摘要:

AbstractThe fine structures of emulsion polybutadiene prepared at temperatures ranging from 55°C. to −20°C. and of various butadiene‐styrene copolymers prepared at −20°C. have been studied by x‐ray methods. The ability of emulsion‐polymerized butadiene to crystallize was found to depend to a large extent on the temperature of polymerization. Butadiene polymerized at 30°C. and above showed no evidences of crystallization when cooled unstretched to −70°C. as observed by x‐ray diffraction methods; however, butadiene polymerized at 20°C. and below showed crystallization effects when cooled unstretched to −70°C. These crystallization effects became more pronounced for samples polymerized at lower temperatures. Layer‐line diffraction patterns of butadiene polymerized at 30°C. and below were obtained by stretching the polymer at about 0°C. From these patterns the geometrical repeat distance along the polymer chains was found to be 5.1 ± 0.1 Å. This corresponds to a fully extended butadiene unit in thetransconfiguration. An anomaly was observed in the diffraction patterns of crystallizable polybutadiene stretched at 0°C. Some of the layer‐line spots varied in position with per cent elongation of the sample. This suggests that the molecules in crystallites of the polymer are inclined to the stretch axis at low elongations and that they become more nearly parallel to the stretch axis at higher elongations. A small addition of styrene as comonomer at −20°C. polymerization temperature did not prevent crystallization and preferred orientation effects in the polymer, since these effects could still be found in a 90/10 charge copolymer. Larger amounts of styrene did prevent crystallinity and preferred orientation as shown by the amorphous nature of an 80/20 charge copolymer. The ability of a compounded vulcanizate of a given polymer to crystallize is less than that of the purified polymer under the same conditions. This may be due to the combined effects of milling, vulcanization, and the presence of carbon black particles in the polymer. A description of the apparatus and techniques used for cooling and

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030401

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractThe attempt to replace chlorine in polyphosphonitrilic chloride with alkoxyl groups is successful except that oxygen rather than alkoxyl substitution occurs to some extent. The amount of oxygen substitution and the extent of degradation are minimized if the polyphosphonitrilic chloride is swollen prior to alcoholysis. The substituted product is insoluble until treated with boiling tetrachloroethane. The final products, the esters, are very tacky when pure but can be incorporated with other polymers to give desirable products.

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030402

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractA new method is investigated to determine by means of potentiometric titration the degree of ripening of viscose. It is found that when the e.m.f. of a characteristic inflection in the potentiometric titration curve is plotted against a measure of the degree of viscose ripening a sharp minimum occurs at a point corresponding to the optimal degree of ripening. Moreover, evidence is offered to indicate the formation of sodium dithiocarbonate in viscose during ripening. This last fact leads to a reasonable postulation of the complete scheme of reactions taking place in a ripening viscose.

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030403

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractAn expression for the amount of chain transfer occurring in a copolymerization carried out in solvent media can be derived in a manner similar to the composition‐kinetic treatment for tripolymer formation. As a result, the relative reactivity of the chain‐transfer solvent can be determi

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030404

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractThe rates of decomposition of benzoyl, lauroyl, bis(p‐chlorobenzoyl), and bis(2,4‐dichlorobenzoyl) peroxides, 0.0133 molar in styrene, have been determined at 34.8, 49.4, 61.0, 74.8, and 100°C., and the corresponding rates of polymerization of styrene have also been determined. Assuming the initial rate of polymerization of styrene, produced by benzoyl peroxide at an initial concentration of 0.0133 m./l. at each of the five temperatures used to be unity, the relative initial rates of polymerization produced by the peroxides studied are as follows: bis(2,4‐dichlorobenzoyl) 2.15, lauroyl 1.52, and bis(p‐chlorobenzoyl) 0.87. The rate data have been subjected to an approximate kinetic analysis, from which one may conclude that the order of intrinsic effectiveness of the peroxides as chain‐initiating agents in styrene is benzoyl>bis(p‐chlorobenzoyl)>lauroyl>bis(2,4‐dichlorobenzoyl), and that the effectiveness increases with increasing temperature. The activation energy for the peroxide‐initiated polymerization of styrene was found to be 21 kcal. per mole. The molecular weight of polystyrene appears to be an inverse function of the temperature, the polymerization rate, the peroxide decomposition rate, and the extent of wasteful decomposition

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030405

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractPolymeres Indol, das in Gegenwart von Sauerstoff dargestellt wurde, kann durch Fällen mit Methylalkohol in 2 Fraktionen getrennt werden. Polyindol ist unlöslich. Die methylalkohollösliche Fraktion kann aus Benzol mit Petroläther als ein weisses, pulveriges “Polyindolperoxyd” ausgefällt werden. Fraktionierung führte zu Substanzen mit Molekulargewichten zwischen 300 und 3000. Bromtitration deutete darauf hin, dass die niedrigmolekularen Proben ungefähr eine Doppelbindung pro Polymermolekül enthielten. Die qualitative Prüfung für Peroxyd war positiv, aber die jodometrische Titration einer Probe ergab nur 42.5% des berechneten aktiven Sauer

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030406

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractEs wird gezeigt, dass die Reaktion von Indol mit Schwefel zu einem Polymer führt, das ein Schwefelatom pro Indoleinheit enthält. Der Brechungsindex und das Absorptionsspektrum des Polymers werden mitgeteilt. Die Kinetik der Schwefelreaktion, mit und ohne Zusatz von Beschleunigern, wird untersucht um den Einfluss der Beschleuniger auf die Reaktiongeschwindigkeit und die Temperaturabhängigkeit der Reaktion festzustell

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030407

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractEine Probe von Polyindol (mittleres Molekulargewicht 400) wird sorgfältig in 9 Fraktionen von steigendem Molekulargewicht von 300 bis 800 zerlegt. Die Beobachtung von Whitby und Katz, dass Bromtitrierung zu einer Doppelbindung pro Polymermolekül führt wird bestätigt. Diese Doppelbindung ist aber nicht länger zur Polymerisation fähig, da sich die Molekulargewichte verschiedener Fraktionen nicht mehr wesentlich änderten, wenn sie Polymerisationsbedingungen—Erhitzen für 500 Stunden bei 175° in Stickstoffatmosphäre—ausg

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030408

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractThe evidence for the nature of the side chains in lignin resulting from investigations of the reactions of model substances has been summarized. The studies have involved investigation of the reactions with (a) sulfite, (b) alkali and nitrobenzene, and (c) hot alkali.(a)Reaction with sulfite occurs readily for model substances with β‐hydroxyl or α,β unsaturated keto groupings (“aldol type”). Hydroxyl groups adjacent to a ring are somewhat reactive but or‐hydroxyketo groupings (“acyloin type”) do not react.(b)Alkaline oxidation to aldehyde or carboxyl with nitrobenzene is effective in degrading a side chainparato a free hydroxyl group having an oxygen atom on the α‐carbon atom. Conversion of the para‐phenolic hydroxyl to a methyl ether neutralizes its promoting influence.(c)Cleavage to an aldehyde with hot alkali in the absence of air is specific for the “aldol type” grouping in the side chain. This is regarded as a reverse aldol condensation and it has been demonstrated that acetaldehyde can be isolated from such degradations.These results, together with the behavior of lignin and its derivatives, are interpreted in terms of probable structures for the sid

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030409

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY

摘要:

AbstractThe influence has been studied of systematic alterations in the amount of cross linking in elastomers upon diffusion coefficients and permeability constants in elastomers of homologous paraffin hydrocarbons. In a number of such media the influence of chain length of the paraffins upon the transport phenomena has also been investigated, using CH4, C2H6, C2H4, C3H8, andn‐C4H10.Apparent activation energies for permeation (Ep) and for diffusion (ED) for degrees of vulcanization up to 11.3% combined sulfur are in the decreasing order:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm butane } > {\rm propane } > {\rm }_{{\rm ethylene}}^{{\rm ethane}} {\rm } > {\rm methane } > {\rm nitrogen}$$\end{document}For low vulcanizates,EPis not very sensitive to the per cent sulfur. However for higher percentages of sulfur,EPtends to rise, especially when the migrating molecule is a large one.EDis rather more sensitive both to molecular size and to per cent combined sulfur.BothEPandEDfor natural rubber vulcanizates show definite temperature coefficients, manifested as curvature when log10Dor log10Pis plotted against 1/T. Such curvature was absent, however, in butyl rubber.The results have been interpreted in terms of the molecular nature of elastic networks and in terms of the kinetic‐statistical (zone) theory and the transitionstate theory. All treatments indicate the need for a considerable zone of activation for each unit diffusion process, confirming an earlier investigation. When, in the Arrhenius equation,D=D0e −E D/RT, one plots log10D0againstED/T, the clear functional relationship:\documentclass{article}\pagestyle{empty}\begin{document}$$\log _{10} {\rm }D_0 {\rm } = {\rm } - 3.6{\rm } + {\rm }0.14{\rm }{{E_D } \mathord{\left/ {\vphantom {{E_D } T}} \right. \kern-\nulldelimiterspace} T}$$\end{document}emerges. A simple interpretation of this and of similar functional relationships for other “activated” physical and chemical rate processes h

ISSN:0022-3832    

DOI:10.1002/pol.1948.120030410

出版商:Interscience Publishers, Inc.    

年代:1948

数据来源: WILEY