Liquid crystal thermoset resins for high temperature composites and adhesives

Abstract

Herein a new series of all aromatic thermotropic liquid crystalline thermosetting polymers (LCTs) is presented. Liquid crystalline thermosetting polymers offer excellent thermal (T _g>200°C, T^5%_d>450°C) and mechanical properties (E′>4 GPa), and they can be melt processed into fibre reinforced composites with superior mechanical and physical properties over PPS or PEEK based composites. The fully cured polymers exhibit excellent mechanical properties, i.e. TA/HQ/HNA(25)-5K displays a flexural strength of 110 MPa, flexural modulus of 8 GPa, a tensile strength of 66 MPa and a room temperature elongation at break of 5·5%. These LCTs were also successfully applied as high temperature (150°C) adhesives for metal substrates. When used as resins in carbon fibre reinforced composites, significant improvements in critical composite properties were found, such as a high in-plane shear strength (154 MPa) and tensile strength (696 MPa).