bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Solids Synthetic Latex Directly from Reactor
Authors: Chittenden F. D. , McCleary C. D. , Smith H. S. 
Published: February 2011

Abstract
In the ten-year period preceding the outbreak of hostilities with Japan, imports of natural latex into the United States assumed a sharply rising trend. (Figure 1 shows that the 1940 figure is somewhat high owing to the inception of stockpiling.) Roughly 80 per cent of this latex was shipped in as a concentrate of 60–65 per cent solids, since this eliminated shipping excess water originally present in the latex, and constituted a material suitable for various applications in which the normal latex could not be used. Although small quantities of special-purpose synthetic latices had been produced domestically before 1941, it was not until 1944 that substantial production of a general-purpose synthetic latex got under way (Figure 1). With this production, there arose the problem of producing a concentrate for use in applications where a high-solids latex is essential. Natural rubber latex can be concentrated readily, either by centrifuge or a creaming process, since it has a large particle size. Synthetic rubber latex, on the contrary, has a very small particle size, which makes concentration a more difficult and costly operation. In practical creaming operations a significant amount of polymer is usually lost in the serum. This article presents a description of two new synthetic latices made to 55–60 per cent solids directly in the reactor and a short description of the methods of preparation. Since the production of these high-solids latices is only slightly more expensive than the production of low-solids types, they can be sold at only a small increase in cost over the latter.
Quantitative Estimation of GR-S in Rubber Reclaim
Authors: Le Beau D. S. 
Published: February 2011

Abstract
The method is none too accurate above 90 per cent of either natural or synthetic rubber present, unless the reclaim analyzed is well known. If the degree of deviation for a given reclaim is well established, it is possible to determine the mixtures up to 95 per cent of either component. However, if the degree of deviation is only an average figure, derived by such critical scrutinization of a number of reclaims as shown in Table I, greater accuracy cannot be expected in the estimation of the components of mixtures containing more than 90 per cent of either natural or synthetic rubber. The GR-S or natural rubber content of reclaims containing a great variety of scraps, such as some of the so-called victory reclaims, can be estimated only with a lesser degree of accuracy than ±2.5 parts. Difficulties in the estimation of the polymer components may also be encountered in light colored reclaims. However, such estimations are seldom necessary because of the peculiar compounding technique required by GR-S for proper physical performance.
Hardness Testing of Vulcanized Rubber. VIII. Hardness Tests with a Conical Indentor
Authors: Scott J. R. 
Published: February 2011

Abstract
The relation between load and depth of indentation for a conical indentor has been investigated. The theoretical relationship applicable to perfectly elastic materials (indentation proportional to square root of load) is found to hold for all the rubbers examined except one very hard sample, whose comparative inelasticity causes some deviation from this relationship. This result further confirms the correctness of the theoretical investigation on indentation hardness testing of rubber by indicating that the forces required to produce indentations of similar shape, but different sizes, are proportional to the squares of corresponding linear dimensions of the indentations. With a conical indentor under a constant load, the depth of indentation is approximately inversely proportional to the square root of the elastic modulus of the rubber at small elongations. A conical indentor is preferable to a ball indentor in that it shows more nearly uniform sensitivity to small differences in modulus (i.e., true hardness) at all parts of the hardness scale. It has previously been shown that the ball is superior to a flat-ended plunger in this respect. To approach still nearer to uniform sensitivity would presumably require a pointed indentor having a profile with concave sides. This would be difficult to make accurately, and very likely to damage on account of its sharp point; this might, indeed, be a disadvantage of the conical form also.
Hardness Testing of Vulcanized Rubber. XI. Influence of Gauge-Spring Pressure and Friction in the Indentation Hardness Test
Authors: Scott J. R. 
Published: February 2011

Abstract
A discussion is given of the effects of the spring which, in many dial micrometer gauges, applies a small upward or downward force to the gauge stem, and of the effects of friction in the gauge. When hardness tests are made by the differential method, the reading being taken as the difference between the indentations produced by a small zero load and a much larger total load, the errors introduced by unbalanced gauge spring pressure and by friction may be much more serious than when a direct hardness reading, i.e., without an initial zero load, is taken. Other things being equal, the resulting percentage error in the hardness reading is greater the smaller indenting load. This is a further reason, additional to that already advanced3, for limiting the reduction of ball size and load which has been advocated to reduce the influence of the thickness of the rubber. If the gauge contains a spring, or if friction is present, it is not possible to adjust conditions so as to eliminate the resulting errors in the differential readings on all rubbers. The errors can, however, be minimized in the following ways. (1) By increasing the ratio (z) of zero load to total load. An excessive zero load, however, is undesirable for other reasons; a value of 0.05 for z is a suitable compromise. (2) By adjusting the unbalanced spring pressure to zero when the gauge stem is in a certain position which depends on the value of z and the hardness of the rubber under test. Taking z as 0.05 and the average B.S. hardness number of normal rubbers as 75 (i.e., an indentation of about 0.75 mm.), this position is that in which the tip of the indenting ball is 0.5 mm. above the surface of the rubber.
Some Problems Involved in the Grading and Testing of Natural Rubber. A Progress Report
Authors: Fletcher W. P. 
Published: February 2011

Abstract
In the establishment of grading and testing procedures for natural rubber based on the properties of vulcanizates, four main questions arise. First it is necessary to decide on the property to be measured, and reasons are given for the choice of elongation at a fixed load for the purpose, elongations being below 250 per cent. Secondly the method of test had to be decided, and a simple version of the National Bureau of Standards' strain tester has been developed and is in use. Thirdly a standard test mix, into which the raw rubber samples are compounded, must be selected; the well known No. 1 compound of the Crude Rubber Committee of the American Chemical Society has been found to be defective because of its great sensitivity to moisture, whereas a mixed mercaptobenzothiazole-diphenylguanidine stock and a stock accelerated with N-cyclohexyl-2-benzothiazole sulfenamide appear suitable. Finally the interpretation of results is discussed. The use of a single cure for classification of rubbers is felt to be inadequate, and to determine both the maximum modulus of which the rubber is capable in the compound and also the cure time to obtain this condition, it is proposed to define the property with tolerance limits at three cures. Incidental problems arising include mixing error, and some investigation of this is described.
Effect of Soil Microörganisms on Rubber Insulation
Authors: Blake John T. , Kitchin Donald W. 
Published: February 2011

Abstract
Evidence is presented that some of the rare failures of nonleaded rubber-insulated underground cables were caused by soil microörganisms. Laboratory conditions deliberately chosen to favor microbial attack made possible greatly accelerated tests in which failures like those found after ten years or more in service have been produced in a few weeks or months. These failures are characterized by discrete, minute low resistance spots. Drastic decrease of insulation resistance was used as the criterion of failure. The exact distribution of low-resistance spots has been shown by an electrolytic test. Parallel tests in sterile and in active soil proved that the failures in soil were caused by living microorganisms. Soil exposure tests have been made on natural and synthetic rubbers and several other plastic insulations. Natural rubber compounds were found to be the most susceptible. In some soils GR-S compounds proved stable up to two years, but failed in a more active soil. The exact mechanism of attack is not known. In some cases there is drastic electrical failure without visible surface effect. In actual operation of underground cables the exact combination of conditions necessary for producing failure by microbial attack can occur only rarely. The purpose of the severe laboratory tests is to make possible the development of insulations stable under all soil conditions.
Tear Initiation and Tear Propagation
Authors: Buist J. M. 
Published: February 2011

Abstract
(1) Both the crescent and angle tests are group (2) tests; therefore the width of the sample must fee taken into account when the tear resistance is being calculated. (2) There is one exception to the above, and that is the case of knotty tears in group (2) tests. When knotty tears occur, the test becomes a direct tear test [group (1)], and the width is no longer important. (3) When knotty tears occur with group (1) tests, the width must be considered for, in reality, the test has become a group (2) test. (4) Some rubbers exhibit fibering during tearing, and this is explained by the cohesive forces between fibers reaching a limiting value before the limiting value of the breaking strength of a fiber is reached. (5) Differences in the mechanism of tearing with different fillers have been noted. (6) Practical evidence of the existence of maximum shear stress in subsurface planes of the material has been obtained, and a mathematical solution for a simple case has been given. (7) The angle tear method is a combination of tear initiation and tear propagation, and can be regarded as complementary to the crescent test. It cannot be regarded as a replacement for the crescent test. (8) With certain rubber compounds the component of stress in the direction of pull is too high in the case of the angle test-piece. (9) It is suggested that the unnicked crescent be used in preference to the angle test-piece for tear initiation measurements, as the unnicked crescent test-piece has more discriminating power. (10) The same proportion of straight and knotty tears occurs with both the crescent and angle methods. (11) A preliminary evaluation of the I.G. tear cutter indicates that the fairest comparison with other methods requires a single slit to be inserted in the outside circumference of the ring.
The Velocity of Propagation of Ultrasonic Waves and the Form of the Molecules of High Polymers
Authors: Natta Giulio , Baccaredda Mario 
Published: February 2011

Abstract
The velocity of propagation of ultrasonic waves in numerous substances of high molecular weight was determined. For substances not fusible at temperatures below 100° C, this velocity was determined by extrapolation from solutions considered ideal. For linear macromolecules without side chains, the ultrasonic velocity appears to be practically equal, within the limits of experimental error, to that calculated by the formula of Rao and on a basis of the additive values of the bond velocity of Lagemann and Corry. For molecules which have many side chains, the velocity is lower than the calculated value, whereas for compounds of low molecular weight this deviation is relatively small, viz., less than 10 per cent; it becomes much higher, viz., almost up to 40 per cent, for macromolecules. The form factor is defined as the ratio of the velocity determined experimentally to the velocity calculated by the formula of Rao. This form factor is equal to 1 for polymers without side chains or with very few side chains, such as paraffins, polyethylenes, Nylon, polyethylene oxides, and polyoxymethylenes; is only 0.89–0.90 for natural rubber; only 0.82–0.84 for Buna and for hydrogenated Buna, poly-α-butylenes, and polystyrenes; only 0.79–0.80 for polyisobutylenes; only 0.89 for polymethacrylates; only 0.78 for polyvinylisobutyl ethers; only 0.65 for Butyl rubber; and only 0.63 for polymethyl methacrylates. The form factor is thus affected by the frequency and length of the side chains, and by any secondary side chains which may be present.
Propagation of Audiofrequency Sound in High Polymers
Authors: Witte R. S. , Mrowca B. A. , Guth E. 
Published: February 2011

Abstract
Velocity and attenuation measurements were made in thin strips of rubber from 0.5 to 5 kc and from −5° to 90° C to obtain the dynamic viscoelastic constants of Butyl and GR-S gum stocks. Above room temperature velocity and attenuation are higher in Butyl gum than in GR-S. In all cases, the velocity increases with decreasing temperature and increasing frequency. The attenuation shows a peak with temperature. For Butyl, the peaks are broad and occur at higher temperatures than for GR-S. For both stocks an increase in frequency gives peaks which are higher, sharper, and shifted to higher temperatures. In some instances, there are indications of peaks in the attenuation versus frequency at frequencies beyond our range of measurement. The behavior of the dynamic modulus in the temperature and frequency range studied is similar to that of the velocity. These results, combined with low temperature static measurements and very low frequency dynamic measurements, indicate a U-shaped modulus-temperature curve whose minimum broadens and shifts to higher temperatures with increasing frequency. This may be explained by a generalization of the kinetic theory of rubber elasticity, taking into account intra- and intermolecular forces, and considering time effects.
Propagation of Ultrasonic Bulk Waves in High Polymers
Authors: Ivey Donald G. , Mrowca B. A. , Guth Eugene 
Published: February 2011

Abstract
The propagation of supersonic waves in bulk rubbers has been studied from 40 kc per second to 10 Mc per second and from −60° to 60° C. The wave velocity was found to increase with decreasing temperature, level off both at high and low temperatures, and increase slightly with frequency. Peaks in attenuation as a function of either temperature of frequency were observed; these occurred at lower temperatures for lower frequencies. The peaks of Butyl, a high-loss rubber, are broader and higher than those of GR-S and Hevea, which are lower-loss rubbers. The results are in qualitative agreement with data obtained by strip methods at audiofrequencies. However, for bulk waves the real and imaginary parts of two elastic constants, the bulk and shear moduli, determine wave velocity and attenuation; hence, independent measurements of shear wave properties are necessary to evaluate these constants. A three constant theory is discussed, assuming a shear viscosity only, so an effective modulus K+4μ/3 is obtained, where K and μ are the bulk and shear moduli. Relaxation times of the order 10™6–10™8 second are indicated. Approximate values of the dynamic Young's modulus are obtained from the effective modulus by assuming that the high frequency dispersion is due to the appearance of a “crystalline” shear elasticity. These results are correlated with low frequency data, and the dynamic Young's modulus and the loss factor are plotted. The loss factor exhibits a maximum in the dispersion region. Results are plotted in the range from 1 to 107 c.p.s., which covers a wider range of frequency than earlier investigations. The necessary distribution of relaxation times is discussed.
Mastication of Rubber. I
Authors: van Rossem A. , Hoekstra J. 
Published: February 2011

Abstract
Plasticity measurements with the Williams-type (parallel-plate) balance and steam plastometers confirmed the well known influence of time, temperature, and energy consumed on mastication of raw rubber on rolls. Reproducibility of results proved fairly high. The effect of storing plasticized rubber was a slow and unimportant hardening. On hot storing, hardening during the first days took place, followed by slow softening. With the steam plastometer, a stiffening value was determined for several fillers when mixed into masticated rubber. Some experiments were done on the influence of the concentration of such fillers and on the influence of softeners, accelerators and sulfur on plasticity. The influence of the degree of mastication of the mixes on the vulcanized stocks was investigated in a few cases. Apart from the well known influence of extreme mastication on breaking strength, a remarkable influence of the temperature of mastication on modulus was found.
Mastication of Rubber. II
Authors: Hoekstra J. , van Rossem A. 
Published: February 2011

Abstract
Recovery of masticated rubber was measured at different temperatures. Recovery was found to be influenced, but not governed, by plasticity. A quick method, working at 100°, gave information on the influence of fillers and of storage at room temperature and at 70° C. The influence of recovery and plasticity on set up after calendering was determined.
Investigations in the Field of Rubber Vulcanization. IV. Phenomenon of Vulcanization Optimum in Mixtures with a Large Proportion of Constructive Agent
Authors: Dogadkin B. , Karmin B. 
Published: February 2011

Abstract
1. In mixtures with a large content of constructive (vulcanizing) agent, the vulcanization-optimum phenomenon is connected with the formation of dense space-lattices in the structure of the vulcanizate, which inhibit the formation of crystalline or highly oriented segments during elongation. 2. In contrast to mixtures with a small content of vulcanization agent, the vulcanization optimum of which is explained by superimposition of oppositely directed constructive and destructive processes, the case noted in the preceding paragraph shows a maximum only on the kinetic curve representing the change in strength. The kinetic curves representing relative elongation, swelling, and solubility are monotonic in character. 3. The maximum on the kinetic curve representing the change in strength in mixtures with a large content of constructive agent occurs before complete combination of the latter with the rubber. 4. In consequence of the absence of oppositely directed actions on the part of sulfur and oxygen, the vulcanization of sodium-butadiene rubber mixtures shows a maximum only on the kinetic curves representing the change in strength. 5. The position of the strength maximum in mixtures with a large content of constructive agent depends on the rate of deformation. As the rate of deformation is decreased, the maximum appears after more prolonged vulcanization periods of the mixtures. 6. The strength of natural rubber vulcanizates at the vulcanization optimum is a linear function of the quantity of crystalline phase formed during elongation.
Effect of Chemical Agents on Heat Deterioration of GR-S
Authors: Mesrobian Robert B. , Tobolsky Arthur V. 
Published: February 2011

Abstract
A detailed study of Tables III and IV, in which the effect of chemical agents on high temperature aging are evaluated by relaxation and oxygen absorption indexes and conventional test indexes, shows a much higher evaluation consistency for the Table III indexes and presents some doubt regarding the significance of the data given in Table IV and Figure 8. Although the conventional tests have the advantage of speed and convenience, the difficulties of obtaining truly significant correlation between laboratory aging tests and practical performance are considerable. The methods reported in this paper may, therefore, be of value in supplementing the numerous aging tests already in use in various laboratories.
Plasticizers for Polar Synthetic Rubbers
Authors: Cheyney La Verne E. 
Published: February 2011

Abstract
Natural and synthetic rubbers may be grouped in two broad classes—polar and nonpolar. Dipole linkages are involved in the plasticization of the polar group; hence they possess certain resemblances to the polar thermoplastics in this respect. Plasticizers are employed with such polymers for two general purposes: increasing plasticity of the uncured rubber; and increasing flexibility or corresponding effects in the cured material. Plasticization of the polar rubbers is a complex problem because of structural variations inherent in diene polymers and copolymers; the vulcanization process; and effects of other additives—for example, carbon black. Available data are extremely confusing because of these factors and the fact that much of the information reported is meager. Many of the materials which have been employed may be grouped into a few broad chemical classes. The effects of these vary widely among a given class because of structural variations and differences in physical properties. It is possible to generalize concerning a few types of effects, but more and better data are required before an adequate picture of the plasticization of the polar synthetic rubbers will be available.
Role of Adsorption in Reinforcement of GR-S
Authors: Barnett C. E. , Jones H. C. 
Published: February 2011

Abstract
1. The reinforcement of GR-S is influenced to an appreciable extent by the adsorption characteristics of pigments compounded in this polymer. 2. The relation between surface activity and reinforcing properties of a pigment in GR-S is demonstrated in the case of a basic zinc carbonate calcined through a range of temperatures. 3. Twelve pigments were immersed in GR-S cement, and the recovered polymer was evaluated. The mineral pigments, ELC magnesia and calcium silicate, selectively remove fatty acids and soaps from GR-S cements. The adsorption by EPC black is not selective with respect to fatty acids and soaps. The effects obtained on testing the recovered polymer vary in line with the amount and nature of the adsorption. 4. With ELC magnesia and calcium silicate, the effect of adsorption is predominantly due to the removal of fatty acids and soaps, and this affects the vulcanization chemistry. The process is different with EPC black, but a clear interpretation is not possible on the basis of present experimental data.
Improved-Processing GR-S by Variations in Compounding
Authors: Crawford R. A. , Tiger G. J. 
Published: February 2011

Abstract
The data indicate that treating GR-S for 5 minutes in the Banbury at 380° F in the presence of the combinations of cross-linking agents listed brings about improvement in processing and stress-strain properties, equal or superior to those produced by sulfur and Captax together. In turn, this GR-S polymer, treated with sulfur and Captax, was shown to be superior to GR-S-60 and to GR-S-60/GR-S blends in ratios higher than 30/70, after mastication and compounding of the polymers in a hot Banbury at about 380° F. The properties of the sulfur-Captax cross-linked GR-S closely approached the excellent processibility and excelled the poor stress-strain characteristics of GR-S-60 compounded by milling at normal temperatures.