Computational Studies of the free surface flow behavior for nematic LCPs in injection moulding process

Pedro Alexandre da Cruz¹; Murilo Francisco Tomé²

¹ UFT - Universidade Federal do Tocantins; ² USP - Universidade de São Paulo

doi:10.20906/CPS/COB-2015-2701

Resumo

Nematic liquid crystalline polymers (LCPs) are anisotropic materials and they are important engineering materials because of the wide range of their applications. When the nematic liquid crystalline polymers are used for industrial products, the molecular orientation inside the products is important because characteristics of products of liquid crystalline polymers highly depend on it. In polymer processing such as most injection molding, molecules of LCPs are easily aligned by the flow and keep the alignment until solidification. The material properties of the nematic LCPs are highly affected by the processing flows. In the injection moulding process the injected polymer flows through the sprue and gate to the cavity. This flow in moulded channels depends on many factors, like the properties of polymer used, processing conditions and injection mould design . This flow in molds can be controlled by the design, the mold technology and the processing conditions in order to obtain molded parts with expected properties, shape and surface. The cavity in the injection mould should be filled totally during the injection phase and the way of filling should be laminar and with a wide flow front the stream flow should be avoided. During the entire process of injection molding various rheological phenomena may occur. These phenomena must be known and studied due to economic reasons, such as decrease in material waste and the need of shortening the injection cycle time, as well as the quality requirements for moulded parts. Seeking a better quality and efficiency of the injection molding process it is necessary to monitor and control this process. Thus, research in the area of the numerical simulation as in the experimental area, to study phenomena that occur during the flow of nemactic LCPs in injection molds is valuable importance.

Palavras-chave: Nematic Liquid Crystals; Free-surface flows; Injection moulding process; Finite difference; Ericksen-Leslie model