Overview on Foam Forming Cellulose Materials for Cushioning Packaging Applications

Wet foam can be used as a carrier in the manufacturing of lightweight materials based on natural and man-made fibers and specific additives. Using a foam forming method and cellulose fibers, it is possible to produce the porous materials with large area of end-using such as protective and cushioning packaging, filtering, hydroponic, thermal and sound absorption insulation, or other building materials. In comparison with the water-forming used for conventional paper products, foam-forming method provides many advantages. In particular, since fibers inside the foam are mostly trapped between the foam bubbles, the formed materials have an excellent homogeneity. This allows for using long fibers and a high consistency in head box without significant fiber flocking. As result, important savings in water and energy consumptions for dewatering and drying of the foam formed materials are obtained. In cushioning packaging, foam-formed cellulose materials have their specific advantages comparing to other biodegradable packaging (corrugated board, molded pulp) and can be a sustainable alternative to existing synthetic foams (i.e., expanded polystyrene or polyurethane foams). This review discusses the technical parameters to be controlled during foam forming of cellulose materials to ensure their performances as cushioning and protective packaging. The focus was on the identification of practical solutions to compensate the strength decreasing caused by reduced density and low resistance to water of foam formed cellulose materials

Green Approaches on Modification of Xylan Hemicellulose to Enhance the Functional Properties for Food Packaging Materials—A Review

Based on the environmental concerns, the utilisation of hemicelluloses in food packaging has become a sustainable alternative to synthetic polymers and an important method for the efficient utilisation of biomass resources. After cellulose, hemicellulose is a second component of agricultural and forestry biomass that is being taken advantage of given its abundant source, biodegradability, nontoxicity and good biocompatibility. However, due to its special molecular structure and physical and chemical characteristics, the mechanical and barrier properties of hemicellulose films and coatings are not sufficient for food packaging applications and modification for performance enhancement is needed. Even though there are many studies on improving the hydrophobic properties of hemicelluloses, most do not meet environmental requirements and the chemical modification of these biopolymers is still a challenge. The present review examines emerging and green alternatives to acetylation for xylan hemicellulose in order to improve its performance, especially when it is used as biopolymer in paper coatings or films for food packaging. Ionic liquids (ILs) and enzymatic modification are environmentally friendly methods used to obtain xylan derivatives with improved thermal and mechanical properties as well as hydrophobic performances that are very important for food packaging materials. Once these novel and green methodologies of hemicellulose modifications become well understood and with validated results, their production on an industrial scale could be implemented. This paper will extend the area of hemicellulose applications and lead to the implementation of a sustainable alternative to petroleum-based products that will decrease the environmental impact of packaging materials

Analysis of the Anisotropy of Sound Propagation Velocity in Thin Wooden Plates Using Lamb Waves

The objective of the study was to analyze the influence of coating treatments on sound propagation speeds in thin boards, along the longitudinal and radial directions of resonance wood. The samples studied were thin boards made of spruce and maple wood with dimensions of 240 mm × 80 mm × 4 mm (length × width × thickness) subjected to different coating treatments (oil-based varnish and alcohol varnish) as well as unvarnished samples, exposed to radiation UV, and specimens treated in the saline fog. The test method consisted of evaluating the propagation speeds of Lamb waves applied to thin plates, according to a semicircular test model, so that the results highlighted both the acoustic response in the longitudinal and radial directions as well as the variation in the anisotropy of the samples with the change in the sound propagation direction relative to wood fibers. Based on the statistical analysis, sound propagation speed profiles were obtained in each of the 38 directions analyzed for all wood samples. The results highlighted that the oil-based varnish led to a decrease in the speed of propagation in the radial direction, compared to the alcoholic varnish, whose major effect was in the longitudinal direction, on the spruce wood. On maple wood, increasing the number of varnish layers, regardless of the type of varnish, led to a decrease in the anisotropy ratio between the longitudinal and radial directions

Tunable Acoustic Properties Using Different Coating Systems on Resonance Spruce Wood

Abstract The study investigates the effect of the type of varnish and the number of layers on some acoustic properties of the resonance spruce in combination with the changes produced in some physical, morphological, and chemical properties of wood. In addition to color changes and surface chemistry, the surface roughness and morphology are modified by the thickness of the varnish film, 10 layers being optimal from this point of view, as well as the oil‐based finish. The sound absorption coefficient increases with the number of varnish layers and varies with the sound frequency range, varnish type, and wood quality, all contributing to the acoustic tunability. For example, for a sound frequency of 1.5 kHz, it is observed that the oil‐based varnish with 5 and 10 layers contributes to a full sound, while the alcohol varnish, due to a lower absorption coefficient for this frequency, can lead to some nasal sounds. Applying more than 10 layers of varnish does not improve the sound performance as it will soften the sound in an oil‐based finish and make the sound too sharp in the case of alcohol–varnished wood