Testing and characterization of high-temperature degradation performance of para-aramid fibres

Para-aramid fibres possess excellent properties, including high modulus, high strength, and high-temperature resistance, making them highly practical and cost-effective reinforcement materials. To further analyse the usage performance of para-aramid fibres under extreme conditions and explore their degradation behaviour and mechanisms at high temperatures, this paper investigates para-aramid fibres through high-temperature annealing. Various tests, including thermogravimetric analysis, infrared spectroscopy, X-ray diffraction, Ubbelohde viscometry, and universal material testing, were employed to analyse changes in the thermal degradation temperature, molecular structure, and mechanical properties of para-aramid fibres. Tests have shown that after high-temperature treatment of para-aramid fibres, different protruding particles and pits appear on the surface of the fibres, and the molecular structure gradually undergoes cleavage and cross-linking. This results in varying degrees of increase in the crystallinity, intrinsic viscosity, and apparent grain size of crystal planes in different directions of the para-aramid fibres with rising temperatures. On the other hand, the degree of orientation, the rate of the second type of lattice distortion, thermal performance, and mechanical properties show a declining trend. The thermal degradation conforms to the kinetics of a second-order reaction.