Thermally Stable Polypropylene Superhydrophobic Surface Due to the Formation of a Surface Crystalline Layer of Microsized Particles

Polypropylene is a potential material for the fabrication of superhydrophobic surfaces. In this paper, two isotactic polypropylenes made from a metallocene catalyst (miPP) and Ziegler–Natta catalyst (ziPP) were employed to prepare superhydrophobic surfaces. The results showed that the superhydrophobicity and thermal stability of the miPP film were much better than those of the ziPP film. The water contact angle (CA) and sliding angle (SA) of the miPP film were 155° and 10°, respectively, after being heated at 100 °C for 5 h, while the water CA and SA of the ziPP film were 135° and 90°, respectively. This difference in the thermal stability was attributed to the miPP easily forming a surface crystalline layer on the microsized particles, which resulted in an increased roughness and improved thermal stability. These results were supported by the dyeing experiment, high-resolution transmission electron microscopy (HRTEM) images, and selected-area electron diffraction patterns. Furthermore, the morphology and roughness of the spin-coated miPP and ziPP films were explored by atomic force microscopy (AFM), and the results also showed that the good thermal stability of miPP film resulted from the increased crystallinity.