bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Expansion, Free Volume, and Molecular Mobility in a Carbon Black-Filled Elastomer
Authors: Kraus Gerard , Gruver J. T. 
Published: February 2011

Abstract
The thermal expansion of a butadiene-styrene copolymer filled with carbon blacks differing tenfold in mean particle size (HAF and MT) was investigated. The glass transition was unaffected by MT and was raised only 0.2° C for every 10 parts per hundred by weight of polymer of HAF black added. The coefficient of expansion of the polymer component of the composite in the rubbery region was substantially unaffected by either carbon black, but decreased markedly with increasing black loading in the glassy state. These results suggest that free volume is not altered appreciably by the presence of the filler in the rubbery state, but expands with decreasing temperature below Tg. The latter effect is explained by dilatation due to stresses set up around filler particles, arising from differences in the expansion coefficients of filler and polymer, which are not relieved in the glassy state. The near invariability of Tg and of the rubbery coefficient of expansion with filler content indicate that segmental motion is little affected by adsorption of polymer segments on the carbon black surface. A conservative rough estimates indicates that restriction of segmental motion is confined to a 30 A layer around the particles in which Tg is elevated by only 10° C.
Overall Kinetics of Natural Rubber Vulcanization at High Temperatures I—review of Investigation Techniques, Methods and Previous Results of Kinetic Analysis
Authors: Redding R. B. , Smith D. A. 
Published: February 2011

Abstract
Analysis of previously published cure data illustrates the importance of correct determination of the ultimate level of network chain density in the absence of reversion, and the correction of each kinetic data point for “reversion contributions”. A graphical procedure is described for the determination of kinetic parameters which takes these precautions into account.
Chemorheological Treatment of Crosslinked EPDM
Authors: Murakami Kenkichi , Tamura Saburo 
Published: February 2011

Abstract
Stress relaxation mechanisms were investigated on three types of (EPDM) ethylene-propylene terpolymers in air at 109° C. These polymers differ only by the structure of the crosslinkage in which there is a carbon-carbon bond, a polysulfide linkage −Sx⁁− or a monosulfide linkage (—S—). All the stress relaxation of peroxide-cured EPDM polymer was not due to the oxygen-induced cleavage of the main chain but to a physical flow. In the case of sulfur-cured EPDM polymer, the relaxation curve is divided into three straight lines when the procedure X is used and log f(t)/f(0( is plotted linearly with time. It was concluded that this graph was in agreement with an interchange reaction of the polysulfide linkage by an oxidative cleavage of the monosulfide linkage. On the other hand, a TT-cured EPDM polymer gave a plot with a straight line. This stress relaxation could be explained by an oxidative cleavage of the monosulfide linkage.
The Thermal and Oxidative Stability of Chlorosulfonated Polyethylene Vulcanizates as Measured by Stress Relaxation
Authors: Haaf F. , Johnson P. R. 
Published: February 2011

Abstract
Stress relaxation measurements of chlorosulfonated polyethylene vulcanizates show that curing with m-phenylene-bis-maleimide gives thermally more stable crosslinks than the conventional metal oxide/sulfur accelerator system. The superior thermal stability of the bis-maleimide cure is based on the covalent nature of the crosslinks. In conventionally cured vulcanizates interchange reactions of the metal sulfonate and polysulfide crosslinks occur at elevated temperatures. The interchange reactions of the crosslinks cause a rapid stress decline at the beginning of the stress relaxation process. Over longer aging periods stress relaxation due to oxidative degradation becomes apparent in vulcanizates of both types. The activation energies of oxidative stress relaxations are very similar for the bis-maleimide and the conventional cure. The similarity of the activation energies indicates that oxidative degradation follows the same path. The site of the oxidative attack is established for bis-maleimide cured vulcanizates. Oxidative degradation is found to occur in the polymer chains rather than in the crosslinks. The effects of fillers and stabilizers are investigated and their mode of action is explained on the basis of the stress relaxation results.
Applications of Elastomers in Solid Rocket Powerplants
Authors: Sayles D. C. 
Published: February 2011

Abstract
Application of elastomers in the manufacture of solid-propelled powerplants is discussed. Thermal, ablative, and erosion-resistant properties of elastomeric composite materials are influenced by the composition of the elastomeric binder, the shape and composition of the reinforcing filler, filler loading, and the filler-to-elastomer ratio. The development of high performance motors, operating at higher chamber pressures, higher combustion flame temperatures, and for longer burning durations clearly point to the need for further advances in the insulative motor components for the liner, motor case, slivers, and nozzle if the requirements for improved future rocket designs are to be met.
Thermal Conductivity of Soft Vulcanized Natural Rubber, Selected Values
Authors: Carwile Lois C. K. , Hoge Harold J. 
Published: February 2011

Abstract
Literature on thermal conductivity of natural rubber has been critically evaluated. Best values of thermal conductivity as a function of temperature were selected, and are presented in both graphical and tabular form. An attempt was made to consult all work that could significantly affect the choice of best values. Relevant references in the papers themselves were followed up until a substantially “closed system” had been generated, as shown by the fact that no new references were being turned up.
Tables of Physical Constants of Rubbers
Authors: Wood Lawrence A. 
Published: February 2011

Abstract
Where a range is given, available observations differ. In most cases the differences are thought to be real, arising from differences in the rubber specimens, rather than from errors of observation. Where a single value is given, it is either because no other observations are available or because there seems to be no significant disagreement among values within the errors of observation. Where no value is given, no data have been found. Where dashes are shown, either the physical measurement is impossible or the constant in question is not adequately defined under the given conditions. Values are given, in most instances, in terms of the units used by the respective authors. Where the calorie has been used, it may be defined, with sufficient accuracy for the purposes of these tables, as the thermochemical calorie, which is equal to 4.1840 joules. The kilogram weight is taken as 980.665 dynes (0.00980665 newton). Values are given for 25° C and 1 bar (=106dyne cm2=106newton m−2), equivalent to 0.986923 (= 1/1.01325) normal atmosphere.
Adsorption of Macromolecules from Solution
Authors: Patat F. , Killmann E. , Schliebener C. 
Published: February 2011

Abstract
This publication arranges published papers on adsorption of polymers with special regard to experiment and theory. A summary is given of all investigated systems. Experimental methods are outlined and amounts adsorbed are discussed as a function of the system and experimental parameters (polymer, adsorbent, solvent, molecular weight, concentration, time, and temperature). Calculated and experimental amounts for saturation, number of contact points per molecule adsorbed, thickness of the adsorbed layer, adsorption isotherms, heats of adsorption, and effects of desorption are compared. Assumptions are made and discussed as to the structure of the adsorbed layer and the mechanism of polymer adsorption.
Aging and Stabilization of Raw and Cured Rubbers
Authors: Kuz'minskii A. S. 
Published: February 2011

Abstract
In recent years a number of monographs and survey articles have been published on individual problems of aging, from which we can compile an idea of the modern state of the problem. In this article we shall attempt to generalize certain new results, analysis of which may be of interest for further development of work on aging and stabilization of raw and cured rubbers. The substantial differences in the mechanisms and rates of aging of purified and technical raw and cured rubbers prepared from them have many times been noted in the literature The presence in technical raw rubbers of contaminants, introduced with the monomers, as well as residues of the catalysts, initiators, and regulators of polymerization exert a vital influence on the aging of rubbers and the behavior of inhibitors. It is also known that introduction of a large number of ingredients into raw rubbers (sulfur, vulcanization accelerators, carbon blacks, plasticizers) radically changes the character of the processes of aging of rubber mixtures. Free impurities and ingredients in most cases weaken, and sometimes suppress the action of antioxidants. For example, sulfur substantially reduces the effectiveness of secondary aromatic amine antioxidants. Other cases are also known when the action of antioxidants is intensified by certain ingredients. Thus, both negative and positive synergic effects may appear in rubber mixtures. Impurities contained in the monomers enter the structure of the polymer chains during polymerization, disturb their regularity, and frequently are the weak sites with which their thermal and thermooxidative decomposition begins. Hence the tendency to produce purer polymers from purified monomers, which will promote a substantial increase in their stability to aging, has now been outlined.
Growth Rate of Natural Rubber Crystallites
Authors: Hammett R. E. , Wingard R. E. , Land J. E. 
Published: February 2011

Abstract
The melting range and growth rate curves for natural rubber crystallites have been studied by the differential thermal analysis technique. The results obtained compare favorably with the growth rate curves obtained by dilatometric techniques. The use of differential thermal analysis revealed details of the crystallite melting which were not apparent when the dilatometer was used; however, no quantitative data on heat effects or the degree of crystallinity were calculated.
Low Temperature Expansion of Polysulfide Rubbers
Authors: Hunter B. A. , Kleinfeld M. J. 
Published: February 2011

Abstract
A novel method for producing a cellular cured rubber product at room temperature has been developed. Pourable liquid polysulfide polymers are treated with a conventional oxidizing curative and selected water-sensitive or oxidation-sensitive blowing agents. Standing at ambient temperature the viscous liquid mixture gradually “rises” and cures to form a finely porous cellular rubber product. Conventional curatives employed include oxidizing agents such as lead peroxide and cumene hydroperoxide. These convert terminal or pendant thiol groups in the polysulfide polymer chains to chain-connecting disulfide linkages. Water is a byproduct of the curing reaction. In the presence of water-sensitive blowing agents such as, (1) metal salts of azodicarboxylic acid or, (2) metal hydride compounds the water produced in the cure reacts to form copious amounts of nitrogen or of hydrogen. Alternatively, oxidation-sensitive blowing agents such as p, p′-oxybis-(benzene sulfonyl hydrazide) react directly with the oxidizing curative to form nitrogen gas. The blowing reactions are concurrent with cure and efficient and controllable expansion can be achieved. The unique process offers possible economies and special properties in applications of liquid polysulfide rubbers as potting compounds, joint sealants, solvent resistant forms, and cold casting compounds.
Self-Diffusion Coefficients and Tack of Some Rubbery Polymers
Authors: Skewis John D. 
Published: February 2011

Abstract
Self-diffusion coefficients for natural rubber, styrene butadiene rubber, ethylene propylene rubber and butyl rubber, are reported. Rates were determined by application of a layer of radioactively labeled polymer to the top of an unlabeled polymer base film and following the decay of radioactivity at the surface of the system, which decreased as a result of self-absorption. Macroscopically, diffusion is very slow, in fact difficult to measure, but on a microscopic scale it is rapid enough to cause considerable intermingling of polymer chains across an interface within a few seconds after two layers of polymeric material are brought into close contact. However, there were no major differences of self-diffusion coefficients between several types of polymers of comparable molecular weights. Therefore, the magnitudes of the coefficients suggest that diffusion may well be an important step for development of tacky adhesion, but the results also suggest that variations in observed tackiness among polymers cannot be simply ascribed to variations in diffusion rates.
Ethylene Propylene Copolymers. I. Monomer Reactivity Ratios
Authors: Bushick R. D. 
Published: February 2011

Abstract
Copolymerization of ethylene and propylene with diisobutylaluminum chloride and various vanadium-containing compounds gave a series of reactivity ratio values for ethyleno which decreased in the order: VO(O−n−Bu)3&gt;VOCl(OEt)2&gt;VOCl2OEt&gt;VO(OEt)3≃VOCl3. All of the catalyst systems were extremely sensitive to changes in the ethylene feed concentration. The reactivity ratio product suggested a random arrangement of monomer units with each catalyst system except VOC13.
Oxidation of Two Isomeric Elastomers: Poly(Propylene Oxide) and Poly(Vinyl Methyl Ether)
Authors: Norling Parry M. , Tobolsky Arthur V. 
Published: February 2011

Abstract
Rates of oxygen absorption and chain scission have been measured for benzoyl peroxide initiated oxidation of the two isomeric hydrocarbons, poly(propylene oxide) and poly (vinyl methyl ether) in the temperature range 80–100° C and in the solid phase. Oxygen absorption data show that poly(propylene oxide) forms hydroperoxides 3.5 times as fast as poly (vinyl methyl ether). This may be attributed to steric hindrance in the propagation reaction. Chain scission, measured by stress relaxation of crosslinked samples, demonstrates that each initiating radical produces one scission in the poly(propylene oxide). The process appears to be less efficient in the poly(vinyl methyl ether). Two possible reactions are proposed to explain this observation.
Dynamic Behavior of Rubber During Moderate Extensions
Authors: Schallamach A. , Sellen D. B. , Greensmith H. W. 
Published: February 2011

Abstract
The stresses and energy losses during simple extension cycles to about 130 per cent maximum elongation have been determined for unfilled vulcanizates of natural rubber and acrylontrile-butadiene rubber at various rates of extension and temperatures. The results obey the Ferry transform, with the exception of natural rubber at the larger strains near the high temperature end of the experimental range. The stress-strain curves at increasing strain cannot be described as the product of one strain function and one time function, but the two-term Mooney equation with time dependent coefficients represents the results over a large strain range. Maxima in the strain-increasing stress curves have been observed which are not connected with necking. A suggestion is made as to why the negative slopes in these curves need not necessarily lead to instability.
Thermal Expansion and Viscoelasticity of Rubber in Relation to Crosslinking and Molecular Packing
Authors: Mason P. 
Published: February 2011

Abstract
Effects of crosslinking on specific volume, thermal expansion coefficient, glass transition temperature (Tg) and viscoelasticity of rubber have been studied. Materials were prepared by heating purified natural rubber with varying amounts of cumyl peroxide. This procedure formed networks by intermolecular carbon-to-carbon bonding, and an approximately sixty-fold range of crosslink density was obtained. Crosslink density could be estimated with reasonable confidence up to about 1020/g. At this level the effects observed were, approximately, a one per cent decrease in specific volume; 23 per cent and 6 per cent decreases in the thermal expansion coefficients respectively below and above Tg; 5° C increase in Tg; and a displacement of the viscoelastic response by +5° C. These changes are accounted for in terms of the reduction in free volume consequent on crosslinking. There was also a qualitative change in behavior, the thermal expansion and viscoelastic transitional regions widening as crosslinking increased. The thermal expansion behavior is explained in terms of a linear increase in the variance of monomeric free volume with crosslinking up to 1020/g. At higher densities crosslinks are so close that their packing effects interact and the nature of the phenomenon changes.
Solution Polymerization Initiated with Alkyllithiums
Authors: Hsieh H. L. 
Published: February 2011

Abstract
To summarize, solution polymerization of dienes and styrene with alkyllithiums offers many advantages. Two new elastomers have been developed, based on this system. The random copolymer (Solprene 1204) exhibits advantages over SBR, particularly with regard to hysteresis properties, abrasion resistance, electrical properties and color. The block copolymer (Solprene 1205) is well suited to applications requiring outstanding extrusion characteristics, high hardness and modulus and excellent low temperature properties. The versatility of this polymerization system makes it possible to produce copolymers at will with different molecular weight, molecular weight distribution, microstructure, comonomer ratio, block length, and degree of branching. Each can be “tailor-made” for specific applications.
Use of C14 Tagged Cumyl Peroxide to Study Peroxide Vulcanization of Ethylene Propylene Copolymers
Authors: Ballini G. , Baldi L. , DiGiulio E. 
Published: February 2011

Abstract
Peroxides are used today as crosslinking agents for elastomers in general, and for saturated elastomers in particular. Among peroxides, cumyl peroxide merits special attention because of the small danger in handling since it decomposes appreciably only above 120–130° C. The mechanism of the vulcanization reaction has been considered very simple, leading to the formation of carbon-to-carbon bonds between polymer molecules. The path of the reaction can be followed if one can determine at every instant the amount of crosslinking and of peroxide decomposition products, or the quantity of residual peroxide. From the existing literature, it appears evident that the degree of crosslinking in natural rubber and the recovery of peroxide fragments justify the reactions proposed in the chemical scheme. However, in the case of ethylene propylene rubber these lead to the conclusion that the peroxide is only partly used. This different fate of cumyl peroxide, depending on whether the decomposition occurs in natural rubber or in an ethylene propylene copolymer, demonstrates that other reactions occur, which involve primary peroxide radicals or the secondary polymeric radicals, or both, in a manner different from the proposed scheme.
Photodegradation of Rubber
Authors: Morand Mme J. 
Published: February 2011

Abstract
If we consider a cumyl peroxide vulcanizate, prepared from deproteinized crepe and from which all vulcanization residues have been extracted after cure, the variation of the overall quantum yield for chain scissions ϕ, as a function of wavelength, deduced from relaxation measurements in the air at 30° C, presents several discontinuities. At the beginning of the solar ultraviolet, ϕ equals 5.4×10−2 near 330 m/µ, it then presents a minimum value of 3×10−2, at about 340 mµ, before reaching a very pointed maximum of 5.3×10−2 at 355 mµ. Afterwards, it vanishes at the start of the visible radiation. It should be noted that ϕ in the ultraviolet region is of the same order of magnitude as the corresponding value found in the case of polymethyl methacrylate (1.2×10−2). In investigating the different parts of the spectrum in which the dissociation of chemical bonds present in the isoprene unit is energetically possible two assumptions seem justified: one, the high value of ϕ near 330 mµ may be due to photolysis of the main chain C—C bonds adjacent to the double bond; this will be manifest directly as a random breaking in the polymer chain, and two, the maximum of ϕ at 355 mµ presumably results from the photochemical dissociation of the α-methylenic C—H bonds. The radicals so formed initiate an autoxidation process, producing in the termination step oxidative cleavage of the chain. On the other hand, sulfur vulcanizates prepared from deproteinized crepe, vulcanized with mercaptobenzothiazole and sulfur and extracted after cure, contains some residues of vulcanization, namely zinc oxide and zinc sulfide, which are not extracted by the solvents employed. In this case, a determination of the overall quantum yield for scissions will not be adequate for theoretical purposes. From the practical point of view, an investigation of the influence of free substances present in different vulcanizates shows, once again, that non-rubber constituents display a protective effect. Otherwise, the action of vulcanization residues clearly depends upon their nature. Mercaptobenzothiazole and sulfur considerably slow down degradation by solar ultraviolet; zinc oxide protects only against radiation below 370 mµ, but it presents a sensitizing effect in the near visible. As a result, the most harmful rays for the greatest part of pure gum vulcanizates are found, not at the beginning of the ultraviolet sunlight, but in the region of 400 mµ.
Aging Behavior of Butyl Vulcanizates
Authors: Edwards D. C. 
Published: February 2011

Abstract
Network degradation measurements on gum vulcanizates have shown a large improvement in air aging with increasing unsaturation for sulfur and quinoid cures, and have indicated that the distinction is due to a relative increase in the rate of oxidative crosslinking. Solubility data have provided evidence that crosslink scission occurs in sulfur cures, while quinoid or resin cures produce relatively stable crosslinks. Mechanical tests support this conclusion. Degradation rates of resin cures are not dependent upon polymer unsaturation, a fact which may be ascribed to antioxidant activity on the part of the resin. Water of itself causes no degradation at 177° C, nor does thermal degradation occur to a measurable extent at this temperature. Severe surface damage results when oxygen and water are simultaneously present. Finally, data have been shown for “practical” resin vulcanizates, illustrating the diversity of behavior of these systems with respect to air aging, water absorption and surface degradation.