Influence of capillary die geometry on wall slip of highly filled powder injection molding compounds

Abstract

Uneven distribution of solid particles contained in the feedstocks used in the process of powder injection molding (PIM) is observed in the close vicinity of the walls. A particle-free thin layer adjacent to the walls is formed by the binder only and is characterized by so-called wall slip. Wall slip is a key to successful modeling of injection molding step of PIM. For its determination we used capillary rheometers equipped with the dies of different entrance angles applied to four PIM feedstocks. The entrance angle has been found to be a crucial parameter to intercept wall slip. Conical dies are more suitable to obtain reliable slip velocity values of highly filled compounds than capillaries having plane entrance, which are used in the majority of studies. © 2017 Elsevier B.V.