Scientific Reports - Transparent wood composite prepared from two commercially important tropical timber species
Lignin modification and response The lignin content of both timber species before and after lignin removal process was determined. The untreated rubberwood contained 22 ± 0.5% lignin while ailanthus wood veneer was estimated to have 28 + 1.02% acid insoluble lignin prior to lignin modification. These values are consistent with previous findings, which reported a range of 20–35 wt% lignin in wood matrix23,24. The time required for delignification to produce a cellulose-rich white template varied according to species and treatment conditions. In certain cases, wood samples need to be cooked/treated until they appear to be white25,26. In the present study, substrate with satisfactory brightness was obtained after 4 h of lignin modification from rubberwood. At this stage bleached rubberwood was found to have 57% of retained lignin. Whereas for ailanthus wood, 69% lignin retaining white cellulose-rich template was obtained after 3 h lignin modification reaction. Therefore, here we have optimized the treatment duration suitable for TW preparation from two wood species representing different density classes and lignin content. In addition, we calculated the percentage reduction in lignin content in each species consequent to lignin removal. Partial lignin removal strategy reported by Li et al. was followed in the present work to obtain the delignified samples with well-preserved microstructures25. The greater amount of retained lignin inside the bleached provided ample strength to the wood template to facilitate its further processing. Rao et al. followed a similar protocol for lignin removal and reported optimum delignification in poplar wood samples with 88% retention of lignin27. Identical strategies involving the selective removal of colour inducing chromophores without drastically removing constituent lignin inside the wood was replicated elsewhere to acquire suitable substrate for TW preparation20,28,29,30,31. Our study thus validated the efficiency of sodium…
Anish, M. C., Institute Of Wood Science, Technology, Bengaluru, Department Of Forest Products, Utilization, College Of Forestry, Kerala Agricultural University, Thrissur