Verteilungsfunktion die besten Werte fiir die Molekulargewichtsverteilung. Unter den Methoden, die auf einer Verwendung der mittleren Molekulargewichte des gesamten Polymeren in Verbindung mit einer Verteilungsfunktion beruhen, zeigt die Methode, die die ScHuLzsche Verteilungsfunktion verwendet, die beste fjbereinstimmung mit den Ergebnissen der GPC. Verteilungsfunktionen, denen nur ein Wert fiir das mittlere Molekulargewicht zugrunde liegt, gabea weniger zufriedenstellende Resultate.Die Assoziation der PVC-Molekiile in Tetrahydrofuran fiihrt bei diesem Polymeren wahrend des Fraktionierungsvorgangs und bei anderen Charakterisierungsmethoden zu einem anormalen Verhalten. Die Assoziation nimmt mit der Syndiotaktizitat der Probe zu. Um den uuerwiinschten EinfluB solcher ubermolekularer Strukturen zu vermeiden, wurde eine Wirmebehandlung der PVC-Losungen durchgefiihrt. Die Abweichung der log [q] vs. log mii,-Kurven von der Linearitat wurde auf diese Weise auf eine Assoziation und nicht auf eine Kettenverzweigung zuriickgefiihrt.
SYNOPSISThe thermomechanical degradation of stabilized and unstabilized poly (vinyl chloride) VVC) has been investigated by use of a Brabender Plastograph. All degraded samples were analyzed by gel permeation chromatograph (CPC) and some of them were studied by infrared measurements and viscometry. The association of PVC molecules seemed to affect the CFT measurements for weight average molecular weights exceeding about 70,000. The heat treatment of solutions of degraded PVC before fractionating by GPC was very important in order to obtain real values of Gw.After the degradation point was reached, the BaCd stabilized samples showed a faster increase in Mw than the Sn stabilized or the unstabilized samples did.The emulsion polymer had not as good stability as the corresponding suspension polymer, presumably due to its larger content of remaining polymerization additives. No noticeable chain scission occurred for the low molecular weight PVC, PEVIKON R-150. This polymer also showed a very slow increase in BW when treated without any stabilizer. The average number of trifunctional branch units per molecule was found to be only 0.3 for PEVIKON R-150 and 0.5 for PEVIKON R-341, but increased during the degradation. The agreement between the results from the GF' C, viscometry, Brabender tests, and the infrared measurements are excellent.
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