Comparative evaluation of delignification strategies for the preparation of transparent wood composites
摘要
Transparent wood composite (TWC) is an innovative material that combines the natural aesthetic of wood with desirable mechanical and optical properties, making it ideal for creative design applications and energy-efficient construction. This study compares three different delignification techniques for producing TWC from rubberwood veneers: lignin modification (Method-I), acid delignification (Method-II), and a novel hybrid approach (Method-III). Each method was evaluated based on treatment duration, structural integrity of the cellulose template, and the resulting TWC characteristics. The hybrid method (Method-III) adopts a combination of peroxide–acetic acid pretreatment, chosen for rapid lignin cleavage, followed by a lignin modification step (Method-I). This approach achieved extremely rapid and high delignification (~ 95%) within two hours, but resulted in notable structural weakness. On the other hand, Method-I, which involves only lignin modification rather than complete delignification, improved handling and mechanical strength of the cellulose substrate. Further, the conventional NaClO2-based Method-II removed a substantial amount of lignin but compromised structural robustness, resulting in increased fragility. The excessive lignin removal significantly increases the incompatibility between the polymer matrix and the cellulose cell wall resulting in a reduction in both the mechanical properties and the optical transparency of the resulting composite. The quality of TWC depends on achieving an optimal balance between lignin removal and the preservation of the structural integrity of the cellulose template. Although Method-I yielded the best overall performance of the composite, the rapid and scalable hybrid method (Method-III) offers a practical route for the sustainable production of TWC.