bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Modifying Resins on the Viscoelastic Properties of Styrenic Block Copolymers
Authors: Class J. B. 
Published: February 2011

Abstract
Viscoelastic data from dynamic measurements show that modifying resins produce complex changes in the properties of styrenic block copolymers. These property changes are generally consistent with compatibility concepts. Resins which are compatible with the midblock of these polymers, Resins AL-1, Al-2, and RE, will increase the tan δ peak temperature and reduce plateau modulus, as is observed with other elastomers. They will also reduce the temperature of entry into the terminal zone. This is believed to result from a reduction in the concentration of the endblock phase as well as dilution of the entanglement network at elevated temperatures. A resin which is incompatible with the midblock, Resin AR, has no effect on the tan δ peak temperature but does cause an increase in the plateau modulus of S-B-S and S-EB-S, as seen with typical high molecular weight rubbers. However, in the S-I-S polymers, Resin AR appears to be at least partially compatible at the low volume fractions examined. It does not increase the plateau modulus, but appears to reduce it slightly. The aromatic resin, Resin AR, has no effect on the G′, G″ crossover temperature of S-EB-S or S-I-S(20) at the concentration examined. However, it increases the temperature of the high diblock S-I-S(40) and lowers the temperature of S-B-S, suggesting at least partial compatibility at elevated temperatures. G′(tan δmin ) data are useful for estimating the compatibility of resins with styrenic block copolymers. Minimum and maximum values, calculated from rubber elasticity theory and filler effects, can serve as reference points for compatibility.
Effect of Brown Vulcanized Vegetable Oil on Ozone Resistance, Aging, and Flow Properties of Rubber Compounds
Authors: Botros Samir H. , El-Mohsen Fawzia Fabd , Meinecke Eberhard A. 
Published: February 2011

Abstract
The addition of accelerator to vegetable oils during the preparation of brown V.V.O. results in a decrease of the free sulfur and the acetone extract values of the obtained V.V.O. In addition, the reaction time necessary to achieve the gel state is reduced. NR vulcanizates containing brown V.V.O. based on soybean oil are superior in retention of their tensile strength and 100% modulus after aging to those containing V.V.O. based on boiled linseed oil and dehydrated castor oil. The heat resistance of NR vulcanizates which contain brown V.V.O. increases as the amounts of the free sulfur and the acetone extract in the V.V.O. decrease. Addition of small amounts of brown V.V.O. to NR and SBR compounds helps to maintain the tensile strength after aging. However, the addition of high concentrations of the V.V.O. reduces the aging properties. The addition of brown V.V.O. based on soybean oil and TMTD to NR compounds used for the manufacture of printer rolls and rubber hoses enhances the ozone resistance of the rubber vulcanizates. Furthermore, the addition of this type of V.V.O. to NR and SBR compounds is advantageous because of: (1) delay of the onset of melt fracture, (2) reduction of extrudate swell, (3) smoother extrudate surfaces, (4) dimensional stability of NR and SBR extrudates.
Characterization of Polymers by GPC-LALLS. III. Branching Structure of EPDM
Authors: Shiga S. , Sato Y. 
Published: February 2011

Abstract
Gamma ray-irradiated EPM's, as the model polymers of branched EPDM, are investigated using the relationship g′=gb, where g′ is the ratio of intrinsic viscosities of the branched and the linear molecules of equal molecular weight, [η]br/[η]l, and g, the ratio of the mean square radii of gyration of the two, 〈s2〉br/〈s2〉l. The molecular weight distributions measured by GPC-LALLS coincide well with theoretical curves of tetrafunctionally and statistically branched polymers obtained by the ideal degradation and crosslinking of the raw EPM, which was assumed to have the most probable molecular weight distribution, and the b-value is then determined to be 1.1. EPDM samples, polymerized with a soluble vanadium compound—alkyl aluminum halide type catalyst in a continuous well-stirred pilot-reactor, are characterizedas to the number of branching points per molecule for various molecular weights by using the b-value. The higher the molecular weight, the smaller the distance between neighboring crosslinking points. The reason is discussed. The unsaturated bond of dicyclopentadiene crosslinks more readily in the manufacturing process than 5-ethylidene-2-norbornene. The largest high molecular weight portion and the broadest molecular weight distribution are observed in the EPDM with the maximum dicyclopentadiene content.
Structural Characterization of Diene Block Copolymers by GPC and Ozonolysis—GPC Measurements
Authors: Tanaka Yasuyuki , Sato Hisaya , Adachi Junichi 
Published: February 2011

Abstract
The sequence distribution and block structure of styrene units in commercial styrene—butadiene and styrene-isoprene copolymers were analyzed by GPC measurements on the original copolymers and on ozonolysis products. Tapered-block structures are clearly differentiated by ozonolysis—GPC measurements. The content of large block styrene sequences in S-B-S type block copolymers was found to be 77 to 99% or more. S-B and S sequences in addition to the S-B-S sequence were observed for most of the triblock copolymers. A star-shaped S-B-S copolymer was distinguished from a linear copolymer by comparison of the molecular weight and chemical composition of the main and shoulder peaks by GPC and also by reference to the molecular weight of the block styrene sequence determined by ozonolysis—GPC measurements. A mixture of block copolymers was estimated for a high-styrene thermoplastic elastomer by GPC and ozonolysis—GPC measurements together with the measurement of chemical composition distribution. In a similar way the block structure was analyzed for S-I-S triblock copolymers.
The Kinetics of Crazing and Shear Yielding in Rubber-Toughened Plastics
Authors: Bucknall C. B. 
Published: February 2011

Abstract
The work presented and reviewed in this paper leads to the following conclusions: (a) The kinetics of creep in HIPS containing 0.2 µm diameter core-shell rubber particles are similar to those in more conventional HIPS containing larger multiple-inclusion particles. Both deform by multiple crazing. (b) Comparisons of mechanical properties should be made on the basis of equal rubber volume fractions ϕ rather than equal elastomer contents. (c) The kinetics of creep in rubber-toughened PMMA, also containing small core-shell particles, are quite different from those of HIPS. Deformation occurs by shear yielding accompanied by a small volume increase which is probably due to cavitation in the rubber particles. (d) The dependence of deformation rates upon applied stress and temperature is well described by the Eyring model for activated flow. (e) Analysis based on the Eyring slopes can be used to compare stress concentration factors γ in toughened plastics. In polymers that deform by shear yielding, absolute values of γ can be obtained by comparison of data from toughened and untoughened plastics. Difficulties remain in applying a similar approach to polymers that deform by multiple crazing. (f) The rate-determining step occurs in regions of maximum stress concentration in HIPS and appears to be identified with initiation of crazing. (g) The rate-determining step in toughened polymers that deform by shear yield is not associated with regions of maximum stress concentration.
A High-Performance Curing System for Halobutyl Elastomers
Authors: Edwards D. C. 
Published: February 2011

Abstract
1. In halobutyl elastomers, zinc oxide interacts synergistically with aromatic amine antioxidants such as APDA 86, DPPD, or DNPD, to produce fast, tight cures. 2. In the case of DNPD, compound storage stability appears to be satisfactory, and the resistance to scorch at processing temperatures is ample. 3. The cure behavior of these systems, particularly in bromobutyl, is exceptionally favorable: a rapid rise to a remarkably flat plateau. 4. The vulcanizates exhibit excellent thermal stability (compression set) and excellent ozone resistance. Measurable elastic properties are retained following 72 h air aging at 200°C.
Effect of Chain Length Distribution on the Tearing Energy of Silicone Elastomers
Authors: Yanyo L. C. , Kelley F. N. 
Published: February 2011

Abstract
The tearing energies of two endlinked PDMS networks, one a monomodal distribution of chain lengths and the other a bimodal mixture of very short and rather long chains, at the same average molecular weight between crosslinks, were compared. The bimodal network exhibited higher tearing strengths than the monomodal network under the same experimental conditions. At threshold conditions, the bimodal network tearing energy was 70% higher than the threshold strength of the monomodal network. A rederivation of the Lake and Thomas theory for the threshold tearing strength which includes a bimodal probability distribution of chain lengths is shown to predict the observed behavior. The strength increase of these bimodal networks is attributed to the presence of the long chains which increases the energy required for fracture while maintaining the same number of chains crossing the fracture plane as in the monomodal network of the same crosslink density, by including a large number of short chains.
A Postcrosslinking Accelerator System for Natural Rubber Based on Thiocarbamyl Sulfenamides
Authors: Layer Robert W. 
Published: February 2011

Abstract
Thick natural rubber articles require long cure times in order for the central portion of the article to reach optimum cure. Even at relatively low cure temperatures, using conventional cure systems, the outer portions of the article become overcured and lose physical properties due to reversion of the crosslinking process. The primary result is a decrease in the number of crosslinks and a loss of modulus. To lessen reversion, low sulfur and/or sulfur donor cure systems are used. These systems produce fewer of the thermally labile polysulfide crosslinks and more of the more thermally stable di and monosulfide crosslinks. But even these EV systems undergo reversion, albeit much more slowly than conventional cure systems, due to the slower cleavage of the disulfide crosslinks. Even better reversion resistance can be obtained with a sulfurless cure system, such as TMTD, which produces only very thermally stable monosulfide crosslinks. Unfortunately, fatigue properties become progressively poorer as one goes from polysulfide to disulfide to monosulfide crosslinks. Thus, in practice, a compromise between thermal stability and fatigue resistance is reached for each particular application. For many applications, such as treads of large off-the-road tires and aircraft tires, the heat generated during the demanding service conditions to which they are exposed is itself sufficient to cause reversion. This reversion is self-perpetuating since it lowers the modulus, which in turn speeds the heat buildup. The final result can be premature failure. Consequently, efforts continue to find ways to improve reversion resistance. Recently, the use of “postcrosslinking” additives, which form new crosslinks to replace those lost by reversion, have been reported. It is also known that certain accelerators show a postcrosslinking effect in NR, but only when high levels of sulfur are used. No accelerators have been reported to give postcrosslinking in a low-sulfur EV-cure system. We now find that an OTOS/OBTS (2:1) synergistic EV-cure system continues to generate new crosslinks on overcure. This can be utilized to improve physical properties or to slightly raise cure temperatures.
Molecular Weight of Rubber Contained in Guayule Bark, Wood, and Whole Stem
Authors: Estilai A. 
Published: February 2011

Abstract
Guayule bark not only produces most of the plant's rubber, its rubber Mw and Mn are also significantly higher than those of the wood. Further studies are expected to throw light on the mechanisms that control the production of different-sized polymers in different guayule tissues. This investigation shows that every guayule genotype may yield rubbers with three different molecular weights. Based on needs of the industry, whole guayule shrub, its bark, or its wood may be processed for rubber extraction. Since, depending on genotypes, 70 to 85% of the rubber is in the bark, and since bark rubber has the highest molecular weight, the possibility of processing only bark needs serious considerations as new cultivars with increased rubber yield become available. Based on the observed variation of molecular weight relative to the tissues used, the genotype, and the age of the plant, it is critical to develop standardized procedures for molecular-weight determination so that molecular-weight values, obtained by different laboratories, may be compared.
Solid State Carbon-13 NMR Studies of Vulcanized Elastomers. III, Accelerated Sulfur Vulcanization of Natural Rubber
Authors: Zaper A. M. , Koenig J. L. 
Published: February 2011

Abstract
In summary, the solid state C-13 NMR technique has proven to be a significant method for the detection of crosslinks and other structural modifications in accelerated sulfur-vulcanized NR systems. When the amount of accelerator is high in proportion to the amount of sulfur used, the network structure appears to be simpler with less crosslinking, less main chain structural modification, and fewer cyclic sulfide structures as observed in the C-13 NMR spectra. Polysulfidic crosslinks have been detected in addition to polysulfides terminated by accelerator residues. Cis-to-trans chain isomerization is also evident in these vulcanizates.
Flow Visualization Investigations of the Addition of Carbon Black and Oil to Elastomers in an Internal Mixer
Authors: Min Kyonsuku , White James L. 
Published: February 2011

Abstract
Internal mixing is one of the most important of processing operations, being used to incorporate fillers, oils, and other compounding ingredients into elastomers and plastics. The development of internal mixers has a long history largely described in the patent literature. Published experimental studies of flow in an internal mixer have been few, and primarily involved measurements of energy consumption, temperature histories, and characteristics of dumped mixes. It is only recently that efforts have been made to directly observe the motions of elastomers in an internal mixer. Freakley and Wan Idris and Asai et al. have made flow visualization studies of the motions of silicone rubber and aqueous carboxymethyl cellulose solutions at room temperature. Freakley and his coworkers and Toki et al. have followed motions of rubber in an internal mixer using mounted pressure transducers. More recently, the present authors have developed experimental techniques to visualize the flow of commercial elastomers and plastics at processing temperatures. The first study visualized flow in the plane perpendicular to the rotor axes and contrasted the behavior of various synthetic rubbers (polybutadiene, butadiene-styrene copolymer), natural rubber, and thermoplastics. In a later study, Min has made observations of flow in the plane parallel to the rotor axes for various rotor designs. The techniques developed in the first two papers were subsequently applied by Min to investigate the blending of an elastomer and a thermoplastic. It is the purpose of the present paper to present a detailed investigation of the addition of the primary compounding ingredients of carbon black and oil to an internal mixer. Much has been theorized and written about the incorporation of carbon black and oil. However, this has largely been conjecture based upon observations of torques, power consumption, temperature profiles, and the condition of dumped compounds. We present in this paper a unique flow visualization investigation of the flow phenomena and material distribution resulting from the addition of these ingredients to elastomers in an internal mixer. This paper continues our investigations of flow visualization during rubber processing.
The State of the Art of Rubber-Seal Technology
Authors: Nau B. S. 
Published: February 2011

Abstract
The understanding of the engineering fundamentals of rubber seals of all the various types has been developing gradually over the past two or three decades, but there is still much to understand, Tables V–VII summarize the state of the art. In the case of rubber-based gaskets, the field of high-temperature applications has scarcely been touched, although there are plans to initiate work in this area both in the U.S.A. at PVRC, and in the U.K., at BHRA. In the case of reciprocating rubber seals, a broad basis of theory and experiment has been developed, yet it still is not possible to design such a seal from first principles. Indeed, in a comparative series of experiments run recently on seals from a single batch, tested in different laboratories round the world to the same test procedure, under the aegis of an ISO working party, a very wide range of values was reported for leakage and friction. The explanation for this has still to be ascertained. In the case of rotary lip seals, theories and supporting evidence have been brought forward to support alternative hypotheses for lubrication and sealing mechanisms. None can be said to have become generally accepted, and it remains to crystallize a unified theory.
Structure and Mechanical Properties of Rubberlike Proteins in Animals
Authors: Gosline John M. 
Published: February 2011

Abstract
Polymer networks formed from protein molecules that adopt kinetically-free, random-coil conformations are found in many animals, where they play a number of important roles. The 5 rubberlike proteins isolated and studied to date indicate that animal rubbers, like their synthetic counterparts, contain random networks which are usually stabilized by covalent crosslinks. Long-range elasticity in rubberlike proteins is based on changes in the conformational entropy of random-coil molecules. Further, these protein networks show viscoelastic glass transitions similar to all other amorphous polymer networks. Future research on protein sequences should increase our understanding of how polypeptide chains can function as random-coil molecules, and studies into the mechanical state of elastin in arterial tissues may provide important clues about the mechanisms of some forms of human disease.
Chromatographic Analysis of Elastomeric Polyurethanes
Authors: Vimalasiri P. A. D. T. , Burford R. P. , Haken J. K. 
Published: February 2011

Abstract
Both alkali and acid fusion reactions can be used to cleave polyurethane polymers successfully. Fusion reaction rates are much faster than conventional aqueous alkali or acid fusion methods. Separation of fragments could be carried out using the liquid-liquid extraction procedures described. After quantitative and qualitative analysis of fragments using GC, SEC, and HPLC, chemical structure of the polymer can be established. Although the work described uses only elastomeric polyurethanes for the development of the analytical schemes, these schemes can be used to analyze other types of polyurethanes such as “Spandex” fibers, adhesive coating films, and plastics. The procedures described have also been used for the analysis of polyamide resins which are condensation products.
The Development of a Real-Time Control System for Internal Mixers
Authors: Freakley P. K. , Matthews B. R. 
Published: February 2011

Abstract
The Batch Condition Control System has been shown to give good batch-to-batch repeatability of both viscous flow behavior and crosslinking characteristics for both fixed speed and variable speed mixing. It has also been shown to be capable of adjusting the mixing treatment to compensate for substantial changes in the properties of NR. Stress-relaxation results showed unexpectedly broad distributions. Lack of a comprehensive history of stress-relaxation results from the Negretti TMS biconical rotor rheometer makes it difficult to reach firm conclusions. The results for highly filled and thixotropic compounds are not comparable with those from other stress relaxometers such as the Monsanto SRPT and the BFGoodrich DSR, due to the small initial strain imposed on the sample by these instruments. Two possible causes of the broad distributions can be identified: 1) The sensitivity of the stress relaxation measurement. 2) The mode of flow in the chamber of a Farrel Banbury Mixer.
J-Integral and Crack Opening Displacement as Crack Initiation Criteria in Natural Rubber in Pure Shear and Tensile Specimens
Authors: Lee R. F. , Donovan J. A. 
Published: February 2011

Abstract
For PS and SEN specimens: 1) Jδ (one half Jθ) can be determined from one specimen and is independent of crack size and specimen geometry. 2) J and T at initiation differed. 3) J at initiation increased with carbon black content, but the critical crack-tip radius did not.
Transient Electromechanical Behavior of Carbon-Black-Filled Rubber
Authors: Parris Donald R. , Burton Larry C. , Siswanto Muliawati G. 
Published: February 2011

Abstract
This work has shown the sensitivity and uniqueness of conductivity and dielectric constant transient response to compressional stress for natural rubber filled with specific types of carbon black. The strong correlation between conductivity and capacitance (both steady-state magnitudes and transients) is attributed to the polymer itself. A qualitative model for these effects is based on changes of conductive and resistive microelements due to fracture of the carbon black matrix. Transient electrical measurements of this type should be applicable to carbon-black- (or metal-) filled dielectrics over a large range of resistivity.
HPLC Procedure for the Determination of Free Sulfur in Natural Rubber Formulations
Authors: King R. J. , Mondimore D. M. 
Published: February 2011

Abstract
The conventional ASTM method for the determination of the percent of free sulfur is a time-consuming method. Additionally, because of the many steps involved and the necessity of subjective endpoint determination, the data would vary from operator to operator. This lack of precision is detrimental in a quality-control type environment, and a retest can literally hold up production. The HPLC method described is almost totally automated. Sample preparation involves no exposure to such toxic chemicals as formaldehyde, cadmium salts, or glacial acetic acid. Quantitation is a computer operation negating operator to operator variations which can cause up to 20% relative standard deviation.
Structure and Properties of a New Synthetic Tire Rubber: High-Trans SBR
Authors: Fabris H. J. , Hargis I. G. , Livigni R. A. , Aggarwal S. L. 
Published: February 2011

Abstract
Solution SBR's are presently widely used as tire rubbers, and can be tailor-made for specific property advantages. Although still at an early stage of evaluation, high-trans-1,4 SBR's (HTSBR's) must certainly be considered serious contenders for at least partial replacement of NR to increase tire durability. Their excellent green and tack strengths, excellent oxidative stability and, in blends with NR, good fatigue life constitute valuable assets for radial tire sidewall constructions, while their outstanding abrasion resistance combined with acceptably low hysteresis properties will make them highly useful as components in tire tread compounds.