Properties of PAN Fibers Solution Spun into a Chilled Coagulation Bath at High Solvent Compositions
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.
Effect of jet stretch on polyacrylonitrile as‐spun fiber formation
In this article, the effect of jet stretch ratio on the extrudate die-swell effect of polyacrylonitrile spinning solution and the structure and properties of as-spun fibers was systematically analyzed by means of X-ray diffraction (XRD), electron microprobe analysis, and the measurement of die-swell ratio, boiling-water shrinkage, porosity, mechanical properties analysis, etc. It revealed the formation mechanism of the die-swell effect and spin orientation and its influences on the structure and properties of as-spun fibers. It showed that with the increase of the jet stretch ratio the die-swell ratio became smaller, both the degree of spin orientation and the crystallinity increased, the microstructure of as-spun fibers became compact and homogeneous, and the cross section tended to be circular. As a result, the breaking tenacity of as-spun fibers and resultant precursors all increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3348–3352, 2007
[Effects of dance exercise on exercise intention and exercise-related affect of postmenopausal women].
PURPOSE
A dance exercise program was performed to investigate the effects of exercise on exercise intention and exercise-related affect as these are important determinants of exercise behavior.


METHOD
The subjects were overweight (23< or =BMI< or =25) or obese (BMI> or =25) postmenopausal women (n=14), who participated in an exercise program from May, 2003 through November, 2003 at one public health center located in Kyong-gi Province. Data was analyzed with an SAS PC program.


RESULT
Exercise intention was significantly increased after the exercise program (t=-2.24, P=0.04). Exercise-related affect was also increased, but there was no statistically significant change (t=1.81, P=0.09).


CONCLUSION
This study suggests that exercise participation can increase the level of future exercise behavior by increasing exercise intention and exercise-related affect.