High-performance composites based on all-aromatic liquid crystal thermosets

In this study, a new high-performance liquid crystal ester-based thermoset for composite applications was investigated. All-aromatic liquid crystalline thermosets (LCTs) are a promising class of polymers that offer a unique combination of properties such as solvent resistivity, high modulus, high strength, low coefficient of thermal expansion and high after cure glass-transition temperatures (T_g ? 150 °C). Fully cured LCTs offer superior thermo-mechanical properties over high-performance thermoplastic polymers such as PPS, PEEK and PEI. For this study we used a 9000 g mol⁻¹ ester-based LCT based on cheap and readily available monomers, i.e. 4-hydroxybenzoic acid (H), isophthalic acid (I) and hydroquinone (Q), abbreviated by us as HIQ-9. Composite panels prepared from T300 carbon fiber (5-harness satin weave) showed in-plane shear strength of 154 MPa and an in-plane shear modulus of 3.7 GPa. The tensile strength and modulus were measured to be 696 MPa and 57 GPa, respectively. A post-mortem inspection showed that the interfacial strength was excellent and no delamination was observed in the test specimen. Preliminary results show that LCT-based composites exhibit a better combination of (thermo) mechanical properties over PPS and PEI-based composites.