Wrinkled Graphene Oxide-Based Films Coatings for Liquid Repellency in Personal Protective Equipment

Graphene oxide(GO) is a two-dimensional material derived from graphite that contains epoxide, carbonyl, carboxyl, and hydroxyl functional groups. Graphene oxide’s novel properties make it a breathable barrier that prevents permeation of toxic chemicals. This has generated interest in its usage as a functional layer in personal protective equipment. The hydrophilic groups present in graphene oxide allow both water and potentially toxic polar organic liquids to wet and spread. Therefore, one aspect of developing GO films for personal protective equipment is modifying its surface to repel liquid droplets.

The goal of this study was to explore methods to modify the surface chemistry and surface structure of GO films to increase liquid contact angles. The test films were created by drop-casting 1ml of GO onto a nitrile glove surface and air drying for 24 hours. The films were roughened by a wrinkling process in which the nitrile substrate is stretched before the deposition of the GO solution. Following the air drying, the films were de-stretched, sprayed with one of five commercially available hydrophobic coatings, and left to air dry for an additional 24 hours. Four degrees of pre-stretching were examined: 0%, 33%, 66%, 100%.

To assess the liquid-repellent properties of the treated coatings, water and diethyl-malonate (a chemical warfare agent simulant) contact angles on the surface of the film were measured. Images of 5μL droplets of the two liquids deposited on the surface of the film were analyzed to determine the contact angle. Data was collected for twenty cases with different commercial coatings and degrees of wrinkling. The results show that surface coating can successfully switch GO films from hydrophilic to hydrophobic and can also increase the contact angle with diethyl malonate. Wrinkling enhanced the liquid repellency in most cases. These findings suggest that wrinkled and coated GO films are promising barrier layers in personal protective applications where both stretching and liquid repellency are desired.