Modelling on-axis microdiffraction to investigate crystallographic texture within high-performance polymer fibres

Radial crystallographic texture in high-performance polymeric fibres is a common structural feature. Quite why such preferred orientation should exist and how it impacts upon the mechanical properties of the fibre is still not fully understood. This study reports the use of a modelling approach to investigate radial texture in the poly(p-phenylene benzobisoxazole) fibre type. The model allows azimuthal scattering profiles to be calculated corresponding to an on-axis microdiffraction geometry. The results show that, in order to model experimental data successfully, an offset is required between the a unit-cell axis and the fibre radial direction. The origin of this offset is tentatively attributed to solvent outflow during coagulation, which aligns the planar molecular chains. Meanwhile, textural differences between different fibre types can be explained by processing differences.