Preparation of Polypropylene Microspheres for Selective Laser Sintering via Thermal-Induced Phase Separation: Roles of Liquid-Liquid Phase Separation and Crystallization

Although selective laser sintering (SLS) has been widely applied in many fields, more research work is needed to develop proper polymer microspheres for SLS. Thermal-induced phase separation (TIPS) is a facile way but rarely reported to prepare the polymer microspheres. The roles of liquid-liquid phase separation (LLPS) and crystallization in the TIPS process are not clear. In this study, proper polypropylene (PP) microspheres for SLS are successfully prepared via TIPS with xylene. The diameters and morphologies of these PP microspheres can be regulated easily by changing the PP concentration and the quench temperature. The large undercooling drives the solution into the metastable LLPS region and produces PP microspheres with smooth surfaces. The PP crystallization occurs both on the LLPS interface and inside the polymer-rich phase when the solution is quenched to a temperature near the binodal line, and the tiny bent lamellae are formed on the microsphere surface. At higher temperature only PP crystallization occurs, which results in the formation of PP particles consisting of packed lamellae. The PP microspheres prepared here are suitable for SLS and promote the development of SLS potentially. (C) 2016 Wiley Periodicals, Inc.