摘要:

AbstractElastomer processing operations are discussed and classified as unit operations. The theory of nonlinear viscoelasticity is applied to processing unvulcanized amorphous rubber and the significance of the maximum relaxation time τmis emphasized

ISSN:0021-8995    

DOI:10.1002/app.1967.070110301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractGel permeation chromatography was used to follow changes in the molecular weight distribution of a polyisobutene, initialMv= 466,000, during degradation induced by sonic irradiation. Seven samples taken at times of 200–163,500 sec. were studied. In general, a steady decrease in molecular weight was observed, although a bimodal distribution was present after 20,000 sec. irradiation. Various measures of inhomogeneity,Mw/Mn,U, etc., were examined. The function, σn/Mw, where σnis the standard deviation of the number distribution, is considered as a measure of the relative distribution. It is shown to be almost constant throughout the degradat

ISSN:0021-8995    

DOI:10.1002/app.1967.070110302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe nature of the room temperature density–dose relationships in polytetrafluoro‐ethylene (PTFE) have been studied over the dose range of 104to 109rads. Under various conditions, samples of PTFE were irradiated in combinations of neutron and gamma (reactor and60Co) radiation fields resulting in density increases up to approximately 5%. For the dose range 105to 108rads, the increase in density measured at 0°C. is approximately proportional to the logarithm of the radiation dose. For doses less than about 105rads, the increase in density appears to be directly proportional to the dose, while above 108rads the density reaches a maximum and then begins to decrease. By examining the changes in slope and displacement of the curves which occur under various conditions, several effects are discernible. Compared to the effects of γ‐rays alone, the density increase per dose in the 105to 108rad region is lower for cases where both neutrons and γ‐rays are present in the radiation field. This may suggest that competing processes are involved in producing density changes. The discernible difference between effects of γ‐radiation and reactor radiation appears to be unique in polymers. The ambient temperature during irradiation and the post‐irradiation heat treatment of the specimens affect the changes in density. For dose rates over the range 0.1 × 106to 13 × 106rads/hr., no dose rate effects have thus far been observed. The feasibility of using PTFE for some types of radiation dosimetry has been demonstrated, and its possible usefulness is b

ISSN:0021-8995    

DOI:10.1002/app.1967.070110303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractPrevious studies by Black and Blomquist on the degradative failure of polymer–metal adhesive bonds have shown that composite failure depends largely on the type of metal substrate employed. In the work reported herein, metal powders of high surface area have been employed to maximize the metal–polymer interface. The composite systems studied consisted for aluminum and iron with polycondensates of bisphenol A–diglycidyl ether, phenol–formaldehyde and poly‐2,2′‐(m‐phenylene)‐5,5′‐bibenimidazole. The composites were prepared in the absence of air and thermally degraded in a time‐of‐flight mass spectrometer while the degradation products were continuously monitored from mass 1 to 200. In the polymer and polymer–metal systems investigated, iron accelerated the decomposition of all polymers studied. This was determined by plottingm/eagainst degradation temperature for the more common mass peaks such as hydrogen and carbon monoxide for the carbon–hydrogen–oxygen‐containing polymer and hydrogen cyanide and ammonia for the carbon–hydrogen–nitrogen‐containing polymer. This technique offers promise in determining the nature of the interface as well as the effect

ISSN:0021-8995    

DOI:10.1002/app.1967.070110304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractVorliegende Arbeit befasst sich mit der Möglichkeit, Diäthylenglycol‐bisallylcarbonat Polymerisate als optisch wirksame Bauelemente zu verwenden. Es wird die Problemtik der Herstellung des Materials und der Formgebung dargestellt. Bei der Diskssion der Eigenschaften des Polymerisates werden Messmethoden und ‐probleme erörtert, z.B. hinsichtlich der Steuerung des Polymerisationsvorganges, der Widerstandsfähigkeit des Polymerisates gegenöber mechanischen Oberflächenbeschädigungen und Klimaein‐ flüssen. Die Arbeit zeigt, dass Diäthylenglycol‐bisallylcarbonat die Reihe der bisher in der Optik verwendeten Kunststoffe in wertvoller Weise ergänst. Bezüglich der Beständigkeit gegen mechanische Oberflächenbeschädigungen wird gezeigt, dass eine Steigerung und Weiterentwicklung möglich ist; das ist gleichzeitig ein Beitrag zum Formulierung und Standardisierung des Beg

ISSN:0021-8995    

DOI:10.1002/app.1967.070110305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractSome crystalline organic compounds containing a β‐naphthyl group stiffen rubbers considerably. This paper discusses the dynamic behavior of these systems when subjected to oscillatory strain of increasing amplitude. Modulus–strain amplitude plots similar to that in carbon black–natural rubber systems are obtained. The implication of these results to reinforcement theory is dis

ISSN:0021-8995    

DOI:10.1002/app.1967.070110306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractInteraction between carbon black and polymer starts during the mixing process; a primary agglomerate is formed, the composition of which is dependent upon the structure. The important carbon black properties are surface area, specific activity, structure (void, volume, anisometry), and porosity of the particles. On heat treatment of black at 3000°C., it loses its sites of high specific activity. Structure and specific activity determine incorporation time and further dispersion. During mixing, bound rubber is formed which is used as a measure of specific surface activity. In the final vulcanizate, the filler–polymer interaction is evident in reduced swelling in solvents (benzene, chloroform, cyclohexane,) etc. Below a certain critical degree of swelling, the percentage swelling is no longer dependent upon the amount of filler in the vulcanizate. Graphitized black vulcanizates exhibit in all solvents the same degree of swelling as the unfilled vulcanizate. This phenomenon is explained by the assumption of mobile adsorption of rubber chains on the carbon black surface. In untreated blacks the mobility on the surface is limited by sites of high energy of adsorption. In graphitized blacks such sites are no longer found, and swelling is unhindered by the presence of black. Reinforcement is explained by the more homegeneous distribution of tension between molecular chains due to slippage on the carbon surfa

ISSN:0021-8995    

DOI:10.1002/app.1967.070110307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractTransparent propylene glycol monoacrylate (PGMA) hydrogels become reversibly opaque when the temperature is rapidly increased to above 30°C. Water permeation, driven by a hydrostatic pressure difference through three PGMA membranes differing in water content and thickness was determined at several temperatures. At room temperature, the permeability to water is relatively low (less than 10 × 10−16cm.2) and is dominated by a diffusion mechanism. When the temperature is suddenly increased, the water permeation rises quickly (up to fifteen times or more depending on the temperature), and viscous flow predominates over diffusive flow. The rapid flow slows down after some time at the same temperature, or on lowering the temperature, and may be interpreted as caused mainly by the reversible transformation of the membrane from the heterogeneous to the homogeneous form. When the temperature is increased gradually, the permeability of the membrane is in the same order of magnitude as that found at room temperature, because no phase separation occurs. The permeation of water decreased in successive measurements made under the same pressure gradient. An increase of the pressure difference also resulted in decreased permeation, indicating that water was pressed out of the gel. Dehydration of the gel caused by increases in temperature (exothermic swelling) and in pressure and changes in the viscosity of water with temperature are some of the factors which are considered in the interpretation of the resu

ISSN:0021-8995    

DOI:10.1002/app.1967.070110308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractBueche's theory is modified to account for the effect of polydispersity on viscosity of polymeric fluids. Results indicate that the ratio of weight‐average to number‐average molecular weight, 〈Mw/Mn〉, though a common measure of polydispersity, is insufficient to account completely for the effect of polydispersity on vi

ISSN:0021-8995    

DOI:10.1002/app.1967.070110309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractLe méthacrylate de méthyle a été greffé a la cellulose en utilisant l'acide de Caro en présence de sel ferrique comme initiateur. L'effet de la durée du greffage, de la concentration en ions ferriques et du rapport cellulose‐monomere sur le pourcentage du greffage a été étudié. Au départ d'études du mécanisme de réaction, a des composés modèles, on a admis que les greffages ne se passent pas via les unités glycols 1,2 ou à l'unité hémiacétalique ' la fin de la molécule cellulosique. Des dégradations concommittantes de la cellulose en cours de la copolymérisation greffée a été examinée. Une relation linéaire entre le pourcentage de greffage et le nombre de chaînes cellulosiques briées par hydrolyse a été trouvée, d'où il semble que la structure du copolymère greffé était plutôt du type séquencé. La structure du copolymere greffé a aussi été étudiée par détermination des poids moléculaires des branches de polyméthacrylate de méthyle greffées apres hydrolyse de la chaîne cellulosique. Dans tous les cas, indépendamment des conditions de réaction, les poids moléculaires des ramifications greffées étaient tres élevés et leur nombre faible. Le nombre de branches greffées par chaîne cellulosique a été calculé au départ du pourcentage de greffage, des poids moléculaires des branches de polyméthacrylate et des poids moléculaires de la chaîne cellulosique. Ce nombre a

ISSN:0021-8995    

DOI:10.1002/app.1967.070110310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY