Chainawakul, A., Sangkas, T., Kamthai, S. and Manokruang, S. 2025. Reducing Sink Mark Defect of Cup Plastic Injection by Biodegradable Material with an Injection Rate. RMUTL Engineering Journal. 10, 1 (Apr. 2025), 27–34. DOI:https://doi.org/10.14456/rmutlengj.2025.4.