Self-healing PU coating shields electronics

The coating combines a dynamically crosslinked waterborne polyurethane with Ti3C2Tx MXene, an electrically conductive two-dimensional material. It is intended for flexible electronics and other applications in which electromagnetic shielding must withstand repeated bending, scratching or mechanical damage.

Electromagnetic interference can disrupt electronic components and communications systems. Conductive coatings can protect devices by reflecting or absorbing electromagnetic radiation, but cracking can break the conductive network and reduce shielding performance.

The researchers addressed this problem by constructing the polyurethane around reversible hindered urea bonds. These bonds allow the crosslinked polymer network to rearrange when heated, closing cracks and restoring the coating’s mechanical properties.

The polyurethane also provides hydrogen-bonding sites that interact with the surface of the MXene sheets. According to the researchers, this strong interface allows the conductive particles to be dispersed efficiently and improves load transfer between the polyurethane and MXene phases.

The composite reached its electrical percolation threshold at a MXene loading of 1.6 wt%. Above this point, sufficient contacts formed between the conductive sheets to create a continuous electrical network through the coating.

At a MXene content of 8.2 wt%, the composite achieved an electromagnetic-interference shielding effectiveness of 55.6 dB. At the same loading, tensile strength increased by 55% and Young’s modulus rose by 335% compared with the unfilled polyurethane.

The researchers also reported good adhesion to several plastic substrates, an important consideration for coatings intended for electronic housings, flexible devices and automotive components.

Damage could be repaired by heating the coating, which enabled the hindered urea bonds to exchange and the polymer chains to reorganize. This produced near-complete recovery of its electrical and mechanical properties.

The researchers also demonstrated localized repair using near-infrared irradiation. MXene converts the incident light into heat, allowing a damaged region to be treated without heating the complete coated component.

The dynamic polyurethane network allowed the material to be thermally reprocessed several times while retaining almost 100% of its original mechanical properties. This could make damaged coatings easier to repair or rework and reduce the amount of material discarded during manufacturing.

Potential applications include flexible and wearable electronics, electronic enclosures and components used in electric vehicles. Electromagnetic compatibility is becoming increasingly important in vehicles as the number of power-electronic systems, sensors and communications devices increases.

The work was conducted by researchers from the Korea Institute of Science and Technology, Korea University, the University of Science and Technology and coatings manufacturer KCC Corporation.

Illustration credit: Korea Institute of Science and Technology, Korea University/Springer Nature

The paper, “High-performance and self-healable electromagnetic interference shielding coatings based on waterborne dynamic polyurethane and Ti3C2Tx MXene composites,” was published in Advanced Composites and Hybrid Materials on July 25.