Modified cellulose nanofibrils in co-stabilized Pickering foams and supraparticles

Abstract

Two-phase dispersions, such as foams, are thermodynamically unstable structures and the phases tend to separate eventually. Considering that these systems have a wide variety of applications, improving their stability is essential. Traditionally, surfactants have been used to increase the stability of multiphase systems; however, the surfactant effect is reversible. As a result, an alternative way to enhance these systems' stability was established by using particles. This method is called the Pickering stabilization.

This thesis's main objective was to fabricate foams and fiber-particle composites stabilized by particles and reinforced with cellulose nanofibers (CNF), as well as to investigate the characteristics of the formed systems, including volume, stability, morphology, and mechanical properties. Regarding the fabrication, hydrophobic particles (silica and polytetrafluoroethylene), CNF (isobutyrilated, acetylated and nonmodified) and a suspension of water-ethanol as the foaming media were used. The results showed that the presence of hydrophobic CNFs improved the volume and stability of wet foams significantly. Also, the presence of CNFs improved the cohesion of hydrophobic particulate materials, where a balance between interfiber and fiber-particle can be tuned based on the fiber's surface chemistry.