The synthesis and characterisation of reactive poly(p-phenylene terephthalamide)s: A route towards compression stable aramid fibres

Herein we report on the synthesis of reactive poly(p-phenylene terephthalamide) (PPTA) oligomers and the preparation and characterisation of aramid fibres thereof. Methacrylate and maleimide reactive end-groups were found to be sufficiently stable in H₂SO₄ at 85 °C and they were used to prepare reactive PPTA oligomers. Lyotropic spin-dopes could be prepared with up to 20 wt% of reactive oligomer (M_n = 3900 g mol⁻¹) and this modification did not interfere with the fibre spinning process and had no effect on the fibre tensile properties. The as-spun fibres did indeed show a modest (+0.1 GPa) improvement in compression strength. A high temperature treatment at 380 °C resulted in fibres which all show a significant increase in compressive strength over their as-spun precursors, i.e. from 0.7 to 0.9 GPa. When fibres were treated at 430 °C the compression values of the oligomer-modified fibres dropped somewhat, whereas unmodified PPTA displayed a compressive strength of 1.1 GPa. Other favourable fibre properties such as modulus and tenacity were not compromised.