Enhancing the optical properties of transparent wood by plasma modification

Abstract Transparent wood is a promising sustainable alternative to glass, yet its large-scale production is often constrained by harsh chemical delignification, poor polymer compatibility, and limited interfacial control. This study introduces a solvent-free strategy for enhancing the optical and mechanical properties of transparent balsa wood through volumetric plasma modification using Atmospheric Discharge with Runaway Electrons (ADRE). The plasma treatment generates fast electrons capable of activating the entire wood volume, forming oxygen-containing functional groups that improve surface energy and polymer affinity. Morphological analyses (optical microscopy and SEM) revealed that plasma-treated samples exhibit homogeneous resin infiltration and the elimination of interfacial voids observed in untreated transparent wood. FTIR spectra confirmed the introduction of polar carbonyl and hydroxy groups, indicating enhanced chemical interaction between cellulose and the acrylic matrix. Consequently, the plasma-treated transparent wood achieved a visible light transmittance of 91% at 550 nm and reduced haze by 11% compared to non-treated samples. Mechanically, the plasma-treated transparent wood exhibited the highest bending strength in three-point bending tests (89.6 MPa), outperforming non-treated transparent wood (84.5 MPa) and raw wood (41.4 MPa), while partially modified wood showed the lowest strength. Hardness also increased from 83.3 to 86.7 Shore D after plasma activation, corroborating the improved interfacial adhesion and structural integrity. This solvent-free plasma activation approach replicates the interfacial benefits of chemical acetylation without toxic reagents or lengthy processing, providing a scalable and environmentally benign route toward high-performance, optically clear, and mechanically robust cellulose-based composites.