Fabrication of superrepellent microstructured polypropylene/graphene surfaces with enhanced wear resistance

Fabrication of biomimetic laminated polypropylene/graphene powder (PP/GP) nanocomposites by template method to form the highly structured micropillars with submicron villi on top is presented in this work. Microstructures on PP surfaces are stretched and warped by the considerable force between the PP material and microcavities in the template during demolding, changing from micropillars to micropyramids. With the addition of 9% GP, the surface adhesive force is reduced from ~ 571 to ~ 215 μN on smooth surfaces and is almost as weak as ~ 4 μN on microstructured PP/GP surfaces, contributing to the successful demolding of microstructures from microcavities. The droplet of less than 10 μL would rather adhere to the syringe needle than the microstructured PP/GP surface. Apparently, the microstructured PP/GP surface with an extremely small roll-off angle of ~ 0.5° is slippery and superhydrophobic, exhibiting lotus effect. With the ability to work under a water pressure of up to 1500 Pa, the microstructured PP/GP surface exhibits a high-efficiency self-cleaning performance by a combination of droplet bouncing and rolling behaviors. The submicron villi forming on the top of PP/GP micropillars are caused by a mild stretch. This phenomenon might be attributed to a weak adhesion between PP/GP nanocomposites and the microcavities during demolding, facilitating the formation of the sufficiently robust Cassie–Baxter state. After a 1000 mm abrasion length, the newly formed tapering microfibers increase the roughness on the top of the micropillars and help the worn microstructured surface transform to the sticky superhydrophobicity, i.e., petal effect.