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Mechanism of HDPE Thermal Expansion Coefficient Distributions under Extrusion Process
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Terada, Kousuke / Yamabe, Masashi / Shimbo, Minoru / Miyano, Yasushi / Kajiwara, Toshihisa / Funatsu, Kazumori
The shrinkage degree ƒÌ of polymer products must be considered when the molds are at the stage of designing. On the calculation ofƒÌ, the descending temperature ƒ¢T of polymer products after molding process and ƒ¿ (the coefficient of thermal expansion) are necessary.
It was found that ƒ¿ has the typical distributions at the various layers along the machine direction (MD) and the traverse direction (TD), especially under HDPE melts flow in the dies. Consequently, ƒ¿ distributions should be predicted for estimation of accurate ƒÌ of HDPE products. In this study, we have investigated the experimental data of HDPE ƒ¿ distributions under extrusion process and calculated the strain distributions by polymer melts flow analysis using finite element method. The following results were obtained.
(1) The measured data of ƒ¿ (MD) distributions correspond to the strain distributions which generate along the flow direction within the inner and the outer die.
(2) The measured data of ƒ¿ (TD) distributions correspond to the strain distributions which generate along the ƒÆ direction within the inner and the outer die.
(3) The measured data of ƒ¿@distributions in this study showed the correlation between the strain distributions much better than the shear stress distributions.
Key words: HDPE / Extrusion process / Polymer melts flow / Coefficients of thermal expansion / Shrinkage degree