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137 zur Folge haben, dab bei wachsender Temperatur die Viskosit~t kleiner wird. Fiir die Diskussion und FSrderung dieser Arbeit danke ich tterrn Professor Dr. K.-H. Hellwege und Herrn Dr. W. Knappe. Zusammen/assung Es wird die Druekabh~ngigkeit des nicht-Newtonschen FlieBverhaltens yon Polyolefinschmelzen (Hochdruck-, Niederdruck-, Phillips-Poly~thylen und Polypropylen) experimentell untersucht und gefunden, dab dcr durch GI. [1] deflnierte Druckkoeffizient ~ § mit zunehmender Deformationsgeschwindigkeit (~ = 1,2 ... 120 sec -1) kleiner wird und dabei die (im einzelnen in der Tabelle 1 angeffihrten) Werte a § = 1,46 9 10 -3. .. 0,32.10 -a em 2. kp -1 annimmt. Der Druckkoefflzient der Polyolefinsehmelzen ist ebenso wie fiir viele Newtonsche Fliissigkeiten bis 2000 kp cm -2 unabhangig vom Druck, er wird mit zunehmender Temperatur kleiner und nimmt mit zunehmender Verzweigung zu. Die MeBergebnisse werden mit Hilfc eines Aufweitungsvolumens interpretiert. Es wird gezeigt, dait eine Deutung des FlieBverhaltens yon Polyathylen durch das freie Volumen allcin nicht mSglich ist.

SynopsisThe steady state shear rheological properties of solutions of a rodlike polyamide, poly-p-phenyleneterephthalamide (PPT), in 100%sulfuric acid have been compared with those of solutions of a flexible chain polyamide, nylon 6,6, in the same solvent. For solutions of similar concentration (c) and molecular weight (M), it was found that the primary normal stress difference (N d and the viscosity (1J), compared at the same shear rate (1'), were an order of magnitude greater for solutions of PPT. It was believed that this behavior could be accounted for through the formation of an enhanced entanglement network in the PPT solutions. Plots of the zero shear viscosity (1Jo) versus cM w , where M w is the weight average molecular weight, for both systems revealed that "bends" occurred in the data corresponding to a critical entanglement molecular weight (Me) of 1180 for PPT (this corresponds to 30 main chain atoms (a) and to 5260 (z = 330) for nylon 6,6. More significantly, 1Jo was found to be proportional to (CM w ) 6.S for solutions ofPPT and to (cM w )3.4for nylon 6,6 solutions. 1J versus l' curves were similar in shape for both systems and could be reduced to the same master curve with the only difference being that the relaxation times or shifting factors were considerably greater for the PPT solutions. This suggested that the process of destroying entanglements may be similar for both polymers.The overlap parameter el1J], where 11J] is the intrinsic viscosity, provided a much better correlation of 1Jo data from the two sets of solutions than did the segment contact parameter cM w . This suggested that the structural variable controlling the onset of entanglements may be a parameter such as the radius of gyration. Because of the inability of rodlike molecules to coil around each other, further insight into the nature of entanglements is obtained.

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SynopsisFor two polymer melts spun in a side-by-side configuration through a capillary, interface shape and spinneret exit angle data are presented as a function of viscosity ratio, spinneret dimensions, and relative polymer-steel wettability. Nylon-nylon versus nylon-polyurethane bicomponent flow systems are compared. A surface tension phenomenon is postulated to be significant in controlling the bicomponent fiber interface shape for capillary length-to-diameter ratios of the order of unity.