The Design of Dies for High-Speed Wire Coating

摘要

It was shown experimentally that the critical shear rate was increased by using smaller taper angles in the flow channel and by improving the flow properties. Improved flow properties can also be obtained by using a higher melt index resin or higher melt temperatures. It was shown that there was an optimum land length, and in this case the ratio of land length to orifice diameter was 11.34. Further work is being done to determine if the same ratio holds for different orifice sizes and if small tapers just prior to the land affect the land length. Thus, for a particular polyethylene, a die for high-speed wire coating can be designed successfully by giving proper consideration to the programming of the rate of increase in shear rate, the effect of the angles and lengths of the tapers, and the ratio of the land length to the orifice diameter. (Author)