Figure 3.

Spreading dynamics following the droplet impact on polystyrene. (a) Evolution of the spreading diameter D(t)/D₀ in terms of the time from impact. As observed, the spreading diameter of the Triton 1 CMC (a slow surfactant) is similar to that of water. In contrast, Surfynol (a fast surfactant) presents larger maximum spreading and equilibrium diameters. (b) Dynamic contact angle θ_D in terms of the contact line velocity (u_cl). As seen, at u_cl > 2 m s^–1, the contact angle is not the same for all the solutions, i.e., θ_D = 108 ± 8° for Triton. The impact velocity for these experiments is U₀ = (0.88 ± 0.02) m s^–1.