Elaboração de pastas cerâmicas de alumina para deposição direta: influência da polietilenimina (PEI) e do teor de sólidos na extrusão e na secagem

Abstract

This study explores the development and characterization of alumina ceramic pastes for additive manufacturing via direct deposition, evaluating the influence of solid content and the polyethyleneimine (PEI) on the rheology, extrusion, and drying of the formulations. Alumina (Al₂O₃) was selected due to its superior mechanical and chemical properties, making it widely applicable in the biomedical, aerospace, and automotive sectors. Formulations with 50%, 60%, 70%, and 75% Al₂O₃, as well as variations in PEI concentration (0%, 1%, and 2%), were tested to assess their impact on viscosity, shear stress, and printability. Rheological tests indicated that an increase in solid content significantly raised viscosity and shear stress, improving structural stability after extrusion but making the flow process more difficult. The formulation containing 1% PEI exhibited the highest viscosity and yield stress, whereas 2% PEI resulted in a more fluid paste, but with lower stability. Formulation with values lower than 1% PEI and above 75% Al₂O₃ resulted in high viscosity, proving to be unsuitable for the process direct writing. During drying, samples with 70% Al₂O₃ maintained better structural integrity, whereas formulations with a lower solid content suffered brittleness and cracking. The results highlight that formulation optimization is crucial to ensure printability and dimensional stability of 3D-printed ceramic parts, reinforcing the need for an adequate balance between solids, additives, and processing conditions.