## 4 Discussions
[24] have provided an overview of the physical properties of thermoplastic starch made of natural resources, stating that as a blend component for PLA, starch offers important advantages in terms of cost, mechanical properties and biodegradability. However, the hydrophilic characteristics of starch and the hydrophobic features of PLA cause low miscibility between the two compounds, necessitating good melt-blending techniques and the addition of compatibilizers to ensure successful interaction [47]. Furthermore, PEG content in PLA material was observed to increase biodegradation rate, indicated by the enhancing weight loss over time in the previous studies [48; 49; 50]. The high PEG will increase the hydrophilic behavior than the ones with lower content, thus it was easier to dissolve in PBS solution. These findings suggest that it might be more beneficial in terms of mechanical properties when only one of the materials, either sago starch or PEG, is mixed with pure PLA for the implant at the specified injection temperature. On the other hand, sago starch is required to enhance the biodegradability rate, whereas PEG is needed to increase the homogeneity of the mixture and minor elastic modulus. Injection molding parameters play a key role in balancing both mechanical and biodegradation performances, with higher injection temperatures generally accelerating the degradation rate and break elongation percentage of the PLA/sago starch/PEG miniplates. Previous findings [27] have shown inadequate interfacial interaction between starch and PLA, evident in the consistent reduction of tensile strength with higher concentrations of sago starch. Another study by [PERSON] et al. [43] indicated that the addition of PEG plasticizers significantly reduces tensile strength and modulus of elasticity. Despite this, PEG remains necessary as it improves the homogeneity interaction between PLA and starch interfaces, acting as a molecular bridge [51]. This is crucial because PLA is hydrophobic, while sago starch is hydrophilic, resulting in expected poor interaction [52; 53]. The additional PEG molecular chain acts as an efficient compatibilizer in the PLA/sago starch mixture. Consequently, adding PEG plasticizers to the PLA/sarch mixture leads to a reduction in both the modulus of elasticity and tensile strength. This finding is supported by [PERSON] [38] and [PERSON] [54], who observed that the addition of PEG significantly increased the drawability of the miniplate but decreased the elastic modulus. During the injection molding process, as the PLA matrix deforms under pressure and increased shear forces, the PEG interface effectively forms around the starch particles. As a result, the PEG can impede the formation of fractures, leading to a significant increase in the break elongation of the miniplate. An exception in this study was only observed in SPLA20P10 at 170 \({}^{\circ}\)C, showing better performance in elastic modulus and elongation at break, indicating the role of injection temperature in molding the miniplate implant. Based on the findings of this study, miniplates comprising PLA/sago starch/PEG fall short of meeting the mechanical requirements for bone implants. To enhance the mechanical properties of the miniplates, which possess favorable mechanical properties and degradation capability, can be considered [55; 56]. The ability to withstand bending loads is particularly critical for materials used in bone implants, especially in high-risk areas such as the bones of the arms and legs, which are subjected to significant bending loads during various activities. For example, cortical bone exhibits a bending strength ranging from 130-180 MPa, whereas miniplates SPLA20P10 and SPLA20P20 demonstrate strengths below this threshold. Consequently, miniplates composed of PLA/sago starch/PEG are better suited for application in bone tissues that do not necessitate high bending loads, such as skull fractures and craniofacial fractures.