Effect of the pressure drop rate on the cell formation in a high pressure foaming process

High-pressure foam injection molding (HP-FIM) with core-back technology is known for its ability to produce a uniform foam morphology with a high cell density that exceeds that of conventional foam injection molding. The advantage of HP-FIM is that it is possible to control the formation and expansion of cells by controlling the pressure drop through the expansion of the cavity volume. This study examines the influence of pressure drop as a fundamental parameter in cavity expansion, leveraging pressure control as a tool for foam morphology optimization. In order to comprehend the behavior of polycarbonate foam formation when saturated with nitrogen, a mini-batch foaming process is used to replicate the pressure history of the injection molding process. Various process configurations are set up to achieve the in pressure drop history. As a result, variations effect of the pressure drop rate on the expansion is studied in situ, and the resulting density reduction and cell morphology are investigated. Batch foaming results are compared with HP-FIM, showing a good agreement and proving the utility of purposefully designed, lab-scale experimental campaign to instruct process design in industrially-relevant technologies.