The monomer droplets were stably dispersed in water, retaining the size distribution. The Pickering emulsion in this work was quite stable, even when it was kept at room temperature for more than a week. The emulsion using solid particles as a dispersion stabilizer is generally termed a Pickering emulsion. In contrast, in the present system, CNFs were adsorbed onto the water/styrene interface, metastabilizing the system. Pickering emulsion simulation shear free#As the interfacial free energy between styrene and water is high, usually, styrene and water ultimately undergo phase separation without being homogenously mixed. This mixture then underwent ultrasound treatment, which resulted in the formation of a CNF-stabilized styrene-in-water emulsion (Fig. First, an aqueous dispersion of CNFs was mixed with styrene monomers, into which an initiator was dissolved. In this study, polystyrene (PS) was used as a matrix. Furthermore, we report the synthesis of core-shell microparticles using this Pickering emulsion as a template. Several studies on polymer composite preparation through Pickering emulsions have been reported, where nanocelluloses, microfibrillated lignocellulose, or chitin nanofibrils were used as stabilizers. In the present study, a CNF-stabilized monomer-in-water emulsion was used as a starting point to design a CNF/polymer composite structure. Therefore, Pickering emulsions generally show better stability than emulsions stabilized by surfactants. Compared to surfactant molecules, the solid particles more strongly adsorb at liquid/liquid interfaces. Pickering emulsions are emulsions stabilized by solid particles. CNFs are known to serve as an excellent emulsifier and form stable Pickering emulsions. In this review, we sought to develop a homogenous composite of CNFs and a hydrophobic plastic using an aqueous solution process, which does not require organic solvents or melt blending procedures. However, such a process is highly time and energy consuming. Homogeneous CNF/polymer composites can be prepared by drying a mixture of a plastic and CNF dispersions in organic solvents. Moreover, tailoring the chemical structure of the carboxy groups effectively enables the dispersion of CNFs in various organic solvents. The increased osmotic pressure between the fibrils and mild mechanical treatment in water allow the preparation of CNFs with nanosized widths and good colloidal stability in water. The oxidation selectively introduces carboxylate groups onto the surface of cellulose microfibrils. TEMPO-mediated oxidation is a chemical reaction that enables selective conversion of primary hydroxy groups into carboxylate groups in water. To date, we have sought to develop homogeneously mixed CNF/polymer composites using a CNF prepared through chemical pretreatment termed 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. Therefore, the composition difficulty poses the biggest challenge for the production of such materials. However, obtaining a homogenous composition of CNFs and commodity plastics has been difficult due to the high interfacial energy. To fully elicit the reinforcing effect of CNFs, CNFs must be homogenously dispersed in a composite material. Taking advantage of these characteristics of CNFs, ongoing research has been extensively focused on utilizing them as a reinforcing material for plastics since the mid-1990s. They have been demonstrated to have excellent mechanical and thermomechanical properties, with high strength (2‒6 GPa), high elastic moduli (130‒150 GPa), and low thermal expansion coefficients (4‒6 ppm K −1). In particular, wood-derived CNFs have a characteristic shape and are ~3 nm in width and several micrometers in length. In recent years, cellulose nanofibers (CNFs) have been used as a natural carbon-neutral reinforcing material. However, as the energy demand for the production and discarding of these reinforcing materials is high, plastic reinforcement using environmentally friendly materials has become a priority toward the implementation of a low-carbon society. Common reinforcing materials include glass and carbon fibers hence, composite materials acquire the strength and thermal dimensional stability that plastics cannot attain on their own. Reinforcing materials are often added to these plastics to improve their mechanical properties. Plastics are used for multiple purposes as parts of automobiles, home electrical appliances, food packaging materials, and medical equipment and thus constitute essential materials in our lives.
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