Chitin nanocrystals as Pickering stabilizer for O/W emulsions: Effect of the oil chemical structure on the emulsion properties.

Chitin nanocrystals (ChNCs) produced by hydrochloric acid hydrolysis of chitin were used as stabilizing agent for oil-in-water (O/W) emulsification of soybean oil (SO), acrylated soybean oil (ASO), and epoxidized soybean oil (ESO). The emulsion stability, droplet size, and rheology of the emulsion were found to be significantly affected by the oil chemical structure. Strong interaction between ChNCs and the oil droplets enhanced the stabilizing efficiency of ChNCs through a Pickering effect, resulting in emulsions with low droplet size and long-term stability. The use of ChNCs as stabilizer for O/W emulsions in replacement of synthetic surfactants opens new avenues to produce emulsions for a wide variety of applications, including cosmetic products, coating, inks and adhesives.

Cellulose nanocrystal as ecofriendly stabilizer for emulsion polymerization and its application for waterborne adhesive.

Soap-free emulsion polymerization of vinyl acetate (AVM) in the presence of cellulose nanocrystals (CNCs) was performed using persulfate/metabisulfite as initiator. The effect of the addition of MPEG comonomer on the locus of CNCs with respect to polymer particles was investigated. It was shown that the presence of MPEG strongly favors the accumulation of CNCs on the polymer particle thus contributing to a stabilization of polymer particle through Pickering effect. The rheological properties of the dispersion as well as the reinforcing effect of CNCs were also meaningfully affected by the presence of MPEG. For purpose of application, the polyvinyl acetate (PVA)/CNC nanocomposite dispersion was used as binder to produce PVA-based waterborne adhesive for wood. This open the way to produce high-value one pot nanocomposite dispersion ready for use, free from any surfactant likely to be used for waterborne adhesive or coating with higher mechanical performance.

Surfactant-free emulsion Pickering polymerization stabilized by aldehyde-functionalized cellulose nanocrystals.

Aldehyde-functionalized cellulose nanocrystals (CN) with two aldehyde contents were produced by periodate oxidation and gentle sonication. The aldehyde-functionalized CNCs were shown to be an effective stabilizer in the Pickering emulsion polymerization of acrylate monomers using potassium persulfate (KPS)/metabisulfite redox initiation system at 50 °C without any added surfactant. The effect of CNC content on the particle size, zeta-potential, colloidal stability and film properties were discussed. CNCs with the highest aldehyde content impart better colloidal stability to the polymer dispersion and lower particle size. The stabilization process was explained by the reaction of bisulfite with aldehyde groups borne by CNC, forming an adduct that contributes to the initiation of the polymerization and nucleation of polymer particles. This favors the effective attachment of CNCs onto the polymer particle, which is prerequisite for the effective Pickering stabilization process. The optical and mechanical properties of the nanocomposite films obtained by simple casting of the polymer dispersion and water evaporation were also investigated by transmittance and dynamic mechanical analysis (DMA). Better transparency was observed for films prepared in the presence of CNCs with the highest aldehyde content, while a reverse trend was noted for the mechanical properties.

CNFs from twin screw extrusion and high pressure homogenization: A comparative study.

Cellulose nanofibrils (CNFs) from oxidized never dried Eucalyptus pulps have been produced by using twin screw extrusion (TSE) and high pressure homogenizer (HPH), and their properties were compared. CNFs from TSE are produced at 10% solid content and then diluted to 1% for purpose of comparison against HPH. The nanosized fraction (NF) was around 90% for CNFs from HPH compared to 70% when TSE was used. Difference in the fibrillation extent has led to a higher transparency degree for CNFs gel from HPH. However, the rheological properties of two CNFs gels are quite similar with a solid-like aspect. The elastic modulus is one order of magnitude higher than viscous modulus and nearly frequency-independent. Analysis of the nanosized fraction with AFM has revealed long nanosized fibrils 3-4 nm in width for both CNFs types. When mixed with waterborne polymer dispersion, transparent to translucide nanocomposite films were obtained. However, the reinforcing potential of CNFs from HPH has been shown to be stronger than that from TSE.