Melts of bimodal (tube) polyethylenes relax considerably more rapidly than normal monomodal specimens. At exit from an l/d = 20 capillary, a melt of bimodal polyethylene behaves like an unrelaxed melt, whereas normal polyethylene does not manage to relax entirely even at exit from an l/d = 30 capillary. The obtained results point to one of the reasons for the high durability of polyethylene tubes with a bimodal molecular weight distribution.
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