Abstract
Wet spinning of nylon 6 of molecular weight 3×104 was studied by using five solvent systems of phenol (Ph), o-chlorophenol (OCP), sulfuric acid (SA), formic acid (FA) and dichloroacetic acid (DCA). Each of the solvent systems except OCP contained 10% water.
It is found by X-ray analysis that the crystalline structure of the wet spun filament of Ph, OCP and SA solvent systems is always the α-form, while that of FA solvent system is the γ-form when the coagulating bath temperature is low (30°C) and the alkali concentration is high (4%). The spun filament of DCA solvent system also has the γ-form at the low (30°C) coagulating bath temperature. The presence of these γ-form is confirmed by DTA thermogram in which appears a shoulder at the lower temperature side of the fusion peak, and is also confirmed by IR spectrum in which the absorbance of 970cm-1 is stronger than that of 960cm-1. It is supposed that the formation of the γ-form crystal is controlled with some factors such as the effect of solvent in the spinning solution, the effect of alkali in the coagulating bath, and the effect of the coagulating rate.
In the case of Ph, OCP and SA solvent systems having the α-form crystal, the X-ray diffraction intensity increase by drawing, especially the (002) intensity increase remarkably. The γ-form crystal of FA solvent system is converted by drawing into the α-form, intensity of which increased by succesive drawing, while that of DCA solvent system does not convert into the α-form.
The drawing process is followed in terms of the (200) orientation, the half value width and the density, and it is found that the wet spun filaments can be drawn without the destruction of crystal in spite of their higher crystallinity, owing to their fine-structural characteristics.
