Hot-stretch-induced Orientation and Collapse of Wet-spun Acrylic-fibre Structure and Effects on Gel-dyeing

The effect of stretch-induced orientation and structural collapse of as-formed wet-spun acrylic fibre on subsequent gel-dyeing characteristics is assessed. Tbe gel-dye rate is shown to increase with increasing stretch ratio. This is demonstrated to be a consequence of tbe reduced time spent in the steam-stretch tunnel, leading to less reduction of porosity at higher stretch ratios, rather than the polymer orientational effects observed. The link between steam-tunnel residence time and structural collapse is extended to examine the dynamics of stretching and introduces the notion of a stretch point, that distance travelled by a fibre bundle in the tunnel at which stretching takes place. This dictates the residence time in the tunnel and hence the level of collapse. The mechanism is offered as a possible cause of fibre-shade variation.