Oscillation Injection Molding
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Control of the molecular orientation during polymer processing is achieved in the case of injection molding by applying an oscillatory movement to the moving part of the mold cavity. It generates an oscillatory flow field which "isotropizes" the molecular orientation during the mold filling stage of the injection cycle, and thus results in products with controlled molecular orientation. The extent of molecular orientation can be determined most conveniently with glassy polymers, e.g., poly(methylmetacrylate) (PMMA), by measuring the optical retardation or birefringence at different sections of the molded specimens. The concept of oscillatory flow is also applicable in other polymer processes, e.g., extrusion, for the preparation of polymer products with balanced mechanical properties.