Environmental and health concerns are driving the need for new materials in food packaging to replace poly- or perfluorinated compounds, aluminum layers, and petroleum-based polymers. Cellulose nanofibrils (CNF) have been shown by a number of groups to form excellent barrier layers to oxygen and grease. However, the influence of lignin-containing cellulose nanofibrils (LCNF) on film barrier properties has not been well reported. Herein, thin films (16 g/m²) from LCNF and CNF were formed on paper substrates through a filtration technique that should mimic the addition of material at the wet end of a paper machine. Surface, barrier and mechanical attributes of these samples were characterized. The analysis on the surface free energy and water contact angle pointed to the positive role of lignin distribution in inducing a certain degree of water repellency. The observed oxygen transmission rate (OTR) and water vapor permeability (WVP) values of LCNF-coated samples were nearly similar to those with CNF. However, the presence of lignin improved the oil proof performance; these layered designs exhibited an excellent resistance to grease (kit No. 12). The attained papers with LCNF coat were formed into bowl-like containers using metal molds and a facile oven drying protocol to evaluate their resistance to oil penetration over a longer period. The results confirmed the capability of LCNF layer in holding commercially available cooking oils with no evidence of leakage for over five months. Also, an improvement in the tensile strength and elongation at break was observed in the studied papers. Overall, the proposed packaging material possesses viable architecture and can be considered as a fully wood-based alternative for the current fluorocarbon systems.

Cellulose nanofibers (CNFs) are an exciting new renewable material produced from wood fibers. Even at low solids content, CNF-water suspensions have a complex rheology that includes extreme shear-thinning as well as viscoelastic properties and a yield stress similar to other suspensions of nanoscale particles. When characterizing the rheology of CNF suspensions, the measurement method may influence the results due to a water layer expected at the boundary, but it is unclear how the behavior near walls influences the measurement method. Parallel-plate, Couette, and vane geometries were used to compare yielding and flow of CNF suspensions obtained by steady-state shear and oscillatory rheological measurements. Five different techniques were compared as methods to obtain a yield stress. Cone and plate geometries were found to lead to sample ejection at low shear rates: Floc-floc interactions can explain this ejection. The suspensions violated the Cox-Merz rule by a significant amount; this behavior has been explained in the past as weak gel structures that break down in shear, but for this material it seems that the acting mechanism involves the formation of a water-rich layer near the solid boundaries in steady shear, while for oscillatory tests, these layers do not form. For suspensions lower than 3% solids, the yield stress measured by different procedures was within 20% of each other, but for high solids suspensions, differences between the methods could be as large as 100%; the water-rich layer formation likely is the cause of these results. Oscillatory methods are suggested as a method to obtain yield stress values for this type of material. The Couette geometry data were below the power-law lines fitted to the parallel-plate geometry data from steady-shear measurements perhaps again attributable to different water-rich layers that form in these different geometries.

A novel method to obtain a high conversion of Ca(OH)₂ powder to CaCO₃ is reported. The method uses supercritical CO₂ containing water that is passed over the dry Ca(OH)₂ powder. Conversions greater than 98% are obtained. The dominant crystal structure is calcite. The process has the advantages of the conventional solution based process in terms of high conversion and the advantages of a gas–solid based process in that dry, non-agglomerated particles are obtained by simple venting of the solvent.

Films formed from cellulose nanofibrils (CNFs) are known to be good barrier materials against oxygen, but they lose this feature once placed in humid conditions. To tackle this issue, we applied an optimized pressing condition under elevated temperature to increase the films’ density and improve their barrier performance. Furthermore, a water barrier coating was employed on the surfaces to control the moisture uptake at high relative humidity (RH). Neat self-standing films of CNF with the basis weight of 70 g/m² were made through a filtration technique and pressed for 1 hour at 130 °C. The resulting nanostructures were covered on both sides using a water-borne barrier layer. Hot-pressing resulted in a significant reduction in oxygen transmission rate (OTR) values, from 516.7 to 3.6 (cm³/(m²·day)) and to some degree, helped preserve the reduced oxygen transmission at high relative humidity. Introducing 35 g/m² of latex coating layer on both sides limited the films’ swelling at 90% RH for about 4 h and maintained the OTR at the same level. A finite element model was used to predict the dynamic uptake of water into the systems. The model was found to over-predict the rate of water uptake for uncoated samples but gave the correct order of magnitude results for samples that were coated. The obtained data confirmed the positive effect of hot-pressing combined with coating to produce a film with low oxygen transmission rate and potential to maintain its oxygen barrier feature at high relative humidity.