熱延伸機構について

Abstract

The deformation behaviour of a synthetic filament yarn which is stretched in a hot air bath, and its influence on the qualities of filament yarn were investigated. In the case of the hot drawing process by the hot air bath, the tension of the filament yarm between the draw roller is constant, and the temperature of the feeded filament yarn rises up to the temperature of the air bath. In order to know the deformation behaviour, the recording instrument for the flow curve of filament under the constant tension was constructed.PVA filament yarn producted by dry spinning method is applied for specimen. To examine the differences of deformation curves caused by the differences of the temperature transition state of the filament, the unit length filament is preheated and its deformation curve is measured at a determined temperature. From the curved surface of drawing temperature-time-draw ratio, we can recognize the deformation behaviour of the filament under the temperature transition state by means of plotting the temperature rising curve of the filament on the drawing temperature-time plane. Examining the curved surface from the viewpoint of the drawing temperature, there are no remarkable differences of the deformation curves among the hot drawing temperature 160-0210°C, and the rate of deformation increases rapidly above 210°C. These deformation curves belong to the range of large deformations, but the tendency of the curve is similiar to an ordinaly creep curves, and then the curve can be separated into the part of retardation deformation and of viscous flow. From the curves, we can recognize that the viscous flow is predominant above 210°C. The influence of the temperature transition state of the filament on the deformation curves were examined. A large rate of temperature rising brings a peak of the rate of deformation at about 210°C, and a small rate of it brings two peaks of the rate of deformation at about 160°C and 215°C, which is similiar to so-called “2 step drawing”.The relationships between the deformation behaviour and the filament yarn qualities were also examined. The hot drawing mechanism of crystalline high polymers can be separated into two parts. The first step of the deformation is the uncoiling of chain molecules come from the deformation of the network which consist of the entanglement of chain molecules or crystallite. Such deformation corresponds to the retardation deformation at rather low temperature.The second step of the deformation is the slippage of chain molecules which brings the close packing of each chain molecules. Such deformation corresponds to the viscous flow at high temperature. In the case of former deformations, a large rate of deformation at low temperature is supposed to be effective in order to obtain good tenacity. But the case of latter deformations, in order to obtain good tenacity, a small rate of deformation at high temperature for allowing an enough time to set the molecule at each stable position is supposed to be effective.