Discrete element modeling of the compression molding of polymer–crystal composite particles

Cold compression molding of polymer–crystal composite particles is a widely applied technique in chemical engineering fields. In this study, a discrete element modeling (DEM) method was developed and used to investigate the densification process and micromechanics of polymer–crystal composite particles undergoing compression. This method considered the realistic particle shape and internal microstructure of component crystals and polymeric binder, based on information from X-ray micro-computed tomography (μCT) and scanning electron microscopy (SEM) analyses of polymer–crystal composite particles. A series of single-particle crushing tests and comparative DEM simulations were conducted to verify and calibrate the novel DEM modeling method and the DEM parameters used to represent polymer–crystal composite particles. Furthermore, an in situ μCT scanning compression test and corresponding DEM simulation were conducted to investigate the densification process and micromechanics of polymer–crystal composite particles subjected to compression molding. The experimental and DEM results proved the efficiency and accuracy of the novel DEM method in modeling the fracture behaviors of molded polymer–crystal particle specimens. Various micromechanical behaviors were observed within these specimens, related to such aspects as interparticle pore structures, crystal grading, fracture development, and contact forces. These findings provide deep insights into the densification process and microstructural changes that occur in polymer–crystal composite particles during the compression-molding process.