Production of PBT/PC particle systems by wet grinding

Abstract

Comminution of plastic or visco-elastic materials is known to be energy-intensive and costly. Typically impact mills, cutting mills and jet mills are applied for comminution and the feed material frequently is pre-cooled using liquid nitrogen or solid carbon dioxide. Therefore, especially the production of fine polymer particles by the aforementioned dry grinding methods is challenging. We demonstrate that wet grinding of polymers is a feasible approach for production of fine polymer particles that e.g. may be used as a starting material in a process chain for production of spherical polymer particles that can be used in in additive manufacturing. Wet comminution of polymers will be discussed for polybutylene terephthalate (PBT) and polycarbonate (PC). The products are thoroughly characterized by means of vibrational spectroscopy, X-ray diffraction and dynamic scanning calorimetry. The dependency of the grinding result on fundamental process parameters like stirrer tip speed, grinding media size, process time, process temperature and system composition will be discussed. In any case high load conditions, i.e. high stress energies are needed to initiate breakage of polymer materials. Optimization of the process with respect to process time and energy consumption by appropriate selection of process temperature and solvent will be addressed. The selection of appropriate solvents allows for remarkable reduction of mass-specific comminution energy needed.Comminution of plastic or visco-elastic materials is known to be energy-intensive and costly. Typically impact mills, cutting mills and jet mills are applied for comminution and the feed material frequently is pre-cooled using liquid nitrogen or solid carbon dioxide. Therefore, especially the production of fine polymer particles by the aforementioned dry grinding methods is challenging. We demonstrate that wet grinding of polymers is a feasible approach for production of fine polymer particles that e.g. may be used as a starting material in a process chain for production of spherical polymer particles that can be used in in additive manufacturing. Wet comminution of polymers will be discussed for polybutylene terephthalate (PBT) and polycarbonate (PC). The products are thoroughly characterized by means of vibrational spectroscopy, X-ray diffraction and dynamic scanning calorimetry. The dependency of the grinding result on fundamental process parameters like stirrer tip speed, grinding media size, process ...