A green approach to preparing hydrophobic, electrically conductive textiles based on waterborne polyurethane for electromagnetic interference shielding with low reflectivity

A green method was employed to fabricate a coated textile with hydrophobic surface that provided electromagnetic interference shielding performance with low reflectivity. First, two-component waterborne polyurethane dispersions modified with hydroxyl-terminated polydimethylsiloxane were synthesized. Multi-walled carbon nanotubes (CNT) and graphene were well dispersed in water via high pressure microfluidizer. Waterborne polyurethane and fillers containing 80% CNT and 20% graphene were applied to textiles by dipping method. The water contact angles of the polyurethane coating and the coated textile were 103.4° and 153.6°, respectively, when the polyurethane contained 10% hydroxyl-terminated polydimethylsiloxane. The electromagnetic interference (EMI) shielding effectiveness (EMI SE) of the coated textile (3% filler loading) could achieve 35 dB with a thickness of only 0.35 mm and the reflectivity is ca. 41.4%. By dipping a textile into polyurethane dispersions with different filler loadings (1% and 3%) to obtain a coated textile with a two-layer structure coating. EMI SE of the coated textile reached 30 dB and the reflectivity was only ca. 26.5%, indicating 26.5% of the electromagnetic waves is reflected during the propagation process when 99.9% electromagnetic waves is attenuated. Possible attenuation mechanisms of electromagnetic waves such as dielectric loss, multiple reflections, scattering and conductive loss were discussed. The mechanical properties, thermal conductivity and thermal stability of the coatings and coated textiles were studied. The coated textiles fabricated in a green and facile approach with excellent electromagnetic shielding performance and low reflectivity have great potential in advanced EMI shielding applications.