An investigation of the structure–property relationships in melt-processable high-acrylonitrile copolymer filaments

A comprehensive investigation was undertaken to understand why the structure of a high-acrylonitrile (AN) resin renders it melt processable, how it affects the microstructure, and what filament properties it supports. High-AN homo- and copolymers have excellent chemical and ultraviolet light resistances that make them suited for many engineered industrial applications. Traditionally, these AN-copolymers are dissolved in a solvent and extruded into fibers by dry and wet spinning, because they tend to degrade rather than melt. Recent advances in copolymer synthesis have created the first AN-resins that can be melt processed, and, are produced more economically and in an environmentally friendly way. The block distributions were examined using solution nuclear magnetic resonance. Thermal behavior of the solid-to-ductile transitions was observed with differential scanning calorimetry to gain insight into the nature of the temperature-dependent solid-state interactions between chains. Filament extrusion was conducted utilizing a range of parameters to obtain filaments varying in structures and properties. Wide-angle X-ray diffraction was used to gain insight into the solid-state conformations and organization of the copolymer chains. It is concluded that melt-extruded filaments do not develop a distinct semi-crystalline morphology, but instead tend to develop a paracrystalline ordered structure. Mechanical properties can be varied, and under optimal conditions, compare favorably with those found in other melt-extruded polymer fibers that are not, resistant to chemical and UV exposure.