The aim of the study was to characterize and compare films made of cellulose nanocrystals (CNC), nano-fibrils (CNF), and bacterial nanocellulose (BNC) in combination with chitosan and alginate in terms of applicability for potential food packaging applications. In total, 25 different formulations were made and evaluated, and seven biopolymer films with the best mechanical performance (tensile strength, strain)—alginate, alginate with 5% CNC, chitosan, chitosan with 3% CNC, BNC with and without glycerol, and CNF with glycerol—were selected and investigated regarding morphology (SEM), density, contact angle, surface energy, water absorption, and oxygen and water barrier properties. Studies revealed that polysaccharide-based films with added CNC are the most suitable for packaging purposes, and better dispersing of nanocellulose in chitosan than in alginate was observed. Results showed an increase in hydrophobicity (increase of contact angle and reduced moisture absorption) of chitosan and alginate films with the addition of CNC, and chitosan with 3% CNC had the highest contact angle, 108 ± 2, and 15% lower moisture absorption compared to pure chitosan. Overall, the ability of nanocellulose additives to preserve the structure and function of chitosan and alginate materials in a humid environment was convincingly demonstrated. Barrier properties were improved by combining the biopolymers, and water vapor transmission rate (WVTR) was reduced by 15–45% and oxygen permeability (OTR) up to 45% by adding nanocellulose compared to single biopolymer formulations. It was concluded that with a good oxygen barrier, a water barrier that is comparable to PLA, and good mechanical properties, biopolymer films would be a good alternative to conventional plastic packaging used for ready-to-eat foods with short storage time.

This study investigated the effect of hemp fiber pretreatments (water and sodium hydroxide) combined with silane treatment, first on the fiber properties (microscale) and then on polylactide (PLA) composite properties (macroscale). At the microscale, Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy investigations highlighted structural alterations in the fibers, with the removal of targeted components and rearrangement in the cell wall. These structural changes influenced unitary fiber properties. At the macroscale, both pretreatments increased the composites’ tensile properties, despite their negative impact on fiber performance. Additionally, silane treatment improved composite performance thanks to higher performance of the fibers themselves and improved fiber compatibility with the PLA matrix brought on by the silane couplings. PLA composites reinforced by 30 wt.% alkali and silane treated hemp fibers exhibited the highest tensile strength (62 MPa), flexural strength (113 MPa), and Young’s modulus (7.6 GPa). Overall, the paper demonstrates the applicability of locally grown, frost-retted hemp fibers for the development of bio-based composites with low density (1.13 to 1.23 g cm⁻³).

Cellulose nanocrystals (CNCs) and chitosan (Cht) have been studied extensively for oxygen and water vapour barrier coatings in biodegradable, compostable or recyclable paper packaging. However, rare studies have been performed by using scalable, inexpensive, and fast continuous slot-die coating processes, and none yet in combination with fast' and high-throughput near-infrared (NIR) light energy drying. In this frame, we studied the feasibility of a moderately concentrated (11 wt%) anionic CNC and (2 wt%) cationic Cht coating (both containing 20 wt% sorbitol related to the weight of CNC/Cht), by using plain and pigment pre-treated papers. The effect of coating parameters (injection speed, dry thickness settings) were investigated on coating quantity (dry weight, thickness) and homogeneity (coverage), papers' structure (thickness, grammage, density), whiteness, surface wettability, barrier (air, oxygen and water vapour) properties and adhesion (surface strength). The coating homogeneity was dependent primarily on the suspensions' viscosity, and secondarily on the applied coating parameters, whereby CNCs could be applied at 1–2 times higher injection speeds (up to 80 mL/min) and versatile coating weights, but required a relatively longer time to dry. The CNCs thus exhibited outstanding air (4.2–1.5 nm/Pa s) and oxygen (2.7–1.1 cm³ mm/m² d kPa) barrier performance at 50% RH and 22–33 g/m² deposition, whereas on top deposited Cht (3–4 g/m²) reduced its wetting time and improved the water vapour barrier (0.23–0.28 g mm/m² d Pa). The balanced barrier properties were achieved due to the polar characteristic of CNCs, the hydrophobic nature of Cht and the quantity of the applied bilayer coating that can provide sustainable paper-based packaging.

Starch-based pH-sensing films with bacterial nanocellulose (BNC) and red cabbage anthocyanins (RCA) as active components were investigated in this research. Their structural, physical, surface and colorimetric properties were analyzed, mainly as a function of BNC concentration. The aim of the research was to relate the changes in the intermolecular interactions between the components of the films (starch, anthocyanins and BNC) to the physical, surface and colorimetric properties that are important for the primary intended application of the produced films as pH indicators in smart packaging. The results showed that maize starch (MS) was more suitable as a matrix for the stabilization of anthocyanins compared to potato starch (PS). PS-based films showed a lower value of water contact angle than MS-based films, indicating stronger hydrophilicity. The swelling behavior results indicate that the concentrations of BNC in MS-based films (cca 10%) and the concentration of about 50% BNC in PS-based films are required if satisfactory properties of the indicator in terms of stability in a wet environment are to be achieved. The surface free energy results of PS-based films with BNC were between 62 and 68 mJ/m² and with BNC and RCA between 64 and 68 mJ/m²; for MS-based films, the value was about 65 mJ/m² for all samples with BNC and about 68 mJ/m² for all samples with BNC and RCA. The visual color changes after immersion in different buffer solutions (pH 2.0–10.5) showed a gradual transition from red/pink to purple, blue and green for the observed samples. Films immersed in different buffers showed lower values of 2 to 10 lightness points (CIE L*) for PS-based films and 10 to 30 lightness points for MS-based films after the addition of BNC. The results of this research can make an important contribution to defining the influence of intermolecular interactions and structural changes on the physical, surface and colorimetric properties of bio-based pH indicators used in smart packaging applications.

The aim of the study was to isolate lignin from organosolv, beech tree (Fagus sylvatica), and Japanese knotweed (Reynoutria japonica), to use it for paper surface and to replace part of the non-renewable product resources with bio-based ones. A total of nine coated samples with different lignin formulations and starch were compounded, prepared, and evaluated. The basic (grammage, thickness, specific density), mechanical (elongation at break, tensile, burst and tear indices), and barrier properties (contact angle, water penetration, water vapour permeability, kit test) of the coated papers were investigated. The analysis showed no significant difference in tensile properties between uncoated and coated samples. Furthermore, the decrease in water vapour transmission rate and the lower contact angle for coated samples were nevertheless confirmed. The novel coating materials show promising products with very good barrier properties. Finally, the correlation between structural, morphological, and (other) natural lignin-based factors was revealed, highlighting the importance of parameters such as the equivalence ratio of aliphatic and phenolic hydroxyl groups or the average molecular weight. Tuning functionality by design could optimise performance in the future.

Polymers have become an important part of everyday life, but most of the polymers currently used are petroleum-based. This poses an environmental problem, especially with respect to products that are quickly discarded. For this reason, current packaging development focuses on sustainable materials as an alternative to synthetic ones. Nanocellulose, a relatively new material derived from cellulose, has unique properties such as high strength, low density, high surface area, and good barrier properties, making it popular in various applications. Additionally, 3D printing technologies have become an important part of industrial and commercial processes, enabling the realization of innovative ideas and functionalities. The main aim of this research was to develop a hydrogel of bacterial nanocellulose with suitable rheological properties for the 3D printing of polymer foils. Three variations of bacterial nanocellulose hydrogel differing in ratios of bacterial nanocellulose to cationic starch were produced. The rheological studies confirmed the suitability of the hydrogels for 3D printing. Foils were successfully 3D-printed using a modified 3D printer. The physical-mechanical, surface, and optical properties of the foils were determined. All foils were homogeneous with adequate mechanical properties. The 3D-printed foils with the highest amount of cationic starch were the most homogeneous and transparent and, despite their rigidity, very strong. All foils were semi-transparent, had a non-glossy surface, and retained poor water wettability.