bluuebunny/crossref_metadata_2025 huggingface dataset:
Behavior of Rayon Tire Cord during Latex Dipping
Authors: Gillman H. H. , Thoman Ray
Published: February 2011

A study of the behavior of two types of rayon tire cord during latex dipping was made with a laboratory treating unit. Results of the tests showed certain facts. The concentration of the latex bath increased as rayon tire cord was dipped. No change occurred in dipping cotton. Based on the weight of cord dipped, sulfonated oil cord caused a higher increase in bath concentration than waxy ester cord; based on the weight of latex consumed, the order was reversed. Waxy ester cord had relatively slow wetting-out characteristics compared to sulfonated oil cord; compared to both, cotton is infinitely slow. The ratio of water-to-solids pickup with both cords is identical for all concentrations of the bath examined. Because of this characteristic both cords behave identically in the bath provided the squeeze rolls are adjusted to give equal solids pickup. Ratio of water-to-solids pickup decreases as the concentration of the bath increases. Stable fibers, both cotton and rayon, need no adhesive treatment for satisfactory bonding to rubber. In contrast, continuous filament rayon cannot be used until it is treated. Adhesion is a function of solids pickup. Sulfonated oil cord picks up two to four times as much solids as waxy ester cord under a variety of conditions because of better wetting-out properties. By changing either the squeeze-roll pressure or the bath concentration solids pickup is changed. Cord produced from staple rayon picks up more solids than continuous filament cord because of protruding fiber ends. An increase in concentration of the latex bath causes an increase in solids pickup. Viscosity acts similarly. Particle size has no appreciable effect on solids pickup. Surface tension does not affect solids pickup by waxy ester cord; it does affect sulfonated oil cord to a minor degree at or below 46 dynes per cm. An increase in cord tension through the latex bath decreases solids pickup. As the speed of processing is increased, solids pickup increases. A wiping action on the dipped cord decreases solids pickup. No relation between contact time and solids pickup could be established.
Determination of Resistance to Abrasive Wear. IX. Influence of Grain in Tire Tread Rubber
Authors: Scott J. R.
Published: February 2011

Results of the Akron-Croydon abrasion test on rubbers of the tire-tread type are not appreciably influenced by the direction of the grain. Consequently, it is considered satisfactory to test such rubbers by using the normal (edge) type of specimen, prepared by vulcanizing, in a suitable mold, a disc cut from a sheet of the unvulcanized stock about 13 mm. thick.
Determination of Resistance to Abrasive Wear. X. Investigation of the Durability of a Bonded Abrasive Wheel on the Du Pont Machine
Authors: Newton R. G. , Scott J. R.
Published: February 2011

The results reported here entirely confirm those of Lambourn, who found that marked deterioration occurred with all the types of abrasive wheel which he used. In the present investigation on a bonded wheel, it was concluded that the wheel was appreciably less abrasive after each period of. 50 hours' wear, while Lambourn concluded that one side of a wheel can be used for a period of two months when subjected to 40 hours of wear per week. Lambourn also concluded that the deterioration is caused by smoothing or disintegration of the abrasive particles and not by clogging with rubber dust, and points out that variation in abrasive wear can be compensated by daily tests on samples of a standard compound. He also states that a grain coarser than 24 should not be used, since the abrasion is too rapid. Since the standard emery papers vary among themselves, and the bonded abrasive wheel deteriorates when it is used, it is evident that attention should be paid to the statistical planning of these tests, so that these factors can be reduced or eliminated. The coefficient of variation of a test result, i.e., the mean of three 10-minute runs, each on duplicate specimens, (six individual readings) as normally measured, seems to be independent of the type of abrasive employed (emery papers or bonded disc) and the uncertainty of the result is about ±5 per cent when measured on the basis of volume loss per hour and about ±3.5 per cent when determined as the volume loss/H.P.-hr. Test results will therefore be required to differ by about 7 and about 5 per cent, respectively, for a significant difference to be demonstrated.
Determination of Resistance to Abrasive Wear. XI. Influence of the Type of Abrasive
Authors: Newton R. G. , Scott J. R. , Willott W. H.
Published: February 2011

Tests with the du Pont machine show that the practice of expressing abrasion test results as an abrasive index, i.e., abrasion-resistance relative to a standard rubber, does not enable different types of abrasive to be used indiscriminately because these are found to give widely different abrasive indices for the same rubber; thus, some abrasives may give four times as high an index as others. If attention is confined to abrasive papers, as distinct from bonded abrasive wheels, this variation is reduced, but is still large enough to be a serious factor in accurate work. It is clear that, even when this comparative method of testing is used, standardization of the abrasive paper is essential to reduce discrepancies between results obtained in different laboratories. Discrepancies will still exist, however, because abrasive paper is not uniform, and there is evidence that abrasive indices determined on different portions of the same paper may differ as much as those from different types of paper. To minimize the effect of this nonuniformity, two courses are open. (1) All the rubbers to be compared could be abraded on one and the same area of paper, preferably a large area to avoid wearing the surface, e.g., by giving each rubber a short run on each of the several paper discs used, instead of using a different disc for each rubber. (2) Different specimens could be tested on the two sides of the machine provided this has a pivotted arm. It is shown that this technique has several advantages. The factors that cause the abrasive index to vary from one abrasive to another are not known; it appears, however, that the degree of abrasiveness is not a determining factor. The two methods of calculating abrasion loss—as cc. per hr. and cc. per H.P.-hr.,—usually do not give the same abrasive index; in any standard test method it is therefore essential to state which is to be used. The variation of the abrasive index from one abrasive to another is the same whichever method of calculation is used.
Determination of Resistance to Abrasive Wear. XII. Comparison of Akron and Du Pont Abrasion Machines. Value of an Abrasive Index
Authors: Scott J. R.
Published: February 2011

Abrasion tests on several sole and heel rubbers have been made on the Akron and du Pont machines to determine whether the same abrasive index (abrasion-resistance relative to a standard rubber) is given by both methods. The following conclusions are drawn from the results. (1) The two methods do not give the same abrasive index for the same rubber; a study of published data shows that this is true of at least some other abrasion test methods. In using an abrasive index to specify or control the quality of manufactured articles it may, therefore, be necessary to establish a separate index figure for each type of machine used. (2) Broadly speaking, the higher the abrasive index of a rubber by any one method, the higher is its indices by other methods, so abrasive indices can be converted approximately from one method to another by using a suitable factor or conversion formula; a formula for interconverting Akron and du Pont results is given. (3) Such conversions from one method to another are only approximate, however, because indices determine by different methods are by no means exactly related. The magnitude of the errors involved is indicated and discussed; in the present experiments the average discrepancy between an index measured directly and that calculated by the formula from the index given by the other machine, is about 20 per cent; corresponding figures from published data range from about 6 to 40 per cent. (4) Errors similar to those just mentioned, occur in predicting the relative service wear of different rubbers from laboratory abrasion tests. Although these errors seem large, the chances of a rubber that gives a satisfactory test result proving really poor in service are small. (5) The adoption of any system that prevents unsatisfactory material being put on the market is a valuable means of saving rubber. On the basis of the present results with the Akron and du Pont machines, it can be shown that by the application of a laboratory abrasive index test the resultant saving of rubber is at least two-thirds of what would be saved if acceptance or rejection could be based on actual service wear results—an ideal but impracticable procedure. (6) There is evidence that among rubbers of similar composition, e.g., sole and heel rubbers made by any one manufacturer, abrasive indices obtained by different methods are more closely related than among rubbers in general. For control and development work within the factory, therefore, the abrasive index system should prove more satisfactory than when applied to a varied assortment of rubbers of unknown composition. (7) Abrasion methods may differ in their power of discriminating between rubbers; thus, in the present experiments, the Akron test shows wider differences in abrasive index than the du Pont test, although the latter has the higher power of discrimination.
Qualitative Detection of Titanium Dioxide in Rubber
Authors: Hammond G. L.
Published: February 2011

Titanium dioxide, either as such or in the form of the composite titanium whites, is now used to such an extent as a rubber pigment that a test for titanium is frequently necessary in the analysis of a compounded rubber. Owing to the insoluble nature of titanium dioxide, troublesome fusions are required to detect it by the normal qualitative tests in the ash remaining when a rubber is incinerated. The following method is offered as a quick and easy means of detecting titanium. A small portion (about 0.01 gram usually suffices) of the ash from the sample is placed in a clean glazed 15-cc. Porcelain crucible. One drop of concentrated sulfuric acid is then added, and the whole is heated on a hot plate for 30 seconds, i.e., until most of the acid is evaporated. The crucible is allowed to cool, and 2 drops of 6 N sulfuric acid added, followed by 1 drop of a 5 per cent aqueous solution of the sodium salt of chromotropic acid (1,8-dihydroxynaphthalene-3,6-disulfonic acid). A brownish red to purple coloration is obtained if titanium be present. In place of the chromotropic acid, 1 drop of 10-volume hydrogen peroxide is added in a second test, when the well-known golden yellow color is obtained.
Stresses and Birefringence in Rubber Subjected to General Homogeneous Strain
Authors: Treloar L. R. G.
Published: February 2011

The conclusion to be drawn from the preceding analysis of the stress-strain relations may be summarized in the following way. As a first approximation the equations derived from the statistical treatment of a molecular model provide a basis for the interpretation of the elastic properties of rubber. A closer approximation is obtained by including an additional term in the stored-energy function, i.e., by the use of Mooney's Equation (3). This appears to give an accurate representation of the properties of a swollen rubber, but is still inadequate when applied to a dry rubber, for which a third approximation, including at least one more general term, is likely to be required. It is necessary to emphasize that the use of the second or higher approximations does not in itself throw any light on the physical mechanism responsible for the behavior observed. It is, in fact, the 3-dimensional analog of simple curve-fitting. It must also be borne in mind that any physical model that might be postulated must necessarily lead to results which may be represented by some combination of the stored-energy functions discussed in the section on the theoretical interpretation of the data.
The Thermodynamics of a Strained Elastomer. I. General Analysis
Authors: Mooney M.
Published: February 2011

The thermodynamic functions of principal interest in a strained elastomer are the entropy and energy of deformation. The volume is of secondary importance, and it can be assumed, with sufficient accuracy for most purposes, that the volume is linear in the temperature and the mean pressure. The basic partial differential equations of thermodynamics can then be integrated, yielding expressions for the energy and entropy of deformation in terms of observable quantities. In the present analysis the volume effects caused by changes in mean pressure and crystallinity are taken into account, and the effects associated with change in shape are sharply separated from those associated with change in volume. It is shown that the superelastic functions of deformation previously published have a very general validity.
The Thermodynamics of a Strained Elastomer. II. Compressibility
Authors: Copeland L. E.
Published: February 2011

Adiabatic compressibility coefficients were measured on a series of cured polymers of commercial types under pressures up to 5000 pounds per square inch. In most eases, the second order as well as the first order coefficient could be determined from the data. The linear isothermal compressibility also was calculated from the measured linear adiabatic coefficient. Preliminary measurements of the thermal expansion of a stretched Hevea gum stock show that there is a slight decrease in expansion at the 200 per cent elongation, presumably due to partial crystallization.
The Thermodynamics of a Strained Elastomer. III. The Thermal Coefficient of Modulus and the Statistical Theory of Elasticity
Authors: Copeland L. E. , Mooney M.
Published: February 2011

Published thermoelasticity data are critically analyzed by means of thermodynamic equations developed in the first paper of this series. Equations known to be of the proper form are fitted by least squares to the experimental data, which were first corrected to allow for the changes in shape when tested under variable temperature and constant length. If the measurements are accepted as truly reversible, the data show that several different elastomers depart considerably in some respects from the predictions of the statistical theory of elasticity. Some thermoelasticity measurements in torsion are reported which seem to give the most reliable evidence that stress is proportional to absolute temperature.
The Formation and Structure of Vulcanizates
Authors: Bardwell J. , Winkler C. A.
Published: February 2011

The characteristic mechanical properties of vulcanized rubber are believed to result from a network structure made up of chainlike molecules bonded together by occasional cross-linkages. In relating the physical properties of the vulcanizate to the structure of the network, it is therefore necessary to consider the concentration of cross-linkages and the molecular-weight distribution of the rubber molecules before cross-linking. Various theories have been proposed for the dependence of elastic properties on these structural factors, but experimental proof of the suggested relations has been meager, largely because of the complexities met with in, vulcanization reactions. In the present investigation some of these difficulties have been overcome, and the quantitative relations between the elastic behavior of GR-S and its network structure have thereby been revealed.
The Unsaturation of Butadiene Rubbers. I
Authors: Vasil'ev A. A.
Published: February 2011

1. The data on the unsaturation of butadiene rubbers previously obtained by using the method based on the reaction with iodine bromide have been checked and confirmed with the aid of the reactions with pyridine sulfate dibromide and with iodine chloride. 2. The influence of various factors on the unsaturation of butadiene rubbers has been checked, and the possibility of estimating changes in unsaturation with the aid of the reaction with iodine bromide has been established. 3. The present investigation shows that, during the reaction between butadiene rubbers and halogens, it is impossible to attain a degree of saturation exceeding 85–90 per cent of the theoretical values. This is apparently due to the existence of intramolecular cyclization, to the presence of intermolecular connecting bridges, and possibly to the presence of double bonds resistant to halogenation or of conjugated double bonds in the molecules of these rubbers. The reaction with halogens offers no possibility of confirming these suppositions experimentally.
The Abnormal Melting of Raw Rubber
Authors: Isihara Akira
Published: February 2011

The experimental results on the abnormal melting of crystallized raw rubber by Wood and Bekkedahl are studied theoretically. The effect can be explained by the fact that the relaxation time for the thermal expansion of crystalline particles differs from that of amorphous particles. At the point where the melting begins, the time interval of observation becomes comparable to the relaxation time of amorphous particles. The point becomes higher as the time rate of heating increases, and also as the relaxation time itself becomes larger. The point at which fusion is complete is determined by the relaxation times of the amorphous and crystallized states, heating rate, and previous history. This effect becomes large at a suitable heating rate, and is larger in natural rubber than in vulcanized rubber.
Structural Changes in Rubber Brought about by Molecular Oxygen. III. Properties of Disintegrated Vulcanized Natural Rubber
Authors: Dogadkin B. , Tarasova Z. , Pasynskii A.
Published: February 2011

1. The product of destructive solution of vulcanizate contains 50 mg. of oxygen per gram of substance; of this quantity, 3.77 mg. falls to the share of oxygen contained in free carboxyl groups. 2. The disintegrated vulcanizate is soluble in ordinary rubber solvents, as well as in binary mixtures of associated and unassociated liquids. 3. The viscosity and light diffusion of a broad range (up to 6 per cent) of disintegrated vulcanizate solutions are linear functions of the concentration. 4. The average molecular weight of the disintegration product of a vulcanizate, as determined from the coefficient of diffusion, is 3600; according to the viscometric and optical data, the molecules represent very large, elongated entities with an axial ratio of 1:24. The distribution curve of diffusion coefficients has a sevenfold dispersion. 5. The mechanical strength and elasticity of films prepared from a disintegrated vulcanizate are very much lower than those of films made of vulcanized rubber.
Measurements of Diffusion in Rubber
Authors: Grün F.
Published: February 2011

The diffusion constants of various substances in rubber as the diffusion medium were measured. Quantitative determinations of the internal mobility of rubber can be carried out on the basis of the values obtained.
Flow Phenomena in Rubber. I. Flow Curves for Natural Rubber
Authors: Saundeks D. W. , Treloar L. R. G.
Published: February 2011

From the flow curves, the readings to be expected in the standard (shearing-disc) Mooney viscometer were calculated. These differ from the observed figures by about 15 per cent. The temperature dependence of the rate of flow is accounted for on the basis of the simple Eyring formula, and a value of 8.1 k. calorie per mole was obtained for the energy of activation involved in the flow process.
Polymerization. VIII. The Action of Metalating Reagents on Rubber
Authors: Morton Avery A. , Ramsden Hugh E.
Published: February 2011

When metalating agents act on natural or Alfin rubber, gel is formed. The amount of gel increases with the activity of the metalating agent and the severity of the conditions under which it is used. Metallic sodium or potassium does not cause gel to form in natural rubber. Under very severe conditions these metals metalate the highly active hydrocarbons, fluorene, triphenylmethane and diphenylmethane, in fair to poor amounts, depending on the hydrocarbon, but they metalate toluene only slightly, even under highly favorable conditions.
The Reaction of Sulfur and Sulfur Compounds with Olefinic Substances. IV. The Thermal Decomposition of Organic Polysulfides, and Its Contribution to the Sulfur Olefin-Reaction
Authors: Bloomfield George F.
Published: February 2011

At temperatures in the region of 140°, organic polysulfides undergo disproportionation resulting from thermal fission of S—S bonds and recombination of the fission products. In the presence of olefins a considerable proportion of the fission products become attached to ethylenic centers of the olefin, forming mixed mono- and polysulfides. The major part of the monosulfide product is fully saturated, hydrogen capture occurring during, or subsequent to the formation of adducts from the olefin and sulfurated fragments; unsaturation, however, appears in the polysulfide portion. The polysulfides are capable of producing monothio cross-links between the original olefinic molecules only in so far as they are able to yield up elementary sulfur to the olefin, and when the original olefin is a polyisoprene, the tendency towards the formation of a high proportion of intramolecular cyclic sulfide still further reduces the opportunity for formation of intermolecular sulfur-cross-linked products.
X-Ray Studies of Low-Temperature Polybutadiene and Butadiene-Styrene Copolymers
Authors: Beu Karl E. , Reynolds W. B. , Fryling C. F. , McMurry H. L.
Published: February 2011

Although it is now generally recognized that the temperature of polymerization affects profoundly the properties of emulsion elastomers, there is very little evidence available pertaining to the cause of the variations of properties. It is felt by some that the improved properties of low-temperature elastomers can be related to variations in molecular weight and molecular-weight distribution. In this laboratory, however, the opinion has prevailed that the lower emulsion polymerization temperatures appreciably alter the fine structure of the molecules with an increase in the regularity of the polymer chains. If there were actually less branching and cross-linking in low-temperature polymers, and less 1,2-addition to monomer components, the increased order should be evident from x-ray diffraction patterns. To provide information on the above questions, x-ray studies were made with four purposes in view: (1) to determine the effect of polymerization temperature on the crystallization properties of unstretched and stretched polybutadienes; (2) to determine the influence of styrene content on the crystallization of butadiene-styrene copolymers; (3) to study some effects of compounding and vulcanization on crystallizable polybutadiene; and (4) to use the preferred orientation patterns obtained from some of these polymers for structural evaluations. To accomplish these objectives, x-ray patterns were obtained at several temperatures of some unstretched and stretched polybutadiene polymers, butadiene-styrene copolymers, and a vulcanized and compounded polybutadiene. The polybutadienes were prepared by emulsion polymerizations at 55°, 40°, 30°, 20°, 5°, −10° and −20° C. Since the −20° C polybutadiene showed the most marked crystallization patterns, the effects of compounding and of styrene addition were studied, using polymers prepared at this temperature for comparison. Three butadiene-styrene copolymers containing, respectively, 10, 20, and 30 per cent styrene in the monomer charge and one vulcanized polybutadiene compounded with Wyex carbon black were studied.
Influence of Structure on Polymer-Liquid Interaction. III. Swelling and Mechanical Properties of Some Partly Crystallized Polymers
Authors: Salomon G.
Published: February 2011

We have shown in the first part of this work the influence of association on liquid-polymer equilibrium, while a study of nitrile copolymers revealed that mechanical properties are much more sensitive to certain changes in polymer structure (such as the introduction of methyl groups) than are swelling equilibria. In partly crystallized polymers, however, a close correlation between liquid-polymer interaction and mechanical properties exists, as is seen from the present paper.
Reaction Kinetics of Adiabatic Systems
Authors: Gordon M.
Published: February 2011

Conventional kinetic measurements, based on isothermal reaction runs, have hitherto been used to evaluate the reaction parameters required for the description of a chemical rate process. These parameters are the order n of the reaction, its activation energy E, and its frequency factor X. A new technique is here proposed in which adiabatic reaction runs are employed. The temperature change is used to follow the reaction progress. The theory of the heat-effect of adiabatic reactions is deduced, and the mathematical working-up of adiabatic time-temperature data for the evaluation of n, E and X is set out on the basis of stated assumptions. A critical discussion of the method follows, and shows that it is of particular value in polymer chemistry and wherever viscous rubbery or solid reaction media are encountered. The difficulties of heat exchange associated with isothermal measurements are avoided. To what extent the proposed method may be complementary to the conventional in general appears as yet a matter of speculation.
Adiabatic Reaction Kinetics of Buna-S Vulcanization
Authors: Gordon M.
Published: February 2011

In a previous paper a technique for making kinetic measurements adiabatically instead of isothermally was discussed, and the possible advantages of this technique in reactions involving polymers was indicated. In the present communication, the theory is supported by an analysis of published data relating to the vulcanization of butadiene-styrene copolymer. There are considerable gaps in our knowledge of the overall chemical changes concerned in the vulcanization of various rubbers, quite apart from the kinetic interpretation of rate measurements and the postulation of elementary steps. Because of the difficulties involved, isothermal rate measurements have not yet given much insight into the kinetics or the chemistry of the time-honored sulfur vulcanization discovered over a hundred years ago. The difficulty of maintaining the temperature constant against the considerable heat of reaction is only one of the obstacles ; that of finding a convenient and accurate measure of the progress of vulcanization considered as a chemical reaction is perhaps even greater. The difficulties of the adiabatic technique are essentially different in nature.
Progress in Polymerization Theory of Interest in Synthetic Rubber Production
Authors: Morgan L. B.
Published: February 2011

During the last few years considerable advances have been made in the theory of polymerization processes, and these have a direct bearing on the manufacture of synthetic rubbers and plastics and the properties of the various products of this type that are now handled by the rubber industry. The most important industrial process involves emulsion polymerization. This is used in the production of types, such as GR-S, Perbunan, and Neoprene, and also in the production of polyvinyl chloride. World production of these emulsion polymeric materials is in the region of hundreds of thousands of tons per annum, and the process is probably one of the more important chemical manufactures developed in the last decade. No large manufacture of synthetic rubber has been developed in Great Britain, mainly because of war-time exigencies and economic considerations, and the only significant contribution made by British chemical industry to alleviate the war-time scarcity of natural rubber was to develop a large-scale production of polyvinyl chloride to satisfy the requirements of the cable trade. There has, however, been some research activity on synthetic rubber in this country since 1935 in the laboratories of the Dyestuffs Division of Imperial Chemical Industries, Ltd. Activity in the main was concentrated on the diene emulsion interpolymer types and a large number of second components were examined for interpolymerization with both butadiene and chloroprene. Comparatively few interpolymerize to give rubbers with reasonably good vulcanizate properties. These have been disclosed in the patent literature. Parallel work was being carried out in the laboratories of I. G. Farbenindustrie and later in America, and the results of much of this have now appeared in the technical literature and in the accounts that are now available on German war-time activities. The general conclusions were similar.
Refractometric Determination of Second-Order Transition Temperatures in Polymers. IV. Butadiene-Acrylo-Nitrile Copolymers
Authors: Wiley Richard H. , Brauer G. M.
Published: February 2011

A previous study of the low-temperature properties of a series of vulcanized butadiene-acrylonitrile copolymers indicated an approximately linear relation between composition and brittle temperature. This study provides information relating low-temperature properties to copolymer composition for a series of industrially available butadiene-acrylonitrile copolymers of varying acrylonitrile content. The refractometric technique for determining second-order transition temperatures (Tm) as previously described was used to determine Tm.
Process Problems in Low-Temperature Emulsion Polymerization
Authors: Troyan J. E.
Published: February 2011

When emulsion polymerization of butadiene and styrene is conducted at temperatures in the range of 0° to 41° F, high elastomers possessing greatly improved properties are produced. However, low temperature operation involves several major process problems not encountered in the manufacture of standard GR-S at 122° F. These are the use of activated reaction recipes, the refrigeration of polymerization equipment, and the use of emulsion antifreezes. Redox-type activated systems which have been developed for low temperature runs in the pilot plant result in reaction rates approaching those of normal GR-S even at 14° F. Heat transfer characteristics of typical activated recipes at 41° and 14° F have been investigated in a 260-gallon reactor and compared to similar results for GR-S at 122° F. Variation in overall heat transfer coefficients with conversion has been established at each temperature. Minimum U values of 43, 39 and 23 B.t.u./(hr.) (sq. ft.) (° F) were obtained at 50 to 55 per cent conversion in polymerizations run at 122°, 41° and 14° F. Using experimental heat transfer data, refrigeration requirements for a standard 30,000 ton/year plant operating at 41° F and 14° F are calculated as 450 and 599 tons, respectively. When emulsion polymerizations are conducted at about 0° to 35° F, special antifreezes such as methanol must be included in the reactionrecipe. Methanol is recovered from latex during the usual stream stripping of latex to remove unreacted styrene. A ternary equilibrium solubility diagram for the system styrene-methanol-water has been established to facilitate analysis of the two-phase condensate obtained during stripping.
Effect of Light on Neoprene. I. Discoloration of GR-M Vulcanizates by Direct Sunlight
Authors: Sanders P. A.
Published: February 2011

1. White GR-M vulcanizates discolor differently in direct sunlight from what would be predicted from results obtained with standard light-aging devices. 2. Accelerated light-aging tests are of value for preliminary screening purposes if the control (of known stability to sunlight) is discolored to about the same extent as it would be by sunlight. Under these circumstances accelerated light tests indicate the other stocks to be relatively more stable with respect to the control than does exposure to direct sunlight. 3. Stocks most stable to light are obtained by using high proportions of the rutile crystalline form of titanium dioxide as white pigment. Variations in curing time affect only the initial color of the stock before exposure to light and not its resistance to discoloration by sunlight. 4. The results in this paper apply only to GR-M and to no other Neoprene, and only where outdoor exposures are involved. Preliminary results obtained by aging GR-M in indirect sunlight (behind glass) indicate that the effects produced by direct and indirect sunlight differ.
A Study of Electrostatic Charges Produced during Mastication of Rubber and of GR-S
Authors: Havenhill R. S. , Carlson L. E. , Rankin J. J.
Published: February 2011

A new electrostatic field strength meter has been described which measures and records, not only the magnitude of electrostatic fields, but also their polarity. This device has been used in a study of the mastication of rubber, and has furnished data which indicate that rubber becomes less negative, and may actually become positive, as mastication proceeds ; this indicates in turn an oxidation of the molecules as well as an electronic rearrangement and orientation of the rubber molecular chains. Data on GR-S polymerized at different temperatures show entirely different electrostatic breakdown curves, which, with other physical characteristics, indicate unusual properties of the crude low-temperature polymers; e.g., high molar weight, long-chain molecules, already or easily oriented, which do not oxidize or break up appreciably on mastication. A partial correlation of Mooney viscosity and electrostatic contact-potential and field strength has been shown for rubber and GR-S which have been masticated on a rubber mill. The new electrostatic-field strength meter shows promise as a new tool which can be used in processing control, and also as a research instrument for obtaining fundamental information on mastication, pigment dispersion and incorporation, as well as an aid in forming new concepts concerning the structure of matter.
Physical Properties of Fractions of GR-S and Their Vulcanizates
Authors: Yanko John A.
Published: February 2011

A large-scale precise fractionation of GR-S (X-55) was carried out at 25° C, using a fractional precipitation technique. Nine fractions, each weighing approximately 150 grams and comprising about 11 per cent by weight of the original unfractionated sample, were obtained, with number-average molecular weights varying from 4000 to 1,650,000. High molecular fractions undergo gelation rapidly, even when dried in the absence of light at reduced pressure, and the higher the molecular weight of the fraction, the greater the amount of gel formed. Compared to unfractionated butadiene-styrene copolymers of similar gel contents, the gel portions of the higher molecular fractions had unusually high swelling indices, indicating qualitatively that the average molecular weights between points of effective cross-linking in the three-dimensional gel structure were higher than those found in the past in unfractionated samples of similar gel contents. Through the concentration range studied, the intrinsic viscosity values varied as a straight-line function of the concentration terms for all the fractions. However, the negative slopes of these lines increased as the molecular weight of the fraction increased, demonstrating the greater dependence of the intrinsic viscosity values of the higher molecular fractions on the concentration variable. The relationship between number-average molecular weight, as determined by osmometric measurements, and limiting intrinsic viscosity of the GR-S fractions is given by the equation: [η]0=5.4×10−4 M0.66, which is similar to that obtained by French and Ewart. The μi values calculated from the equation of Huggins were essentially the same (0.35) through the molecular range 12,400 to 723,000.
Plasticization of Natural and Synthetic Rubbers. II. GR-S
Authors: Piper G. H. , Scott J. R.
Published: February 2011

Continuing the work described in Part I, experiments have been made to determine the separate effects of heat, oxidation, mechanical working on rolls or in an internal mixer, peptizing agents (used in hot milling), and absorption of softener on the softness, elastic recovery, and plastic flow relation (between applied force and rate of flow) of GR-S. Heat alone, without oxygen or mechanical action, does not soften GR-S, but makes it harder and more elastic, presumably by inducing cross-linking of the chain molecules; GR-S thus differs fundamentally from natural rubber, which can be softened by heat. Absorption of softener (mineral oil) softens GR-S and reduces its recovery, but these effects are too small to form a practicable plasticizing method. Either oxidation or mechanical working softens GR-S considerably, reduces its elastic recovery, and brings its plastic flow relation nearer to that of well masticated natural rubber, i.e., approaching ordinary viscous or Newtonian flow (flow rate proportional to stress). Peptizing agents such as benzaldehyde phenylhydrazone or iron naphthenate promote the effect of hot milling, presumably by accelerating oxidation, which is shown to occur during hot, but not appreciably in cold, milling. Of the methods tried, those which plasticize GR-S most quickly are (1) hot milling with a peptizing agent, and (2) oxidation at 125° C and 15 lb. per sq. in. oxygen pressure ; if the latter is continued too long, however, hardening sets in. The results show that GR-S, like natural rubber, can be plasticized by mechanical breakage of the chain molecules by the shear stresses set up during mastication, as well as by oxidation, which presumably causes breakage of the molecules at the double bonds. Mechanical and oxidative treatments, however, do not give the same properties ; mechanical breakdown in the cold gives a product completely soluble in benzene, whereas oxidation does not, and is less effective in reducing recovery, and there may be other differences not yet revealed. In view of these differences and the fact that heat has effects opposite to oxidation or mechanical working, it follows that the various possible ways of plasticizing GR-S, since they involve heat, oxidation, and mechanical action in different combinations and degrees, give plasticized batches with very different properties, even if the length of the treatments is so adjusted as to give, say, the same Williams or Mooney plasticity reading. These differences are fully discussed in the present paper; the main conclusions are:
Stability of Accelerators as Affected by High Processing Temperatures
Authors: Holbrook F. L. , Fitzgerald T. H.
Published: February 2011

In high-speed Banbury mixing, sufficiently high temperatures may be generated at least to partially damage some rubber accelerators and decrease their effective activity. Thus, at a processing temperature of 360° F, the following stability relationships hold. 1. Thiazoles, thiazole derivatives, and activated thiazoles show little loss of activity. 2. Thiurams and dithiocarbamates may be severely affected. 3. Guanidines, as represented by diphenylguanidine, are only moderately affected. 4. Aldehydeamines range in stability from moderate to good. This effect of high temperature on accelerator stability may be considered as constituting a processing hazard. The proper selection of accelerators and the careful consideration of any processing changes which may significantly increase temperature minimize the danger and allow avoidance of harmful results. The fact that some accelerators are relatively unstable at high temperatures does not preclude their use. It is simply necessary to incorporate these materials into the mix at a sufficiently low temperature, such as that at which it is normally considered safe to add sulfur.
Analysis of Natural and Synthetic Rubber by Infrared Spectroscopy
Authors: Dinsmore H. L. , Smith Don C.
Published: February 2011

This report describes an investigation of the applicability of infrared spectro-scopic methods to the quantitative determination of the elastomer composition of industrial rubber products. Generally satisfactory techniques for obtaining a valid spectrum of the elastomer content of any rubber specimen have been developed and evaluated and have been applied to the development of detailed analytical procedures for the identification and qualitative analysis of elastomer mixtures, to the quantitative analysis of natural-GR-S blends, and to the determination of the nitrile content of nitrile copolymers. An accuracy corresponding to ° 1 per cent average error has been obtained in these determinations. The methods can be extended to analogous problems with a minimum of alteration, and the same order of accuracy can be expected in general. A discussion of the correlations between spectral absorption and molecular structure is also included. Infrared spectroscopy is finding increasing application as a means for the identification of organic materials and the analysis of complex mixtures. Spectroscopic methods are not only rapid and generally conservative in sample requirements, but the results are often more specific than those obtained by chemical analysis, distillation, etc., and in many cases furnish detailed structural information of importance to research and development. The advantages of infrared analysis are that : (1) the spectrum of a molecule is a unique physical property which is not altered by any changes in which molecular identity is maintained, and (2) the individual features of the spectrum relate in a definite manner to the chemical bonds comprising the molecule and can thus be interpreted, regardless of the total configuration.
Properties of Ebonite. XXXIV. Influence of Organic Accelerators of Vulcanization
Authors: Fisher D. G. , Newton R. G. , Norman R. H. , Scott J. R.
Published: February 2011

1. An investigation was made of the influence of several organic accelerators, of the types commonly used in soft rubber, on the vulcanization of ebonite and the properties of the product. This includes the study of zinc and magnesium oxides as activators, and of variation in the proportion of accelerator used. 2. Most of the accelerators are effective in the vulcanization of ebonite, and it is definitely established that they accelerate the final “hard rubber” phase of the rubber-sulfur reaction. The degree of acceleration, however, is much less than in soft rubber, and the different accelerators do not show the same relative efficiencies. 3. Neither zinc oxide nor magnesium oxide functions as an accelerator activator in the hard-rubber reaction. 4. The effects of accelerators and metallic oxides on the maximum safe rate of vulcanization, i.e., consistent with avoiding excessive exothermic temperature rise, have been examined. All the accelerators improved the maximum safe rate of vulcanization; the most effective were butyraldehyde-aniline and diphenylguanidine, the former being considerably the better. Zinc oxide reduced the maximum safe rate when added to an accelerated mixing ; magnesium oxide caused a further improvement. Butyraldehyde-aniline plus magnesium oxide was thus the most effective combination for enabling the vulcanizing period to be reduced without risk of overheating due to the exothermic hard-rubber reaction. The fact that certain accelerators or accelerator metallic oxide combinations make possible quicker vulcanization without increased exothermic temperature rise suggests the possibility of developing special ebonite accelerators possessing this useful characteristic in an enhanced degree. 5. For speedy set-curing, a mixing containing either diphenylguanidine or butyraldehyde-aniline with magnesium oxide appears best, particularly the latter, since it can be used at a higher vulcanizing temperature without excessive overheating. The activating effect of zinc oxide in the early (soft-rubber) stage of vulcanization is of no use in speeding up set-curing ; indeed, zinc oxide usually delays the formation of a satisfactory set-cured product. 6. Accelerators do not alter the relationship between combined sulfur content and physical properties, as they do in soft rubber ; their function is simply to increase the rate of the rubber-sulfur reaction, and, perhaps as a consequence of this, to enable more of the added sulfur to become combined. 7. The technically important effects of accelerators on the properties of ebonite are : increase in resistance to plastic yield, decrease in impact strength, increase in resistance to swelling liquids, and increase (usually) in dielectric loss at normal temperatures, though the loss at elevated temperatures may be reduced. The first three of these effects result from the more complete combination of sulfur noted above.
The Molecular Structure and Arrangement in Stretched Natural Rubber
Authors: Fisher Dorothy G.
Published: February 2011

Although there are still some minor discrepancies to be resolved, the appearance of the diffuse-zone electron-diffraction pattern arising from thin films of stretched natural rubber is adequately explained on the basis of the thermal oscillations of the long-chain rubber molecules in the crystalline regions, this pattern being analogous to that which would be given by a stream of oriented molecules in a pseudo-gaseous condition. As Charlesby, Finch and Wilman pointed out, the diffuse-zone pattern has distinct advantages in the examination of complex molecules, since it gives a direct indication of the configuration of the molecule, independent of its mode of fitting into any particular crystalline lattice. In spite of the diffuseness of the patterns with which we are dealing a study of the diffuse zone or molecular pattern has shown that it is possible to discriminate decisively between two postulated atomic configurations which do not differ greatly. In the case of natural rubber, neither of the two configurations investigated agrees in every respect with experiment, but the evidence brought forward above supports the view that the atomic arrangement in the stretched rubber molecule approximates to a simple form having planar units and standard bond lengths and angles, rather than to the more complex form hitherto considered.
Elastomers from Fluoroprene
Authors: Mochel W. E. , Salisbury L. F. , Barney A. L. , Coffman D. D. , Mighton C. J.
Published: February 2011

As the first member of the haloprene or halogen-substituted butadiene series, fluoroprene (2-fluoro-1,3-butadiene) occupies a position between butadiene and chloroprene in most of its properties and characteristics. For example, it polymerizes at a rate approximately twenty-five times that of butadiene under comparable conditions, but it is somewhat slower than chloroprene in its rate of polymerization. However, fluoroprene resembles butadiene in that it copolymerizes readily in wide proportions with most 1,3-dienes and many monovinyl compounds, whereas chloroprene copolymerizes only incompletely with many monomers. In sharp contrast to the other haloprenes, fluoroprene polymers, like those of butadiene, have an amorphous rather than crystalline structure in the stretched state, and they require reinforcement with fillers to develop high tensile properties in their vulcanizates. Polyfluoroprene rubbers obtained in 85 to 90 per cent conversions using selected emulsion systems have exhibited tensile strengths of 2800 to 3200 pounds per square inch at 400 to 500 per cent elongation in tread type of vulcanizates. These vulcanizates are highly freeze resistant and have the good oil resistance of corresponding chloroprene polymers. The resilience of the vulcanizates is excellent and their resistance to ozone and sunlight is good although not so outstanding as that of corresponding polychloroprene products. Polyfluoroprene vulcanizates, unlike those of polychloroprene, propagate a flame when ignited, but they burn at a much slower rate than GR-S or natural rubber. In electrical properties they are superior to polychloroprene vulcanizates, and approach natural rubber in resistivity and power factor.
Viscosity—Molecular Weight Relations for Various Synthetic Rubbers
Authors: Scott Robert L. , Carter Walter C. , Magat Michael
Published: February 2011

Measurements of six different high polymers have shown that the intrinsic viscosity of the solutions depends on approximately the two-thirds power of the molecular weight. Dependence of the viscosity on the weight per chain atom of the polymer is indicated.