Nonaqueous foam stabilization mechanisms in the presence of volatile solvents

Lorenzo Lombardi; Soledad Roig-Sanchez; Amar Bapat; John M Frostad

doi:10.1016/j.jcis.2023.05.156

Nonaqueous foam stabilization mechanisms in the presence of volatile solvents

J Colloid Interface Sci. 2023 Oct 15:648:46-55. doi: 10.1016/j.jcis.2023.05.156. Epub 2023 Jun 2.

Authors

Lorenzo Lombardi¹, Soledad Roig-Sanchez², Amar Bapat³, John M Frostad⁴

Affiliations

¹ Department of Chemical, Materials and Production Engineering, University of Naples Federico II, P.le Tecchio 80, Naples, 80125, Italy. Electronic address: lorenzo.lombardi@unina.it.
² Chemical and Biological Engineering, University of British Columbia, 2360 E Mall, Vancouver, V6T 1Z3, BC, Canada; Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, V6T 1Z1, BC, Canada.
³ Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur, 721302, West Bengal, India.
⁴ Chemical and Biological Engineering, University of British Columbia, 2360 E Mall, Vancouver, V6T 1Z3, BC, Canada; Food Science, University of British Columbia, 2205 E Mall, Vancouver, V6T 1Z4, BC, Canada.

PMID: 37295369
DOI: 10.1016/j.jcis.2023.05.156

Abstract

Hypothesis Nonaqueous foams are found in a variety of applications, many of which contain volatile components that need to be removed during processing. Sparging air bubbles into the liquid can be used to aid in their removal, but the resulting foam can be stabilized or destabilized by several different mechanisms, the relative importance of which are not yet fully understood. Investigating the dynamics of thin film drainage, four competing mechanisms can be observed, such as solvent evaporation, film viscosification, and thermal and solutocapillary Marangoni flows. Experiments Experimental studies with isolated bubbles and/or bulk foams are needed to strengthen the fundamental knowledge of these systems. This paper presents interferometric measurements of the dynamic evolution of a film formed by a bubble rising to an air-liquid interface to shed light on this situation. Two different solvents with different degrees of volatility were investigated to reveal both qualitative and quantitative details on thin film drainage mechanisms in polymer-volatile mixtures. Findings Using interferometry, we found evidence that solvent evaporation and film viscosification both strongly influence the stability of interface. These findings were corroborated by comparison with bulk foam measurements, revealing a strong correlation between these two systems.

Keywords: Binary mixtures; Bubble coalescence; Film viscosification; Nonaqueous foams; Single-bubble interferometry; Solutocapillary Marangoni flows; Solvent evaporation; Thermal Marangoni flows.