bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solubility of Zinc Oxide in Preserved Hevea Latex
Authors: Van den Tempel M. 
Published: February 2011

Abstract
The solubility of zinc oxide in Hevea latex, and in model solutions containing an ammonium salt together with free ammonia, has been measured by means of polarography. It is found that the solubility, at a given value of the pH, is proportional to the concentration of ammonia and ammonium salt together. At a constant concentration of ammonium ions plus free ammonia, the solubility shows a maximum at pH 9.4 A relation between the solubility of zinc oxide in Hevea latex and the concentrations of ammonium ions and free ammonia is given. The relation is checked with a number of latex samples of varying origin, and with samples produced therefrom by the addition of silicofluoride, formaldehyde, or trypsin.
Bisalkylation Theory of Neoprene Vulcanization
Authors: Kovacic Peter 
Published: February 2011

Abstract
Among the organic compounds that are recommended for use with magnesia and zinc oxide as vulcanizing agents for Neoprene are ethylenethiourea (2-imidazolidinethione), p,p′-diaminodiphenylmethane and the di-o-tolylguanidine salt of dicatechol borate. In the absence of sulfur, these agents in combination with zinc oxide do not vulcanize natural rubber. This points up a marked difference in the way these elastomers vulcanize. Although a major structural difference is the chlorine atom in Neoprene in place of the side methyl group in natural rubber, the small amount of tertiary allylic chlorine formed by 1,2-polymerization is the important functional difference. The labile chlorine amounts to about 1.5 per cent of the total chlorine in a general-purpose Neoprene made at 40° C, such as Neoprene Type W used in this work. In Neoprene latex, this active chlorine is gradually liberated, and the polymer becomes cross-linked. This paper demonstrates the importance of the labile chlorine in the vulcanization of dry Neoprene, accounts for the difference in the vulcanization of Neoprene and natural rubber, and suggests a bisalkylation theory of Neoprene vulcanization.
Softening of Vulcanized Carbon Black-Loaded Rubber during Extension
Authors: Marshall D. G. , Walker D. L. , Smith J. G. 
Published: February 2011

Abstract
The results of the observations recorded in this paper may be summarized by the following items. 1. A difference between the first and second load-extension curves is to be expected in any viscoelastic material, although the behavior of black-loaded rubber at large extensions differs in some fundamental respects from a simple viscoelastic material. 2. Within the experimental limits of about ±10 per cent, all of the energy used in softening the black-loaded rubbers studied appears as heat. 3. The ratio between the area of the hysteresis cycle obtained on first stretching a specimen of black-loaded rubber and that obtained during the second extension varies only slightly from compound to compound in the range of extensions studied. 4. Although the modulus of a black-loaded rubber decreases with increasing temperature, the ratio between the hysteresis area of the first extension and that of the second extension remains roughly constant over the temperature range studied. 5. There are electrical resistance changes that correspond closely to the mechanical softening effects experienced with black-loaded rubber. Result (2) suggests that if cross-linkage breaking or changes of state of rubber are specified as mechanisms for producing softening, then the potential energy changes required must be small, compared with the mechanical energy available. Result (5) shows that changes in arrangement of the carbon black particles are associated with the softening process, and therefore suggests that the softening is related to internal strains in the rubber. These results do not prove that the softening observed in rubber is similar in principle to the behavior of a simple viscoelastic model during the first and other extensions. However, these observations are consistent with this view, except for the difficulty connected with the relationship between the softening and the permanent set in the simple viscoelastic material, and the difficulty connected with the persistence of softening. A simple linear model is obviously bound to have considerable limitations in describing the properties of a black-loaded rubber at high extensions. The limitations may arise from the nonlinearity of rubber elasticity and the non-Newtonian nature of rubber flow; alternatively, it may be necessary to postulate some entirely different process, such as rubber heterogeneity or mechanical bond breaking.
Determination of Free Sulfur in Hard Rubber
Authors: Wynne-Evans C. 
Published: February 2011

Abstract
The volumetric method for the determination of sulfur by means of aqueous sodium sulfite has been adapted for the determination of free sulfur present in hard-rubber vulcanizates. This work was carried out because there was not a speedy free sulfur method applicable to hard rubbers, and the investigation has shown that, by the use of aqueous sodium sulfite, it is possible to obtain reliable and extremely accurate free sulfur results in a little over three hours, against the usual three to four days by other methods which are discussed.
Carboxylic Elastomers
Authors: Brown Harold P. , Gibbs Carlin F. 
Published: February 2011

Abstract
Carboxyl groups can be introduced into elastomers by adding olefinic acids to suitable emulsion systems prior to polymerization. In general, such carboxyl groups elevate the elasticity temperature range, impart superior filming properties, increase resistance to swelling by hydrocarbon solvents, and render the polymers susceptible to cross-linkage, gelation, and vulcanization by polyvalent reagents. In vulcanization recipes based on sulfur but containing polyvalent metal salts, the presence of as little as 1 per cent of a carboxylic monomer is recognizable through its influence on vulcanizate properties. Carboxylic elastomers can be cross-linked by reactions of the carboxyl groups. Salt formation with zinc oxide, without pigmentation, gives stocks having stress-strain properties equaling or surpassing those of black-pigmented sulfur-cured vulcanizates of analogous noncarboxylic polymers. Several divalent metal oxides and other salts can be used as vulcanizing agents. The metal oxide vulcanizates possess excellent stress-strain properties, but poor compression sets. Certain vulcanizates are improved by the inclusion of small amounts of organic acids. An excess of organic acid causes devulcanization. Carbon blacks function principally as loading rather than reinforcing pigments.
Steady Flow and Dynamic Viscosity of Branched Butadiene-Styrene Block Copolymers
Authors: Kraus G. , Naylor F. E. , Rollmann K. W. 
Published: February 2011

Abstract
Steady flow and dynamic viscosities were determined for symmetrical linear and star-branched block copolymers of butadiene and styrene above their upper (polystyrene) glass transition. Block structures examined were B-S-B, (B-S-)3, S-B-S, (S-B-)3 and (S-B-)4. At constant molecular weight and total styrene content viscosities were greater for polymers terminating in styrene blocks, irrespective of branching. Branching decreased the viscosity of either polybutadiene-terminated or polystyrene-terminated block polymers, compared at equal Mw. However, comparisons at equal block lengths showed that the length of the terminal blocks, not the total molecular weight, governs the viscoelastic behavior of these polymers to a surprisingly good approximation. This unusual result is rationalized in terms of the two-phase domain structure of these polymers, which persists to a significant degree in the melt. Below the glass transition of the polystyrene blocks the effects of branching were masked by differences in the morphology of the domain structure unrelated to branching.
Chemorheological Study of Vulcanized Rubbers under Mechanical Stress
Authors: Kusano T. , Suzuki Y. , Murakami K. 
Published: February 2011

Abstract
Below the glass transition temperature, the cleavage of molecular chains of extended vulcanized rubbers will occur. The crosslink density of vulcanized rubbers, which were placed at room temperature for about 4 h in a nitrogen atmosphere, increased about 17 per cent after extension of 200 per cent at −76° C. This may be due to the recombination of cleft chains, and this can be shown by the Maxwellian type of curves resulting from a plot of crosslink density as a function of forced strain. The decreasing proportion of crosslink density in the presence of radical acceptors in the rubbers and the increasing crosslink density in the absence of radical acceptors, because of recombination of cleft chains, was ascribed to the recombination of unstable chains produced by the added mechanical stimulus.
Processing of Powdered PVC-NBR Polyblend Compounds
Authors: DeMarco R. D. , Woods M. E. , Arnold L. F. 
Published: February 2011

Abstract
The processing of PVC-NBR compounds in powdered form has been discussed. Advantages of powder over conventional processiag were reviewed. The special requirements of NBR for blending with PVC were noted. Thermal stability requirements, in particular, were emphasized. Typical compound formulations for nonvulcanized applications were given. And the effect of compound variations on physical properties indicated. Injection molding of shoe soles was given as an example of end-product production directly from these powdered compounds.
Solution Autoxidation of EPDM and Termonomers
Authors: Schnecko H. , Walker J. S. 
Published: February 2011

Abstract
Oxygen uptake of 3 low molecular weight ethylene-propylene terpolymers (EPDM) and their respective bicyclic diolefin termonomers (dicyclopentadiene, ethylidene norbornene, and methyl endomethylene hexahydronaphthalene) has been measured at ⩽70°. From the kinetic behavior and from the activation energy, it has been concluded that ethylidene norbornene reacts differently from the other two monomers; its autoxidation is much slower. In all cases, conversion is not very high due to formation of an unidentified inhibitor.
Lithium Polymerization Catalysts. Charles Goodyear Medal Address—1972
Authors: Stavely Frederick W. 
Published: February 2011

Abstract
The growth of the Lithium Polymerization Catalysts system has been an interesting and intriguing study. Abraham Lincoln, in one of his addresses, indicated that no one would long remember what was said or done there on that occasion. Thus unwittingly, he may have forecast the insignificance of this paper in its effect on the scientific world. It is presumed that none of you here, unless he may have been a Charles Goodyear medalist, can recall many of the important statements or thoughts expressed on this occasion by prior Charles Goodyear Medalists. Therefore, you need not recall anything that is said here today. When one starts a research project, the first thing that is done is to review the literature to find out what has already been done in that field. Thus, we find that in 1826, Faraday published his first analysis of rubber latex. He found that it contained water, rubber, vegetable matter rich in nitrogen and extractable material. He also established that rubber contained the elements of Carbon and Hydrogen. His was the first significant publication about rubber since that of de la Condamine in 1751 to the Academie of Science in Paris. There were several other publications prior to the end of that century, but they did not seem too significant from a scientific standpoint. A German scientist, Frederich Karl Himly, had been studying in Göttingen for a year and a half, about rubber and its destructive distillation products, and he discussed his findings in his Doctors dissertation in 1835. Himly's thesis was published in a small paper back booklet but it did not get wide distribution, possibly due to the fact that it was written in Latin, as was often the case in those days. A copy of this publication was found in the Research Library of The Firestone Tire & Eubber Company about 1922. Imprinted on the cover was the name of M. J. Sehleiden and written on the outside, the name of M. Prinzhom. Also there was the name of C. C. Goodrich, and H. W. Kugler, who later became the Chief Chemist of The Firestone Tire & Rubber Company.
Kinetics of Sulfur-Free Thiuram Vulcanization
Authors: Ducháček Vratislav 
Published: February 2011

Abstract
Sulfur-free thiuram vulcanization has been investigated at temperatures from 160° to 190° C over 0.5 to 600 min. Continuous measurements in a VUREMO curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Simultaneously the values of the network chain density were calculated from swelling measurements on the vulcanizates. The cure curves show clearly an induction period (ti), then fast crosslinking, a partial degradation, a “long-time” crosslinking, and finally a slow, limited degradation. Apart from the induction period, the kinetic graphs are satisfactory represented by a rate equation assuming three independent first-order reactions: fast crosslinking, degradation, and slow crosslinking. The rate equation contains seven kinetic parameters. Over the temperature range studied, there is no difference between the values of activation energy for fast crosslinking, for degradation, for slow crosslinking, and for ti−1. Due to the presence of thiourea, the values of the induction period, the rate constant, and the extent of slow crosslinking are decreased. Simultaneously the activation energies calculated from degradation and slow crosslinking are significantly increased. On the basis of the above results, the mechanism of the sulfur-free thiuram vulcanization, in which ionic and radical reactions take place, is discussed.
Thermodynamics of Solutions of Poly(Dimethylsiloxane) in Benzene, Cyclohexane, and Chlorobenzene
Authors: Flory P. J. , Shih Hsiang 
Published: February 2011

Abstract
Excess volumes have been measured at 25° for mixtures of poly(dimethylsilo xane) (PDMS) of high molecular weight with each of three solvents: benzene, cyclohexane, and chlorobenzene. Chemical potentials have been determined for solutions in the first two of these solvents by high-pressure osmometry and by vapor sorption. These results, in conjunction with osmotic measurements by Kuwahara and coworkers in chlorobenzene at 20 and 60°, and the heats of mixing determined by Delmas and coworkers for each of these systems permit a comprehensive analysis of the thermodynamic properties of the PDMS mixtures. They are characterized by entropies of dilution and excess volumes that are abnormally low compared with theoretical calculations.
Characterization of Polymers under Large Deformation. I. Repeated Chemical Stress Relaxation of Vulcanized Rubbers
Authors: Kusano Takae , Murakami Kenkichi 
Published: February 2011

Abstract
In this investigation, repeated chemical stress relaxation measurements were carried out to observe the relaxation behavior at large deformation. It was found that the repeated chemical stress relaxation curves were affected by both measurement temperature and the extension ratio of rubber. It was suggested on the basis of the results that temperature and mechanical stimulus have a similar effect on the stress relaxation curves.
Large Deformation Isotropic Elasticity—On the Correlation of Theory and Experiment for Incompressible Rubberlike Solids
Authors: Ogden R. W. 
Published: February 2011

Abstract
Many attempts have been made to reproduce theoretically the stress-strain curves obtained from experiments on the isothermal deformation of highly elastic ‘rubberlike’ materials. The existence of a strain-energy function has usually been postulated, and the simplifications appropriate to the assumptions of isotropy and incompressibility have been exploited. However, the usual practice of writing the strain energy as a function of two independent strain invariants has, in general, the effect of complicating the associated mathematical analysis (this is particularly evident in relation to the calculation of instantaneous moduli of elasticity) and, consequently, the basic elegance and simplicity of isotropic elasticity is sacrificed. Furthermore, recently proposed special forms of the strain-energy function are rather complicated functions of two invariants. The purpose of this paper is, while making full use of the inherent simplicity of isotropic elasticity, to construct a strain-energy function which: (i) provides an adequate representation of the mechanical response of rubberlike solids, and (ii) is simple enough to be amenable to mathematical analysis. A strain-energy function which is a linear combination of strain invariants defined by ϕ(α)=(α1α+α2α+α3α)/α is proposed; and the principal stretches α1, α2, and α3 are used as independent variables subject to the incompressibility constraint α1α2α3=1. Principal axes techniques are used where appropriate. An excellent agreement between this theory and the experimental data from simple tension, pure shear and equibiaxial tension tests is demonstrated. It is also shown that the present theory has certain repercussions in respect of the constitutive inequality proposed by Hill.
Viscoelastic Behavior of Butadiene-Acrylonitrile Copolymers at Small and Large Deformations and Their Ultimate Properties
Authors: Nakajima N. , Bowerman H. H. , Collins E. A. 
Published: February 2011

Abstract
With four samples of butadiene-acrylonitrile copolymers the following viscoelastic measurements have been performed: dynamic mechanical measurements in tension at 110 Hz from −60 to 180° C, tensile stress relaxation measurements with 100 per cent elongation at 25, 54, and 97.5° C, capillary flow measurements at 70, 100, and 125° C, and high-speed tensile stress-strain measurements carried to break at 25, 54, and 97° C. All the data have been treated with the same equation for the time-temperature conversion. The complex viscosity-frequency curves calculated from the dynamic measurements were found to be in good agreement with the capillary viscosity-shear rate curves. From the stress-strain relationship at the yield point the viscosity is estimated; such viscosity as a function of the strain rate is similar to the viscosity-shear rate curve. Good agreement was found with some samples. The elongation to break may be predicted with some samples from the treatment of stress relaxation data together with steady shear flow data.
Unperturbed Polymer Chain Dimensions from Intrinsic Viscosities Determined in Good Solvents
Authors: Stacy C. J. , Arnett R. L. 
Published: February 2011

Abstract
Experimental criteria are presented to determine the region of validity of the intrinsic viscosity-molecular weight relation proposed by Stockmayer and Fixman for use in good solvents. Use of these criteria in several good solvents yields the same value for unperturbed polymer dimensions as do measurements made at “θ” conditions. Intrinsic viscosity determinations conforming to these criteria, made in two good solvents, allow the determination of weight-average molecular weights of the polymer solute.
Network Changes in Nitrile Rubber at Elevated Temperatures
Authors: Lee T. C. P. , Morrell S. H. 
Published: February 2011

Abstract
The network analysis of the aged sulfur vulcanizates of nitrile rubber serves to re-emphasize the complexity of the structural changes which can occur at elevated temperatures. Three factors control the rate and degree of crosslinking in these systems. First there is the crosslink structure. An essential feature for heat resistance in sulfur compounds is that they should contain, as near as possible, 100 per cent monosulfide crosslinks. Systems which contain polysulfide crosslinks, and probably to a lesser extent disulfide crosslinks, are prone to purely thermal crosslink shortening or cleavage reactions. The physical effect of these thermal changes would be superimposed on the effects brought about by thermooxidative changes. Despite their thermal stability monosulfide crosslinks can oxidize and cleave, a process which will result in stress relaxation if the sample is held in tension or compression. Hence for truly inert systems one will have to turn to non-sulfur cure in conjunction with a suitable stabilizer. Because the results indicate that scission associated with chemistry at the monosulfide crosslink is reversible, this cleavage does not contribute to the change in modulus or hardening during aging. This brings in the second controlling factor. The degree and rate of hardening depends on the nature of the products of vulcanization, and also possibly on those species intermediate between crosslink and accelerator, the pendent accelerator groups. In acting as an antioxidant ZDMC is apparently oxidized to a new source of sulfur. The more heat resistant cadmate system contains no such products and also a minimum of pendent accelerator groups. This leads to the third factor—the added antioxidant. For its heat resistance the cadmate system relies on an antioxidant. It is this which stops crosslinking reactions through autooxidation of the polymer backbone. The efficiency with which the antioxidant (dioctyldiphenylamine) works suggests that there is a synergistic effect in operation, which in some way involves cadmium. Thus the best heat resistance will be obtained where the compound yields monosulfide crosslinks, an uncomplicated network structure, unreactive vulcanization products, and contains a highly effective antioxidant system. Many facets of the aging of nitrile rubber are still open to explanation. Not the least of these is why crosslinks formed during the aging of the TMTD/S vulcanizate, which, by reason of their reactivity to methyl iodide, are thought to be sulfidic, are not themselves oxidized in a manner similar to the original monosulfide crosslinks. Model compound studies would answer this and other questions.
The Discovery of Polychloroprene Charles Goodyear Medal Address—1973
Authors: Collins Arnold M. 
Published: February 2011

Abstract
I will start by giving you some background from the early twenties, a time which many of you may not remember. There was a rapidly growing automotive industry. Since all cars then ran on tires of natural rubber, there was a question as to whether enough rubber could be produced from the trees of southeast Asia for future needs. Other plant sources of rubber were being investigated. A synthetic rubber had been made from isoprene in Germany during World War I but it was expensive and of poor quality. There was also at this time a well established organic chemical industry, which had developed largely from the dyestuff manufacture established during World War I and included a substantial rubber chemicals industry. Chemistry was a popular subject, both in the universities and in the public mind. Most “fundamental research” was done in the universities. Industrial laboratories were just beginning to do research for which no immediate practical results were expected. Polymers and polymerization were little understood.
1,1,4-Derivatives of Thiosemicarbazide—New Non-Staining Antiozonants
Authors: Zolotarevskaya L. K. , Lipkin A. M. , Grinberg A. E. , Angert L. G. 
Published: February 2011

Abstract
In the nature of non-staining antiozonants, a new class of compounds, 1,1,4-derivatives of thiosemicarbazide, are proposed. The mechanism of reaction of thiosemicarbazide derivatives with ozone is analogous to the mechanism of this reaction with thiourea derivatives. Within this, the rate constant of the initial reaction of the thiosemicarbazide derivatives with ozone is somewhat higher than that of the thiourea derivatives. 1,1,4-Trialkyl-substituted thiosemicarbazides appear to be the most effective antiozonants, not changing the color of light vulcanizates. Of the investigated compounds, 1,1,4-tributylthiosemicarbazide, being distinguished by a large protective effect against ozone, inhibiting activity in the process of heat aging of the vulcanizates, and lesser ability for leaching out of the vulcanizates by water than tributylthiourea, presents the greatest practical interest.