Transparent Bioplastics from Super-Low Lignin Wood with Abundant Hydrophobic Cellulose Crystals
Liangliang Zhu, Ben Dang, Kairui Zhang, Jun Zhang, Mei Zheng, Ning Zhang, Guanben Du, Zhijun Chen, Rongbo Zheng
Abstract
Bioplastics (BPs) prepared from lignocellulose are an excellent replacement for petrochemical-plastics (PCPs) due to their renewability and biodegradability. The presence of residual/added/regenerated lignin reduced the water sensitivity; however, these BPs possessed a deep color and low transmittance and were prone to photodegradation. Herein, we developed a UV- and water-insensitive, colorless, transparent, and sustainable wood-derived BP (W-BP) by pressing delignified wood (DW) with 0.21% lignin and abundant hydrophobic crystal plane (200) of cellulose. The DW was obtained by the pretreatment of the wood sample with NaOH/Na2SO3 followed by H2O2 steam conditioning. The abundant hydrophobic crystal plane (200) of cellulose in DW was demonstrated by a large ratio of the crystal plane (200) to (110), the presence of two-dimensional (2D) nanosheets of defibrated cellulose, and a low moisture uptake of 8.7% of the freeze-dried DW. The aged W-BP with a thickness of about 50 μm displayed good photostability with a ΔE* value of 2.3 and a transparency of 84% transmittance at 550 nm. Additionally, W-BP also possessed water stability with a wet tensile strength of 74 MPa and a low water uptake of 28.3%. These values exceeded those of lignocellulosic BPs and some commercial PCPs. The W-BP could replace transparent PCPs and provide indirectly experimental support to the lignin–cellulose interaction.