Highly Transparent Nanocomposites Based on Poly(vinyl alcohol) and Sulfated UV-Absorbing Wood Nanofibers

Abstract

Unbleached lignocellulose fibers were studied for the fabrication of wood-based UV-absorbing nanofibers and were used to produce transparent nanocomposites. Groundwood pulp (GWP) and sawdust were selected as raw materials thanks to their low processing degree of fibers and abundant availability as a low-value industrial side stream. Both materials were first sulfated using a reactive deep eutectic solvent. The sulfated wood and sawdust nanofibers (SWNFs and SSDNFs, respectively) were fabricated using a mild mechanical disintegration approach. As a reference material, sulfated cellulose nanofibers (SCNFs) were obtained from bleached cellulose pulp. Our results showed that both GWP and sawdust exhibited similar reactivity compared with bleached cellulose pulp, whereas the yields of sulfated lignin-containing pulps were notably higher. The diameters of both SWNFs and SSDNFs were approximately 3 nm, which was similar to those of the SCNFs. When 10 wt % of lignin-containing nanofibers were mixed together with poly(vinyl alcohol), the fabrication of nanocomposites with only a minimal decrease in transparency in the visible light spectrum was achieved. Transmission in the UV region, on the other hand, was significantly reduced by SWNFs and SSDNFs, whereas SCNFs had only a minor UV-absorbing property. Although the reinforcing effect of lignin-containing nanofibers was lower compared with that of SCNFs, it was comparable with those of other UV-absorbing additives reported in the literature. Overall, the wood-based UV-absorbing nanofibers could have a valuable use in optical applications such as lenses and optoelectronics.

Transparent lignin-containing wood nanofiber films with UV-blocking, oxygen barrier, and anti-microbial properties

“…The widths of the CWNFs were in line with previous results obtained from sulfated WNFs produced from sawdust 48 and groundwood pulp 49 and CWNFs produced from groundwood pulp using DES. 33 However, compared to CWNFs obtained previously, in the current study, the large particles were present to a lesser extent.…”

“…Previously, WNFs with a gel-like appearance have been obtained by sulfation with reactive DESs. 48,49 Sulfate groups are more hydrophilic compared to tertiary amine groups introduced into wood in the current study 50 and the sulfated WNFs exhibited signicantly higher charge density compared to CWNFs produced here, both contributing to their high viscosity values. Generally, the viscosities of the nanobers produced from high lignin-containing starting materials are lower compared to those obtained from bleached (lignin-free) cellulose.…”

Mechanochemical and thermal succinylation of softwood sawdust in presence of deep eutectic solvent to produce lignin-containing wood nanofibers

“…In this study, we used planetary ball milling to intensify the succinylation of sawdust; however, our aim was not to produce WNFs directly using ball milling, but to improve the succinylation efficiency of sawdust. Although the surface of sawdust can be chemically modified using reactive DESs, the disintegration before chemical modification is required to facilitate the production of WNFs (Sirviö and Visanko 2019). Therefore, simultaneous size reduction and chemical modification of the sawdust was studied.…”

“…Due to the exclusion of process steps related to biomass fractionation (e.g., delignification and bleaching), the raw materials in LCNFs can be more cost-effective and have lower environmental impact (i.e., due to the consumption of lesser toxic chemicals). In addition, lignin and hemicellulose can elevate the feasibility of the LCNFs in many applications compared to CNFs, for example, by improving the metal-removal efficiency (Sirviö and Visanko 2020) and providing UV-protection (Wang et al 2018;Sirviö and Visanko 2019;Liu et al 2020). However, high crosslinking density (Hanhikoski et al 2020) as well as hydrophobicity (Figueiredo et al 2018;Solala et al 2020) of lignin can hamper the fibrillation effect of materials with high lignin content (Spence et al 2010), making the production of LCNF generally more cumbersome process compared to CNF.…”

Hydrogen‐bonding assembly of heteropolyacid and poly(vinyl alcohol) for strong, flexible, and transparent UV‐protective films

“…Specially, there is high demand for the UV‐shielding capacity in many fields to avoid the harmful impact of UV rays and to maintain a safe and healthy environment, such as UV‐protective films and coatings for food, biomedical, and optoelectronic products . In order to improve the UV‐shielding property of PVA and thus expand its application fields, many investigators were devoted to the design and development of UV‐protective PVA products .…”