Paper-Based Oil Barrier Packaging using Lignin-Containing Cellulose Nanofibrils

Abstract

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.

Tuning Lignin Characteristics by Fractionation: A Versatile Approach Based on Solvent Extraction and Membrane-Assisted Ultrafiltration

“…Variations in these characteristics due to different lignin origins and processing/extraction methods can cause significant alterations in the performance of the final product [24]. A critical dependence on lignin properties was found for several high-value applications [25][26][27][28], such as the production of polymers [16], antioxidants [29], aromatic compounds [30], the synthesis of vanillin [31], and the development of high-performance concrete water-reducing agents [32]. The availability of effective fractionation processes for obtaining lignins with tailored physico-chemical properties and a defined molecular weight distribution is therefore a key requirement to effectively cope with both the upstream material variability and the downstream application requirements.…”

Enhancing the Oxygen Barrier Properties of Nanocellulose at High Humidity: Numerical and Experimental Assessment

“…For the uncoated CNF film, this increase continues for around 24 h before the equipment stops the test, indicating a steady state is reached. It was reported by our group and others that OTR increases at high humidities [13,29]. The changes seen in Figure 3b are likely caused by the water uptake of the CNF film and the subsequent swelling due to the loss of hydrogen bonding.…”

“…The quality of this barrier feature however can be affected by several factors, such as temperature [9], penetrant molecules and pore size [10], crystallinity, fiber morphology (morphology governs the diffusion and tortuosity) [11] and more importantly, humidity of the surrounding environment [12][13][14]. Among the abovementioned parameters, water sorption/diffusion within such matrices is the most fundamental aspect that directly or indirectly weakens the physical and barrier facets [15].…”

“…Among the abovementioned parameters, water sorption/diffusion within such matrices is the most fundamental aspect that directly or indirectly weakens the physical and barrier facets [15]. The hydrophilic nanocellulose can easily absorb the water molecules, causing the cellulosic fibers to swell and disrupt the chain linkages, consequently damaging the airtight network to a significant extent [13]. This points to the sensitivity of nanocellulose barrier properties to moisture and thus it is critical to better comprehend how the rate of oxygen permeation within a nanocellulose layer can be altered by the presence of water being absorbed.…”

“…First, the employed formula had a low water permeability and thus should not permit the water vapor through the cellulosic network [25]. Second, the restriction of water passage means a stable oxygen transmission rate (OTR) at humid environment [13]. The attained films were compared with those coated with polyethylene as the reference.…”