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SynopsisMany HDPE samples show peculiar behavior of melt viscosity a t low shear rate and melt strength a t constant extrusion rate in a temperature region of about 200" to 25OOC. It was found that the degree of the peculiarity of the behavior was affected by temperature, residence time at a temperature, the temperature rise rate, and the kind and quantities of additives. It was concluded that the peculiar effects were due to the crosslinking that a chemical reaction produced. An attempt was made to express the different behaviors of temperature dependence of melt viscosity among many HDPE samples by some simplified equations. It is suggested that both the peculiar changes with temperature of the melt viscosit,y and those of the melt strength may be produced by the same mechanism. The similarity of the phenomena between HDPE samples exposed to high temperatures and those crosslinked by ?-rays was found. Finally, a possibility is discussed of predicting the processability of the resin and properties of final products before the processing operation.

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