ARTICLE IN PRESS
JID: JOBAB
[m3GeSsc;February 6, 2026;11:5]
Z. Wei, J. Liu, Y. Wang et al.
Journal of Bioresources and Bioproducts xxx (xxxx) xxx
Fig. 1. Schematic diagram illustrating the application of a PVA/LNPs/SA (PLS) emulsion coating to fabricate high-performance, biodegradable paper LNPs: lignin nanoparticles; PVA: polyvinyl alcohol; SA: stearic acid; PLS: PVA/LNPs/SA.
as its water vapor barrier properties and tensile strength ( Fig. 1 ). Moreover, all components of the coating are biodegradable, enabling the coated paper to retain its environmentally friendly characteristics and degrade completely in soil within 120 d. These promising results indicate that the PLS emulsion coating effectively addresses key challenges related to barrier performance and mechanical strength in paper-based materials, offering a potential solution for developing high-performance, sustainable green packaging.
2. Material and methods
2.1. Materials
Industrial alkali lignin was supplied by Shandong Duoyuan Co., Ltd. (Liaocheng, China). Sodium hydroxide (NaOH, ≥ 96%) was purchased from Tianli Chemical Reagent Co., Ltd. (Tianjin, China). Hydrochloric acid (HCl, 37%) was obtained from Shanghai Hushi Chemical Co., Ltd. (Shanghai, China). Dimethyl sulfoxide (DMSO, ≥ 99.75%) was supplied by Tianjin Fuyu Fine Chemical Co., Ltd. (Tianjin, China). Stearic acid (SA, ≥ 99.75%) was obtained from Tianjin Guangfu Technology Development Co., Ltd. (Tianjin, China). Toluene ( ≥ 99.5%) was obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The n -heptane ( ≥ 98%), castor oil (chemically pure), and PVA1799 (degree of alcoholysis: 99.17%, acetyl group content: 0.79% ( w )) were acquired from Shanghai Aladdin Biochemical Technology Co., Ltd. (Shanghai, China). Fluorescein sodium (85%) was purchased from Macklin Biochemical Technology Co., Ltd. (Shanghai, China). Lumogen F Red 305 was purchased from BASF Aktiengesellschaft (Ludwigshafen, Germany). Uncoated bleached paper was provided by Yueyang Forest & Paper Co., Ltd. (Yueyang, China). Uncoated corrugating medium paper was purchased from Xiaoying Paper Co., Ltd. (Suzhou, China). All experiments were conducted by using deionized water.
2.2. Preparation of LNPs
The LNPs were fabricated through a solvent exchange method. Initially, industrial alkali lignin was subjected to a purification process. Specifically, the lignin was dissolved in a NaOH solution with a pH between 12 and 13. After complete dissolution, the solution was filtered to remove insoluble impurities. Under continuous stirring, HCl solution was slowly added to the filtrate to adjust the pH to 2–3, inducing the precipitation of the alkali lignin. The precipitate was collected by vacuum filtration and washed three times with deionized water to remove residual impurities. The purified alkali lignin was subsequently dissolved in DMSO to obtain a 10 mg/mL solution. This solution was then injected dropwise into a 10-fold volume of deionized water under continuous magnetic stirring. The obtained LNPs suspension was transferred to a dialysis bag with a molecular weight cut-off of 14 000 and dialyzed against deionized water for 96 h with water changes every 12 h to ensure the complete removal of DMSO.
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