgroups within the GO sheets and carbonyl and carboxyl at the edges of the GOsheets.

Evaluations of the coated aramid fibre are to be tested for strength and for interface adhesion with the epoxy resin.

In this study, the GO and bioinspired PDA were used to functionalize aramid fibre, aiming toimprove the interfacial adhesion between aramid fibre and epoxy matrix. SEM and XPS confirmed that the aramid fibres were successfully coated by PDA and GO-PDA. XPS demonstrated that more polar functional groups were introduced onto aramid fibre after the treatments, which could affect the fibre surface activation. Besides, the strong π–πbonding usually makes the surface stacking quite stable against rinsing or other solution processing, which result in an improvement of the interfacial shear strength between fibre and matrix. The SEM observation displayed uniform coating of PDA and GO on the surface of fibre and themodification of GO increased the roughness of fibre surface. As a result, the interfacial shearstrength of GO-PDA-aramid fibre composites was improved by 210%. The usefulness of theGO-PDA coating has demonstrated significant increase in IFSS. The surface modification has also protected the bulk structure of fibres without decreasing the tensile strength of single fibre.

This study provides a novel method for surface modification of chemically inert high-performance fibres, which is believed to be beneficial for interface improvement for compos-ites. Furthermore, the polydopamine and graphene oxide grafting will lead to the feasible application of high-performance fibres in the composites industry, aerospace and ballistic protection area.