bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology and Crystallization Behavior of Lightly Crosslinked Natural Rubber in Blend
Authors: Kawazura Tetsuji , Kawahara Seiichi , Isono Yoshinobu 
Published: February 2011

Abstract
Isothermal crystallization of natural rubber (NR) dispersed in styrene-butadiene rubber (SBR) was made at −25 °C to investigate effects of both gel fraction of the rubber and morphology of the blend on the crystallization. NR, thus used, was lightly crosslinked model compound (model-NR), which was cured with dicumylperoxide at 160 °C after mastication. The model-NR was mechanically mixed with a large amount of SBR to form droplets of the rubber, a size of which was dependent upon both gel content and crosslink density of the gel fraction. The crystallization of the model-NR in the droplets was quite slow, corresponding to the level reported in the previous work. A rate of crystallization and Avrami exponent were dependent upon the size of the droplets, but not on the gel content and the crosslink density of the model-NR. The suppression in the crystallization was attributed to the homogeneous nucleation occurring in the droplets. This finding was proved, using rubbers obtained from two clones of Hevea brasiliensis, i.e. RRIM600 and RRIM2025, respectively.
Axial Loading of Annular Bonded Rubber Blocks
Authors: Horton J. M. , Tupholme G. E. , Gover M. J. C. 
Published: February 2011

Abstract
Closed-form expressions are derived using a superposition approach for the axial deflection and stress distribution of axially loaded rubber blocks of annular cross-section, whose ends are bonded to rigid plates. These satisfy exactly the governing equations and conditions based upon the classical theory of elasticity. Readily calculable relationships are derived for the corresponding apparent Young's modulus, Ea, and the modified modulus, Ea′, and their numerical values are compared with the available experimental data. Elementary expressions for evaluating Ea and Ea′ approximately are deduced from these, in forms which are closely analogous to those given previously for blocks of circular and long, thin rectangular cross-sections. The profiles of the deformed lateral surfaces of the block are discussed and it is confirmed that the assumption of parabolic lateral profiles is not valid generally.
Some Benchmark Problems for FEA from Torsional Behavior of Rubber
Authors: Yeoh O. H. 
Published: February 2011

Abstract
Two commercial finite element analysis (FEA) programs, ANSYS and FLEXPAC, were compared in benchmark problems involving torsion of cylindrical rubber specimens. The effects of using different element types, material models, bulk moduli and specimen geometry were studied and compared with Rivlin's theoretical solution. This was done as an exercise to help build confidence in the analyst's ability to use these codes properly and in the reliability of the results. Some problems with certain element types were identified. With suitable choices, FEA results consistent with the theoretical solution were obtained.
Effect of Non-Rubber Components on Storage Hardening and Gel Formation of Natural Rubber During Accelerated Storage under Various Conditions
Authors: Yunyongwattanakorn Jintana , Tanaka Yasuyuki , Kawahara Seiichi , Klinklai Warunee , Sakdapipanich Jitladda 
Published: February 2011

Abstract
The phenomenon of storage hardening in solid natural rubber (NR) is presumed to occur by means of reactions between some non-rubber components and abnormal groups in rubber molecule. The main non-rubber constituents in NR are composed of proteins and lipids. The storage hardening behavior of NR purified by enzymatic deproteinization and transesterification was analyzed under high and low humidity conditions using phosphorus pentoxide (P2O5) and sodium hydroxide (NaOH). The NR obtained from centrifuged fresh natural rubber latex (CFNR) and deproteinized NR latex (DPNR) showed significant increase in the hardening plasticity index (PH) value during storage; while that of the transesterified NR (TENR) and transesterified DPNR (DPTE-NR) was almost constant during storage. After keeping samples under high humidity conditions, the fresh natural rubber (FNR), CFNR and DPNR showed constant PH value, while that of the TENR and DPTE-NR decreased during storage. The FNR, CFNR and DPNR showed a clear increase in the gel fraction after the occurrence of storage hardening reaction. The gel fraction showed molecular weight between crosslinks (Mc) of about 104. Glass transition temperature (Tg) of gel fraction was higher than that observed in the case of sol fraction. The formation of crosslinking and branching during accelerated storage was presumed to be due to the chemical bonding between the active functional groups in the long-chain fatty acid of phospholipids at the terminating end of rubber molecules under low humidity conditions.
A Phenomenological Model for the Effect of R Ratio on Fatigue of Strain Crystallizing Rubbers
Authors: Mars W. V. , Fatemi A. 
Published: February 2011

Abstract
The fatigue crack growth rate in strain crystallizing rubbers depends not only on the maximum energy release rate experienced during a loading cycle, but also on the minimum, or equivalently, the R ratio. The R ratio is the quotient of the minimum and maximum energy release rates occurring during a loading cycle. This article proposes a simple phenomenological model for the effect of R ratio on fatigue crack growth rate in strain crystallizing rubbers. The model may also be applied for Wohler-style (S-N style) fatigue life curves. The model is compared against experimental results reported by Lindley, by Cadwell, Merrill, Sloman, and Yost, and by the authors. The ability of the model to represent the experimental data is found to be reasonable. The model provides a simple approach to estimating fatigue performance when limited data are available, and may find application in the analysis of load histories from actual service. Such variable amplitude load histories typically contain cycles covering a wide range of R ratios.
Study of Vulcanization and Degradation Chemistry in Natural Rubber by Solid-State 13C NMR and Physical Property Measurements
Authors: Mori Makio 
Published: February 2011

Abstract
Sulfur-vulcanization and heat aging of natural rubber was investigated by solid-state 13C NMR along with the measurements of physical properties. 13C NMR detects all of the sulfurization occurring in natural rubber network including inter- and intra-molecular crosslink and pendant linkages, while physical measurements such as modulus at small strain and equilibrium swelling postulate detect only an amount of physically effective crosslinks. By comparing those two approaches, the efficiency of sulfur bonding in contributing to physical strength can be determined. It was found that the efficiency became lower for the samples with higher curing temperature, longer cure time, and also at higher sulfur level.
It was assumed by 13C chemical shift analysis that all of the sulfurized isoprene units were cis-to-trans isomerized during the vulcanization and heat aging, even for ineffective sulfurization. Furthermore, it was found that the configuration of those units remained in the trans-1,4 form after the desulfurization at either reversion or heat aging. The nature of the trans-1,4 form in the isoprene series was assumed to be more rigid compared to that of a cis-1,4 form. This resulted in an introduction of chain scission at large deformation for the rubber with higher trans-1,4 content. Comparing several samples with different cure temperatures, cure degrees, and sulfur levels, it was postulated that such cis-to-trans isomerization is a main factor governing a degradation chemistry at elevated cure temperature, overcuring and heat aging.
The Influence of Block Copolymers on Silica-Filled Polyisoprene
Authors: Gurovich Daniel , Macosko Christopher W. , Tirrell Matthew 
Published: February 2011

Abstract
In the present work, precipitated silica, liquid polyisoprene, and PDMS-PI block copolymer are mixed in different formulations. The dynamic rheological properties of the resulting uncured materials are measured and are used to assess filler-filler networking. In small-amplitude tests, composites containing PDMS-PI exhibit lower values of the dynamic storage modulus (G′) than those observed in control samples prepared without copolymer additives. The control samples remain stable during several months of storage, while samples containing low molecular weight block copolymers show evidence of an aging process. The rheological manifestations of this aging include a pronounced decrease in small-amplitude G′ with time, accompanied by weakening amplitude-dependence of both G′ and G″. These suggest a progressive reduction of filler-filler interactions, presumably caused by the development of a block copolymer layer at the filler-polymer interface. The make-up of that interfacial region is investigated by means of magic-angle spinning solid-state 1H NMR experiments carried out on bound polymer fractions that survive extraction in a good solvent. Spin-spin relaxation times and the intensities of the relaxation modes associated with these characteristic times are used to identify the proportion of both PDMS and polyisoprene among the segments strongly immobilized by close contact with the silica surface and among the rest of the bound (un-extracted) interfacial layer. The changes in mechanical properties are correlated not with the overall composition of the bound polymer fraction, but with the increase in PDMS segments in close contact with the filler surface.
Microstructure-Properties Correlation in Silica-Reinforced Dynamically Vulcanized EPDM/PP Thermoplastic Elastomers
Authors: Bazgir S. , Katbab A. A. , Nazockdast H. 
Published: February 2011

Abstract
Silica filled dynamically crosslinked thermoplastic elastomers (TPEs) based on ethylene-propylene diene monomer (EPDM) and polypropylene (PP) with 60/40 (w/w) ratio have been prepared to investigate the effects of silica upon the interfacial interaction between the two phases as well as microstructure/properties relationship. Blends loaded with 10 to 30 phr silica (premixed with EPDM) showed more reduction in the mixing torque after the maximum torque peak with lower and constant viscosity and hence better melt processability compared with similar but unfilled sample. This is showed to be due to the formation of tight agglomerate structure as a result of lower EPDM/PP viscosity ratio for the unfilled sample. Increasing the concentration of silica to 50 phr leads to the sharp increase in the mixing torque during dynamic vulcanization with high final melt viscosity. SEM examination showed that silica remains shelled by EPDM, but at high concentration, migration of silica occurs from EPDM onto PP during melt mixing leading to the enhancement of the adhesion between the PP shelled rubber particles which gives rise to the formation of strong networks. Rheometric mechanical spectrometer (RMS) showed less fractionation of the relaxation times for the PP segments in the silica filled samples with lower damping behavior (Tan. δmax). Addition of functionalized PP promotes the interfacial interaction between the matrix and the silica filled crosslinked rubber networks. More rubbery behavior and increased extensibility observed for the blends incorporated by 10 to 30 phr silica, while the 50 phr filled sample is characterized by higher elastic modulus. Crystallization of the highly silica filled blends is promoted as the migrated silica acts as nucleating agent for PP.
Increasing the Force Torque Transducer Sensitivity of an RPA 2000 by a Factor 5 – 10 via Advanced Data Acquisition
Authors: Hilliou L. , van Dusschoten D. , Wilhelm M. , Burhin H. , Rodger E. R. 
Published: February 2011

Abstract
The sensitivity of an RPA 2000 under oscillatory shear conditions can be extended by a factor of 5 – 10 into the low torque region. This increases the overall dynamic range of this robust industrial instrument to 5 decades. This dynamic range is close to that of rheometers used in academic environments. This increased sensitivity is not a result of mechanical improvement, but the result of an advanced, but straight forward, data treatment of the raw torque transducer output in the time domain using “on the fly” averaging. This method is possible through the availability of modern ADC-cards. The underlying ideas of this averaging procedure, together with experimental verification on polyethylene are described in detail.
The Influence of Filler-Filler and Filler-Polymer Interactions on the Physical Properties of Silica-Filled Liquid Polyisoprene
Authors: Gurovich Daniel , Macosko Christopher W. , Tirrell Matthew 
Published: February 2011

Abstract
The dynamic rheological properties of uncured dispersions of silica in liquid polyisoprene are measured and are used to assess filler-filler networking. An increase in the dynamic storage modulus (G′) is observed with decreasing polyisoprene molecular weight and with increasing silica concentration. For sufficiently high silica concentrations, a low-frequency plateau is observed in the frequency-dependence of G′, indicating the presence of a volume-spanning filler-filler network. The height of this plateau scales with silica volume fraction to the power of 5.2, consistent with several models describing the elasticity of polymer materials filled with fractal clusters of colloidal particles. Treatment of the silica filler surface with a silane coupling agent leads to a decrease in the modulus of the resulting dispersion. The properties of the filler-polymer interface were further investigated by bound polymer measurements and by solid-state 1H NMR experiments on the bound polymer fractions. The mobility of the polymer segments immediately adjacent to the filler surface is significantly reduced, as evidenced by faster spin-spin relaxation. The bound polymer per m2 of silica surface increases with increasing silica concentration, primarily due to entrapment of loosely bound polymer chains in the filler-filler network.
Effect of Zinc Oxide on the Reaction of TESPT Silane Coupling Agent with Silica and Rubber
Authors: Reuvekamp L. A. E. M. , Debnath S. C. , Ten Brinke J. W. , Van Swaaij P. J. , Noordermeer J. W. M. 
Published: February 2011

Abstract
The addition of a coupling agent to silica-rubber compounds enhances filler-matrix compatibility. The coupling agent under study, TESPT, can also act as a sulfur donor, which leads to premature scorch in the mixer. The effect of the presence of zinc oxide in the internal mixer at higher dump temperatures was demonstrated by dynamic mechanical testing. A lower tendency to scorch was seen when zinc oxide was omitted during the internal mixing stage and added only later together with the curing additives on a two roll mill. Zinc oxide primarily interferes with the reaction between the coupling agent and the silica surface, as shown by the reaction rate constants obtained with rheological experiments. Further confirmation was obtained by HPLC-experiments: the reaction rate constants of TESPT with silica for the samples with zinc oxide present, were lower at higher temperatures in comparison with samples without zinc oxide. XPS data confirmed that zinc oxide can indeed react with the silica surface. When zinc oxide is included in the internal mixer stage, shorter scorch times are obtained for curing when compared to compounds where no zinc oxide is included during mixing and only added later on. These shorter scorch times are the result of filler flocculation of the silica during the curing stage.
Spectroscopic Studies on Reaction between Squalene and Vulcanizing Agents in the Presence and Absence of Zinc-2-Mercaptopyridine-N-Oxide
Authors: Pierre C. C. , Datta R. N. 
Published: February 2011

Abstract
Model compound vulcanization in combination with reversed-phase high-performance liquid chromatography and NMR spectroscopy was used to elucidate the reactions of accelerator, sulfur, zinc stearate and zinc-2-mercaptopyridine-N-oxide (ZPNO) in natural rubber vulcanization. Studies of different curing ingredient formulations in squalene have been done to determine the influence of each component during the vulcanization. It was found that 2-mercaptopyridine-N-oxide bridged adducts (R-Sx-Pyr(O)) were formed when squalene was heated in the presence of sulfur, curing ingredients and 2,2′-dithiobis(pyridine-N-oxide) (PyrO-S2-PyrO). Possible interactions of R-Sx-Pyr(O) with carbon black have been proposed.
Study on the Compressible Hyperelastic Constitutive Model of Tire Rubber Compounds under Moderate Finite Deformation
Authors: Xia Yong , Li W. , Xia Yuanming 
Published: February 2011

Abstract
In this paper, the Automated Grid Method is applied to the uniaxial tension test of tire rubber compounds under moderate finite deformation. The test precision is improved, and the strains along axial and transversal directions are obtained simultaneously, so that compressibility of the rubber compounds can be studied directly. Based on the Eight-Chain model, and inspired with the physical idea of Van der Waals model, we put forward a modified Eight-Chain model, and generalize it into compressibility. All of the model parameters can be determined with the data obtained merely in uniaxial tension test with the Automated Grid Method, without the dependence on the data of any other test form. Fitted results show that modified Eight-Chain model can better characterize the hyperelastic mechanical behavior of incompressible and compressible rubber compounds under moderate finite deformation.
Neural Network Based Constitutive Model for Rubber Material
Authors: Shen Y. , Chandrashekhara K. , Breig W. F. , Oliver L. R. 
Published: February 2011

Abstract
Rubber hyperelasticity is characterized by a strain energy function. The strain energy functions fall primarily into two categories: one based on statistical thermodynamics, the other based on the phenomenological approach of treating the material as a continuum. This work is focused on the phenomenological approach. To determine the constants in the strain energy function by this method, curve fitting of rubber test data is required. A review of the available strain energy functions based on the phenomenological approach shows that it requires much effort to obtain a curve fitting with good accuracy. To overcome this problem, a novel method of defining rubber strain energy function by Feedforward Backpropagation Neural Network is presented. The calculation of strain energy and its derivatives by neural network is explained in detail. The preparation of the neural network training data from rubber test data is described. Curve fitting results are given to show the effectiveness and accuracy of the neural network approach. A material model based on the neural network approach is implemented and applied to the simulation of V-ribbed belt tracking using the commercial finite element code ABAQUS.
Stress-Induced Crystallization Properties of Natural and Synthetic CIS-Polyisoprene
Authors: Trabelsi S. , Albouy P.-A. , Rault J. 
Published: February 2011

Abstract
Stress-induced crystallization and melting of natural and synthetic cis-isoprene are compared by simultaneous Wide Angles X-ray Scattering (WAXS) and mechanical measurements.
Natural (NR) and synthetic polyisoprene (SR) rubbers have the same composition and sulfur crosslink density. At fixed elongation and during cyclic deformation, the properties X of the semi crystalline phase are determined as function of draw ratio λ; X being crystallites dimensions and orientation, half-time of crystallization, melting temperature, crystallinity and crystalline zone dimensions around a crack tip. It is shown that all the curves X(λ) of both types of rubber at room temperature can be superposed by a simple translation δλ along the draw ratio axis. This translation factor of the order of 0.5 to 1 does not depend on the property X. These effects are explained by the decrease of the melting and crystallization temperatures due to the presence of chain defects in synthetic rubber.
Strain-Induced Molecular Orientation and Crystallization in Natural and Synthetic Rubbers under Uniaxial Deformation by In-situ Synchrotron X-ray Study
Authors: Toki Shigeyuki , Sics Igors , Ran Shaofeng , Liu Lizhi , Hsiao Benjamin S. , Murakami Syozo , Tosaka Masatoshi , Kohjiya Shinzo , Poompradub Sirilux , Ikeda Yuko , Tsou Andy H. 
Published: February 2011

Abstract
In-situ synchrotron wide-angle X-ray diffraction (WAXD) studies and simultaneous measurements of stress and strain during uniaxial stretching of various vulcanized rubbers were carried out (at room temperature and 0°C) to reveal the strain-induced molecular orientation and crystallization relationships. Rubbers evaluated included natural rubber (NR), synthetic poly-isoprene rubber (IR), poly-cis-1,4-butadiene rubber (BR) and butyl rubber (IIR). Some universal features were observed in these systems: (i) At high strains (&gt; 5.0), the majority of the chains (up to 50 ≈ 75%) in natural and synthetic rubbers remained in the un-oriented amorphous state with only a small amount of crystalline fraction formed (10–20%). The rest of the chains were in the oriented amorphous state. (ii) During deformation, the oriented amorphous chains acted as precursors to strain-induced crystallization. A network of micro-fibrillar crystallites is formed within the closely populated vulcanization points, leading to the enhancement of mechanical properties at high strains. Different rubbers exhibited different behaviors during strain-induced crystallization. For example, poly-isoprenes (NR and IR vulcanized with sulfur and peroxide) showed strain-induced crystallization at a low strain of 2.5, resulting in larger crystalline but smaller oriented amorphous fractions. In contrast, BR and IIR crystallized at a higher strain of 4.0 lead to higher molecular orientation, higher oriented amorphous, but smaller crystalline fractions. The relationship between the molecular orientation and crystallization in strained rubber depends on the intrinsic crystallizability of the chains and the topology of the crosslinked network.
Specialty Elastomer Modifiers with Isotactic Propylene Crystallinity for Polypropylene Modification
Authors: Dharmarajan N. , Williams M. G. , Datta S. 
Published: February 2011

Abstract
Specialty elastomers possessing isotactic propylene crystallinity are a novel class of polyolefins made possible by advances in metallocene polymerization. These polymers contain a propylene rich component endowed with isotactic crystallinity, and the balance of the composition is ethylene with other alpha olefins. Typical molecular weight of these elastomers is greater than 100,000. These polymers, when used as modifiers for toughening polypropylene (PP) homopolymers demonstrate improved impact strength to stiffness balance, enhanced low temperature toughness and improved impact to flow balance over conventional ethylene alpha-olefin modifiers.
Morphological features of the blends were determined using Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The detailed morphological characterization indicates that the isotactic propylene crystallinity species of the elastomers function by localizing themselves at the interface of the polypropylene matrix and the ethylene-alpha olefin component of the modifier. We believe that such a tailored localization is effective because of the simultaneous co-crystallization of the isotactic propylene crystallinity elastomers with the isotactic PP matrix, and the thermodynamic compatibility of the propylene crystallinity species with the other elastomeric components of the modifier.