Preparation and properties of UV-absorbent lignin graft copolymer films from lignocellulosic butanol residue

• A novel approach for UV-absorbent film.
• The BBL copolymer film has highly efficient absorption of ca. 96.2% in the UV range.
• BBL copolymer film exhibited excellent mechanical strength and thermal stability.
• Improved utilization of biobutanol lignin (BBL).

The aim of this study was to develop economically UV-absorbent and visible-transparent films. For this purpose, lignin was selected because of its strong ultraviolet (UV) absorbing property. Lignocellulosic butanol residue, as the by-product of lignocellulosic butanol production, is rich in biobutanol lignin (BBL). Herein, BBL was modified with acryloyl chloride and then copolymerized with n-butyl acrylate (BA) and methyl methacrylate (MMA) by free-radical polymerization. The chemical structure of poly(BA-co-MMA) chains was identifiable by 1H NMR and 13C NMR spectroscopies, combined with UV–visible spectra to confirm the existence of the aromatic groups that are attributed to BBL in the copolymer. This provided evidence that a BBL graft copolymer was successfully synthesized. The optical, photo-stability, chemical resistance, thermal and mechanical properties of the copolymer were evaluated. The copolymer film can absorb 96.2% of UV light, while allowing 70% or higher transmittance in the visible spectrum when the surface concentration of BBL-AC was 240 μg cm−2. In addition, the copolymer film retained excellent absorption capacity in the UV region and high transparency in the visible light region after 75 min continuous UV-irradiation or when heated at 100 °C, rendering it potential to use as a UV-absorbent film. The copolymer exhibited good chemical resistance, thermal and mechanical properties compared with pure poly(BA-co-MMA). This strategy not only provides a novel approach for UV-absorbent films but also greatly extends the comprehensive utilization of BBL.

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