5] s, almost to that of a Newtonian fluid, the die swell ratio
reaches 40% at a distance of 2 cm below the spinneret due only to the elasticity of the core layer.
The die swell ratio
of the composites and the fiber-matrix morphology of the extrudates have also been analyzed.
Experimental methods for measuring the die swell ratio of polymer melts have involved many difficulties such as draw-down effects, molecular relaxation at the die exit, contraction due to cooling, and crystallization (1).
This can be achieved by knowledge of radial die swell ratio profiles and their dependence on processing conditions.
Therefore, die swell ratio values at any radial positions across the die were averaged and obtained at the piston displacement range of 85-92 mm down the barrel.
Table 5 shows the effect of blend composition on the extrudate die swell ratio
of nylon/NBR blends.
The die swell ratio becomes smaller as the melting temperature and melting residence time are increased.
Wong and Liang demonstrated the relationship between the die swell ratio and melt flow index of high-density polyethylene .
Comparison of the die swell ratios of polymer melt through the original die and modified dies indicated that the modified die produces larger swell than the origina1 die.
0] is the capillary diameter, is defined as the die swell ratio and used as a measure of die swell.
poly(vinylchloride) whose variation of die swell ratio with shear rate sometimes shows a maximum or a minimum (18).
At all the temperatures investigated, the die swell ratios of the PEK-C increase with increasing shear rate, as shown in Fig.