IN-SITU DIMENSIONAL CHANGES OF POWDER INJECTION-MOLDED COMPACTS DURING SOLVENT DEBINDING

Defects such as cracking, slumping, and sagging are frequently found i n powder injection-molded (PIM) compacts. These defects are partly rel ated to the swelling of the binders during solvent debinding. However, little quantitative analysis has been reported to date. The in situ l ength changes of PIM specimens during debinding were measured in this study using a laser dilatometer designed by the authors specifically f or these experiments. A total linear expansion from 0.5 to 2% was obse rved and was influenced by the binder, the solvent type, and the debin ding temperature. This expansion is attributed to the interaction betw een the solvent and the binder, particularly the insoluble backbone bi nder components such as low-density polyethylene and polypropylene. Th ese iii situ measurements on the length and temperature changes help e xplain how the defects formed during debinding. Based on the results o bserved, guidelines for designing binders and debinding schedules are recommended. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Sci ence Ltd. All rights reserved.