EFFECT OF EXTRUDER TEMPERATURE PROFILES ON STRESS-CRACK RESISTANCE OF A POLYETHYLENE SHEATHING COMPOUND,
Abstract
Experiments with an 8 in production extruder equipped with a thermocouple instrumented screw have shown the importance of selecting the proper extruder barrel heater settings if environmental stress-crack (ESC) degradation is to be minimized. A group of 2.37 in cable cores were jacketed with a low density polyethylene sheathing compound to determine the effect of various combinations of feed and metering zone barrel temperature settings on the ESC resistance of the polyethylene jacket. An experimental design was used which permitted the estimation of the best fitting second degree response surface. The resulting equation for ESC as a function of feed and metering zone temperatures did not have a single optimum but predicted increasing stress-crack resistance with increasing temperatures as high as the experimental temperatures were carried, which for the metering zone was 520F and for the feed zone was 560F. The ESC time as determined by an accelerated constant strain test on heat aged samples varied from 1.1 to 6.8 hours when changing from the worst to best extruder profile. The effect of the different extruder profiles on the change in melt index was also assessed and in general, melt index changes are minimized with higher barrel temperature settings. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1966
- Accession Number
- AD0646527
Entities
People
- H. N. Padowicz
- J. R. Apen