bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneous Structure in Blends of Rubber Polymers
Authors: Walters M. H. , Keyte D. N. 
Published: February 2011

Abstract
The phase contrast microscope has been used to examine blends of rubber polymers. Mixing on a molecular scale was never observed, the more homogeneous blends consisting of a pair of interlocking “networks” with a mesh diameter of about a micron. Blending was less perfect when the polymers were of widely different viscosities, and in the worst cases consisted of lumps of the stiffer polymer embedded in the softer polymer. Blends prepared by drying mixed solutions were always exceedingly heterogeneous. Physical properties of gum stocks were not greatly affected by the size of this heterogeneity, although there was evidence from electron microscope surface replicas that rupture surfaces tend to follow the interface between the polymers. The distribution of filler, zinc oxide and protein in blends was studied using a variety of techniques. It was found that these materials (and probably many other compounding ingredients) are not always evenly distributed between the polymers, and this may be expected to affect adversely the physical properties.
Determination of Cis-1,4 and Trans-1,4 Contents of Polyisoprenes by High Resolution Nuclear Magnetic Resonance
Authors: Chen Hung Yu 
Published: February 2011

Abstract
A method is described for the determination of the cis-1,4 and trans-1,4 contents of 1,4-polyisoprene by nuclear magnetic resonance techniques. The error of the method is estimated to be less than 0.5%. The method can be extended to include the determination of the 1,2 and 3,4 contents of polyisoprenes. The error in these cases is estimated to be between 2 and 3%. The results obtained with three synthetic polyisoprenes are presented.
Creamed Latex Concentrate
Authors: Duckworth I. H. 
Published: February 2011

Abstract
Concentrated natural rubber latex accounts for nearly 10 per cent of the total Malayan rubber exports (120,000 tons in 1963). Over 90 per cent of this latex is concentrated by centrifuging. About one quarter of the remainder (2,800 tons in 1963), for which there is a steady demand particularly in America, is produced by the creaming process. In this paper a commercial process for preparation of creamed concentrate is described and the properties and uses of the product are discussed.
A Transition in Cis-1,4-Polybutadiene
Authors: Bianchi Umberto , Bianchi Estella 
Published: February 2011

Abstract
This paper deals with measurements of the internal pressure, Pi, carried out on cis-1,4-polybutadiene (97% cis structures). The values obtained for Pi, which represents a measure of molecular cohesive forces, show that a sharp drop in internal cohesion takes place at a temperature of about 57° C. This accounts for the behavior exhibited by this elastomer when processed on a roll mill at the same temperature.
Vulcanization with Maleimides
Authors: Tawney P. O. , Wenisch W. J. , van der Burg S. , Relyea D. I. 
Published: February 2011

Abstract
Mono- and bismaleimides were evaluated as curing agents to determine the effect of structure on crosslinking ability. Activity of N-phenylmaleimide derivatives (monomaleimides) as crosslinking agents is highly dependent upon the substituent on the phenyl group. Activity of bismaleimides is likewise affected by the nature of the moiety connecting the maleimide rings. Isomaleimides and itaconimides are less effective curatives. Initiators for maleimide cures include peroxides and sulfur accelerators of the thiazole type. Saturated and unsaturated hydrocarbon rubbers, except those containing a high percentage of isobutylene units, are vulcanized by a maleimide-initiator system. One of the attractive features of a maleimide curing system is that physical properties of the cured rubbers are independent of curing temperature. Further, these vulcanizates have the good aging characteristics typical of nonsulfur-cured vulcanizates. In contrast to sulfur vulcanization, the maleimide curing systems do not markedly affect the ability of elastomers to crystallize when stretched. Therefore, the T50 test cannot be used to assess the state of cure of maleimide-natural rubber vulcanizates. Maleimides containing an appropriate second functional group can be used as self-accelerating curing agents or as adhesives.
Crosslink Formation during Aging of Natural Rubber Vulcanizates
Authors: Maisey L. J. , Scanlan J. 
Published: February 2011

Abstract
The effect of antioxidant on the crosslinking reaction occurring during the oxidation of sulphur vulcanizates of natural rubber was investigated by using both continuous and intermittent stress relaxation measurements. Similarly, by means of continuous stress relaxation and equilibrium swelling measurements the cross-linking reaction in vacuum was followed. The presence of antioxidant or removal of air reduced considerably both continuous and intermittent relaxation and also the difference between them, which measures the crosslinking. The crosslink formation must therefore form part of the sequence of oxidative reactions.
Influence of Chemical Structures of Polyurethans on their Crystallization Capacities
Authors: Myuller B. E. , Apukhtina N. P. , Klebanskii A. L. 
Published: February 2011

Abstract
1. The relationship between chemical structure of urethan polymers and their crystallization capabilities has been studied. 2. It has been shown that synthetic polymers based on glycol esters; di-, tri-, and hexamethylene adipate urethans, and also polymers with side groups (methoxy-methyl- and propylethylene adipate urethans) are amorphous polymers. 3. It has been established that tetramethylene adipate urethan has the highest crystallization rate, followed by pentamethylene adepate urethan (2.2 per cent per hour), and then trimethylene- and ethylene adipate (0.11 and 0.06 per cent per hour, respectively). The half-times of crystallization for the latter three are 40, 1120, and 1060 minutes, respectively, and the degree of crystallization, 2.1, 1.7 and 1.0 per cent.
Laboratory Testing of Tread-Stock Abrasion Resistance at Constant Transmitted Power II. A New Laboratory Abrasion Instrument
Authors: Davison S. , Deisz M. A. , Meier D. J. , Reynolds R. J. , Cook R. D. 
Published: February 2011

Abstract
The first paper in this series described the results of laboratory measurements and road evaluation tests on a series of tread stocks over a wide range of severities, and indicated the various advantages and limitations involved in the laboratory and road measurements. It is the purpose of the present paper to describe in greater detail the abrasion instrument used in these studies. The laboratory measurement of abrasion resistance was reviewed by Buist in 1950. The paper describes 21 laboratory abraders. Developments in abrasion instruments and methods which have since appeared in the literature have been primarily concerned with modifications and refinements on these basic types. A novel type of instrument described by Newton, Grinter and Sears, uses stationary knife blades to scrape a rotating rubber disc. The research group at the Emeryville Shell Development laboratories investigating characterization of elastomeric properties some years ago decided that its requirements in laboratory abrasion testing could best be satisfied by an abrader of the Dunlop-Lambourn type because of its versatility in providing control of angular velocity, load, slip, energy transfer, and temperature. Also, in the Lambourn abrader, the motor-driven vulcanizate wheel driving a braked abrasive wheel resembles the action of a driven tire rolling on a pavement. A given section of the tire tread surface is subjected to stressing and abrasion only during the portion of the cycle when in direct contact with the abrading surface. Cooling and relaxation occur during the portion of the cycle when the section is not in contact with the surface. Viscoelastic and abrasion mechanisms can operate in the laboratory at frequency levels approximating those encountered in road tests.
Infrared and Nuclear Magnetic Resonance Studies of Microstructures of Polychloroprenes
Authors: Ferguson Raymond C. 
Published: February 2011

Abstract
High resolution infrared and nuclear magnetic resonance spectra confirm the structure of cis-polychloroprene prepared by a stereospecific route. Head-to-tail, head-to-head, and tail-to-tail sequence isomerism in both as- and trans-polychloroprenes has been discovered and measured quantitatively by high resolution NMR spectroscopy. The irregularity in the microstructure of neoprenes proves to be more extensive than was previously suspected.
Effect of Blending on Molecular Weight Distribution of Polymers
Authors: Haward R. N. , Wright B. , Williamson G. R. , Thackray G. 
Published: February 2011

Abstract
The effect of blending polymers of different molecular weight on the Q value (Q=Mw/Mn) of the blend has been considered. A mathematical expression is derived, and it shows by a simple application to monodisperse systems that blending over a wide molecular weight range is necessary to give high Q values. These principles are then applied to the ease of Ziegler and Phillips type high density polyethylenes having wide log-normal molecular weight distributions. In this way it is shown that only blending over a very wide melt index range, e.g., 1000/1, can be expected to have a measurable effect on Q. A series of physical measurements on blended and homogenized Ziegler polyethylenes shows no significant differences between blends and directly produced polymers.
Crosslinking Efficiencies of Cumyl Peroxide in Unsaturated Synthetic Rubbers
Authors: Loan L. D. 
Published: February 2011

Abstract
Crosslinking efficiencies of cumyl peroxide in SBR, cis-polybutadiene, acrylonitrile-butadiene rubber, and polychloroprene have been measured. For the first two rubbers approximately ten crosslinks are formed per molecule of peroxide decomposed, while for the acrylonitrile-butadiene rubber an efficiency close to unity is found. With polychloroprene approximately two molecules of peroxide are used for each crosslink formed. Analysis of the low molecular weight products of the reaction shows that ease of hydrogen abstraction by cumyloxy radicals decreases in the order given above.
Crosslinking in Low Unsaturation Rubbers
Authors: Crespi G. , Arcozzi A. 
Published: February 2011

Abstract
Vulcanization kinetics of low unsaturation rubbers (butyl rubber, ethylene propylene dicyclopentadiene terpolymer, and ethylene propylene cyclooctadiene terpolymer) have been studied by assuming that it involves a crosslinking reaction and a cleavage of sulfur bridges already formed. The crosslinking reaction can be explained by assuming a second order mechanism with respect to the concentration of the double bonds, whereas the cleavage reaction can be explained by assuming a first order mechanism with respect to the concentration of the sulfur crosslinks already formed. The overall vulcanization reaction has been followed through the variations of the moduli (at 200 per cent and at 300 per cent) and of the elongation at break. The crosslinking rate constant has been found to vary depending on the type of elastomer; decreasing in the order ethylene propylene cyclooctadiene terpolymer &gt; butyl rubber &gt; ethylene propylene dicyclopentadiene terpolymer.
Readily Curable Chlorinated Poly-α-Olefins and Ethylene-α-Olefin Copolymers
Authors: Makowski Henry S. , Cain William P. , Wei Peter E. 
Published: February 2011

Abstract
Chlorinated polyolefins have been prepared which are readily curable at 287° F at low chlorine contents. Their preparation depends primarily on using a chlorination solvent, generally an aromatic compound, which introduces both reactive chlorine and unsaturation. A process has been developed wherein ethylene propylene copolymers are first prepared and then chlorinated in the same aromatic solvent. Chlorinated copolymers have been cured with a variety of formulations which take advantage of the lability of chlorine atoms or of unsaturation, or of both. Properties of vulcanizates of chlorinated ethylene propylene copolymers are described.
Ethylene Propylene Dicyclopentadiene Terpolymerization
Authors: Sartori G. , Valvassori A. , Faina S. 
Published: February 2011

Abstract
Monomers (both monoolefinic and diolefinic) containing the bicyclo[2.2.1] heptene system copolymerize with ethylene and propylene by opening the double bond of the endo-methylenic system without rupture of the bicycloheptene system itself. Therefore, only diolefinic monomers produced unsaturated terpolymers. The rate of ethylene-propylene-dicyclopentadiene terpolymerization and the relative reactivity of ethylene and propylene are influenced by the concentration of dicyclopentadiene present in the liquid phase. The rate of vulcanization of ethylene-propylene-dicyclopentadiene terpolymers is slower than that of the other synthetic elastomers (butyl rubber, ethylene-propylene-cyclooctadiene-1,5 terpolymer).
Graft Copolymerization : On the Structure of the Graft Phase and the Mechanism of Grafting Polybutadiene Rubber
Authors: Gesner B. D. 
Published: February 2011

Abstract
Polybutadiene rubber undergoes grafting by direct interaction with initiator radicals rather than by transfer with growing radical chains. The insolubility of the grafted rubber is probably caused by crosslinking, which competes with grafting.
Fundamental Properties of High Structure Blacks
Authors: Voet Andries 
Published: February 2011

Abstract
The present study reports properties connected with physical and chemical surface reactivity of HAF and ISAF carbon blacks of a wide variation in structural characteristics. Methods used include determination of bound rubber and of crosslink in density in vulcanizates, adsorption of polar material from solution, adsorption and heat of adsorption of polar and nonpolar gases and vapors in the gas phase, retention of adsorbed vapors after temperature increase, electron micrography, chemical characteristics such as hydroquinone, quinone and oxygen contents and free radical activity. The results fail to show any direct connection between physical or chemical reactivity of the surface and structure. It appears that presumed manifestations of enhanced surface reactivity of high structure blacks either are nonexistent or can be explained from secondary effects not directly connected with reactivity of the particle surface. It could be shown that improved reinforcing characteristics of high structure carbon blacks are directly related to particle structure, either through particle fusion (persistent structure) or though van der Waals' type of attractive forces (transient structure).
Rotating Ring Crack Growth Test
Authors: Beatty J. R. , Juve A. E. 
Published: February 2011

Abstract
Groove cracking of tires is a continuing problem. Cracking takes place in two steps; initiation and growth. Initiation is inevitable in service from ozone cracking, cuts and nicks. This indicates that a study of groove cracking should concern itself with cut growth. A laboratory test has been developed to evaluate crack growth in vulcanizates under a variety of environmental conditions. The apparatus is compact, vibration free, and utilizes a ring-type specimen. Flexing is accomplished by running the specimen around two pulleys like a belt. Specimen preparation is simple and reproducible and a reasonable number may be tested simultaneously. Each specimen weighs approximately twenty grams and fifteen individually initiated cracks are measured on each. The large number of cracks measured makes the data amenable to statistical analysis. Strains and frequency of flexure were chosen to approximate those encountered in the service of a tire tread. Results obtained have been found to predict reasonably performance of tires on the road.
An Improved Flexing Machine. I. Description and Application to Studies of Cut Growth
Authors: Wu R. T. , Sapper D. I. 
Published: February 2011

Abstract
A new flex testing machine has been developed which yields accurate information on cut growth of vulcanizates. Its unique features are accurate temperature control of the test chamber (25°–200° ± 1° C), adjustable work input upon the test specimen by varying both the frequency of flexing (100–600 ± 1 rpm) and flex angle, and accomodation of a large number of test specimens (90–120). Furthermore, provision is made to test with a specific testing atmosphere, either oxidative or inert, depending on the required severity of conditions. Advantages of the test machine are: a) simple operation, once the test conditions are established: b) rapidity of testing, since a large number of specimens can be tested at the same time; and c) excellent reproducibility in preparing test specimens, varying and maintaining test conditions, and measuring cut growth. The maximum standard error for the test is about 12%. A further advantage is that compounds of varying degrees of hardness, for example, tire treads, shoe soles, and belt compounds, can be tested on the same machine by adjusting the severity of the test conditions. Effects of polymer and compounding variables on cut growth are discussed using data obtained with this new flexing machine.
Vulcameter Determination of Best Cure
Authors: Gehman S. D. , Maxey F. S. , Ogilby S. R. 
Published: February 2011

Abstract
Using a continuous cure curve to select a minimum number of stepped cures, it should be possible to vulcanize and test fewer sheets to determine best cure. This procedure is attractive for its potential of expediting the output of physical testing laboratories and especially for reducing the work load of stress-strain testing. Cure curves recorded with the Vulcameter approximated first-order reactions. Equations were derived to calculate the final force and rate constant from recorded force values without carrying the reaction to completion. A chart is suggested to assist in calculating the rate constant. Time for a given fractional rise in force depends only on the rate constant so that a chart for obtaining it is relatively simple. Experience and correlation with service performance in selecting best cures is emphasized. 95% rise times from Vulcameter curves were compared with conventionally selected best cures for a wide variety of compounds. Indications are that experience with the method might reduce the number of test-sheet cures to determine optimum stress-strain properties to one, two, or three depending upon the compound and the exactness required.
Liquid-Metal-Bath Stress-Strain Apparatus
Authors: Hall G. L. , Rigby J. D. , Liska J. W. 
Published: February 2011

Abstract
A simple, reliable apparatus for measuring stress-strain properties of vulcanizates at temperatures up to at least 800° F has been developed. The heating medium is a molten metal bath which provides uniform temperature distribution and rapid heat transfer while excluding atmospheric oxygen. Ultimate tensile strengths are in excellent agreement with those obtained in conventional air-oven tests. Stress relaxation tests show the effects of excluding atmospheric oxygen from the specimens. Somewhat higher ultimate elongations are obtained in the liquid-bath than in air-oven apparatus, for which possible reasons are suggested. Results on vulcanizates of heat-resistant polymers demonstrate that retention of physical properties at 500° F or 600° F cannot be safely predicted from data obtained at 400° F. The curing system, as well as the base polymer, is very important to high temperature resistance. In both Diene and butyl rubber compounds, for example, resin cures were superior in this respect to more conventional curing systems.
Diaphragm Vulcanized Adhesion Test Method
Authors: Taylor C. E. 
Published: February 2011

Abstract
By using a rubber diaphragm as pressure transmitting medium, a cured adhesion test method has been developed which permits controllable curing pressures to be employed. The quest for a new adhesion test method was occasioned by lack of confidence in existing test methods with respect to reproducibility and correlation between testing sites. The diaphragm cures “hi place” with a minimum of rubber movement as compared to excessive press pressures which induce flow. Controllable vulcanizing pressures and temperatures permit accurate adhesion evaluation of individual components in the laboratory under conditions which closely approximate manufacturing methods. A prime goal has been evaluation of true chemical bonding and elimination of all possible mechanical adhesion contributions inherent in most rubber-product fabrications. The diaphragm pressure adhesion test can be used by Quality Control, Development, or Research Department as an accurate tool to evaluate the chemical adhesion potential of rubber and common reinforcing components. Since adhesion values are machine recorded, all laboratory time and error in tabulations and calculations are eliminated. Basic principles of the technique permit evaluation of chemical bonding of rubber to yarns, fibers, and cords with equal effectiveness.
Rheological Properties of Polybutadienes Prepared by n-Butyllithium Initiation
Authors: Gruver J. T. , Kraus Gerard 
Published: February 2011

Abstract
The flow behavior of n-butyllithium-polymerized polybutadienes was investigated as a function of molecular weight, temperature, and shear rate. At low shear rates these polymers exhibit Newtonian flow up to molecular weights of several hundred thousand so that “zero shear” Newtonian viscosities can readily be determined without the risk of long extrapolation. Above 10,000 molecular weight the Newtonian viscosities obey the well-known 3.4 power dependence on weight-average molecular weight. The entanglement spacing molecular weight is estimated at 5600. The temperature dependence of viscosity is substantially independent of molecular weight and shear stress and can be represented analytically by functions proposed in the literature. The apparent activation energy for viscous flow is not constant, but decreases with rising temperature. The flow of the polymers becomes increasingly non-Newtonian with the product of shear rate, molecular weight and Newtonian viscosity. However, the departure from Newtonian behavior is apparently less than for any polymer system whose flow behavior has been described in the literature. The indications are, therefore, that sharp molecular weight distribution and freedom from long chain branching favor Newtonian flow and that the n-butyllithium initiated polybutadienes represent some of the most perfectly linear, narrow distribution polymers known.
Swelling of Filled Rubber Vulcanizates
Authors: Boonstra B. B. , Taylor G. L. 
Published: February 2011

Abstract
A detailed study has been made of the swelling of vulcanizates containing “adhering” and “non-adhering” fillers. The restriction of the swelling of vulcanizates containing “adhering” fillers compared to the swelling of the corresponding pure gum vulcanizate does not take place in solvents with solvent power below a critical value. The solvent power is indicated by the volume fraction of rubber (vr0) in the swollen pure gum vulcanizate. It appears that the critical value, vrc, is not very dependent on the type of black and slightly dependent on the crosslink density. Graphitized (2700° C) blacks differ from all other fillers in that they cause no restriction in swelling for any solvent, nor do they increase the swelling of the apparent matrix as is the case with non-adhering fillers. A semi-quantitative explanation for the observed phenomena is proposed.