bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanochemical Modification of Polybutadiene (SKB) by Maleic Anhydride
Authors: Baramboim N. K. , Popov V. I. 
Published: February 2011

Abstract
In recent years there have been a number of papers devoted to the special features of mechanochemical copolymerization of a number of natural and synthetic polymers with some special comonomer such as maleic anhydride. As a result of this mechanochemical copolymerization there are formed linear and branched products, containing isolated units of maleic anhydride. The anhydride rings of maleic anhydride are easily opened in the presence of moisture, and each unit of maleic anhydride in the copolymeric product forms the group (see PDF for diagram) Thus mechanochemical binding of the maleic anhydride makes it possible to “carboxylate” the polymers, modifying the properties of the original polymers according to the nature and amount of the carboxyl units added. In general mechanochemical modification by maleic anhydride leads to an increase in the stiffness, strength, adhesion to metals, hydrophilic nature and the possibility of carboxyl crosslinking. Thus the properties of modified natural rubber and SKS (butadiene-styrene rubber) approximate to those of carboxylated rubbers. This method of modification offers particular interest as a result of the simplicity and general availability of the mechanical apparatus (mills and internal mixers) required for the process.
Vulcanizate Structure, Relaxation, and Tensile Strength of Polyisoprenes
Authors: Hoffmann M. , Unbehend M. 
Published: February 2011

Abstract
The tensile strength of lightly-filled sulfur vulcanizates of 1,4-cis polyisoprene is lower the more the specimen has undergone deformation after removal of a definite stress. With equal tensile strength, this deformation multiplied by the modulus is proportional to the square of the filler concentration. Along with this deformation the volume of the elongated specimen increases through the formation of internal stress cracks. Rupture originates even at lower stresses in the neighborhood of the filler particles. It is affected by the size of the filler particles as well as by the chemical nature of the filler and by the structure of the network. Encouraged by these results we checked the network structure. We examined the stresses at high elongations, the photoelaetic homogeneity and the turbidities and viscosities of solutions of the degraded vulcanizates, and found small local variations in crosslink density and differences in the number of elastically-ineffective chain ends. The number of these chain ends and the local variations of crosslink density may increase greatly during vulcanization, and substantially reduce the tensile strength.
A Study of Sulfenamide Acceleration
Authors: Morita E. , Young E. J. 
Published: February 2011

Abstract
Sulfenamide—sulfur curing systems containing zinc oxide and stearic acid respond to both ionic and radical reaction conditions. Scorch delay and rate of the vulcanization are determined by the basicity and steric structure of the amine forming the amide, and by the accelerator-sulfur ratio. Sulfenamides derived from heterocyclic amines which form stable sulfides showed progressive improvement in scorch delay as the concentration of the sulfenamides was increased at constant sulfur level. In contrast to this group, the acceleration rates of sterically hindered sulfenamides were slow and their scorch delay decreased with increased accelerator concentration. The assumption that the initial step in sulfenamide acceleration is the dissociation of the sulfenamide into benzothiazolyl sulfenamide and amine radicals does not satisfy these experimental results. Consideration of the rate of sulfenamide-sulfur reaction and the stability of these intermediates has been suggested as an alternate explanation. Higher concentrations of accelerators in general resulted in vulcanizates with higher modulus and a larger number of effective sulfur crosslinks. About 1.5–2 atoms of sulfur per effective crosslink were found for vulcanizates where one mole of sulfenamide was used per atom of sulfur. It was also found that at this high concentration of sulfenamide a considerable fraction of the benzothiazolyl sulfenyl groups was initially bound to the rubber molecule and later released as extractable 2-mercaptobenzothiazole derivatives. Part of these groups which remained bound to rubber were reducible to form 2-mercaptobenzothiazole. Part of the true combined sulfur is released as ZnS in later stages of cure.
Intermolecular Forces and Chain Flexibilities. IV. Internal Pressures of Polyethylene Glycol in the Region of Its Melting Point
Authors: Allen G. , Sims D. 
Published: February 2011

Abstract
Experimental support for the suggestion (Part III), that the freezing-in of chain conformations is a major factor contributing to the low values of internal pressure found in polymeric glasses compared with the glass transition regions for corresponding rubbers, is advanced as a result of tests on a commercial sample of polyethylene glycol. The reliability of the results is considered.
The Cyclization of Natural Rubber
Authors: Lee D. F. , Scanlan J. , Watson W. F. 
Published: February 2011

Abstract
The resinification of natural rubber by acid catalysts has been investigated since the beginnings in 1937 of interest in the chemical reactivity of rubber. During the reaction there is a partial loss in unsaturation but no change in the empirical formula of the rubber, C5H8. No general agreement exists on the decrease in unsaturation, values from 40 to 90% of the original having been quoted. (see PDF for diagram) The reduction in the number of double bonds has been attributed to an intramolecular bond formation leading to formation of cyclic structures. D'Ianni, Naples, Marsh, and Zarney have suggested the generally favored structure I, formed by reaction between pairs of adjacent isoprene units of the rubber chain. Van Veersen on the other hand, has proposed the more highly condensed polycyclic structure II. with the cyclization proceeding along the chain to involve a number of adjacent isoprene groups.
Reaction of Chloral with 1,4-Polyisoprene
Authors: Pinazzi Christian , Pautrat Rene , Cheritat Roland 
Published: February 2011

Abstract
The cis-1,4-polyisoprenes are composed of 2-methyl-2-butene units, the double bonds of which must be favorable to the addition of strongly electrophylic reagents such as certain aldehydes. Chloral is of this type and its ionic reactions with various simple olefins has been described. We found it worth while to transpose these results to polyisoprenic macromolecules, either natural or synthetic. The ionic reactions generally create less modifications of the chain, such as fission or crosslinking, than would result from free radical reactions. Also, if the formation of free radicals is avoided, the possible fixation of chloral on the halogen carrying carbon (group —CCl2—CHO) becomes very unlikely. Pure anhydrous chloral is used as the reagent. A solution of 2% cis-1,4-polyisoprene (natural) in cyclohexane or decalin (free of peroxides) is heated under a nitrogen atmosphere with the reagent and in presence of a catalyst such as AlCl3 or BF3 at a concentration of 1–3% relative to the polyisoprene. The macromolecular product obtained is then subjected to a fractionation by the chloroform-methanol combination. After purification and desolvation of the main fraction an elemental analysis is made and the level of fixation n calculated based on the chlorine content. Table 1 relates some of the results obtained by using AlCl3 or BF3. In the absence of catalyst (Figure 1, A) the level of fixation is low: n=4 and therefore the nature of the reaction remains uncertain. In the presence of AlCl3 or of BF3, n increases rapidly in function of the temperature and of the relative molar concentration of the reagents, as shown by the curves B and C of Figure 1. The highest level of fixation obtained in these experiments is n=22. Figure 2 demonstrates this limit which is reached beyond the molar ratio of m=4, in the presence of AlCl3 (3%). Table 2 shows the particular action of AlCl3 which among all the catalysts tested proves to be as effective as BF3 without yielding any notable crosslinking of the macromolecular substance.
The Indenter Hysteresimeter for Testing Dynamic Properties
Authors: Tangorra G. 
Published: February 2011

Abstract
The results obtained up until now with the indenter hysteresimeter confirm that it is a fast and useful instrument for the technologist. A theoretical analysis, supported by experimental data, suggests a broadening of its field of application by the attainment of specific dynamic mechanical parameters of the tested materials. The instrument can be easily calibrated. Its adaptability permits its advantageous use where a remote control, as for instance inside a thermostat, is required, and allows its combination with electronic units, simply and easily available, for automatic operation when this is necessary.
Identification of Elastomers by Infrared Spectrophotometry
Authors: Fiorenza Aldo , Bonomi Giuseppe 
Published: February 2011

Abstract
The use of infrared spectrophotometry for the identification of elastomers is discussed, after having reviewed the general principles on which spectrophotometry is based and after having considered the principal types of atomic vibration. There follows a description of the principal methods of analysis for solution and pyrolysis, the presentation of the spectra obtained from 14 different elastomers and their mixtures, and finally the assignment of the fundamental bands in the spectra themselves.
Behavior of Sulfenamide Accelerators under Adverse Processing Conditions
Authors: Dibbo A. , Lloyd D. G. , Payne J. 
Published: February 2011

Abstract
The technological target of this work has been to show how the best use can be made of available sulfenamides under the most adverse processing conditions. The overall conclusions are given in Table 5. On balance, therefore, the best recommendation for an accelerator system for use under adverse conditions is one based on a blend of 2-(4-morpholinyl mercapto) benzthiazole plus a nitroso retarder where the accelerator is used at normal concentrations. Because of the linear relationship between additional processing safety and Curetard concentration, the amount of Curetard added can be easily adjusted to meet individual circumstances. The use of higher concentrations of 2-(4-morpholinyl mercapto) benzthiazole can be recommended for those cases where it is possible to reformulate the stock and where a faster cure is essential.
The Determination of Cure Time with the Curometer
Authors: Payne A. R. 
Published: February 2011

Abstract
The vulcanization of rubber is a complex process but its main feature is the introduction of crosslinks between the otherwise independent linear molecules of the raw rubber. It is logical, therefore, to relate cure measurement to this process. The Curometer measurement can be regarded as measuring the introduction of crosslinks but, as initially conceived, determination of the cure time by mere imspection of the trace, allowed too much play for personal judgment and ignored all but one piece of the data provided by the continuous trace. The possibility of measuring the introduction of crosslinks as the reaction proceeds has encouraged consideration of what is meant by adequate cure and has suggested the use of crosslinking cure with a number attached, say 90 to 95% as giving more precision to this concept than is possible in continuing to use the term “optimum”. Optimum can then be used when a specific property is required such as the time to reach the maximum tensile strength. It will be appreciated that scorch can in principle be similarly treated though, as the shape of the commencement of the log/linear plots show, the reaction is less simple, and cannot be regarded even approximately as of the first order. However, extrapolation of the straight line backwards in time does give a reproducible time where the line crosses the abscissa corresponding to zero crosslinking. The use of scorch values is very much a matter of experience and rather arbitrary relative grading of stocks. Obviously further work in association with factory processing would be necessary before the Curometer could serve completely the dual purpose of more exact scorch as well as cure determination. Meanwhile, cure determination is now more firmly based.
Crosslinking Chlorosulfonated Polyethylenes
Authors: Maynard J. T. , Johnson P. R. 
Published: February 2011

Abstract
The broadening practical use of chlorosulfonated polyethylene elastomers for applications where good resistance to heat, oil, light, oxygen, and ozone is needed has been accelerated by the development of several chemically distinct curing systems. Optimum use of these saturated elastomers requires a knowledge of the chemistry of these curing reactions and the effect of the resulting crosslink structures on vulcanizate properties. The high reactivity of the sulfonyl chloride crosslinking sites allows wide latitude in choice of curing chemistry, and crosslink type can be controlled to give a preponderance of ionic salt bonds or to give a mixture of covalent and ionic bonds. The role of water, alcohols, sulfur accelerators and free radical stabilizers in the various practical curing systems is discussed. The development of wholly organic curing systems for chlorosulfonated polyethylenes is reviewed. The properties of vulcanizates of chlorosulfonated polyethylenes are also significantly controlled by the base polyethylene, by chlorine content, and by chlorine distribution. The effects of these variables on vulcanizate properties is briefly reviewed.
The Relation of Transition Temperatures to Chemical Structure in High Polymers
Authors: Boyer Raymond F. 
Published: February 2011

Abstract
The primary purpose of this paper is to summarize some of the general relationships between chemical structure and transition temperatures for polymers. In addition to the two primary transitions, the melting point Tm, and the glass transition TG, other transitions occurring either below TG or between TG and Tm are discussed. A secondary purpose of this paper is to make a preliminary attempt at some rational nomenclature and classification scheme for polymer transitions, especially in the case of polymers having multiple transitions. This article is not intended to be a complete review of the literature on transitions in polymers. Our paper was inspired by a comprehensive lecture on multiple transitions presented by Dr. Karl Wolf in Midland, Michigan, during the summer of 1960. The substance of this lecture has recently been published. Willbourn has also been concerned with the classification of multiple transitions. A recent comprehensive report by Saito, Okano, Iwayanagi and Hideshima called “Molecular Motion in Solid State Polymers” also considers in elaborate detail many of these same problems.
Antioxidants and Antiozonants for General Purpose Elastomers
Authors: Ambelang J. C. , Kline R. H. , Lorenz O. M. , Parks C. R. , Wadelin Coe , Shelton J. Reid 
Published: February 2011

Abstract
The purpose of this article is to review the developments in antioxidants for rubber over the past 25 years since the publication of Davis and Blake's “Chemistry and Technology of Rubber”. The intent is to provide a guide for rational use and further development. Accordingly, the organization of the material is as follows: a) Outline of the mechanism of oxidative attack and antioxidant action. b) Critical review of methods of evaluation. c) Survey of antioxidants in the literature. Numerous reviews of antioxidants in one or more aspects have been published. These have been duplicated only so far as necessary to form a complete outline. Patent references are included only when the specification cites experimental data in support of the claims of antioxidant action. Usage divides rubber antioxidants into four categories: 1) Polymer stabilizers, which are added in the polymerization plant to repress the action of oxygen during drying and storage of the uncured rubber. 2) Antioxidants, which are added in compounding to prolong the useful life of the vulcanizate by retarding the oxidative changes that occur over a long period of service. 3) Flex-crack inhibitors, antioxidants which retard crack initiation or crack growth under conditions of cyclic deformation. 4) Antiozonants, substances which by chemical action (or by a combination of physical and chemical processes) delay the onset or growth of cracks resulting from ozone attack. (This definition is written to exclude waxes, which protect from ozone by forming a chemically nonreactive surface film.) There is a closer fundamental connection between polymer stabilizers and vulcanizate antioxidants than among other classes. The discussion of mechanisms of oxidation and antioxidant action will introduce the first two. Evaluation of the two classes of materials are operationally different and will be discussed separately. The present discussion is limited to “general purpose” elastomers of the present time; namely, NR, IR, SBR and BR.
Resins Used in Rubber
Authors: Powers Paul O. 
Published: February 2011

Abstract
Resinous materials have long been used to aid in the processing of rubber and to impart special properties to the vulcanized product. Resins have been described as various solid or semisolid organic substances. Originally, naturally occurring resins such as rosin were employed but with the advent of synthetic resins, many of these have been used with natural and synthetic rubber. In general the resins considered here are readily fusible and relatively low in molecular weight, the average value often being less than one thousand. However, thermosetting resins are also employed, usually being introduced into the rubber at a low stage of condensation. Resins are frequently added to assist in processing and often are considered as softeners although they are higher in molecular weight than most softeners and their efficiency as softeners is somewhat less. However, they do not soften the resulting vulcanizate and may even increase the hardness.
Effect of Carbon Black Structure Aggregate Size Distribution on Properties of Reinforced Rubber
Authors: Stacy C. J. , Johnson P. H. , Kraus G. 
Published: February 2011

Abstract
1. Broadening of the aggregate size distribution of carbon black leads to significant changes in optical properties, such as lower tinting strength and greater dissymmetry of light scattering. 2. Effects on vulcanizate properties are generally small, the most significant effect being lower hysteresis for blacks of broad distribution. 3. In moderately severe service, treadwear is unaffected by differences in breadth of aggregate size distribution sufficient to cause large changes in tinting strength. 4. Tinting strength is not a reliable criterion of treadwear quality unless carbon blacks of equal structure and breadth of ASD are compared. 5. The results of this study do not contradict earlier results on carbon black blends which show significant losses in treadwear resistance as a result of severely broadened nodule (“particle”) size and, incidentally, also aggregate size distributions.
Capillary Rheometry of Carbon-Black-Filled Butadiene—Acrylonitrile Copolymers
Authors: Nakajima N. , Collins E. A. 
Published: February 2011

Abstract
Capillary rheometry of carbon-black-filled butadiene—acrylonitrile copolymers at 125°C was performed over a wide shear rate range. The data were corrected for pressure loss in the barrel and at the capillary entrance, and for the non-Newtonian velocity profile (Rabinowitsch correction). No appreciable effect of pressure on viscosity was observed. The die swell values were very small, 1.1–1.4. This fact and the shape of the plots of shear stress vs. shear rate imply the presence of a particulate structure, which is probably built by carbon black surrounded with bound rubber. Unlike the behavior of raw amorphous elastomers, the steady-shear viscosity, the dynamic complex viscosity, and the viscosity calculated from tensile stress-strain behavior were significantly different from each other. That is, the capillary flow data indicated an alteration of the structure towards strain softening, and the tensile stress-strain behavior showed strain hardening, indicating retention of the structure up to the yield point. In the dynamic measurement, being conducted at very small strain, the structure is least disturbed. With unfilled elastomers essentially the same deformational mechanism was believed to be responsible in these three measurements, because the results can be expressed by a single master curve.
Identification of Elastomers in Tire Sections by Total Thermal Analysis. II. White Sidewall Compounds of EPDM and Blends
Authors: Sircar A. K. , Lamond T. G. 
Published: February 2011

Abstract
Total thermal analysis curves can identify all polymers in the blends of EPDM and other elastomers that are used for white side walls. DSC and DTG curves in nitrogen are most promising, while those in oxygen can be used as corroborative evidence. There is close correspondence between DSC and DTG peak temperatures for the elastomers that degrade by endothermic reaction (EPDM, CIIR). The difference in glass transition temperature of the many combinations is not big enough, but this also provides corroborative evidence. The method has been tried in analyzing white sidewalls from commercial tires and was found to give results in good agreement with infrared analysis in most cases.
Identification of Elastomers in Tire Sections by Total Thermal Analysis. IV. Innerliner
Authors: Sircar A. K. , Lamond T. G. 
Published: February 2011

Abstract
Butyl and halogenated butyls are clearly indicated by both DSC and DTG in nitrogen. Binary NR/CIIR blends are also easily characterized by combined DSC and DTG techniques. In ternary SBR/CIIR/NR blends, only CIIR and NR show up in DTG curves when SBR occurs as a minor component. Minor indication of SBR is obtained from DSC curves. Thermal methods fail to distinguish between BUR and CIIR. In elastomer blends, DTG peak temperatures may vary over a wide range depending on the type of the second elastomer. The NR peak temperature (365°C), for example, is lowered by blending with SBR, BR (345–350°C) or CR (325–348°C). These latter elastomers degrade by exothermic reaction. An increase in peak temperature was observed in association with the polymers which degrade by endothermic reaction (EPDM, 369–374°C; CIIR, 373–377°C). This may be caused by abstraction of heat by the second elastomer in the overall decomposition process. Another important conclusion drawn from the blends studies in this series is that thermal stability of the polymers is not materially affected by the presence of another polymer, thus giving rise to the weight-loss peaks at well-defined temperatures, characteristic of each polymer. Thermooxidative stability, however, is very much dependent on the type and composition of the polymers present. The effect of secondary reactions on the degradation curves is also considerably greater in the oxidizing atmosphere. Thermooxidative degradation is very much dependent on sample size, characteristic of a diffusion-controlled reaction. However, it provides auxiliary evidence for idsntification. Except for SBR/BR blends, which show a single Tg changing with composition, all other elastomer blends show transitions at the respective temperatures, indicating the inherent incompatibility of elastomers. However, a second or third transition is not observed when (a) the proportion of the polymer is too small and (b) Tg'a are too close to each other. Thus, obtaining a single glass transition temperature in a polymer blend is not always a proof of its compatibility, as has been claimed so often.