## 3 Results and Discussion
### Characterization of Starch/MCC Films
#### 3.2.4 Mechanical Properties  
The mechanical characteristics of packaging films, especially those intended for medical use, are crucial for ensuring their ability to withstand damage and maintain integrity during handling and storage. In this study, the tensile stress-strain curves of cassava starch films with various contents of MCC are analyzed to evaluate their mechanical properties, as shown in Figure 6a. The stress-strain behavior of starch films, as well as those with 1% and 3% MCC contents, indicates soft and flexible materials. These films exhibited elongation at a break of more than 30%, indicating their ability to deform under stress without fracturing abruptly. However, the starch films with 5% MCC exhibited brittle behavior, with less than 5% elongation at break. A material with low elongation at break, such as less than 5%, is typically considered brittle [39]. This suggests that the higher concentration of MCC makes the films more rigid and less able to undergo plastic deformation before fracture. To assess the effects of MCC content on mechanical properties, the tensile strength, Young's modulus, and elongation at break are illustrated in Figure 6b-d and summarized in Table 4. The starch film showed the highest elongation at break (89.94%) while their tensile properties exhibited the lowest, which showed a tensile strength of 2.85 MPa and a Young's modulus of 83.85 MPa. As MCC concentration increased from 1% to 5% (\(w/w\) of starch), Young's modulus and tensile strength of the films increased from 112.12 MPa to 488.89 MPa and 3.21 MPa to 11.18 MPa, respectively, whereas their elongation at break decreased from 44.74% to 4.15%. This is because MCC, being a reinforcing filler, enhances the mechanical properties of the films by providing structural support [11]. The enhanced strength can be attributed to the effective dispersion and favorable compatibility between the MCC filler and cassava starch matrix, facilitated by the formation of a robust H-bonded network, as corroborated by findings from FTIR and FE-SEM analyses. Conversely, the elongation at break diminishes with increasing MCC concentration. This is an anticipated outcome as higher MCC content renders the films stiffer, reducing their ability to stretch before fracturing. This finding aligns with previous literature [11; 40]. Currently, commercial biodegradable packaging films include hybrid films made of nondegradable synthetic polymer and biodegradable synthetic polymer (such as co-polyester/polymactic acid, BIO-FLEX(r) r 6611), as well as packaging films made from a combination of natural and biodegradable synthetic polymers (such as starch/polybutylene adipateerephthalate blend film). The commercial biodegradable packaging films with different types of polymers had different film characteristics. The commercial starch/polybutylene adipateerephthalate exhibited a tensile strength of 5.6 MPa and high flexibility with elongation at a break of up to 137%. On the other hand, the commercial co-polyester/polymactic acid showed low flexibility with elongation at a break of 9.7% but exhibited excellent stiffness with high Young's modulus and tensile strength, as shown in Table 4[41; 42]. Unfortunately, starch films and starch/1% MCC exhibited low mechanical strength, while the starch film with 5% MCC displayed brittle behavior, resulting in mechanical properties inferior to those of both commercial biodegradable packaging films. The starch film with 3% MCC, despite exhibiting less flexibility compared to commercial starch/polybutylene adipateerephthalate, still possesses sufficient elasticity, as evidenced by an elongation at a break of 32.54%. This implies that they can stretch to a certain extent before breaking, a critical quality for packaging materials. Additionally, these films demonstrate enough strength to be effectively used as film packaging, and in fact, they even surpass the strength of commercial starch/polybutylene adipateerephthalate film.