The Long Term Mechanical Behaviour of Filled and Unfilled Injection Moulded Thermotropic Liquid Crystalline Polymers

Abstract

Injection mouldings of thermotropic liquid crystalline polymers (TLCPs) have complex, highly anisotropic layered structures, and correspondingly large spatial variations in orientation and mechanical properties. The room temperature axial mechanical properties of standard tensile test specimens moulded from TLCPs are remarkable (ten-fold and two-fold increases in modulus and strength respectively, compared with conventional resins). Nevertheless, in practice glassfibre or mineral fillers are recommended to overcome problems associated with the anisotropy of unfilled TLCP mouldings, such as warping. The resulting reduction of anisotropy and more uniform local properties are not found to compromise seriously the axial mechanical properties, and indeed may improve both the short and the long-term behaviour, depending on the moulding conditions. Short glass-fibre addition appears particularly beneficial for the creep and fatigue resistance.