Effect of the polymerization degree of photopolymers on the thermal and mechanical properties of ceramic cores

Abstract

A ceramic core must have a high fracture strength before and after heat treatment to reasonably handle the complex and thin parts. To develop such a ceramic core, herein, a photocurable monomer with high network density was applied as an organic binder to increase green strength, and an inorganic binder was additionally introduced to minimize the shape distortion of the core due to the organic–inorganic conversion process. Fused silica beads as a starting material and trifunctional and monofunctional acrylate as an organic binder were used; these slurries with various compositions formed the green body of the core shaped through a pressing process. Next, the green body was subjected to UV irradiation for 10 min to photopolymerize the monomer, followed by heat treatment at 900 °C for 1 h to convert the inorganic binder into a glass phase and to decompose the polymer. The as-prepared ceramic core exhibited a high strength of ∼20 MPa before heat treatment owing to the presence of the crosslinked polymer with high network density. By converting the inorganic binder into a glass phase, it was possible to manufacture the ceramic core at a strength of ∼40 MPa. The photopolymerization behavior of monofunctional and trifunctional acrylate monomers and a mixture of both monomers was analyzed by FT-IR spectroscopy, and the thermal behavior of each ceramic core sample was analyzed by TG-DTA. The relationship between the polymerization degree of the photocurable monomer and strength was investigated via thermal analysis and microstructure measurement.