摘要:

AbstractIt has long been known that a single point determination can not describe the rheological properties of a fluid. A new method applicable to nonconducting fluids with viscosities ranging from a few hundred to more than 15,000 poises is described. The method consists of a cup and ball in which the ball is forced into rather than pulled out of the cup. Viscosity is measured electronically as a function of the time required for the ball to move a predetermined distance under a given load. Shear rates are variable over very large ranges. Rheological studies were made of a blown castor oil, three polyisobutylenes, and a high viscosity polystyrene. In addition certain physical properties of polyisobutylenes are presented.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100301

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractA method for following rapid crystallization in polymers using infrared absorption has been devised. The infrared absorption was correlated quantitatively with the density of polyethylene terephthalate for varying degrees of crystallinity and qualitatively with the change in x‐ray diffraction pattern on crystallization of this polymer. This technique has been applied to measure the crystallization–time curves of thin films of polyethylene terephthalate at intervals of 10°C. for temperatures between 120 and 240°C. Half‐times from these curves show a minimum near 190°C. The temperature dependence of the data is discussed in terms of the Volmer‐Becker‐Turnbull theory of nucleation in condensed systems. An activation energy of 20 kcal./mole for short‐range diffusion of chain segments is obtained from the temperature coefficient of the observed induction time. The data on the kinetics of the crystallization are compared with the results of an analysis of Avrami. A constant,A, was introduced into Avrami's equation to give:\documentclass{article}\pagestyle{empty}\begin{document}$$ V = A(1 - \rm \exp \{ - Bt^k \} )\quad 1\bar < k\bar < 4 $$\end{document}Ais the limiting volume fraction of crystalline material after a long time and was determined from density measurements. The crystallization was found to follow this equation from 2 through 90% transformation for temperatures from 120 to 180°C. Deviation appeared in the region below 10% transformation at higher temperatures. The value ofkwas interpreted as indicating plate‐like growth at crystallites

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100302

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractA criterion for tearing of test‐pieces cut from thin sheets of a natural rubber vulcanizate, similar in form to the Griffith criterion for spreading of a crack, is formulated. This criterion involves a characteristic energy for tearing which is independent of the shape of the test‐piece and of the disposition of the cut. It is shown how this characteristic energy can be found experimentally for a particular vulcanizate and used to predict the force required to tear test‐pieces of the vulcan

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100303

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractUne revue des déterrninations des constantes de Rayleigh pour les liquides montre qu'un nombre appréciable de chercheurs différents arrivent è des réultats concordants en utilisant des m6thodes photographiques; ces rèultats sont considCablement plus bas que ceux de Carr et Zimm et que ceux prévus par la thérie. Le premier groupe de rbultats confirme des considérations thériques modifiées, mais ni ces réultats ni la dbtermination des poi&moléculahes n'apportent de confirmation de la valeur absolue de la constante de Rayleigh. Les auteurs recommandent l'adoption des valeurs déterminks photo

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100304

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractRibonuclease and carboxypeptidase are inactivated by ultraviolet light (2537 A.) with quantum yields of 0.03 and 0.001–0.005 respectively. The quantum yields for low molecular weight proteins are of the order of 0.03 and are higher than those for splitting peptide bonds in typical peptides (0.004–0.0004 or less). It is postulated that the primary process of inactivation involves modification of aromatic residues in proteins. A possible reason for the inverse relationship between quantum yields and molecular weights of enzymes and proteins is discus

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100305

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100306

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100307

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY