“Equatorial small‐angle x‐ray scattering study of porosity and pore‐size distribution in polyester and their influence on dyeing behavior”

For explaining the dyeing behavior of polyester (PET) fibers, the important role played by pores has been speculated upon in modern dyeing theories. In the present work, an attempt has been made to characterize the pore size spectrum in morphologically very different PET fibers by means of equatorial small‐angle X‐ray Scattering (SAXS). The analysis of the scattering curves reveals that all the samples analyzed in the present work have a two‐phase structure, consisting of pores of widely different sizes dispersed within a matrix of the polymer network. This polydispersity of pore sizes is revealed from Guinier plots, as well as from an analysis of intensities in the tail of the scattering curves, which are found to obey Porod's Law. Estimates have been made of pore radii, pore concentration in the substrate, and specific surface. The pore size distribution function has been obtained using a new procedure. Various parameters of the pore size spectrum are discussed in relation to the morphological structure of fibers, as well as their significance to dyeing. The diffusion behavior of solvent molecules within PET is also discussed.