## 3 Results and Discussion
### Handmade Paper Characterization
#### 3.2.2 Mechanical Characteristics of the Paper Samples  
The strength characteristics of paper products are influenced by several factors including the composition and structure of the material, as well as the methods and conditions of technological operations. These factors impact the interfiber bonding forces, which are dependent on parameters such as surface size, the concentration of bonds per unit area, fiber length, strength, flexibility, elasticity, fiber orientation, and the aspect ratio (length-to-width ratio). The average basis weight of the handmade paper samples was found to be 178.87 g/m\({}^{2}\) for the alkali-treated samples and 261.02 g/m\({}^{2}\) for the bleached samples. These values reflect the consistency and uniformity of the paper sheets produced during the experiments. In the analysis of strength characteristics presented in Table 2, the authors did not prioritize achieving exceptionally high mechanical property values. Instead, the focus was on assessing the mechanical properties of cellulose fibers derived from grass clippings in combination with mineral filler, specifically barium sulfate. It is known [90] that the strength characteristics of a cellulose mesh are determined not only by the fiber strength but also by the contact area, the presence of hydrogen bonds between the fibers, and van der Waals forces. The formation of hydrogen bonds between cellulose fibers has been repeatedly proven. For example, using paper casting in non-polar liquids, it was shown that paper cast using a polar liquid (water) has better strength characteristics than a sample cast in ethanol [91]. Research on the folding endurance of paper after alkali treatment is significantly higher than that of paper after the bleaching process. This can be explained by increased crystallinity and improved adhesion between cellulose fibers after alkali treatment. The decrease in paper durability after bleaching by 13.3% confirms the assumption of partial the destruction of cellulose fibers and a decrease in their ability to adhere mutually. [PERSON] and [PERSON] [92] note that with an increase in the weight of a sheet, as well as its thickness, the stiffness of the paper increases, but this negatively affects folding strength. It is worth noting that the difference in the thickness of the samples is 18% in favor of the thickness of the bleached paper, which may also indicate a decrease in strength characteristics when folded. The low values for the number of folds are also consistent with the data in [17], where the number of double folds for handmade paper made from Napier grass and sugarcane pulp ranges from 8 to 106. The low fiber length, strength, and elasticity values explain the low fracture resistance of paper. Among other things, the decrease in hemicellulose content in the sample after the bleaching procedure leads to a decrease in the number of hydrogen bonds between the fibers, which, as a result, negatively affects the flexural strength properties. A decrease in the amount of hemicellulose in the sample can indirectly be evidenced by a decrease in the sample's moisture content after bleaching compared with the sample after alkaline treatment because hemicellulose is better at hydrolyzing and retaining water in the sample compared with crystalline cellulose regions. This fact is also confirmed by the fact that the quality of grinding cellulose pulp is assessed by the water holding capacity indicator [93]. In addition, the relatively high thickness of the paper sheet may indicate a high degree of fiber splitting during the grinding, alkali treatment, and bleaching processes, resulting in the defibrification of cellulose fibers, which leads to a decrease in strength characteristics. Indeed, the results of the EDS analysis revealed that the paper made from bleached cellulose exhibited better retention of mineral filler, with a higher barium content (14.4 wt.%) compared with the paper derived from alkali-treated cellulose (5.92 wt.% barium).