Surface tension of binary and ternary polymer solutions: Experimental data of poly(vinyl acetate), poly(vinyl alcohol) and polyethylene glycol solutions and mixing rule evaluation over the entire concentration range

Critical Solutal Marangoni Number Correlation for Short-Scale Convective Instabilities in Drying Poly(vinyl acetate)-Methanol Thin Films

“…In order to assess the driving forces of Marangoni instabilities, the concentration and temperature-dependent surface tension of several polymer solutions was experimentally investigated over the whole concentration range. It was found that all five binary polymer-solvent solutions under investigation show a non-linear concentration-dependent surface tension [44].…”

“…Several material properties of the used PVAc-methanol solutions are required for experimental evaluation, as well as simulation and Marangoni number calculation: The temperature-and concentration-dependent surface tension σ, being the driving force of Marangoni instabilities, is crucial for a realistic assessment of stability thresholds. For poly(vinyl acetate)-methanol, the surface tension increases from σ MeOH (20 • C) = 22.6 mN/m for pure methanol to σ PVAc (20 • C) = 36.5 mN/m for pure PVAc [44]. As for most materials, σ linearly decreases with increasing temperature, e.g., Reference [79], with ∂σ/∂T = −0.090 ± 0.007 mN/(m • K) between 10 • C and 40 • C [44].…”

“…For poly(vinyl acetate)-methanol, the surface tension increases from σ MeOH (20 • C) = 22.6 mN/m for pure methanol to σ PVAc (20 • C) = 36.5 mN/m for pure PVAc [44]. As for most materials, σ linearly decreases with increasing temperature, e.g., Reference [79], with ∂σ/∂T = −0.090 ± 0.007 mN/(m • K) between 10 • C and 40 • C [44]. The concentration dependency, however, is non-linear: Between a methanol mass fraction of x MeOH = 0.60 to 0.67, the partial derivative is ∂σ/∂x MeOH ≈ −7.6 mN/m, and, between x MeOH = 0.43 to 0.50, it is ∂σ/∂x MeOH ≈ −18.0 mN/m [44].…”

“…An additional level of complexity arises when considering drying of polymer solutions: Primarily, the surface tension changes during the drying process, due to its dependency on temperature, as well as concentration [44]. In addition, the viscosity strongly increases during drying with decreasing solvent content dampening any flow, and the mass diffusion coefficient strongly decreases, especially for low solvent concentrations [4].…”

“…As for most materials, σ linearly decreases with increasing temperature, e.g., Reference [79], with ∂σ/∂T = −0.090 ± 0.007 mN/(m • K) between 10 • C and 40 • C [44]. The concentration dependency, however, is non-linear: Between a methanol mass fraction of x MeOH = 0.60 to 0.67, the partial derivative is ∂σ/∂x MeOH ≈ −7.6 mN/m, and, between x MeOH = 0.43 to 0.50, it is ∂σ/∂x MeOH ≈ −18.0 mN/m [44]. This shows that the assumption of linear concentration dependency, as assumed in most theoretic analyses, is not valid for our experiments.…”