| Rising environmental awareness and the high demand for alternatives to non-renewable petroleum resources has led to extensive research focused on the concept of biomass-based biorenewable materials.Cellulose is the most important renewable resource in nature.However,due to the strong intermolecular and intramolecular forces,it is difficult for native cellulose to be fibrillated into colloidal particles,which limits its applications in the fields of composite materials,food,medicine,dyeing and finishing.In this paper,regenerated cellulose(RC)colloid suspension was prepared by simple solvent dissolution and anti-solvent regeneration and then mechanical force treatment.The physicochemical properties of RC colloid suspension were systematically studied.The RC colloid suspension was used in composite materials,anti-sagging of waterborne coating,and liquid oils structuring in food,etc.,which expanded the application of cellulose colloid materials.First,RC was prepared in high yield(>80%)by simple solvent dissolution and successive anti-solvent regeneration,and then treated by mechanical force.Cryo-transmission electron microscopy measurement showed that the RC has a diameter of 20-40 nm and a length of several microns,which belongs to the category of nanocellulose.In addition to the nature of cellulose,RC colloidal particles also had a higher specific surface area and more reaction accessible areas.X-ray diffraction and Fourier transform infrared spectroscopy was used to characterized RC.The results showed that RC is mainly cellulose II,with low crystallinity and unmodified surface.Furthermore,RC colloid suspension was stable against changes in ionic strength.The zeta potential values of RC were quite low,approximately-10 mV.After high-pressure homogeneous mechanical force treatment,the storage modulus and loss modulus of cellulose were reduced for the disruption of the entanglement between RC.The rheological behavior of RC colloid suspension,including their oscillating shear and time-dependent behavior,as well as yield stress were studied in this work.The water-soluble polymer sodium alginate was used as the RC colloid suspension media and the effect that this inclusion had on the rheology of regenerated cellulose suspensions during shear flow was investigated.The results reveal that the RC colloid suspension exhibited “gel-like” behavior and had a shear-thinning property.At increasing RC concentrations,the yield stress and the extent of viscosity recovery after plastic deformation both increased.The viscoelastic suspension underwent a transition from “solid-like behavior” to “liquid-like” behavior upon sodium alginate addition.Furthermore,introduction of sodium alginate to RC colloid suspension improved their viscosity recoverability and lowered or even eliminated its yield stress.RC colloid suspension from microcrystalline cellulose(MCC)or wood pulp toward improving waterborne polyacrylate(PA)latex sag resistance was evaluated.Rheology behavior of PA latex-RC was investigated.PA latex-RC displayed a “gel-like” behavior and had a desirable shear thinning property.Moreover,sag resistance of PA latex was evaluated by creep behavior.Results showed that deformation of PA latex at constant stress obviously decreased with an increase of RC concentration.Meanwhile,PA latex showed high recovery of strain(>90%)with 2 wt.% RC concentration after removal of stress,which may be related to the reinforcement from the RC entanglements and their interaction.In addition,the properties of dry PA film with RC were also evaluated.The tensile strain and tensile stress and thermal stability of the films were slightly improved,while optical transparency slightly compromised with 2 wt.% RC concentration.Overall,the results suggested that RC is a promising biomass material for improving the sag resistance of waterborne acrylic latex.RC was used to prepare polystyrene/cellulose composites.Specifically,an oil-in-water Pickering emulsion of styrene stabilized by RC was prepared,followed by polymerization of styrene,allowing us to obtain a uniformly dispersed polystyrene(PS)/RC composite.When the RC concentration was above 0.8 wt.%,a network of RC spontaneously formed in the composite,as evidenced by rheological testing.Furthermore,the addition of RC to polystyrene improved the composite’s thermal stability and tensile mechanical properties while minimally impacting average visible light transmission(with a decrease in average transmission by about 1-5%).Regenerated cellulose is a promising nanofiller for polymeric composites due to its environment friendly and cost effective nature,and could be used for preparation of other novel RC-reinforced composites.An edible and structured emulsion gel was successfully prepared from thermo-gelable polysaccharide curdlan and RC,which was characterized by a set of methods,such as,fluorescence microscopy,rheology analysis,etc.The preparation procedures included formulating an oil-in-water emulsion stabilized by RC and curdlan,followed by heat treatment leading to a structured solid system.The stable O/W type emulsion gel was acquired at the RC concentration above 0.5 wt.% and curdlan above 1 wt.%.The fluorescence microscopy proved the adsorption of RC on the oil droplets surface.Besides,the effect of temperature and RC/curdlan concentrations on the rheological behavior of emulsion gel was evaluated.G’,G” and viscosity of the emulsion started to increase at around 50 ℃ and thermal irreversible gel formed at temperature 80 ℃.Due to the reinforcement of entanglements and interactions,increasing RC/curdlan concentration contributed to an improvement of storage(G’)and loss(G”)moduli in emulsion gel,while reduced their creep compliance under microstress according to the creep measurements.A facile,two-step process was used for oleogel production by first preparing an oil-in-water emulsion stabilized by RC and carboxylmethyl cellulose(CMC),followed by freeze-drying to selectively evaporate the water phase.The adsorption of cellulose on the surfaces of the oil droplets was confirmed by confocal laser scanning microscopy.Oscillatory shear rheology was used to evaluate the effect of the RC concentration on the rheological behavior of the emulsions and oleogels.Due to the reinforcement from the entanglements and interactions,an increase in the RC concentration was found to increase the storage(G’)and loss(G”)moduli of the emulsions and oleogels.The oleogels showed a high gel strength of G’>15000 Pa,as well as good thixotropic recovery,thus holding great potential for food processing. |
