## 3 Results and Discussions
### Sorption-Desorption Characteristics  
Natural fibres' specific absorption-desorption properties originate from their intrinsic characteristics. Water absorption results from the synthesis of hydrogen bonds between water molecules and the hydroxyl groups on the cellulose chains of natural fibres. The amount of water absorbed depends on several factors, including surface structure, porosity, crystallinity, and kinds of fiber. Natural fiber dynamic vapor sorption (DVS) isotherm data usually exhibit hysteresis, which indicates that the isotherms both of adsorption and desorption branches do not overlap. This is due to various factors, including capillary condensation, swelling, and the rearrangement of polymer chains. The extent of hysteresis is influenced by the fiber type, crystallinity, and porosity [58]. The untreated and treated Borassus fibers' sorption and desorption curves are not entirely reversible, indicating that the way the fibers absorb water vapor differs from how they desorb that moisture. The intricate microstructure of the fiber, which is made up of cellulose microfibrils embedded in  
Figure 4: Visual observation of the Borassus natural fiber at treatment times of (**a**) 1 h, (**b**) 2 h, (**c**) 4 h, and (**d**) 72 h, showing the alkaline solution’s change in color during the different treatment times. a hemicellulose and lignin matrix, might be the cause of this behavior [16]. The relationship between the amount of water vapor adsorbed onto the Borassus fiber and the equilibrium concentration of the water vapor is displayed by the sorption and desorption isotherm curves. The curves for treated and untreated Borassus fiber displayed an initial linear feature between 0-10% relative humidity (RH). A linear relationship between the amount of water vapor adsorbed and the RH in the range of 0-10% is demonstrated by the linearity at 0-10% RH shown to both treated and untreated fibres. This means that the specific mass (amount of water adsorbed per unit mass of fiber) increases proportionally with the RH. This linearity applies to both sorption and desorption. This information suggests that the Borassus fibers have a high affinity for water vapor at low RH levels [47]. They readily adsorb water vapor in this range, and the amount adsorbed is directly proportional to the humidity. This could be due to the presence of hydrophilic functional groups on the fiber's surface that readily interact with water molecules [59]. Borassus fiber treated after 24 h displayed this linearity from 20% RH, unlike the various treated fibers that displayed it at 10% RH. The 24 h treatment might have altered the surface morphology of the Borassus fibers in a way that promotes uniform water adsorption across the RH range starting from 20%. This could lead to a linear relationship between RH and specific mass addition or dimensional change. After this linear region, both graphs displayed a sharper curve within a 10% RH range. This suggests a more rapid change in moisture content within this specific humidity range. The untreated Borassus fibers exhibited a more pronounced curve compared to the treated fibers. This implies that the treatment process affected the fibers' moisture sorption and desorption differently. Following this sharp region, the graphs tend to flatten out, indicating a less dramatic change in moisture content as the RH continues to increase or decrease. Following this sharp region, the curves flatten out. However, another sharp peak arises at 60% RH and beyond. The sorption and desorption graphs of the untreated and treated fibers are not fully reversible, meaning that the manner the fibers absorb water vapor is not identical to the manner the fibers desorb that moisture. [PERSON] and [PERSON] reported that when a material is first dry, water is absorbed into it causing sorbed water layers to gradually fill the cell wall microcapillaries, while desorption happens from the water's evaporated surface boundary in these microcapillaries [60].