In Situ X-ray Scattering Measurements and Polydomain Simulations of Molecular Orientation Development during Injection Molding of Liquid Crystalline Polymers

摘要

We report a coordinated experimental/computational study of injection molding of commercial thermotropic LCPs. In situ synchrotron x-ray scattering, combined with a customized injection molding apparatus, is used to track development of molecular orientation during mold filling for commercial LCPs in two simple plaque mold geometries: square and T-shaped. While geometrically simple, these flows are characterized by complex inhomogenous mixtures of shear and extension, which influence orientation development. Use of high brilliance synchrotron radiation coupled with a high speed CCD detector provides sufficient time resolution (~12 frames per second) to resolve transient orientation dynamics during mold filling. The experiments are coordinated with process simulations performed using commercial mold filling software. A close analogy between the Folgar-Tucker fiber orientation model and the Larson-Doi polydomain model for textured liquid crystalline polymers is exploited to allow testing of Larson-Doi model predictions in injection molding processing.