摘要:

AbstractSome details for the construction of a modulus balance and thermostat are discussed. A new dumbbell type is developed for aging tests. In four stocks containing different accelerators, the function of copper applied as stearate is investigated. In the case of Santocure, a comparatively high sensitivity is found, and thet1/2(TB) value for aging at 70°C. represents a sensitive measure of the prooxygenic effect, whereas relaxation times at 121° showed a smaller but definite variation. With MBT boosted with DPG only a limited effect was observed. Conversely, for the thiurams, copper addition produced a marked antioxidant effect comparable with the retardation normally effected by 2PHR of ordinary antioxidants. 0.05% copper showed an antioxidant activity equivalent to the 2PHR antioxidant. Consistent results were obtained for aging, relaxation, and rate of oxidation. The factors of retardation as might be expected, however, are not quite comparable. The factor of retardation for copper alone is 4–8 units. The copper develops in the thiuram vulcanizates a strong brown color giving colored solutions upon extraction with acetone and iso‐octane. As the spectrophotometric determination of the colored complex is difficult, owing to the presence of the strong absorbing ZDC, the nature of the colored complex has not yet been ascertained, but it must somehow be responsible for the inverted action of copper found

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100501

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractA reverse polymerization process with random initiation has been calculated. Initial stages of various degradation processes have been considered and the initial rates of formation of monomer have been presented as a function of the total number of monomer units present in the system, the initial chain length, etc.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100502

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractViscosity, sedimentation, diffusion, and osmotic pressure measurements in ethyl acetate are reported on four unfractionated nitrocellulose polymers containing about 13.5% nitrogen and varying in molecular weight from 0.93 to 15 x 105.Detailed viscosity determinations in buret viscometers in the concentration range 0.025 to 0.300 g./dl. and over a range of velocity gradients from about 500 to 5000 sec.‐1are presented. Viscosity data adjusted to fixed shear rates fitted closely the relation ηsp/C= [η] +a2C+a3C2. Plots of ηsp/Cvs.Cat different shear rates were found to diverge rapidly with increasing concentration. For the nitrate of highest molecular weight, the viscosity was strongly shear‐dependent and the intrinsic viscosity appeared to vary from 52 at 3000 sec.‐1to 80 or more at 0 sec.‐1. The other samples displayed these tendencies less markedly with decreasing molecular weight. Other extrapolation procedures are also discussed. The intrinsic viscosity data accumulated at 500 sec.‐1could be represented by the relation [η] =KMα; α = 0.99; the molecular weights were those obtained from sedimentation‐diffusion measurements on the unfractionated nitrocelluloses. Assuming for practical purposes α = 1, thenKm(\documentclass{article}\pagestyle{empty}\begin{document}$\[= \overline {{\rm DP}} /[{\rm \eta ]}\]) is found to have the value 80 ± 3. Assuming a negligible depolymerization during nitration, the analogous factors required for cupriethylenediamine and for cuprammonium were found to be 170 and 230, respectively. The effect of varying shear rate on these factors is illustrated.The sedimentation constants obtained were readily extrapolated to infinite dilution with an expanded sedimentation‐concentration relation,S=S0/(1 +K2C+K′sC2). Diffusion constants were obtained following the second moment method and mathematically extrapolated to zero concentration according to Gralén. Molecular weights were computed with the Svedberg equation. Number average molecular weights were obtained osmotically.Some consideration of the data in terms of the theories of Debye‐Bueche and Kirkwood‐Riseman is given. It is found that both K‐R's and D‐B's theories predict the variation of intrinsic viscosity with molecular weight within twice the standard deviation of the observed slope from the frictional coefficient‐molecular weight data. In both viscosity and sedimentation the polymer appears, therefore, to behave in an approximately equally “free draining” fashion. For the calculated intrinsic viscosity of a sample of intermediate molecular weight a reasonable value is obtained from the latter theory only; but it is not uniformly successful in predicting all [η]'s, particularly those corresponding to low molecular weights.The relation betweenKs, the first interaction coefficient in sedimentation and molecular dimensions, is briefly discussed. Also considered are the interaction coefficients in viscosity, especially as regards

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100503

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100505

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe complete characterization of a branched polymer involves many factors, the most difficult to assess being the average number of elementary linear portions, or branches, of which the polymer is composed, the degree of polymerization of the branches and the extent of cyclic structure formation. A method of analysis of branched polymers is proposed which should be applicable to polymers of any polyfunctional monomer the unsaturated groups of which are separated by saponifiable links. The method is based on the measurement of degree of polymerization and residual unsaturation of the polymer followed by saponification and determination of degree of polymerization of the resulting polymer, and involves the assumptions that branching in the polymer occurs only by the sharing of a monomer unit by two or more linear portions or branches depending on the number of double bonds in the monomer and also that the average degree of polymerization of the branches remains unchanged by the saponification treatment. Evidence from experiments on the saponification and re‐esterification of poly(allyl acetate) and poly(allyl benzoate) indicates, that, in the case of diallyl esters, the above conditions are satisfied. The technique was therefore applied to three polymers of diallyl phthalate, and in each case the average number of chains and degree of polymerization of the chains were estimated. Evidence of considerable extents of cyclic structure formation was found, each individual branch in the polymers consisting of approximately fourteen diallyl phthalate units, six of which are doubly reacted. It is suggested that the existence of extensive formation of cyclic structures may be partly responsible for the poor correlation of predicted with actual degrees of conversion at gelation in polymerizations involving multifunctional monomer

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100506

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe general rate equations for free radical depolymerization previously developed are interpreted for the special case of terminal initiation and absence of transfer in view of recent work by others on the same subject. The discrepancies in the two sets of results are shown to arise from an invalid evaluation of the role of kinetic chain length in this recent analysis.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100507

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100508

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100509

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100510

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY