**4. Conclusions**

In summary, the emulsifier's effect in the distribution and compatibility of thermoplastic starch and PLA phases containing the different percentages of PLA, Starch and emulsifier was investigated. According to the mechanical test and SEM results, the use of ethanol led to a better distribution of the PEG in the matrix and a higher degradation rate. In addition, FTIR results showed the effect of UV radiation on increasing the hydrophilicity of the samples and the degradation rate. The hydrolytic degradation of these samples was investigated under different pH and thermal conditions before and after UV irradiation. The results of the hydrolytic degradation of samples showed that the pH of the basic degradation rate was much higher than the acidic and neutral environments and by increasing the temperature, the degradation became more intense. Moreover, the PLA and starch films with varying PEG percentages were landfilled for 45 days and then studied by SEM. It showed some clear evidence of degradation, such as higher surface roughness, grooves, pores and decay. Various holes and grooves and a coordinating degradation of consortium microbial colonies, including fungi, bacteria and actionists, were observed on the film surfaces. The primary mechanism for biodegradation of polymers with a high molecular weight was oxidation or hydrolysis by enzymes which led to the creation of functional groups and improved the hydrophobic properties. The polymer main chains were then degraded and the samples showed lower molecular weight and mechanical properties. Therefore, it will be more prone to microbial uptake.

**Author Contributions:** Conceptualization, S.M., E.R.G., M.S., S.S.-N., M.A., A.B., F.K., Z.A., M.F., H.A.; methodology, S.M., M.S., S.S.-N., M.A., Z.A., M.F., H.A.; validation, S.M., E.R.G., M.S., S.S.-N., M.A., A.B., F.K., Z.A., M.F., H.A.; investigation, S.M., E.R.G., M.S., S.S.-N., M.A., A.B., F.K., Z.A., M.F., H.A.; writing—original draft preparation, S.M., E.R.G., M.S., S.S.-N., M.A., A.B., F.K., Z.A., M.F., H.A.; writing—review and editing, E.R.G., M.S., S.S.-N., M.A., A.B., F.K., Z.A., M.F., H.A., S.R.; supervision, M.A. and S.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
