Novel approach based on autoclave bead foaming to produce expanded polycarbonate (EPC) bead foams with microcellular structure and controlled crystallinity

Abstract

Polycarbonate (PC) is a widely used engineering thermoplastic. Also, bead foaming technology is a method to produce high-performance, low-density foams with complex geometries. In this work, expanded polycarbonate (EPC) with microcellullar structure and low density have been produced for the first time using the autoclave bead foaming technique. The effect of the processing parameters, such as the saturation temperature and time, on the characteristics of the EPC bead foams, is analyzed. Contrary to the total amorphous structure of the solid material, the obtained EPC foams present a crystalline phase characterized by a melting peak around 235 °C. The crystallization process might be taking place during the saturation of the samples with CO2. Results show that the saturation temperature allows controlling density, whereas foaming time can be used as a tool to control crystallinity degree in the range from 7.5 to 45 min, without a clear influence on the cellular structure. EPC with densities between 116 and 592 kg/m3, cell sizes of approximately 4–5 µm, and crystallinities ranging 0–11% were produced by a proper modification of the foaming parameters. Then, the use of different saturation parameters allows controlling the density and thermal properties of the EPC, thanks to the autoclave bead foaming process.