The use of environmentally friendly, lubricant-free plastic seals in the rotating parts of robots and machines is on the rise. However, variations in seal geometry and operating conditions can influence the contact pressure between the seal and shaft, potentially leading to poor sealing performance, premature wear, or debris ingress. Therefore, advanced design optimization is essential. In this study, we conduct a parametric study and sensitivity analysis to enhance the performance of plastic seals. Finite element analysis (FEA) is carried out using a 2D axisymmetric model with interference fit contact conditions to accurately simulate the behavior of the seal and shaft. We verify the reliability of the analysis by comparing the deformation of the seal diameter before and after shaft insertion with experimental measurements obtained using a 3D tactile measurement device. We analyze four design variables: pressure, temperature, seal diameter, and coefficient of friction, considering seal contact pressure as the objective function. Sensitivity analysis is performed to determine the impact of these design variables on contact pressure and to identify trends.