Spinning of Polyamides from Sulfuric Acid Solution

Abstract

Increasing the aromatic ring content of polyamides results in increased melting points and fiber stiffness. These intractable polymers generally cannot be melt-spun or solutionspun from conventional spinning solvents. A search for general classes of solvents for intractable polyamides resulted in the conclusion that the solvent must act as a sufficiently strong Lewis acid to complex the polymer and have sufficient solvent power to dissolve the resulting complex. Examples are given of this two-step mechanism for solution formation.This led to the selection of concentrated sulfuric acid as a polyamide wet-spinning solvent. Extrusion of sulfuric acid solutions of polyamides into aqueous sulfuric acid is shown to be a general fiber-forming process. The fiber-forming mechanism is interpreted in terms of acid-base reactions, the diffusion of the solvent and precipitant, and the kinetics of precipitation of polymer from supersaturated solution. Diffusion effects in the extreme case led to "incursions" which result in a brittle fiber structure. These are illustrated with the help of motion picture microscopy. The relationships of these physico-chemical phenomena to fiber properties are discussed. , 0 .

Equilibrium phase behavior of the membrane forming water-DMSO-EVAL copolymer system

“…Highly negative interaction parameters between solvent and polymer were also reported by Cheng [9] and Bulte [31] for the formic acid-Nylon systems. It was claimed that hydrogen bonding and protonation effects [32,33] are responsible for the strong interaction forces between these molecules. The interaction parameter between water and EVAL was treated as being concentration independent since Eq.…”

Structural Investigations of Fibers and Films of Poly(p-phenylene benzobisthiazole). Volume 1

“…Rosenthal [42] for nylons in sulfuric acid. These authors' results differ from Knudgen's [43] results for polyacrylonitrile fibers where coagulation bath temperature was the controlling factor.…”

“…These authors' results differ from Knudgen's [43] results for polyacrylonitrile fibers where coagulation bath temperature was the controlling factor. Epstein and Rosenthal [42] interpreted this phenomenon to indicate that, in nylons, coagulation from sulfuric acid occurred by deprotonation -an acid base reaction. This is also a plausible explanation in the present system based upon the work of Shen et al [7] who showed by spectroscopic analysis that PBT model compounds were highly protonated in MSA solution.…”

Thickness Dependence of Macrovoid Evolution in Wet Phase-Inversion Asymmetric Membranes

“…More importantly, the phenomenon of macrovoid formation is of great significance even for normal textile fibers made by wet spinning. 2, [23][24][25] Membrane scientists are divided on the origins of macrovoid formation. Several believe that it most likely originates from thermodynamics, so they have investigated the subject from the perspective of chemical potential gradients and phase diagrams with the aid of the Flory-Huggins theory.…”