<p>Plastic additives are used to strengthen the mechanical properties of polymers, improve processing efficiency, and enhance product durability, thereby enabling their use for diverse applications across many chemical industries. These additives are typically produced in powder form; however, the handling and storage of fine powders in industrial environments present significant challenges, making it necessary to convert them into pellets. The process of pellet formation involves compression of the powder under controlled pressure and temperature. Several models have been developed to explain pelletization in various fields, including biomass, metals, pharmaceuticals, and ceramic production. A common theme of these studies is the use of a continuum approximation for the powder using the Drucker-Prager Cap (DPC) model. These studies relied on an instrumented die to measure the material model parameters. Furthermore, the identification of DPC model cap surface and hardening parameters typically relied on preparing multiple pellets at different target densities, making the parameter calibration process time-consuming and experimentally intensive. In contrast, the present work extracts material parameters from load-displacement data, avoiding extensive pellet preparation without relying on a specialized instrumented die. Additionally, we have presented a modified approach to calculate cap hardening parameters based on global optimization of stress-strain values. Finally, the framework was applied to plastic additive powders and validated against experimental results. An additional sensitivity analysis of the model, based on a full factorial design of experiments (DoE), was performed to evaluate the influence of key parameters on the predicted compaction response. Overall, our findings may help reduce pre-production iterations and improve pellet quality, given the constraints at the factory.</p>