bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Nature of the Particle Surface in Hevea Latex and Pastes of Rubber Hydrochloride and Polyvinyl Chloride
Authors: Schuur G. 
Published: February 2011

Abstract
The colloid-chemical properties of natural rubber latex are influenced by many factors, such as the pH, the concentration of surface-active agents and the presence of ions of different kinds. Many of these factors have been studied intensively. However, it has usually been assumed that the surface of the rubber particles consists of plain hydrocarbon. Up to now it has been impossible to investigate the properties of the surface free from adsorbed soaps and proteins, for the removal of these surface-active agents results in coagulation of the latex. But the latex particles can be obtained in a hard and nontacky form by hydrochlorination and crystallization according to the methods of van Veersen and the author. The various surface-active agents can then be removed by filtering, washing, and extraction with organic solvents, without the loss of the surface by coagulation of the particles. The reactions of most organic chemical groups with hydrochloric acid are fairly well known and, though the original properties of the surface may be modified to some extent by the hydrochlorination, an investigation of the surface of rubber hydrochloride may give useful information regarding the properties of the original surface of the rubber particles. A suitable method for studying the nature of the surfaces of various rubber hydrochlorides would be to investigate the rheological properties of concentrated dispersions in organic media. Dispersions in plasticizers were selected, in the first place, because the experimental work is then not complicated by the volatility of the solvents, and secondly, because these dispersions in plasticizers are of some technical interest, since they can be used for the preparation of monofilaments from rubber hydrochloride.
Some Properties of Polymer Networks Formed from Oriented Chains of Natural Rubber
Authors: Roberts D. E. , Mandelkern L. 
Published: February 2011

Abstract
Highly oriented natural rubber samples prepared by a modification of the racking process described by Feuchter were crosslinked by means of γ-radiation. Some of the physical properties of the networks prepared in this manner were studied and compared with networks formed from chains which were randomly arranged prior to the introduction of the crosslinks. In accord with the theoretical considerations of Flory it was found that the swelling behavior, isotropic length, and isotropic melting temperature of the networks depend not only on the fraction of units crosslinked but also very markedly on the arrangement of the chains prior to network formation. It also was observed that the crystalline oriented racked rubber was crosslinked twice as effectively by γ-radiation as was the amorphous rubber.
Crystallization in Natural Rubber. V. Chemically Modified Rubber
Authors: Gent A. N. 
Published: February 2011

Abstract
Small amounts of crosslinking have been shown to reduce the rate of crystallization of natural rubber by large factors. It has also been inferred from measurements on peroxide and sulfur vulcanizates of various kinds that sulfur combined in forms other than crosslinks may retard the crystallization process efficiently. A simple banned volume mechanism has been proposed to account for the influence of crosslinking and sidegroup combination on the rate and final extent of crystallization, and has been shown to predict the form of the observed dependences for crosslinked rubber, and approximately the relative magnitudes, but good quantitative agreement was not obtained. Measurements are described below of the rate and final extent of crystallization in natural rubber which has been modified by the chemical combination of sidegroups to the rubber molecule. It has not proved possible to account quantitatively for the observed rates of crystallization, but it is thought that a description of the extremely large effects found to accompany slight chemical modifications will be of general interest. The preparation of the modified rubbers is described elsewhere. The substances added were six thiol acids; namely, monochlorothiolacetic, trichlorothiolacetic, thiolbenzoic, 1-thiolnaphthoic, thiolsalicylic, and thiol-stearic acids. The reactions were carried out in the solid phase by addition of the thiol acid to purified rubber on an open mill, in solution by addition of the thiol acid to a solution of purified rubber in benzene, and in the latex phase.
Vulcanization of Elastomers. 18. Vulcanization of Natural Rubber with Sulfur in the Presence of Mercaptobenzothiazole. III
Authors: Lorenz Otto , Echte Elisabeth 
Published: February 2011

Abstract
The present work is concerned with the influence of the concentration of sulfur and the zinc oxide content on the kinetics of the vulcanization of natural rubber with sulfur in the presence of mercaptobenzothiazole, zinc stearate and zinc oxide. The following results were obtained. 1. The velocity constant of the sulfur decrease, kSI, is inversely proportional to the initial concentration of sulfur. 2. The velocity constant of the change with time of the reciprocal equilibrium swelling, kQI, is inversely proportional to the square root of the initial concentration of sulfur. 3. The limiting value of the reciprocal equilibrium swelling, 1/Q∞ (degree of crosslinking), at constant stearate content, is proportional to the square root of the initial concentration of sulfur. 4. The amount of accelerator consumed during vulcanization increases with increase in the initial amount of sulfur. The decrease in the accelerator is a first order reaction having approximately the same rate as the decrease of sulfur. 5. The velocity constants of the sulfur decrease and the change with time of the reciprocal equilibrium swelling are practically independent of the amount of zinc oxide. Other situations exist, of course, for compounds without zinc oxide. 6. Empirical equations were derived to express the dependence of the constants kSI, kQI and 1/Q∞ on the composition of the mixture.
The Influence of Structure on the Chemical Activity and Vulcanizability of Butadiene Polymers
Authors: Dogadkin B. A. , Dobromyslova A. V. , Tolstukhina F. S. , Samsonova N. G. 
Published: February 2011

Abstract
1. Differences between the chemical reactivities of 1,4- and 1,2-structures of butadiene are found in the reactions with perbenzoic acid, iodine chloride, and sulfur. 2. The interaction of perbenzoic acid with solutions of butadiene polymers is represented by kinetic curves with an initial region of a high rate, mainly corresponding to the reaction of the double bonds of 1,4-structure, and a final linear region of a low rate, characterizing the reaction of the double bonds in the vinyl side chains of 1,2-structure. By extrapolation of the linear region to the ordinate axis it is possible to determine the relative contents of the 1,4- (and hence of the 1,2-) structure in the polymer. 3. The kinetic curves for the interaction of the polymer solutions with iodine chloride are of analogous form. The initial region of the kinetic curve represents addition at the double bonds, while the linear region corresponds to the substitution reaction. By extrapolation of the linear region to the ordinate axis it is possible to determine the actual double bond content of the polymer. 4. The kinetic curves for iodine liberation are also of similar form ; here the linear region corresponds to the substitution reaction, and the initial region corresponds to the cyclization reaction. The amount of iodine liberated in this reaction is a linear function of the content of the 1,2-structure in the polymer. 5. Mainly the double bonds of the 1,4-structure react when sulfur interacts with the polymer solutions. The total rate of sulfur addition is a linear function of the content of the 1,4-structure. 6. The activation energy for sulfur addition increases with increasing relative content of the 1,2-structure in the polymer. 7. Formation of sulfur crosslinks in vulcanizates occurs mainly as the result of reactions in the 1,4 polymer structure. In consequence, the degree of crosslinking ΔE/ΔS is a linear function of the relative content of 1,4-structure in the polymer.
Two Stages in the Process of Network Formation in Polymers
Authors: Bartenev G. M. 
Published: February 2011

Abstract
1. The two-stage nature of network formation in polymers is discussed, and a formula is derived connecting the number of chains in the network with the initial molecular weight of the polymer and the number of crosslinks. It is shown that below a certain critical number of crosslinks a network is not formed. 2. The application of the derived relationships in determination of the number of sulfur atoms in the crosslinks, the critical molecular weight, and the degree of globulization of the rubber, has been studied in the case of rubber vulcanization. 3. The first vulcanization stage is shown to be of considerable practical importance, as it determines the correct technological conditions for the vulcanization of rubber in molding presses, multilayer articles, etc. For this reason, determinations of the vulcanization optimum in rubber technology must be augmented by studies of the initial stage of the process. A method for determining the duration of the first stage of vulcanization is described.
Organic Sulfides and Polysulfides. I. Desulfurization Reactions
Authors: Minoura Yuji 
Published: February 2011

Abstract
Mercury, copper, potassium cyanide and sodium sulfite were found to desulfurize organic polysulfides. In the p,p′-ditolyl and in the dibenzyl series, the di-, tri- and tetrasulfides gave disulfide by desulfurization. On the other hand, in the case of diglycolic acids, di-, tri- and tetrasulfides gave monosulfides. The sulfide, which has high polarity in its radical, is easily desulfurized. The relative ease of desulfurization is—diglycolic acid &gt; dibenzyl &gt; p,p′-tolyl. In the same series, the higher the sulfur content, the more unstable it seems to be. Mercury is more reactive with sulfides than is copper.
Organic Sulfides and Polysulfides. V. Reactions with Methyl Iodide
Authors: Minoura Yuji 
Published: February 2011

Abstract
Mercaptan and polysulfides of the benzyl and p-tolyl series were heated with methyl iodide in sealed tubes for two hours at 100° C with the results: 1. Benzyl mercaptan and benzyl mono-, di-, tri- and tetrasulfide gave tri-methylsulfonium iodide. 2. Tolyl mercaptan and tolyl mono-, di-, tri- and tetrasulfides did not react with methyl iodide, contrary to previous thinking for the action of mono and disulfides. 3. Free sulfur did not react with methyl iodide.
A Uni-Rotor Mixer for Rubbers and Plastics
Authors: Watson W. F. , Wilson D. 
Published: February 2011

Abstract
The most pertinent advantages of this one-rotor machine as compared with two-rotor laboratory mixers may be summarized briefly as follows : (1) Simplicity and cheapness of construction and robustness. Energy available of up to 1-hp per g material. Even torque characteristics. No contact of masticating materials with seals or glands. (2) Ease of operation and economy of batch size. No ram required nor feed for additives. (3) A five-fold variability of charge without impairing mixing efficiency. Insignificant charge losses or batch-to-batch retention. (4) Rigid control over temperature and gases present.
Rheological Measurements for the Characterization of High Polymers
Authors: Edelmann Kurt , Horn Edith 
Published: February 2011

Abstract
Since the Umstätter structural viscometer represents the only viscometer that operates on the capillary principle, the most accurate measuring principle in viscometry, with a shear stress range above 104, this paper describes the necessary steps, from the long term experience of the authors with this apparatus, which permit a rapid and true determination of a complete flow curve. Also the necessary calculations are given and explained in an example. From this method, the critical velocity gradient G^, the inflection point of the flow curve, was obtained as a characteristic material constant, dependent only on the molecular weight of the high polymer and its absolute value for inhomogeneity. It is the hope of the authors that scientific practice for characterizing high polymers will increasingly refer to the flow behavior of (their) solutions by determining the flow curve.
The Chemistry of Vulcanization. I. Diphenylmethane as a Model of Rubber Hydrocarbon for Its Reaction with Sulfur
Authors: Tsurugi Jitsuo 
Published: February 2011

Abstract
Following the discovery of vulcanization of rubber by Goodyear, a vast number of experiments and speculations have been carried out, but the final clarification of the mechanism of vulcanization and acceleration has remained unsettled. Overemphasis of physical and technological criteria in the investigation of vulcanization may have contributed to the failure to attach importance to the purely chemical investigation. In fact rubber vulcanizates defy chemical investigation because they are insoluble and infusible. However, in 1947 Farmer and collaborators, using olefinic substances such as cyclohexene, dihydromyrcene and squalene as model compounds, proposed a new theory on the vulcanization of rubber by sulfur. According to them α-methylenic hydrogen adjacent to olefinic double bonds is attacked by sulfur, and a hydrocarbon radical is formed. Then this radical couples with the diradical ⋅Sx⋅ and this leads to polysulfides as primary reaction products. Farmer's theory laid the ground work for the chemical investigation of vulcanization but the reaction of olefins with sulfur is too complex to indicate the reaction mechanism. Diphenylmethane (DPM) contains α-methylenic hydrogen (to a benzene ring) and may be expected to react with relative readiness. Moreover the reaction of DPM with molecular oxygen is already reported to produce water, diphenylmethyl hydroperoxide, tetraphenylethane and benzophenone. It is expected then that when DPM reacts with sulfur, it should give the thio analogs of these compounds. Since the reaction and reaction products of sulfur with DPM are considerably less complex than those with olefinic substances, the reaction mechanism should be elucidated by using the simpler hydrocarbon as a model compound. Comparative studies of the reaction with and without accelerator will present the key to the mechanism and theory of acceleration. As fundamental studies of rubber vulcanization as well as acceleration the following are the two objects of this paper. The first is the reaction mechanism of DPM with sulfur at 180° C and the second is the pyrolysis of the primary product (dibenzhydryl polysulfide) to the secondary product (thiobenzophenone) at the same temperature. Investigations on the reaction of DPM with sulfur in the presence of accelerators will be reported in other papers of this series.
The Chemistry of Vulcanization. V. Action of 2,2′-Benzothiazolyl Disulfide on the Reaction of Diphenylmethane and Sulfur
Authors: Tsurugi Jitsuo , Fukuda Haruko 
Published: February 2011

Abstract
The reaction involving diphenylmethane, sulfur and 2,2′-benzothiazoIyl disulfide is summarized as follows. A. The reaction products and material balance among them are indicated. B. A reaction mechanism was decided upon. C. The rate equation for MBTS consumption was derived from the above mechanism and the results interpreted satisfactorily. The activation energy for thermal dissociation of 2,2′-benzothiazolyl disulfide was found to be 32.7 kcal/mole. D. The accelerating efficiency of this accelerator was defined, discussed and evaluated. These studies are being continued and further communications on the studies of accelerators in the presence of zinc oxide or zinc soap will appear in the near future.
The Structure and Molecular Refraction of Organic Polysulfides
Authors: Minoura Yuji 
Published: February 2011

Abstract
The molecular refraction of benzyl and tolyl polysulfide have been measured. The molecular refraction of benzyl and tolyl polysulfides increases with an increasing number of sulfur atoms by 9–10 units per sulfur atom. From the fact of constancy of increase of molecular refraction per sulfur, the structure of polysulfides is considered to be linear.
Graft Polymers with Preset Molecular Configurations
Authors: Merrett F. M. 
Published: February 2011

Abstract
The concept of “tailor-made” macromolecules when applied to graft polymers implies an effective correlation between the chemical and physical properties of the component parts and the technological properties of the resultant whole. Earlier experiments have indicated that, for a given graft macromolecule of natural rubber and polymethyl methacrylate, one extreme physical configuration could readily be effected in solution, viz., with the rubber trunk chains collapsed and the methyl methacrylate side chains extended. The complementary configuration—rubber chains extended and the methyl methacrylate chains collapsed—seemed equally easy of achievement. If these configurations could be carried through to the solid state then comparison of the properties of the dry rubbers would provide one such correlation between established physical configurations and resultant technological properties. The evidence for these definite configurations is briefly described below followed by preparative methods for bulk quantities of the dry rubbers and the evaluation of their technological properties.
On the Relation between Indentation Hardness and Young's Modulus
Authors: Gent A. N. 
Published: February 2011

Abstract
A relation between British Standard and International rubber hardness and Young's modulus is derived from classical elasticity theory, and compared with the empirical relation given in B.S.903:1950. An experimental examination of the load-indentation relationship for a rigid sphere pressed into a flat rubber pad is described ; it indicates that the theoretical relation is more appropriate than the empirical one for small indentations, corresponding to hardnesses exceeding about 60° B.S. & I.R.H., and equally valid for hardnesses between about 40° and 60°. Moreover, the numerical constants are not subject to experimental uncertainty. If reduced major loads are stipulated for determining the hardness of rubbers of less than 35° to 40° B.S. & I.R.H., the theoretical relation should apply over the entire useful range. An approximate relation between Shore hardness and Young's modulus is derived similarly. The approximate equivalence of the British Standard and International rubber hardness and Shore hardness scales over the major part of the hardness range is confirmed.
The Reaction of Sulfur and Sulfur Compounds with Olefinic Substances. Part VIII. The Reaction of Sulfur with Mono-Olefins
Authors: Bateman L. , Glazebrook R. W. , Moore C. G. , Porter M. , Ross G. W. , Saville R. W. 
Published: February 2011

Abstract
Earlier Parts of this series reported the partial separation and identification of the complex products of certain sulfur-olefin and related reactions chosen as models for examining the mechanism of vulcanization of natural and synthetic rubbers by sulfur. The main conclusion was that sulfur-olefin interaction proceeds by free-radical chain processes, and this has been quoted elsewhere and widely accepted. Results are now presented which extend and correct the earlier findings and lead to the different mechanistic conclusion that the reactions are polar in type, involving heterolysis of S—S and C—H bonds. This paper and Part XI deal with the products of the reactions of sulfur with mono-olefins and a 1,5-diolefin, respectively, and Part X presents a complementary kinetic investigation, the first for such reactions. All the experimental evidence is collated in Part XI in a general theory of sulfur-olefin interaction.
The Reaction of Sulfur and Sulfur Compounds with Olefinic Substances. Part IX. The Reaction of Sulfur with 2,6-Dimethylocta-2,6-Diene
Authors: Bateman L. , Glazebrook R. W. , Moore C. G. 
Published: February 2011

Abstract
Farmer and Shipley showed that reaction of sulfur with 2,6-dimethylocta-2,6-diene (I) at 140° yields a cyclic monosulfide and a crosslinked polysulfide. No detailed investigation of the structures of these cyclic monosulfide or polysulfide products was undertaken, but it was deduced that the former contained 6-ethyl-2,2,6-trimethylthiaeyclohex-3-ene (VIII) and a compound having vinylidene unsaturation, CH2:CRR′, as apparently revealed by the infrared spectrum, and this has formed part of the evidence on which broad mechanistic conclusions have been based. This reaction has now been re-examined in greater detail; the compositions of the cyclic sulfide and crosslinked polysulfide fractions and their variation with time of reaction have been determined. Results and conclusions differing in important respects from those advanced by the earlier workers have been reached, as reported preliminarily elsewhere.
Stability of High Polymer Latexes and Their Electrokinetic Potentials
Authors: Voyutskiĭ S. S. , Panich R. M. 
Published: February 2011

Abstract
The stability of colloid systems is a central problem of colloid chemistry. Therefore, many papers have been devoted to studies of coagulation and to the development of criteria of stability for colloid systems. For a long time a prevalent opinion was that the stability of colloidal particles could be explained by the fact that like charge on the particles prevents agglomeration of particles which collide due to Brownian motion. This opinion was first expressed by Hardy and later developed by Powis, Ellis and a number of other scientists. According to this point of view, electrokinetic potential (ζ potential) is the measure of stability. However, after detailed investigation of coagulation phenomena and accumulation of experimental data the correctness of this point of view became less obvious, and the statement that the electrokinetic potential is a criterion of stability of colloidal systems underwent vigorous criticism. The reasons for the measured values of electrokinetic potentials not always corresponding to the stability of certain systems are as follows: firstly, the exact determination of electrokinetic potential is work of great experimental difficulty which seems to some investigators insuperable. Some of these difficulties are (1) the necessity of performing the mocroelectrophoresis in a medium which has the same characteristics as the colloidal system under investigation, (2) the influence on electrophoresis of the simultaneously occurring electrolysis (3) the wash out of the boundary line between the solution and the colloidal system, and a number of others. In the case of microelectrophoresis, these difficulties are replaced by others, which are not less difficult to overcome.
Foam Stability. A Fundamental Investigation of the Factors Controlling the Stability of Foams
Authors: DeVries A. J. 
Published: February 2011

Abstract
Although the production of foam rubber on an industrial scale has been for a considerable time a rather well-controlled process, all factors involved are still insufficiently known. The most critical phase of the manufacturing process is undoubtedly the gelation of the foam produced. This consists of a clotting of the dispersed rubber particles while a simultaneous destabilisation of the dispersed gas bubbles has, however, to be prevented. In order to gain a better insight into the present and similar processes, a fundamental knowledge of foams in general and of their stability conditions in particular is indispensable. The author studied the technology of foam rubber manufacture in the laboratories of the Rubber-Stichting at Delft and carried out the research described in this review in order to get at the “fundamentals”. Since he comes from the University of Utrecht, the school of thought inherent to the laboratories of physical chemistry there has been the basis of his reasoning. He is indebted to Professor J. Th. G. Overbeek for many helpful suggestions.