Dynamic Wetting Properties of Silica-Poly (Acrylic Acid) Superhydrophilic Coatings

Abstract

Superhydrophilic coatings based on a hydrophilic silica nanoparticle suspension and Poly (acrylic acid) (PAA) were prepared by dip coating. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to examine the morphology of the coating. The effect of surface morphology on the dynamic wetting behavior of the superhydrophilic coatings was studied by changing the silica suspension concentration from 0.5% wt. to 3.2% wt. while keeping the silica concentration in the dry coating constant. The droplet base diameter and dynamic contact angle with respect to time were measured using a high-speed camera. A power law was found to describe the relationship between the droplet diameter and time. A significantly low experimental power law index was obtained for all the coatings. Both roughness and volume loss during spreading were suggested to be responsible for the low index values. The water adsorption of the coatings was found to be the reason for the volume loss during spreading. The coatings exhibited good adherence to the substrates and retention of hydrophilic properties under mild abrasion.

Superhydrophobicity Mechanism and Nanoscale Profiling of PDMS-Modified Kaolinite Nanolayers via Ab Initio-MD Simulation and Atomic Force Microscopy Study

“…The angle, denoted as θ, is the included angle between the gas–liquid interface and the solid–liquid interface. Surfaces with θ values below 10° and between 10 and 90° are defined as superhydrophilic and hydrophilic surfaces, , respectively, while those with θ values higher than 90° are hydrophobic. Surfaces with θ values exceeding 150° and a sliding angle less than 10° are designated as superhydrophobic .…”