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In this study, cellulose-based films were developed by using microfibrillated cellulose (MFC) and lignin-containing microfibrillated cellulose (Lig-MFC) derived from sequentially extracted spruce bark. The films were coated with the hydrophilic extractives from the fractionation, resulting in additional MFC-coated and Lig-MFC-coated cellulose films. A combination of morphological (AFM), surface (water contact angle (WCA), roughness), optical (UV-vis), and mechanical properties was analyzed to assess structure-property relationships. Coated films exhibited significantly enhanced hydrophobicity and UV-shielding, with WCA increasing from 47° to 76° for MFC and from 66° to 71° for Lig-MFC. Notably, MFC-coated films displayed superior mechanical performance, with a tensile strength of 119 MPa and elongation of 11%, surpassing most lignocellulosic-based films in the literature derived from bark. In addition, this tensile strength falls within or above the range of commonly used materials, such as kraft liner, PET, and LDPE, suggesting realistic opportunities for substitution in short-lived packaging applications. AFM analysis revealed a reduction in surface roughness after coating, correlating with an enhanced WCA. Compared with similar biobased films in the literature, the extractive-coated MFC films show superior performance in terms of strength, flexibility, and UV-shielding properties. This valorization route offers both economic and environmental sustainability advantages compared with incineration for energy recovery. A comparative life cycle assessment (LCA) study showed that valorization of the pulp and hydrophilic extractives from the bark biorefinery into different qualities of MFCs gave substantial climate change benefits stemming from the possibility of substituting packaging materials with high inherent environmental impact.
Khalili et al. (Wed,) studied this question.