Effect of Jet Swell and Jet Stretch on the Structure of Wet-Spun Polyacrylonitrile Fiber

Abstract

The jet swell effect in the wet spinning of polyacrylonitrile (PAN) fiber was studied by optical microscopy and the jet swell ratio was obtained through directly measuring the diameter of the freely extruded fibers. For reflecting the actual drawing situation of the fibers in the coagulation process, the jet stretches were then corrected from the apparent values to the true values, and their effect on the cross-sectional morphology, internal structure, and orientation of the wet-spun PAN fibers was studied by optical microscopy, scanning electron microscopy, and X-ray diffraction, respectively. The results showed that jet stretch plays an important role in eliminating the adverse effects caused by the jet swell effect and affects the fiber structure; PAN fibers of uniform denier, dense and homogenous structure, and high orientation can only be obtained at a suitable jet stretch.

Fabrication of High Specific Electrical Conductivity and High Ampacity Carbon Nanotube/Copper Composite Wires

“…The formulation of this structure is due to counter diffusion of solvent/nonsolvent, phase separation during coagulation, and stretching force inside the coagulation bath. [ 114 ] Spun filaments were heated at 300 °C for 1 h to thermally decompose the Na‐CMC polymer and the microstructure of the filaments became very porous, as shown in Figure 1 and Figure S4d in the Supporting Information. The bright cubic blocks distributed throughout the filament surface are believed to be the sodium salt which remains intact after thermal decomposition of CMC during the annealing process.…”

Correlation between fibril structures and mechanical properties of polyacrylonitrile fibers during the dry‐jet wet spinning process

“…A smaller diameter was benefit to allow fibers attaining a higher fraction of the theoretically predicated strength, which was well‐known as the “size effect.” It was clear that there were uniform and fine microfibrils in the surfaces of the PAN Fibers S1 and S2 [Figure (a,b)], which oriented along the fiber axis. They were generated when the fibril backbone were formed by phase separation during coagulating process . The surface was smoother and denser in the PAN Fibers S3–S5 [Figure (c–e)].…”

“…After immersing in the coagulation bath, the double diffusion occurs and a polymer‐rich phase coagulates into the fiber skeleton, while a solvent‐rich phase forms the voids . After coagulation, the fiber is then drawn in washing baths and multiple water steam steps to promote the polymer chain alignment and diameter reduction, which has the key influence on the properties of PAN fibers . In addition, the heat treatment including the process of densifying and heat setting is also utilized to improve the fiber structures and enhance the fiber mechanical properties.…”

Production of hollow ceramic rods by SHS extrusion

“…Упругая составляющая энергии накапливается в системе и затем, после выхода материала из матрицы, высвобождается, что приводит к образованию трещин, разрывов и прочих дефектов. В этих условиях явление разбухания струи является вредным эффектом [8]. Такое поведение полимерных материалов связано с особенностью их строения, а именно с наличием в структуре длинных полимерных молекул.…”