Droplet investigation on hydrophobic artificial and natural surfaces: Molecular weight and viscosity of polymer effects the droplet distortion

Abstract

Contact angle measurement of water, benzyl alcohol, ethylene glycol and glycerol are performed on hydrophobic surfaces of six polymers and four natural surfaces. We performed drop impacts dynamic of water droplets on an artificial polymer hydrophobic surfaces and natural hydrophobic surfaces with different impact velocities. Highest spread length and oscillations were observed on both high-density polyethylene (MI 42) and polypropylene (Bolton) due to the Wenzel regime. Two impacts, sticking and deposition was identified on the polymer samples due to the low static contact angles. Rebound, splashing, fragmentation and vibrational oscillations were observed due to the micro scale roughness on the natural surfaces. Highest static contact angle of water droplet (86.2±2.1) and lowest viscosity was obtained on polyethylene (Mw 35k) surface. Lowest static contact angle (79.9±2.8) and highest viscosity was observed on polypropylene surface. Furthermore, highest static contact angle of water drop (118.02±7.46) was observed on Purple sage (Leucophyllum frutescens) surface and lowest static contact angle (98.38±4.91) was observed on Eucalyptus (Corymbia) surface. The viscosity and critical surface energy of the polymer samples were also measured and discussed.