Properties of PAN Fibers Solution Spun into a Chilled Coagulation Bath at High Solvent Compositions

Abstract

Abstract:In this work, multifilament, continuous polyacrylonitrile (PAN) fiber tow was solution spun mimicking industrial processing at the small pilot scale (0.5 k tow), while carefully altering the composition of the coagulation bath, in order to determine the effect on the resulting fiber shape, density, orientation, and tensile properties at varying points in the spinning process. Novel here are the abnormally high coagulation bath solvent compositions investigated, which surpass those often reported in the literature. In addition, the coagulation bath was maintained at a slightly chilled temperature, contrary to reported methods to produce round fibers. Further, by altering the composition of the bath in a step-wise fashion during a single spinning run, variations in all other process parameters were minimized. We found that with increasing solvent composition in the coagulation bath, the fibers not only became round in cross section, but also became smaller in diameter, which persisted down the spin line. With this decrease in diameter, all else equal, came an accompanying increase in apparent fiber density via a reduction in microvoid content. In addition, molecular orientation and tensile properties also increased. Therefore, it was found that inadequate understanding of the coagulation bath effects, and spinning at low coagulation bath solvent compositions, can hinder the ability of the fiber to reach optimum properties.

Impact of the wet spinning parameters on the alpaca‐based polyacrylonitrile composite fibers: Morphology and enhanced mechanical properties study

“…[21,53] However, by applying higher draw ratio and stretching, the crystallinity index can be increased, as due to the drawing and stretching mechanism, the molecules inside the polymeric matrix are arranged properly rather than a random orientation. [54,55] For example, in our previous study, the crystallinity index of the control PAN_M1 fibers was around 55%. [26] Nevertheless, owing to the doubled draw ratio, the crystallinity index of the control PAN_M2 fibers increased by around 45% in the current study.…”

“…[56] In similar, the internal molecular alignment and the direction of the fibrils may be rearranged with the implementation of the higher proportion of drawing and stretching to the fibers. [52,55] Due to the drawing and stretching, the reduction in the fiber diameter was evident with the elimination of the voids areas, which is also known as cavity healing of the fibers. [52] Furthermore, the crystallinity of the fibers increased and assisted to achieve the higher mechanical properties of the fibers compared to the previous fibers.…”

Investigation on structure and characteristics of alpaca‐based wet‐spun polyacrylonitrile composite fibers by utilizing natural textile waste

“…48 In a diffraction pattern, the halopeaks are due to the higher crystalline region whereas the broader peaks represent the lower crystalline or higher amorphous region. 40 From Table III, it can be found that the control PAN fibers showed around 55% crystallinity whereas it was gradually reduced with the increment of alpaca content in the composite fibers. As the broadness of the peak at 17 of the composite fibers increased (Figure 9), the crystallinity of the composite fibers decreased ( Table III).…”

Wave Characteristics of Coagulation Bath in Dry-Jet Wet-Spinning Process for Polyacrylonitrile Fiber Production Using Computational Fluid Dynamics

“…In this study, five spinning velocities (v s ) of the dope (polymer solution) at the spinneret nozzle were considered with a jet-stretch ratio (v PAN /v s ) of five [7,24,25]. Table 1 indicates the PAN-bundle velocity (v), porosity (φ), and viscous resistance (1/K) according to the five cases.…”