In developing a rheological constitutive equation for crosslinking polymers the determination and explanation of time constants are of great importance. For stoichiometrically balanced and imhalanced reactions of polydimethylsiloxane and polyurethane model polymers with appropriate "cross-linkers", it is shown that the experimental data for the storage and loss moduli are well fitted within a large frequency range by a linear theological constitutive equation with a truncated power law relaxation function.Special attention is given to the problem of estimating the different time constants. A method is proposed for the determination of the terminal relaxation time (in the case below the gel point) and a characteristic retardation time (in the case above the gel point) from the intersection points of the high and low frequency asymptotes of the storage modulus.

In the framework of the Edwards‐Grant model, the ultrasonic attenuation of concentrated polymer solutions is calculated. Entanglements between the chains change the frequency behaviour of the ultrasonic attenuation from ∼ω−1/2zu∼ω−3/4

Acta Polymcria 36 (1965) Xr. 12 652 BERGER and STRAUBE: Ultrasonic attenuation of polymer solutions. I removing of amorphous material in the second process (28% increase of crystallinity degree for t h e isotropic sample and 32% for t h e oriented one). cracks in direction of orientation a n d formation of separ a t e microfibres. T h e morphology of isotactic polypropylene effects its thermal stability. ConclusionsThe oxidation of isotactic polypropylene films occurs in the amorphous regions. These regions are situated, however, in different way in an oriented sample before a n d after annealing than in an isotropic one. This causes different r a t e of t h e oxidation connected with t h e diffusion of oxygen a n d nitric acid into t h e films. T h e reorganization of crystalline and amorphous regions in oriented samples during annealing leads t o t h e creation of perpendicular continuous regions of amorphous material a n d t o t h e formation of cracks perpendicular t o t h e orientation direction in t h e thermo-oxidation process. T h e rate of polymer chain scission is higher for t h e oriented sample with fixed ends (no relaxation) than for t h e oriented sample with free ends. Etching leads t o the creation of References [I] MUCHA, M., and KRYSZEWSKI, M.: Colloid & Polymer Sci. [2] MUCHA, M., and KRYSZEWSKI, M.: IUPAC International [3] MUCHA, M.:The ultrasonic attenuation in dilute polymer solutions is treated in the framework of the KIRKWOOD diffusion equation. A ROUSE-ZIMM type relaxation behaviour of the ultrasonic attenuation results from the calculations, and a relationship between the intrinsic shear and bulk viscosity is derived. Ultraschalldam.pfung in Polymerlosungen. I . Verdiinnte LiisungenDie Ultraschalldampfung in einer verdunnten Polymerlosung Vird im Rahmen der KIRKWOODschen Diffusionsgleichung untersucht. Eine Frequenzabhangigkeit vom ROUSE-ZIMM-TY~ und eine Relation zwischen Scher-und Volumenviskositat werden erhalten. 3amyxanue ynampaaeyxa e n o n w p n m pacmeopax. I . Pa36aenennw pacmeopu B a~y x a~~e y n b~p a a~y~a B paa6aBneHHbl.X n0naslepHbl.x pacmopax AaysaeTcR B p a m a x A H @ @ Y~A O H H O~O ypanae-HAR KAPHBYRA. 06beMHOa BRIKOCTRMU. ITOJIYqeHH 9aCTOTH;LII IaBHCIIMOCTb TAna P A Y B A -q H M M A U COOTHOIUeHHe MeHcAy CABUrOBOa II ZntroductionDuring the last years, increasing interest has been given to the investigation of dynamic properties of polymer solutions. Among other experimental methods ultrasonic attenuation measurements are used to obtain information about the molecular mobility of such polymer systems [I-31. For some polymersolvent systems a ROUSE-ZIMM type behaviour of the ultrasonic excess attenuation a divided by the square of thc frequency ws2 is observed [2, 41 (excess attenuation means that. the attenuation by the solvent is substracted). The simplest explanation of this bebaviour is obtained by substituting the ROUSE-ZIMM results for the frequency dependent viscosity 153 into the attenuation formula of the classical fluid continuum theory (e.g. [S]). However, add...

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The dynamics of polymer solutions are consistently treated by the BIXON-ZWANZIU theory including both hydrodynamic and excluded volume interactions. The results confirm generally the essential features of the "blob" picture in polymer dynamics, i.e. the influence of non-uniform chain expansion on the relaxation time spectra and the intrinsic viscosity, but differs in detail from results by DAOUD and JANNINK and WEILL and DES CLOIZEAUX. Especially no second plateau in [q(o)] is observed. Dynamik nicht gleichformig ausgedehnter Polymerketten in verdiinnten LosungenIm Rahmen der BIxoN-ZwANZIG-Theorie wird die Dynamik von Polymerlosungen unter Beriicksichtigung VOI hydrodynamischen und excluded-volume-Wechselwirkungen konsistent behandelt. Die Ergebnisse bestiitigen die wesentlichsten Eigenschaften des "blob"-Bildes, d. h. den EinfluS der nicht-uniformen Ausdehnung der Kette euf die Relaxationszeiten und die Intrinsic-Viskositat, unterscheiden sich im Detail jedoch von den Ergebnissen vo, DAOUD und JANNINK sowie WEILL und DES CLOIZEAUX. Entgegen den Voraussagen wird ein zweites Plateau il [q(w)] nicht beobachtet.