Fast Fourier Transform Analysis of Melt Fractured Extrudate

摘要

The phenomena of extrudate swell and associated instabilities have received substantial attention, yet they are still the cause of considerable debate~(1-9). Laser micrometers are used routinely to measure extrudate swell in capillary rheometers as well as critical profiles like catheter tubing. The speed of typical laser devices was on the order of 200 samples per second. The commercial availability of newer laser technology allows measurement on the order of 700+ samples per second with accuracy's in the 2.75 micron range. Using these high speed laser micrometers it seemed feasible that the analysis of various types of gross melt fracture and sharkskin ight become more quantitative if viewed in the frequency domain i.e. amplitude of diameter variation as a function of frequency in time. Similarly the frequency of the diameter variation can also be viewed as a function of linear distance ont he extrudate. The finger print of the amplitude spectrum rather than still photography or nebulous descriptive terminology might be used to characterize the phenomena and, perhaps, give some insight into it's origin. This paper is our scouting work on this idea.