bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Latex Particle Size Distributions by Fractional Creaming with Sodium Alginate
Authors: Schmidt E. , Biddison P. H. 
Published: February 2011

Abstract
Knowledge of mass distribution of particle sizes in latex is very important to the latex technologist. Therefore, it is desirable to have available a simple method for the determination of mass distribution of particle sizes. This paper presents a method, based on fractional creaming of latex with sodium alginate, which can be used in any laboratory without special equipment. The method is particularly advantageous for analyzing latexes of very wide particle size distributions. When analyzed with an electron microscope, these latexes require counting a very large number of particles. McGavack found that partial creaming of normal hevea latex with ammonium alginate gives concentrates of larger average particle size than the original latex. He found that the average particle size in the cream approaches that of the original latex as the amount of creaming agent is increased. In a previous paper from this laboratory, Schmidt and Kelsey demonstrated that the phenomenon of fractionation according to particle size with increasing amounts of creaming agent is applicable in a wide variety of anionic latex systems and in colloidal silica. Their results indicated also the existence of a quantitative relationship, independent of the nature of the dispersed particles, between the concentration of creaming agent and size of creamed particles. Maron confirmed fractionation with respect to particle size as a consequence of partial creaming with alginate. He showed that the mass average particle sizes of fractions, determined optically, cumulate to that of the original latex. Although the previous paper by Schmidt and Kelsey implied the basic concept of a method of determining particle size distribution by fractional creaming, it was not exploited at that time. In order to adapt the fractional creaming phenomenon to a quantitative method for particle size determination, we required a more precise knowledge of the relation between creaming agent concentration and size of particles creamed. It was proposed to establish this relationship with the aid of the electron microscope. Various factors influencing the creaming of latex, such as polymer concentration, electrolyte, soap content, and variability of the creaming agent, had to be considered in standardizing the creaming procedure.
A Proposed Method for Estimating Polymer Molecular Weight Distribution without Fractionation
Authors: Rehner John 
Published: February 2011

Abstract
The close agreement which Green has demonstrated between results from the Schulz binomial and the Tung distribution and the applicability of the latter to a variety of fractionation data for different polymers both seem to outweigh possible objection that the present method assumes a particular distribution function. Green's results suggest to us that the apparent exceptions found by Tung for some polyethylenes containing large amounts of low molecular species may possibly be attributed to fractionation inefficiency, rather than to the inadequacy of his function. The internal consistency or smoothness of data does not, of course, constitute proof of precise fractionation. In fact, one can safely say it is no easy matter to find complete fractionation data, of established precision, that can provide a critical test of a distribution function over the entire molecular weight domain. In his study of polyethylenes, Tung suggested that his function tends to exaggerate the low molecular weight end of the distribution, in the sense that the Mn values calculated from his parameters were only about half as large as those obtained by summation of the experimental data for the fractions. His calculated and experimental values of Mw, on the other hand, were in satisfactory agreement. One might be tempted to use this to reconcile the Mn values of the SBR system in Table II with the higher values reported by others. However, this procedure would be indefensible because simply doubling the Mn values would give polydispersity values of less than unity. It would therefore seem incorrect to generalize that the Tung function gives abnormally small Mn values for all polymers, especially when there is some reason to believe that it is better than it seems, even for polyethylenes. Much more likely, the differences between the average molecular weights and the polydispersity of the peroxide-SBR system of Table II, and the corresponding quantities reported by Bueche and Harding for sulfur-SBR and by Booth and Beason for uncompounded SBR, are real and are due to chemical and other factors already mentioned. Although the meager data at hand leave some question as to the accuracy with which the present method can predict absolute values of the various average molecular weights, the key to the matter seems to be the ratio of the true to the physically measured crosslink density for polymers in general, rather than the particular distribution function employed here. Less uncertainty is attached to the polydispersity, since this is a function of only one parameter, b, which is quite insensitive even to large errors in ρ. The method may therefore be useful, even in its present state, for comparative studies in a given system. These might include, for example, the effect of synthesis or processing variables on distribution characteristics and product properties or the effects of stabilizers in aging or other degradative processes.
Mechanical Degradation of High Polymers
Authors: Bueche F. 
Published: February 2011

Abstract
Mastication of rubbers and molten plastics often gives rise to degradation of the polymer molecules. The amount of degradation is severely dependent upon shear rate, melt viscosity, and molecular weight of the polymer, temperature, and the presence of plasticizer. Under certain conditions, usually at low temperatures, one finds that the presence of oxygen is only of minor importance. At high temperatures, at least in certain cases, shear degradation is seriously increased when oxygen is present, even though very little degradation occurs without mastication. In this latter case, oxidative scission does not appear to take place at random along the chain but seems to occur predominantly in the central portion of the chain. The purpose of this paper is to present a molecular theory which unifies these various observations. It will be restricted to the mechanical actions involved during mastication. The effect of oxygen on mechanical degradation will also be considered.
The Mechanochemical Breakdown of Polystyrene by Vibromilling
Authors: Grohn H. , Bischof K. 
Published: February 2011

Abstract
The investigation presented here, including detection of nitrogen, the viscometric investigation, melting point determinations, the ultraviolet and infrared spectra, allow of the qualitative statement that macroradicals are formed in the mechanochemical breakdown of polystyrene by vibromilling. The slight differences between N2 and NO milling may be ascribed in part to a more rapid deactivation of the radicals. On the foundation of the existing knowledge of mechanochemistry there result interesting prospects for science and technology, e.g., the use of macro-radicals as polymerization initiators and as active types of block copolymers and graft polymers by reactions both with monomers and with macroradicals of other polymer materials.
Abrasive Wear Research on Rubber
Authors: Wellinger K. , Uetz H. 
Published: February 2011

Abstract
The abrasion resistance of five different types of rubber were compared with steel (St 37) by various testing methods, such as the abrasive paper method, the abrasion cup method and the sand blasting method. The order of resistance of the various types of rubber against sand blasting is different from the order which is obtained with the sandpaper and abrasion cup methods. However, variations of the testing conditions within one method generally does not change the order. It has been shown, that rubber is more resistant against sand blasting than other materials investigated (basalb, malleable steel, non-alloyed hard castings) if the sand blast is directed essentially perpendicularly against the tested surface.
Non-Linearity in Dynamic Tests. I. Vibration Test Methods
Authors: Gough V. E. 
Published: February 2011

Abstract
In those cases where dynamic tests are to be interpreted in terms of the molecular structure of rubber, there is a definite need for a method of analysis which is wholly free from mathematical assumptions. Such a method of analysis is possible by the use of phase planes of velocity plotted against displacement. This is so because the slope of the trajectory at any point of the motion of any single degree of freedom system can be written solely in terms of physical quantities, namely, driving force, viscoelastic reaction and momentum. The analysis involves no hidden mathematical assumption. Methods of deriving stress strain relationships from phase plane trajectories are described. This phase plane method is discussed in some detail. Examples are given showing the inadequacy of the usual linear analysis in the case of rubberlike materials. Analysis shows that dynamic test machines should either apply a known motion and record a force-deflection curve or apply a force of known wave form and record the resulting motion as a phase plane trajectory. If force and motion are not kept independent of each other in this manner there is an inbuilt mathematical relationship which, more often than not, influences and falsifies the results. An important conclusion is that only when the nature of the non-linearities, or what is the same thing, the character of the functions which correctly describe the actual behavior of a vibrating system have been established by sound analysis of test data, should the phenomena be ascribed to the physical properties of the material. Because of the important consequence of the acceptance of some common mathematical steps in any analysis, certain of these are critically examined and their relevance discussed.
Response of Elastomers to High Temperature Cure
Authors: Smith Frank B. 
Published: February 2011

Abstract
It is well known to production people and to process engineers engaged in manufacturing rubber products that the output of curing operations can be greatly increased by elevating the temperature of vulcanization. For example, work done in the 1920's led to the curing of rubber-covered wire at 400° F using a continuous vulcanization (CV) process. Highly accelerated compounds capable of complete vulcanization in 15 seconds at 400° F are used in the wire industry. More recently the application of high temperature vulcanization methods has been vigorously pressed in the tire industry. While exact curing cycles are closely guarded secrets, it can be stated that passenger tires are vulcanized at temperatures up to 388° F (200 psi steam pressure) using press cycles of the order of 15 to 25 minutes' duration. New automatic presses which shape and then cure the tires at high temperatures—for example, Bagomatic tire curing press, McNeil Machinery & Engineering Co., Akron, Ohio—permit large economies in labor and productivity. Further reductions in curing cycles are anticipated, since the process engineers and rubber technologists continue to develop improved methods of high temperature curing. At this time it appears that the trend to higher temperature vulcanization will not only continue but tend to expand into other lines of rubber products. Considering the economic advantages which a given company may gain by a major advance in high temperature curing of tires or other rubber goods, it is not surprising that there have been only a few disclosures on high temperature curing technology.
Relation of Structure to Properties in Polyurethanes. Effect of Branching
Authors: Cluff E. F. , Gladding E. K. , Rogan J. B. 
Published: February 2011

Abstract
Attaching short N-arylurethane branches to a high molecular weight, linear polyether urethane introduces interchain forces—very likely arising from hydrogen bonding—which increase as the side chains become more polar. These forces are sufficiently strong to increase the bulk viscosity of the raw polymers and, with the more highly polar groups, are strong enough to impart an appreciable elastic memory. At slightly elevated temperatures (80° C) these forces are reduced considerably, which is to be expected if they arise through hydrogen bonding. However they are either not strong enough or are too limited in number to compete with the covalent crosslinks in the elastomer vulcanizates. Thus no significant alteration is observed in the vulcanizate properties which are customarily measured. The marked effect of these short aryl side chains to reduce crystallization tendencies can most likely be attributed to the bulkiness. of the pendant aryl moiety, which prevents—or slows down—the ordering of the polytetramethyleneether chains into a crystal lattice. Long chain branches influence dynamic properties considerably. Present evidence indicates that optimum dynamic properties—as measured by Yerzley resilience—are obtained when “loose ends” are absent.
The Oxidative Aging in Ultraviolet Light of Dicumyl Peroxide Vulcanizates of Natural Rubber in Presence of Various Antioxidants
Authors: Dunn J. R. 
Published: February 2011

Abstract
The oxidative aging of natural rubber vulcanizates at 25° C under irradiation by ultraviolet light of wavelength 365 mµ has been described in a number of communications from this laboratory. At this wavelength naphthylamines were shown to accelerate degradation of peroxide vulcanizates while substituted p-phenylenediamines inhibited it; α-naphthol and a variety of dithiocarbamates were also found to have a protective action. Since some amines and phenolic antioxidants do not absorb light of wavelength 365 mµ but do absorb in the region of 313 mµ, investigations have now been made of the effect of a large number of additives on aging at the shorter wavelength, so that predictions might be made of the most suitable materials to employ in protecting unfilled vulcanizates against crazing in sunlight.
The Chemistry of Carbon Black in Rubber Reinforcement
Authors: Sweitzer C. W. , Burgess K. A. , Lyon F. 
Published: February 2011

Abstract
1. The removal of chemisorbed oxygen from channel black and furnace black, without alteration of the underlying carbon surface, results in only minor effects in reinforcement potential regardless of the curative system employed, whether polar or free radical. 2. When the underlying carbon surface is changed by heat treatment to a state of lower energy, a significant decrease in the reinforcing ability of the carbon black results. 3. Different types of oxygen functional groups added to the carbon surface produce similar effects upon rubber properties. 4. These effects are limited to retardation of cure rate in sulfur curing systems. Only small effects of any kind are produced in the natural rubber-peroxide system. 5. The net conclusion to be drawn is that combined oxygen on the carbon surface plays a relatively minor role in the chemical effect of carbon black upon reinforcement; the nature of the carbon surface itself is of primary importance.
Graft Polymers from PVC and Rubber
Authors: Berlin A. A. , Kronman A. G. , Yanovskii˘ D. M. , Kargin V. A. 
Published: February 2011

Abstract
1. The authors investigate the graft copolymerization of vinyl chloride and butadiene-nitrile rubber by a chain transfer reaction, and also the combined mastication of PVC with various rubbers at elevated temperatures. 2. In physicomechanical properties Viniplasts produced on the basis of the products of graft copolymerization of vinyl chloride with butadiene-nitrile rubber, and also of the modification of PVC by butadiene, isoprene and natural rubbers are not superior to the corresponding characteristics of ordinary Viniplast. 3. In the combined mastication of PVC with Nairit and of PVC with butadiene-nitrile rubber at elevated temperatures compositions are produced which in respect of impact strength are 2 to 4 times superior to Viniplast from PVC. 4. It is suggested that the improvement in the physicomechanical properties in the combination of PVC with SKN-26 is connected with the formation of hydrogen bonds between the molecules of the polymers in question.
Evaluation of Progressive Changes in Elastomer Properties during Vulcanization
Authors: Claxton W. E. , Conant F. S. , Liska J. W. 
Published: February 2011

Abstract
An apparatus and method are described for evaluating state of cure, optimum cure time, rate of cure, induction time for cure, scorch time, induction time for reversion, reversion rate and degree of reversion of elastomeric compounds. Coincident with these determinations vulcanizate specimens are prepared on which more conventional physical test data may be obtained; e.g., compression modulus, compression set, hardness, specific gravity, tensile modulus and elongation. In essence, the method described provides a progressive measure of modulus change during cure or reversion through the change in deformation of a periodically loaded plunger, one end of which is embedded into the specimen. Typical results are given which show application of the apparatus to screening tests, millroom control, reversion studies and to compounds which are too stiff for conventional test methods. Demonstrated advantages for the apparatus include time saving, stock saving and better cure information on a wider range of polymeric compounds than is obtainable from tensile test methods. In a laboratory where a large selection of test instruments is not feasible, the versatility of the apparatus described should prove very advantageous.
The Influence of High-Activity Silica upon the Thermal Aging of Latex Vulcanizates Cured by Thiuram Compounds
Authors: Andresen A. 
Published: February 2011

Abstract
Once it had been shown that high-activity silica, even in comparatively small additions, improves the aging resistance of latex vulcanizates by many times, and that also an effect similar to that of a coactivator is set up by the interaction of high-activity silica with age resistors, ultra-accelerators and atmospheric oxygen in latex mixtures, a like effect was to be expected in sulfur-free latex vulcanizates crosslinked by thiuram compounds. In order to get comparable data it was necessary in the first place to get sulfur-free latex mixtures giving vulcanizates with starting properties in the same order of value as those of latex vulcanizates with the classical sulfur recipe. In addition it was necessary also to develop stocks from which threads could be extruded by the well-known two-stage method, since the investigations mentioned at the beginning were carried out exclusively on vulcanized threads, which lend themselves particularly well to determinations of tensile strength, elongation at break and tensile stress. Above all an attempt was made to manage with vulcanization temperatures below 100° C. To make this possible a thiuram compound active at relatively low temperatures had to be used. Here we had the opportunity of using DPTT (dipentamethylenethiuram tetrasulfide, Tetrone A), which the manufacturers (Du Pont) designate, alone among their thiuram accelerators, as “very active”, and which J. Willums referred to in a German journal as far back as 1944.
Stabilization of Neoprene. I. Protection of Latex Film against Discoloration by Light
Authors: Becker R. O. , Seligman K. L. 
Published: February 2011

Abstract
The tendency for light-colored neoprene vulcanizates made from latex to discolor when exposed to light was inhibited markedly by compounding with triglycerides of long chain fatty acids in combination with non-discoloring (see PDF for table) antioxidants. Effectiveness increased with the degree of unsaturation of the fatty acid up to two double bonds (safflower oil). Resistance to discolorations increased with increasing amounts of oil up to 15 parts. Both the ester linkage and the degree of unsaturation in vegetable oil appeared to influence stability in light. Organo tin compounds were found which functioned synergistically with safflower oil. Discoloration of safflower oil stabilized neoprene latex compounds was not affected appreciably by commonly used acceleration systems, nor by varying the curing conditions up to 120° C. Safflower oil reduced discoloration in all neoprene latex types. Neoprene latex compounds containing safflower oil discolored in sunlight no more than those of SBR or NBR latex. Safflower oil did not affect the discoloration of natural rubber, SBR or NBR latex compounds in sunlight. Other effects of safflower oil on the cured properties of neoprene latex films were reduced modulus and tensile strength but without change in elongation, enhanced heat and ozone resistance and lower brittle temperature.
Time and Temperature Dependence of the Ultimate Properties of an SBR Rubber at Constant Elongations
Authors: Smith Thor L. , Stedry Paul J. 
Published: February 2011

Abstract
A study was made previously of the temperature and strain rate dependence of the stress at break (tensile strength) and the ultimate elongation of an unfilled SBR rubber. In that study, stress-strain curves to the point of rupture were measured with an Instron tensile tester on ring type specimens at 14 temperatures between −67.8° and 93.3° C, and at 11 strain rates between 0.158×10−3 and 0.158 sec−1 at most temperatures. The tensile strength was found to increase with both increasing strain rate and decreasing temperature. At all temperatures above −34.4° C, the ultimate elongation was likewise found to increase with increasing strain rate and decreasing temperature but at lower temperatures the opposite dependence on rate was observed; at −34.4° C, the ultimate elongation passed through a maximum with increasing rate.
The Indentation and Puncture Properties of Rubber Vulcanizates
Authors: Yeh G. S. , Livingston D. I. 
Published: February 2011

Abstract
A detailed study has been made of the indentation and puncture properties of a number of rubber vulcanizates by a puncture method. It is shown that the characteristic relation between the force and depth of penetration, i.e., the two regions of linearity observed in a former study on a log-log plot, can be represented by two equations. The first region, in which the indenter penetrates into the rubber to a depth approximately equal to twice its diameter, can be generally described by Timoshenko's classical relation, FI=2.67 Erd In the second region, an empirically derived equation FII=1.34 Er0.5d1.5 holds. For a given rubber compound, Young's modulus calculated from the second equation is in satisfactory agreement with the modulus obtained from the first. The puncture strength and the puncture depth are both shown to be dependent upon the compounding variations and they provide useful information about the vulcanizates such as stiffness and cure. Valuable information relating to rubber abrasion and road wear may also result from studies of these two puncture properties.