Novel, highly-filled ceramic–polymer composites synthesized by a spouted bed spray granulation process

We present a novel processing route to synthesize homogeneous ceramic polymer composites with ultrahigh (∼78 vol.%) packing density by using the spouted bed granulation technology and subsequent warm pressing. In the granulation process, two ceramic particle size fractions (α-Al2O3) and a thermoplastic polymer (polyvinyl butyral) are assembled to granules. In the process, μm-sized particles are coated with a layer of polymer which contains a second, nm-sized ceramic particles fraction. The mass fractions of each constituents can be adjusted independently. During the warm pressing, the nm-sized particle fraction along with polymer is pressed into the void volume of the μm-sized particles, thus achieving a homogeneous, isotropic composite structure with a very high packing density of ceramic particles. The material, which can easily be produced in large quantities, combines a high modulus of elasticity (up to 69 GPa), tensile strength (∼50 MPa), and pronounced fracture strain (∼0.1%) with an isotropic, biocompatible, metal-free composition. Possible failure mechanisms are discussed, including failure due to necking of the polymer, and failure due to limited polymer–particle-interfacial strength.