Effect of polyvinyl alcohol concentration on the properties of dry-pressed sintered ceramics

Abstract

This study systematically investigates the influence of polyvinyl alcohol (PVA) binder concentration (0-4 wt%) on the sintering properties of dry-pressed alumina ceramics. By establishing a PVA concentration gradient model (0%, 1%, 2%, 3%, 4%) and combining sintering kinetics theory with porosity calculation models, the mechanism of PVA decomposition residues on the formation of closed pores and mechanical properties was quantitatively analyzed. The experiment utilized high-purity α-Al2O3 powder mixed with PVA solution, and ceramic samples were prepared through ball milling, drying, dry pressing, and sintering. Systematic tests were conducted using the Archimedes method, universal testing machine, and scanning electron microscopy (SEM) to evaluate apparent porosity, water absorption, compressive strength, and microstructure. Experimental results indicate that the optimal comprehensive performance is achieved at 2 wt% PVA, with apparent porosity (18.3±0.5%), water absorption (0.12±0.02%), and compressive strength (379±15 MPa) reaching their best-matched values. The bulk density (2.70±0.03 g/cm3) and linear shrinkage (12.1±0.3%) remain stable across varying PVA concentrations. Mechanism analysis reveals that PVA affects material performance through a dual mechanism: moderate addition (1-2 wt%) improves powder compaction. It promotes neck formation during sintering, while excessive addition (>3 wt%) increases closed pores due to thermal decomposition residues, leading to stress concentration. This research provides critical experimental insights for optimizing binder systems in high-voltage insulating ceramics.