ANALYSIS OF THE DELIGNIFICATION PROCESS INFLUENCE ON THE DIMENSIONAL STABILITY OF DENSIFIED WOOD: A SYSTEMATIC REVIEW

Abstract

Background: One of the challenges in the development of densified wood products is maintaining their dimensional stability. Several treatment methods are employed to achieve this stability, including the delignification process. This paper analyzes the efficiency of the delignification process on the improving of the densified wood dimensional stability through a systematic literature review. This research was based on the recommendations of the PRISMA protocol and conducted using Scopus, Web of Science and Google Scholar databases. After the eligibility criteria application and bias analysis, the systematic search sample resulted in 54 articles. The meta-analysis was conducted through a narrative synthesis, including the densification process, wood species, apparent density, delignification process, other wood treatments, and dimensional stability.

Results: Populus was the most used genus on the densification process and most of the species used had an average apparent density of 0.476 g/cm³. The delignification process was employed in approximately 26% of the 54 analyzed articles. Studies indicate sodium hydroxide (NaOH) as the most common delignification reagent and confirm that delignified densified wood achieves improved dimensional stability. After extracting and analyzing the data from these articles, the results indicate that the delignification process has gained prominence as a research topic since 2019, accounting for 25.9% of the analyzed articles.

Conclusion: Although several authors report improvements in dimensional stability with partial lignin removal, the comparative analysis of the data revealed significant heterogeneity in the results. Other methods, such as thermal treatment, are still more commonly used to enhance the dimensional stability of densified wood.