Effect and mechanism of binary surfactant mixture in regulating foam properties, fiber dispersion, and paper structure during foam forming

Abstract

In the practical production process of foam forming, several mixed surfactant systems need to be developed to improve the foam and paper characteristics. Therefore, this study investigated the synergistic mechanisms of surfactant mixture in prolonging foam stability, improving fiber dispersion, and regulating the paper structure. The results suggested that the mixed surfactant system composed of anionic-cationic/zwitterionic surfactants exhibited the most obvious synergistic effect, which increased the foam half-life from 2.78–3.73 to 8.65–14.55 min, changed the viscoelastic modulus of bubble liquid film from 10.71–29.23 to 18.63–23.47 mN/m. Under the combined action of the electrostatic attraction between surfactant headgroups and the hydrophobic force of carbon chains, the interaction parameters of mixed surfactant systems were − 0.74, − 2.49, and − 4.71, respectively. Compared with the single surfactant system, the adsorbed surfactant molecular layer mass at the solid–liquid interface was increased from 42.9–341.8 to 267.1–424.1 ng/cm². When the surfactant concentration was 0.5 mmol/L, there were a significant amount of small bubbles (diameters 5–50 μm) wrapped around the fiber in the mixed surfactant foam system, which reduced the possibilities of fiber collision and flocculation. Furthermore, the response mechanisms of fiber-bubble interaction strength and foam slurry bubble size distribution on fiber orientation and pore size distribution were summarized. These findings are significant for reducing the production cost of foam forming and optimizing the structure of the foam-formed paper.

Graphical abstract