Fiber orientation in divergent/convergent flows in expansion and compression injection molding

Abstract This study compares the fiber orientation patterns of short glass fiber‐reinforced polypropylene developed in conventional and nonconventional injection molding, the latter using a special mold, RCEM (rotation, compression, and expansion mold). This mold allows for a wide variety of operating modes during mold filling, which leads to a great versatility in obtaining different fiber orientation patterns. By incorporating through‐thickness convergent and divergent flows during the filling stage (compression and expansion modes, respectively), the fiber orientation can be tailored. These linear dynamics can be superimposed with a simultaneous rotational movement of one of the mold surfaces. These combined actions induce a high fiber orientation transversely to the radial flow direction, this effect being more pronounced in the expansion mode. POLYM. COMPOS. 27:539–551, 2006. © 2006 Society of Plastics Engineers