Advanced injection molding mold and molding process for improvement of weld line strengths and isotropy of glass fiber filled aromatic polyester LCP

An advanced injection molding tool for measurement of mechanical strength and anisotropy of liquid crystal polymers (LCP)/mineral filler composites was developed. The mold produces thin‐walled LCP specimens that can be used by water cutting technique for production of an injection molded flow direction test bar, a transverse‐to‐injection molded flow direction test bar, a test bar for knit line strength measurement, and a test bar for butt weld line strength measurement. This tool and its use for molding experiments were optimized by experimental research and by computational calculations based on experimental parameters obtained by molding of several LCP test materials. Different pressure profiles and different injection speeds were tested as well as application of mold overflow phenomenon in production of test specimens. It was observed that a pressure controlled X‐melt technique and on the other hand fast injection speeds with overflow in conventional molding methods gave the best strength and isotropy properties for the test specimens. Results indicate that the mold developed is useful for determination of anisotropic and weld line strength properties of LCP composites. When developing “isotropic LCP” by different possibilities of nanotechnology this tool significantly reduces time of LCP material and process development.