Ceramics-Silikáty

This study investigates the influence of hydroxypropyl methylcellulose (HPMC) and ethylene vinyl acetate (VAE) on printability and mechanical anisotropy in a low-water binder system. The effects on fluidity, penetration resistance, printability window, and directional compressive strength were assessed. The results show that HPMC forms a water-retaining gel network that increases viscosity and penetration resistance, thus improving shape retention. However, excessive content (≥0.6%) blocks extrusion. VAE acts as a lubricant, improving fluidity and synergistically extends the printable time. The optimum combination of 0.4% HPMC with 1–3% VAE provides a printable duration of 110–120 min, good buildability and the lowest anisotropy. HPMC reduces early-age strength, while moderate VAE contributes to later-age strength development. Printed specimens consistently exhibit anisotropic strength: X-direction ˃ Z-direction ˃ Y-direction, with the Y-direction being the weakest due to inferior interlayer fusion. SEM analysis reveals that HPMC retards hydration and increases early porosity, whereas VAE forms polymer films, creating an organic–inorganic composite microstructure. This study offers a design basis for mix proportioning in precision 3D printing.