Effect of Diethylene Glycol on the Morphology and Deformation Properties of Fibers Based on Melt-Processable Acrylonitrile Copolymers

Melt-processable acrylonitrile copolymers are of interest as precursors for fibers produced without large amounts of organic solvents. Their spinnability is enabled by low-molecular-weight plasticizers, which reduce viscosity but also affect the structure and properties of the resulting fibers. This study examines the effect of diethylene glycol (DEG) on the rheological state of polymer–plasticizer systems and on the morphology and deformation behavior of fibers based on a melt-processable acrylonitrile copolymer. From a colloid-chemical standpoint, washing is considered as structural rearrangement of a dynamic copolymer–DEG–water ternary system involving mutual diffusion, formation of internal interfaces, and development of a heterogeneous dispersed morphology. Removal of the water-soluble phase produces optically detectable internal heterogeneities, partial relaxation of the oriented structure, and a marked change in polymer molecular mobility. The glass-transition temperature increases from 66.2 to 94.3°C, while the elongation at break rises from 8.7 to 33.8% at virtually unchanged tensile strength. Subsequent heating reduces the severity of the defects formed owing to relaxation of the polymer matrix. DEG thus controls not only copolymer flow and spinning but also phase–morphological transformations upon contact with water and the capacity of the fiber for subsequent orientational deformation.