Waterborne coatings often delaminate and settle during long-term storage, requiring the addition of thickeners. The effects of nanofibrillated cellulose (NFC) and the commonly used thickener, hydroxyethyl cellulose (HEC), on the storage stability of waterborne coatings were compared in this study. The morphology of NFC was characterized using infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The rotational viscosity and rheological properties of the waterborne coatings with NFC and HEC were tested. Stationary settling experiments were also conducted at different temperatures to compare the difference of NFC and HEC on improving the storage stability of the waterborne coatings. The results showed that the waterborne coating with NFC exhibited pseudoplastic fluid characteristics; a small addition of NFC can achieve the same improvement effect on the storage stability of waterborne coatings as HEC. Further, the improvement effect of NFC was not affected by temperature. The waterborne coating with NFC still exhibited good storage stability at high temperatures, which was significantly superior to that of HEC. Therefore, NFC is a feasible agent for improving the prolonged storage stability and warming-induced delamination of waterborne coatings.

To improve the performance of polyurethane films, small amounts of cellulose nanofibrils (CNF) were physically blended with a waterborne polyurethane (WPU) emulsion, and then CNF/WPU composite films were prepared by cast-coating and drying. The particle size of the emulsions and the chemical structure, micromorphology, thermal stability, mechanical properties, and water resistance of the composite films were characterized using a Malvern laser particle size analyzer, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), an electronic strength machine, water contact angle analysis (WCA), and water absorption tests, respectively. The results showed that at a low CNF content of 0.3 wt%, the particle size of the WPU emulsion and chemical structure of the film did not change significantly. In addition, the tensile strength of the composite film increased by up to 108% compared to the neat WPU film, and the thermal stability and water resistance were slightly improved. The addition of CNF greatly enhanced the tensile strength while maintaining the other original properties of the WPU film, which may greatly improve the service life and tear resistance of commercial coatings in the future.

Biodegradable polymers such as poly(butylene adipate-coterephthalate)(PBAT) have attracted great interest as alternatives to traditional petroleum-based polymers. Nonetheless, it is necessary to improve some properties of PBAT, such as mechanical strength. Cellulose nanofiber(CNF) can improve PBAT mechanical strength, but its dispersion and compatibility in the PBAT matrix require further improvement. In this study, octadecylamine(ODA) was utilized to graft-modify CNF to change the fiberto-fiber interaction and improve its compatibility with the PBAT matrix.PBAT composites with 1 wt% CNF were prepared using a masterbatch premixing method to avoid CNF aggregation during extrusion. The effects of ODA graft modification on CNF properties were studied; varying degrees of CNF modification were investigated for their effect on PBAT properties. ODA-modified CNF(OCNF)/PBAT melt-extruded composites possessing17.2% higher tensile strength than pure PBAT polymer were obtained without affecting the thermal stability of PBAT. As a result, surface modification of CNF with ODA is an effective strategy for improving CNF-PBAT compatibility.

In this study, lignin-containing microfibrillated cellulose (MFC) was prepared from corncob residue after xylose extraction via co-grinding with calcium hydroxide. The product was then compared with the MFC obtained by direct grinding and applied to strengthen paper. The chemical composition and morphological structure analysis results showed that the corncob residue can be used to prepare lignin-containing MFC and does not require further purification. Moreover, the co-grinding with calcium hydroxide is easier to fibrillate corncob residue. The MFC obtained by co-grinding with calcium hydroxide had a higher aspect ratio, and its surface was coated with calcium carbonate nanoparticles. MFCs obtained by both the methods mentioned above had an obvious strengthening effect on paper. Compared with the paper without MFC, the tensile index, elongation, burst index, and folding strength of the paper with MFC obtained by co-grinding with calcium hydroxide significantly increased by 17.5%, 22.1%, 19.5%, and 157.1%, respectively. This study provides a novel idea for the utilization of corncob residue, which may enhance the value and promote the comprehensive utilization of corn by-products.

Carboxyethylation pretreatment was used to prepare microfibrillated cellulose (MFC) in this study. In order to evaluate the adaptability of this pretreatment method, carboxyethylated MFC was prepared from six different cellulosic materials. The carboxyl content, degree of polymerization, water retention value, charge density, chemical structure, size distribution, and micromorphology of the materials before and after pretreatment and grinding were studied and compared. The viscosity, ultraviolet (UV) transmittance, and thermal stability of the MFC samples at a certain concentration were determined. The results showed that the carboxyl content, water retention value, charge density, degree of polymerization, size distribution, and micromorphology of the pretreated and ground samples varied with those of the raw materials. The initial viscosity varied based on the type of raw material used. The MFC suspension prepared from cotton linter pulp had the highest UV transmittance, while the MFC prepared from bleached softwood kraft pulp had the highest viscosity at a low shear rate. After thermal degradation, the amount of residual char from the MFC prepared with the thermo-mechanical pulp was slightly higher than that of the other MFCs. This study demonstrates that carboxyethylation is an effective pretreatment method for different cellulosic materials.

Carboxyethylation is a recent chemical pretreatment for preparation of microfibrillated cellulose (MFC). The carboxyethylated MFC film prepared by coating method has compact structure and high mechanical properties. In order to expand its application, three approaches including using organic solvents, different drying methods and cationic additives, have been adopted in this paper to enrich and regulate the pore structure of MFC film. The results show that all the approaches can improve the pore structure but decrease the mechanical properties of MFC film. When organic solvents such as ethanol, isopropanol and n-butanol were used to replace the water in MFC suspension or pre-dried MFC film, the pore structure of films were increased. Additionally, the film obtained by freeze-drying or air-drying after freezing in liquid nitrogen or freezer has high porosity but poor strength. The best drying process is to rewet dry MFC film, freeze in liquid nitrogen and then freeze-dry. Moreover, the addition of cationic polyelectrolytes or alkene ketone dimer (AKD) in MFC suspension can also significantly increase the film's porosity. Through the above approaches, the porosity of carboxyethylated MFC film can be regulated between 20% and 90%.

Functional composite films were successfully prepared from cellulose, graphite(GP), and polyaniline(PANI) using a combination of physical and chemical processes. Cellulosewasdissolved in N-methylmorpholine-N-oxide monohydrate(NMMO) and regenerated in water to form the matrix. GP was dispersed in the NMMO solvent prior to the dissolution of the cellulose, and PANI was deposited on the surfaces of the cellulose/GP films by in situ chemical polymerization. The structures of the PANI/cellusose/GP composite films were investigated using X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy(SEM), and SEM/energy-dispersive X-ray spectroscopy. The mechanical strengths, thermal stabilities, conductivities, and antibacterial activities of the films were studied in detail. The results showed that GP formed a multilayered structure in the cellulose matrix and that the PANI nanoparticles were tightly wrapped on the film surface. The film thickness increased from 40 mm to 100 mm after the addition of GP and PANI. The tensile strength of the composite films was 80~107 MPa, with the elongation at break being 3%~10%. The final residual weight of the composite films was as high as 65%, and the conductivity of the composite films reached 14.36 S/m. The cellulose matrix ensured that the films were flexible and exhibited desirable mechanical properties, while the GP filler significantly improved the thermal stability of the films. The PANI coating acted as a protective layer during burning and provided good electrical conductivity and antibacterial activity against Escherichia coli; both of these characteristics were slightly enhanced by the incorporation of GP. These PANI/cellulose/GP composite films should be suitable for use in electronics, antistatic packing, and numerous other applications.