Water-based Piezoresistive Conductive Polymeric Paint Containing Graphene for Electromagnetic and Sensor Applications

The present invention belongs in the field of nanotechnologies and more specifically regards production of new nanostructured and graphene-based materials, presenting controlled electrical, electromagnetic, and electromechanical properties. In particular, the present invention regards formulation and production of a water-based polymeric paint, which has controlled electrical or else piezoresitive or else electromagnetic properties, starting from a commercial water-based polymeric paint or else from a water-based polymeric liquid solution filled with graphene nanoplatelets (GNPs), obtained by means of exfoliation of expanded graphite. Said paint can be used in electromagnetic-shielding applications (for example, for producing radar-absorbent materials – RAMs) or else for producing antistatic devices or piezoresistive coatings for distributed monitoring of the state of strain of a structure. In addition to the aforesaid electrical, piezoresistive, and electromagnetic characteristics, the coats thus obtained are light, easy to process, and suitable for being laid on any substrate. All the purposes of the invention have been achieved through the process according to Claims 1 to 13. The process developed for producing said paint is simple, inexpensive, fast, and suitable for low-cost mass production. Moreover, it makes use of alcohol-water mixtures as solvent. It envisages the following steps: a) subjecting commercial graphite intercalation compound (GIC) to thermal expansion to obtain known structures such as TEGO, WEG, or expanded graphite (EG), or else using EG of a commercial type; b) dispersing and shredding said TEGO, WEG, or EG structures in water-based paint/ polymer possibly diluted with alcohol-water mixture, in variable concentrations according to the desired final properties; and c) subjecting the suspension to ultrasonication, wherein the parameters of the sonication cycle such as the temperature of the suspension, the energy released and the duration are defined on the basis of the properties of the material that is to be obtained. The paint can be laid with multiple techniques, such as, by way of non-limiting example, spraying, dip-coating, and ink-jet. Advantageously, according to the invention, it is possible to control the electrical, piezoresistive, and electromagnetic properties of the coating obtained with said paint through: 1. the amount of GNPs dispersed within the matrix; 2. appropriate definition and concentration of the alcohol-water mixture used as solvent; and 3. control of the dispersion of the GNPs within the paint, wherein said control is obtained through the sequential action of a mechanical rod stirrer, which has the function of shredding the expanded graphite in suspension, and of a sonicator with ultrasound tip, which has the function of exfoliating and dispersing the expanded graphite previously shredded.