bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sulfur Vulcanization of Vinyl-Substituted Polysiloxanes
Authors: Polmanteer K. E. , Koch R. J. 
Published: February 2011

Abstract
The vinyl content of the polysiloxane polymer affects the rate of vulcanization in such a way that the vulcanization time varies inversely with the vinyl concentration raised to a power less than 1. Furthermore, this power appears to be dependent upon the vinyl concentration, so that a stationary value cannot be quoted. Sulfur alone crosslinks only polysiloxane polymers of high vinyl content. A 4 mole per cent vinyl-containing polymer exhibited no vulcanization after 3 hours at 160° C with sulfur alone. Vulcanization times in the same range as those found with sulfur-vulcanizing organic polymers were obtained in this polysiloxane system by the proper choice of accelerators. Starting with the most active, compounds for accelerating or activating this vinyl-containing polysiloxane-sulfur system were: strong organic bases (TEPA), DPG, thiuram disulfides (TMTD), magnesium oxide, bivalent metal dithiocarbamates, thiazoles (MBT), weak organic bases (aniline), calcium oxide. Zinc oxide and litharge are inhibitors in this system to varying extents, depending on the accelerator present. Organic acids such as stearic acid inhibit vulcanization in this system. For recipes void of elemental sulfur, the following conclusions may be made: Accelerators that vulcanize vinyl-containing polysiloxanes without the aid of elemental sulfur follow very closely the list of compounds capable of vulcanizing organic polymers. (D.P.)c data indicated that two vinyl groups are involved in each cross link.
Disulfide Interchange in Polysulfide Polymers
Authors: Bertozzi E. R. , Davis F. O. , Fettes E. M. 
Published: February 2011

Abstract
A study has been made on the effect of thiols and disulfides on lowering the molecular weight of polysulfide polymers. It was shown that in the presence of aqueous sodium disulfide there is an interchange of chain segments. This effect is observable if a simple organic disulfide is present in the system, resulting in a lower molecular weight. Copolymers can be prepared by heating together in the presence of sodium disulfide, aqueous dispersions of two different polysulfide polymers. When thiols are present in the system, interchange of disulfide groups occurs in the absence of sodium disulfide. The results show that disulfide/disulfide redistribution and thiol/disulfide interchange take place in polysulfide polymers. The occurrence of these same reactions has recently been recognized by workers in the biochemical field. A literature survey of thiol/disulfide reactions showed that results formerly attributed to oxidation reduction reactions could be also explained by an interchange mechanism.
An Investigation of the Molecular Weight Distribution of Polymers with the Aid of the Ultracentrifuge
Authors: Bresler S. E. , Frenkel S. Y. 
Published: February 2011

Abstract
In the present paper a method for studying the molecular weight distribution of linear polymers, involving the following stages, is developed: 1. Fractionation of the polymer into a series of sufficiently narrow fractions and investigation of these fractions with the aid of the ultracentrifuge and diffusion. 2. Plotting the distribution functions of sedimentation constants for each fraction and subsequent summation of curves in order to build up the distribution function of the sedimentation constants for the whole polymer. 3. Discovery of a general functional relation between the sedimentation constants and molecular weights for a given series of polymer homologs and construction of the distribution function of molecular weights of the polymer. The basis of the method developed by us (method of equivalent Gaussian distributions) was confirmed by direct experiment. Application of this method of investigation to a number of industrial polymers will be described in the next paper.
The Nature of Self-Adhesion (Tack) of Polymers. I
Authors: Voyutskiĭ S. S. , Margolina Yu L. 
Published: February 2011

Abstract
At the present time, ideas concerning cohesion, adhesion, and self-adhesion (self-sticking) are widely used for explaining the phenomena observed in gluing with polymeric substances. But the investigators, in developing the theory of gluing, pay most attention to cohesion and adhesion. Self-sticking (self-adhesion) has thus far remained unstudied and has no satisfactory explanation. Researches devoted to self-sticking are very few. Mention should be made here of the work of Zhukov and Talmud, who separated self-sticking from the total complex of adhesive properties, proposed the term autohesion, and were the first to study this property experimentally. Furthermore, we must mention the researches of Priklonskaya and of Maslovskii˘ and Popova, who investigated the self-sticking of industrial materials (rubber mixtures). Finally, the question of self-sticking of polymeric substances was touched upon in a very small number of researches of foreign authors. It should be noted however that these researches appeared considerably later than those of the Soviet investigators and are very speculative in nature.
Behavior of Highly-Filled Rubber Vulcanizates
Authors: Bryant K. C. , Bisset D. C. 
Published: February 2011

Abstract
Examination of the stress-strain curves of vuloanizates containing up to 60 per cent by volume of mineral filler of particle size greater than 1 µ has led to the discovery of a plateau at which the elongation increases several hundred-fold at constant stress. This has been demonstrated for a number of fillers with several rubbers, natural and synthetic. The effect of filler content, particle size, and degree of cure on the stress at which the plateau occurs, and its length, have been investigated. An explanation is suggested and the significance of the observations for the experimental verification of equations relating modulus to filler content is pointed out. The volume changes accompanying the elongation of these vulcanizates have also been investigated at varying filler contents, particle sizes, and degrees of cure, and shown to correlate with the stress-strain curves. The possible bearing of these results on the nature of the rubber-filler bonds, and hence on the reinforcing action of fillers, is briefly discussed.
Chemical Reactions of Antioxidants Used in Vulcanized Rubber
Authors: Schneider P. 
Published: February 2011

Abstract
The work of Farmer and other authors has shown that the oxidation of unsaturated polymers proceeds via primary formed hydroperoxides. The addition of antioxidants, including chiefly compounds of the class of the phenols and secondary aromatic amines, makes it possible to delay to a great extent the chemical changes taking place in unsaturated compounds. The mechanism of the action of phenols in the oxidation has been explained by Bolland. It is difficult to separate from the polymer the reaction products which are formed from the antioxidant by the dehydrogenating action of the polymeric hydroperoxide radical. In view of the fact, however, that the kinetics of oxidation in the presence of added peroxide corresponds to the autoxidation of the unsaturated compound, the reaction between phenols or secondary aromatic amines and organic or inorganic oxidation agents has been studied in detail by several workers. Depending on type, position, and number of the substituents, different reaction products are formed from phenols. Diphenylamine reacts with manganese dioxide to form a mixture of N,N′-diphenylbenzidine and the corresponding quinonedianil. N,N,N′-tri-2-naphthyl-1,2-naphthylenediamine is formed from di-2-naphthylamine with potassium permanganate, whereas under similar conditions phenyl-2-naphthylamine forms N,N′-diphenyl-N-2-naphthyl-1,2-naphthylenediamine. Starting from the deduction that the chemical reaction products of the antioxidants accumulate on the surface of the vulcanized rubber due to decreasing solubility, pure gum stocks of cured natural rubber containing diphenylamine, N-phenyl-1- and 2-naphthylamine have been exposed to atmospheric conditions for 8 months. The dark colored reaction products could be removed mechanically from the surface of the cured goods after wetting with methanol. After evaporation, the residue was taken up in ethylidene chloride and the resulting solution evaporated to dryness. Amorphous mixtures of brown colored compounds were isolated from the vulcanizate containing diphenylamine and N-phenyl-2-naphthylamine, the reaction products of the N-phenyl-2-napthylamine being obtained as a dark colored tar. In addition to other compounds, the presence of the N,N′-diphenyl-N-2-naphthyl-1,2-naphthylenediamine was proved by paper partition chromatography of the resulting azodyestuff obtained from the mixture of the reaction products from phenyl-2-naphthylamine by coupling with diazotized 1-aminonaphthalene trisulfonic acid. The presence of this compound had also been shown by the ultraviolet spectra. In the same manner, small quantities of the N,N′-diphenylbenzidine could be recognized from the corresponding azodyestuff formed from the reaction product of diphenylamine. Due to extensive oxidation, the presence of reaction products could not be proved in any appreciable quantity from the reaction mixture of the phenyl-1-naphthylamine.
The Quantitative Determination of Rubber Chemicals. II
Authors: Scheele Walter , Gensch Christa 
Published: February 2011

Abstract
A quantitative method for the determination of thiuram compounds has been reported. It has been found that tetramethylthiuram disulfide is converted quantitatively to thiuram monosulfide if it is treated with an excess of potassium cyanide. The thiocyanate, which is also formed, can be determined by argentometric conductometric titration. The execution of the analysis requires a good deal of experience. The conductometric titration with acid of the dithiocarbamate, which is formed by the reaction of TMTD with dodecyl mercaptan is much simpler. This method permits a double determination of the thiuram disulfide in which the excess dodecyl mercaptan is titrated conductometrically with alcoholic iodine solution. Solutions of dipentamethylene thiuram tetrasulfide behave like mixtures of tetramethylthiuram disulfide and sulfur. Also thiuram monosulfide and thiuram disulfides are cleaved by alkali and for the monosulfide a stoichiometric course of the reaction has been established. During our studies on the vulcanization of rubber with thiuram disulfides we have found conductometric analysis procedures to be very useful for the investigation of vulcanization extracts. We will report on this in the near future.
Aspects of the Physical Basis of Reinforcement
Authors: Mullins L. 
Published: February 2011

Abstract
Recent developments in rational ideas of what “reinforcement” means physically are described. It is shown that probably the most important characteristic of rubber vulcanizates with good tear and abrasion resistance is their ability to form strong hard tear resistant structures at the tips of growing tears. The significance of this conclusion in relation to the assessment of the quality of rubber vulcanizates is discussed.
Determination of the Molecular Size and the Molecular Form of Natural Rubber by the Measurement of Light Scattering. I. Development of the Method and Orienting Measurements
Authors: Schulz G. V. , Altgelt K. , Cantow H. J. 
Published: February 2011

Abstract
An experimental method of preparing and purifying natural rubber solutions in the absence of oxygen with an ultracentrifuge is presented. The solutions are suitable for optical measurements. Light scattering is measured as a function of concentration, angle, wave length and temperature. By determining molecular weight, diameter of the coiled molecule, and thermodynamic quantities (Δμ1, Δh1, Δs1) in this way it is possible to get information on branching of the rubber molecules. The method was used for cyclohexene solutions of a carefully tapped crepe rubber. The molecular weight was 1.3⋅106 and the end to end distance of the coil 1750 A˚. The heat of dilution was positive (endothermic) the B-value being nearly as high as that found in benzene solution by osmotic measurements. Comparing these results with measurements on unbranched polymethacrylate and polyisobutylene one can conclude that these rubber molecules are not or only slightly branched.
An Extensometer Microscope Stage for Photoelastic Studies in Rubber
Authors: Andrews E. H. 
Published: February 2011

Abstract
The instrument described is designed for attachment to the stage of a polarizing microscope in place of the conventional mechanical stage. Its purpose is to permit the use of a special compensator technique to determine stress distribution at the tip of a tear in an extended sheet of rubber. Examples are given of the stress distribution, both in magnitude and direction, at the tip of a tear in prevulcanized latex sheet, and the relative behaviors of the two principal stresses are briefly discussed.
Branched Chain Natural Rubber Derivatives Obtained by Reaction with Azodicarboxylates
Authors: Ivanov S. S. , Yuzefovich N. A. , Sidorovich A. V. , Fedorova E. F. 
Published: February 2011

Abstract
1. Ethyl azodicarboxylate (EAD) and ethylene dis-ethyl azodicarboxylate (DEAD) react quantitatively with natural rubber to form branched and cross-linked derivatives, respectively. 2. The mechanical properties of vulcanizates from natural rubber containing side branches (obtained with the aid of EAD) differ greatly from the properties of unbranched vulcanizates. 3. Analysis of the load-extension diagrams shows that the introduction of EAD side chains into natural rubber results in the formation of vulcanizates with high extensions at low loads. Vulcanizates without EAD have steeper load-extension diagrams and lower extensions at break. 4. As the temperature rises from 20 to 100°, the elastic modulus and mechanical losses (or the logarithmic damping decrement) of vulcanizates cross-linked with DEAD decreases greatly (about 4–7 times). Addition of 10 per cent (g-equiv.) of EAD side chains approximately doubles the mechanical losses in comparison with vulcanizates without EAD.
The Vulcanization of Elastomers. XI. The Vulcanization of Natural Rubber with Sulfur in the Presence of Mercaptobenzothiazole. I
Authors: Lorenz Otto , Echte Elisabeth 
Published: February 2011

Abstract
1. The decrease of free sulfur occurs according to the first order law during the vulcanization of natural rubber accelerated by mercaptobenzothiazole in the presence of zinc oxide. The activating energy for this reaction amounts to 30.5 kcal./mole. 2. If zinc benzothiazolylmercaptide is used as an accelerator, one obtains the same rate constants for the sulfur decrease as in the presence of mercaptobenzothiazole. These seem to be equivalent as regards their effectiveness of acceleration. 3. A kinetic analysis of the reciprocal swelling, which represents a measure of network formation, indicates that the reaction is first order. Sulfur decrease and reciprocal swelling prove to be equal processes as regards rate. This is true where vulcanization is accelerated with mercaptobenzothiazole or with the zinc salt. 4. During vulcanization there occurs a decrease of accelerator concentration. This is dependent upon the temperature and is tied in with the combination sulfur with rubber. 5. If the quantity of the accelerator added is changed, the rate constants for sulfur decrease and for reciprocal swelling do not change, provided that a minimum quantity of accelerator is present. 6. In vulcanization accelerated with zinc benzothiazolylmercaptide, zinc oxide being absent, sulfur decrease again occurs according to the first order law but considerably faster, without thereby changing the activation energy. These investigations are being continued and the results will be discussed in detail in relation to other published contributions in this field.
Degree of Cure in Filler-Reinforced Vulcanizates by the Swelling Method
Authors: Kraus Gerard 
Published: February 2011

Abstract
The Flory-Rehner theory of swelling allows an estimate of the number of crosslinks in gum vulcanizates. In reinforced rubbers the apparent degree of crosslinking is raised by some fillers, particularly carbon blacks. It has been shown experimentally that, for vulcanizates of a given polymer at a fixed filler loading and type, most physical properties are, in the first approximation, simple functions of the apparent number of network chains per unit volume, regardless of the possible origin of the linkages. Aside from controlling the number of apparent linkages, sulfur and accelerator levels as well as cure time have relatively minor, secondary effects on vulcanizate properties. Comparison of swelling data of gum and black stocks shows that the apparent contribution of the carbon black to crosslinking increases with the level of cure. Softeners and extender oils cause a reduction in the number of linkages, presumably by reducing the efficiency of sulfur utilization. It has been demonstrated that the swelling of vulcanizates in solvents gives an accurate measure of the degree of vulcanization even in filler-reinforced stocks. The results are apparently not obscured by adsorptive linkages between filler and polymer. When chemically different polymers are compared, the swelling volumes may be used to calculate the density of effective network chains; thus a nearly absolute measure of the degree of vulcanization is obtained. The swelling method is not difficult to apply, requires no special equipment, and imposes no limitation on the size or shape of the test specimen. For instance, it has been used with excellent success in this laboratory to check the state of cure in test-fleet tires. A small sample is cut from the side of the first rib of a tire and tested in the usual manner. The data presented offer some insight into the question of reinforcement. The evidence points to the fact that “contributions” of fillers to crosslinking derived from subtraction of the number of network chains or crosslinks in the filled and gum vulcanizates do not quantitatively represent the number of filler-to-rubber linkages. This filler “contribution” depends on the degree of cure, the vulcanization system, and the filler particle or aggregate shape. It depends only slightly on the particle size or surface area of the filler. The most plausible explanation of the observed behavior lies in a superposition of the effects of the filler on the course of vulcanization, filler-to-rubber linkages, and particle shape or aggregate structure.
A Study of Vulcanization Accelerators. I. Compounds Which React Analogously to Rubber
Authors: Shimozato J. , Ura K. 
Published: February 2011

Abstract
1. To elucidate the chemical behavior of rubber toward sulfur, a series of experiments was carried out using model compounds : tetralin, toluene, xylene, aniline, phenol, chlorobenzene, dichlorobenzene and naphthalene. Similar reactivities between rubber and the model compounds were observed. 2. The effects of the accelerators in the reactions of the model compounds with sulfur were different according to whether or not zinc oxide was present in the reaction system. 3. A detailed examination of the quantities of zinc sulfide formed in the reaction of tetralin with sulfur in the presence of zinc oxide showed that several vulcanization accelerators have similar activating effects in rubber vulcanization. 4. With tetralin as reactant, the quantity of zinc sulfide decreased suddenly at the reaction temperature 150° C, which was ascribed to the rapid decomposition of tetralin peroxide at this temperature. 5. The accelerating action of CPB, contrary to that of the other accelerators, was promoted by tetralin peroxide. 6. Tetralin peroxide had only a small inhibiting influence upon reactions with the amine accelerators, which is ascribed to the antioxidative nature of the amine derivatives; the inhibiting influence becomes larger in reactions with thiol derivatives or without any added accelerators. 7. Substituent effect on the hydrogen abstraction of the model compounds was primarily determined by the negativity of the relevant carbon atom. The order of the reactivity was found to be in accord with that toward the general “cationoid reagents”. 8. Analytical methods during and after the reactions were simplified for industry use.
The Quantitative Determination of Rubber Chemicals
Authors: Lorenz Otto , Echte Elisabeth 
Published: February 2011

Abstract
1. Both the precipitation of mercaptobenzothiazole as a silver salt and its oxidation with an iodine solution to a disulfide may be utilized for quantitative determination. 2. Zinc benzothiazolyl mercaptide can be determined iodometrically, either directly or indirectly, after being cleaved by acids. 3. Benzothiazolyl disulfide is determined as mercaptobenzothiazole after reduction with acidic stannous chloride solution. 4. A procedure for the determination of a mixture of mercaptobenzothiazole, zinc benzothiazolyl mercaptide, and dibenzothiazolyl disulfide is described. 5. Experimental conditions are indicated, under which the quantitative determination of free sulfur is possible in the presence of mercaptobenzothiazole, its zinc salt, the disulfide, and the zinc salts of fat acids. In all cases the uncombined sulfur is determined after its conversin to thiocyanate by an argentometric conductivity titration of the thiocyanate.
The Stress-Strain Behavior of Natural Rubber
Authors: Müller F. Horst 
Published: February 2011

Abstract
This treatment of the stress-strain behavior of natural rubber is based upon experimental and theoretical data on the cold stretching of high polymers gathered from work being in progress for some time at Marburg. These investigations indicate that deformation processes of matter should not be treated exclusively as purely mechanical phenomena though this is still being done. Especially in the case of natural rubber there exist very thorough analyses of these heat effects caused by deformation. Their theoretical evaluation furnished the basis for the thermodynamic-statistical theory of rubber elasticity. This created the picture of a molecular mechanism which with new additions permitted the description of a host of details including those for stress-strain behavior. However the relationship between the shape of the stress-strain diagrams and any particular deformation condition can only be explained if the actions of the deformational heat effects upon the course of the deformation are considered. In the following an attempt will be made to discuss the actions of the heat effects, in other words to examine the deformation processes as mechanical-thermal ones. Although there are, at present, no experimental results on hand, the expected consequences for the deformational behavior of rubber will be surveyed. Experimental work is in progress.
Behavior of Rubber in Compression under Dynamic Conditions
Authors: McCallion H. , Davies D. M. 
Published: February 2011

Abstract
At first sight, it would appear that previous investigators, have dealt fully with the main variables affecting the behavior of rubber. For instance, many publications have dealt with the effects of such variables as frequency, amplitude of deformation, and temperature. A closer examination of these publications, however, brings out the fact that no attempt has been made to keep the amplitude of deformation constant in any of the previous investigations into the effect of temperature at low temperatures. It is important that the amplitude of deformation should be kept constant, since both the stiffness and hysteresis energy absorbed per cycle depend on its value. It does not appear that work has been published on the frequency dependence of the hysteresis energy absorbed per cycle at low temperatures, nor even on how the hysteresis energy absorbed per cycle varies with temperature. For these reasons alone, the main investigation was initiated, and the results are presented to show the effects of frequency, temperature, and amplitude of deformation on the dynamic properties of rubber.