Effects of Alkali Treatment and Drying Method on Densification Process of Bamboo

In this study, a two-step process of delignification and densification was carried out on Dendrocalamus Asper bamboo specimens. It is aimed to investigate the densification properties of the bamboo samples after removing the lignin. To delignify the samples, two different approaches were applied. The first group was treated in a room-temperature NaOH + NaSO3 solution, while the second group was treated in the same solution at 100 o C. Afterward, the samples were dried in either an oven with 100 o C or at room temperature of 25 o C. Hence, a total of four different groups of delignified and dried samples were produced with an average moisture content of 7 - 10 %. The samples were then densified to 50 % of their original thickness having the thickness reduction determined a priori using a thermo-mechanical press system at 160 o C. The results indicated that all alkali treated samples required a lower load for the densification process compared to the reference. Average compression stress of 17.0 MPa for the reference, 10.3 MPa for the samples treated with alkali solution at room temperature, and 7 MPa for the boiled alkali solution treated samples were applied to achieve a densification degree of 50%. The drying process also affected the compression resistance of bamboo and oven-dried specimens showed an increase of 30% and 17% for room temperature and boiling temperature treatment respectively. The modulus of rupture, limit of proportionality, and elastic modulus of densified bamboo were all negatively impacted by the pre-treatment, according to the results of the bending test. Overall, untreated and treated bamboo displayed similar behavior for physical attributes in densified samples. After being treated with alkaline solution, bamboo showed reduced levels of lignin as well as hemicellulose and cellulose, according to chemical tests. In conclusion although the treatment facilitates the densification process, the time employed for the treatment and the final properties of the material did not prove to be advantageous