Lignin and Xylan as Interface Engineering Additives for Improved Environmental Durability of Sustainable Cellulose Nanopapers

Abstract

Cellulose materials and products are frequently affected by environmental factors such as light, temperature, and humidity. Simulated UV irradiation, heat, and moisture exposure were comprehensively used to characterize changes in cellulose nanopaper (NP) tensile properties. For the preparation of NP, high-purity cellulose from old, unused filter paper waste was used. Lignin and xylan were used as sustainable green interface engineering modifiers for NP due to their structural compatibility, low price, nontoxic nature, and abundance as a by-product of biomass processing, as well as their ability to protect cellulose fibers from UV irradiation. Nanofibrillated cellulose (NFC) suspension was obtained by microfluidizing cellulose suspension, and NP was produced by casting films from water suspensions. The use of filler from 1 to 30 wt% significantly altered NP properties. All nanopapers were tested for their sensitivity to water humidity, which reduced mechanical properties from 10 to 40% depending on the saturation level. Xylan addition showed a significant increase in the specific elastic modulus and specific strength by 1.4- and 2.8-fold, respectively. Xylan-containing NPs had remarkable resistance to UV irradiation, retaining 50 to 90% of their initial properties. Lignin-modified NPs resulted in a decreased mechanical performance due to the particle structure of the filler and the agglomeration process, but it was compensated by good property retention and enhanced elongation. The UV oxidation process of the NP interface was studied with UV-Vis and FTIR spectroscopy, which showed that the degradation of lignin and xylan preserves a cellulose fiber structure. Scanning electron microscopy images revealed the structural formation of the interface and supplemented understanding of UV aging impact on the surface and penetration depth in the cross-section. The ability to overcome premature aging in environmental factors can significantly benefit the wide adaption of NP in food packaging and functional applications.

Sustainable Wax Coatings Made from Pine Needle Extraction Waste for Nanopaper Hydrophobization

“…In this comparison, the most characteristic peak of cellulose was -OH group absorbance around 3300 cm −1 . The distinct peaks of wax were visible at 2915 and 2849 cm −1 , representing the stretching of CH 2 groups [ 28 , 35 ], which matches well with cellulose CH and CH 2 signals [ 27 ], but in terms of visual appearance are significantly different with the pronounced shape of the two peaks. Unique to wax is the signal at 1731 cm −1 , which corresponds to the carbonyl group of the fatty acid ester linkage [ 28 , 35 ].…”

“…CNP and MNP samples were dip-coated to compare the nanopaper’s microstructure’s impact on the resulting contact angle values ( Figure 6 c). As demonstrated in our previous research, the pure CNP is more porous and has more hydroxyl groups on the surface compared to MNP [ 27 ]. The initial θ values showed that MNP and CNP are both highly hydrophilic, but MNP has an initial value of 31°, which is 3 times higher compared to CNP.…”

“…The region from 1170 to 1000 cm −1 can be referred to as the fingerprint region, with a dense concentration of signals for both wax and cellulose, representing mainly various linkages of C-O. Absorbance at 976 cm −1 has been attributed to C-O stretching in xylan, 895 cm −1 to β-linkage of cellulose, and around 700 cm −1 to CH 2 rocking vibrations [ 27 , 28 , 35 ]. After five layers of dip-coating, the coated MNP showed no -OH signals, and the overall shape of spectra matched the wax absorbance curve; thus, indicating successful hydrophobization of the NP surface.…”

“…Activated charcoal powder, chloroform-d, Kraft lignin, and beechwood xylan were purchased from Merck KGaA (Darmstadt, Germany). Nanofibrillated cellulose (NFC) was produced from old filter paper waste according to the method previously reported by the authors [ 27 ]. NFC sizes ranged from 40 to 120 nm in diameter, and fiber lengths from around 500 to 2000 nm.…”

Approaches for Extracting Nanofibrillated Cellulose from Oat Bran and Its Emulsion Capacity and Stability

“…Nanocellulose, defined as less than 100 nm in diameter, has attracted growing interest for many applications because of its functional properties such as nano size, high surface area, amphiphilic property, low density, high mechanical strength, eco-friendliness, nontoxicity, and low cost [3,4]. Nanocellulose functions as a composite film [5], performs the encapsulation and delivery of vitamin D 3 [6], serves as a reinforcement material [1], an emulsifier [7], and can be used in energy applications [8], active packaging [8], cosmetics [9], and cellulose nanopapers [10]. Nanocellulose has been classified as three types, including (1) cellulose nanocrystal (CNC)/nanocrystalline cellulose (NCC) which is a rod-like crystalline region cellulose; (2) cellulose nanofibril (CNF)/nanofibrillated cellulose (NFC) which is a long entangled cellulose with amorphous and crystalline regions; and (3) bacterial cellulose (BC) produced from bacteria [11].…”