Solvent debinding of injection moulded parts with supercritical carbon dioxide : T. Shimizu et al. (Uthonomiya University, Japan.)

Abstract

Defects such as cracking, slumping, and sagging are frequently found in powder injection-molded (PIM) compacts. These defects are partly related to the swelling of the binders during solvent debinding. However, little quantitative analysis has been reported to date. The in situ length changes of PIM specimens during debinding were measured in this study using a laser dilatometer designed by the authors specifically for these experiments. A total linear expansion from 0.5 to 2% was observed and was influenced by the binder, the solvent type, and the debinding temperature. This expansion is attributed to the interaction between the solvent and the binder, particularly the insoluble backbone binder components such as low-density polyethylene and polypropylene. These in situ measurements on the length and temperature changes help explain how the defects formed during debinding. Based on the results observed, guidelines for designing binders and debinding schedules are recommended.