D research aim to invistigate orientation and weld adhesion of filled liquid crystalline polymers. Prof. A H Windle Liquid Crystalline Polymer mouldings show high strength and rigidity yet their properties are severely compromised by the presence of weld lines . The project will examine the parameters, both materials and process, which affect weld strength with particular attention being paid to the posssible beneficial effect of inorganic fillers. Materials which is used in my experiment are Vectra A950 and Vectra A130, supplied by Hoechst. All specimens with weld line , are injecion moulded in a split mould which has double gates.
Polymer melt flows in cavity, is influenced by fountain flow effect.
Most chains at the melt front align parallel to the shape of the front, so chains prefer to move in the direction perpendicular to the weld line. The low mechanical strength of material at the weld line can be due to a lack of molecular connection bridging the weld line interface. Simulation of fill pattern in mould and an investigation of the solidified melt front by SEM , X-ray diffraction will map out the pattern of the orientation of molecular chains at weld line. Consequently, it will support my assumption of the mechanism of weld line formation .