bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Technique to Quantitatively Characterize Crosslink Density in IR and Brominated Poly(Isobutylene-CO-Paramethyl Styrene) Blends
Authors: Wang Yu F. , Wang Hsien C. 
Published: February 2011

Abstract
The physical properties and application performance of rubber blends are highly dependent on the curing behavior of blend components, morphology, and network structure. Crosslink density or molecular weight between crosslinks characterizes the network structure. It is desirable to develop correlations between product attributes, such as flex, ozone resistance, and permeability with crosslink density of the individual phase in the blend. This will aid developing high performance rubber blends via curative systems, elastomer components and concentration, bromine composition distribution, and processing condition optimization. One major road block is to quantitatively and unambiguously measure the individual phase crosslink density in the blend.
A method has been developed and verified with solvent freezing point depression technique. The method can quantitatively determine the individual phase crosslink density in polyisoprene (IR)/Brominated Poly-(isobutylene-co-paramethyl styrene) (BIMS) blends. The method is based on the principle that the molecular weight between crosslinks does not change in different solvents. This is coupled with mass balance equations to determine rubber volume fraction of each phase in the swollen blends. The crosslink density of each phase is then calculated by the Flory-Rehner equation.
The method can evaluate the effect of curative distribution, processing conditions, and curative systems on GPR/BIMS blend performance. IR and BIMS blends were cured with zinc oxide and sulfur in this study. It was found that the IR and BIMS phase crosslink density reaches a plateau when the amount of the curing agent is greater or equal to 1.25 phr. The IR phase has a greater crosslinking density than the BIMS phase in the blends. These are valuable information to optimize the curative systems and enhance product attributes.
Strain Induced Crystallization in Stereoregular Poly[Methyl(3,3,3-Trifluoropropyl) Siloxane] Networks
Authors: Kuo Chung-Mien , Battjes Kevin P. , Miller Robert L. , Saam John C. 
Published: February 2011

Abstract
Elastomeric networks based on poly[methyl(3,3,3-trifluoropropyl)siloxane] having a minimum level of stereo-regularity crystallize and self-reinforce when stretched at room temperature. The effect is especially pronounced in networks where the cross-links are uniformly spaced. The polymers are made by modification of a recently described anionic ring opening copolymerization of prescribed mixtures of cis- and trans-1,3,5-trimethyl-1,3,5-tris (3′, 3′, 3′-trifluoropropyl) cyclotrisiloxane. This provides polymers enriched in stereoregularity with nearly monodisperse molecular weight distributions and reactive groups at the chain ends. The end-linked networks show markedly enhanced mechanical properties due to self-reinforcement from strain-induced crystallization. In addition to applied strain, self-reinforcement depends on temperature and the amount of stereoregularity introduced to the polymer. Strained specimens having high levels of stereoregularity and pre-existing crystallinity exhibit plastic flow and, upon release of the applied strain, stress-hardening. Wide angle X-ray scattering (WAXS) on strained specimens establishes that, although the relative degree of crystallinity varies, the basic crystal structure is unaltered by cross-linking, amount of strain, or amount of stereoregularity. Unit cell parameters from WAXS indicate a monoclinic crystal and suggest a 4*11 chain conformation.
Wet Skid Properties of Filled Rubbers and the Rubber—Glass Transition
Authors: Heinrich Gert , Dumler Herbert B. 
Published: February 2011

Abstract
The physical relationships between wet skid resistance of filled rubber compounds and the dynamics of the corresponding bulk polymers in the rubber—glass transition zone are investigated. We show how wet grip data and their ratings correlate with dynamic glass transition temperatures in the N(uclear)M(agnetic)R(esonance) time scale for the spin—spin relaxation time T2 that characterizes the relaxation of transverse magnetization. The corresponding frequency is independent of the Larmor frequency of the NMR experiment. The amount of the frequency is located in the frequency region of the glass—rubber transition and depends on the microstructure of the used polymers. Finally, some molecular aspects of the network dynamics in the transition zone are considered. Damping curves of different rubbers can be predicted using the bead-spring-model of Kloczkowski, Mark and Frisch (KMF), considered as an extented Rouse-model of an entanglement network with tree-like connectivity and a certain number of subchains.
Novel Ether Modifiers for Anionic Polymerization of Isoprene
Authors: Hsu W. L. , Halasa A. F. , Wetli T. T. 
Published: February 2011

Abstract
Because of demands on tire skid resistance, polyisoprenes with high 3,4-content are of particular interest to the tire industry due to their inherently better grip properties. Polar bidentate modifiers such as TMEDA and DIGLYME are widely used in organo-lithium catalyzed isoprene polymerization to increase 3,4-content. However, neither modifier is very effective for making high Tg polyisoprenes due to the fact that a retarded polymerization rate was found for the former while a large excess of modifier was needed for the latter. The new modifiers based on the alkyl ethers of tetrahydrofurfuryl alcohol with alkyl groups from one to six carbon atoms were found to be very effective for producing polyisoprenes with high 3,4-contents. Kinetic studies on both TMEDA and the new ether modified isoprene polymerizations were conducted. The results and the plausible explanation of the rate difference for both systems are discussed.
Longitudinal Cracking in a Carbon Black Filled Natural Rubber Vulcanizate during Chemical Stress Relaxation
Authors: Hamed G. R. , Zhao J. 
Published: February 2011

Abstract
Thin specimens of a black-filled, natural rubber vulcanizate have been held in uniaxial tension at 72°C and 200% elongation in a forced air oven. After substantial oxidative attack (inferred from stress relaxation), small edge cracks formed. Initially, these cracks grew perpendicular to the loading direction, but, upon reaching about 0.1 mm in depth, longitudinal crack growth commenced and fracture progressed by a kind of 0°-peel process with “splitting-off” of successive strands of rubber. This phenomenon is attributed to anisotropy in strength caused both by straining and by oxidative attack.
Simulation of Surface Flaw Propagation Associated with the Mechanical Fatigue Wear of Elastomers
Authors: Razzaghi-Kashani Mehdi , Padovan Joseph 
Published: February 2011

Abstract
Employing a moving template finite element strategy, a simulation scheme was developed to model the surface flaw propagation process associated with the mechanical fatigue wear of elastomer surfaces. Special emphasis was given to (1) experimentally establish the potential existence of precursor flaws on the surface of unworn and worn molded rubber products; (2) determine the trajectory of propagation of surface cracks and their effects on particle removal; (3) establish the influence of size and orientation of initial flaws; and (4) determine the effects of the various phases of the asperity-flaw passing process. These various issues are described in a series of parametric sensitivity studies.
A Simple w′(λ) Function for The Valanis-Landel Form of Stored Energy Function
Authors: Landel Robert F. 
Published: February 2011

Abstract
In the Valanis-Landel formulation of the stored energy function W, stresses depend on the function w′(λ)(=dw/dλ). This function exhibits strong curvature, making it difficult to represent analytically with good accuracy. It is found for both SBR and NR that the function λw′(λ) is not only far less curved, it is essentially linear in λ for the range of about 0.4 &lt; λ &lt; 2.0. The long range of simple proportionality to strain invites examination of molecular theories of rubberlike elasticity. Above the linear range the response can be approximated by kλn. These simplifications should make it easier to convert w′(λ) to the W1 and W2 functions employed in finite element analysis.
Nitrosamine Formation in Rubber: I. Influence of Mixing History
Authors: Willoughby Bryan G. , Scott Keith W. 
Published: February 2011

Abstract
Despite much published research, the influence of fillers on nitrosamine formation in accelerated sulphur vulcanization is not well understood. This paper studies N-nitrosodimethylamine (NDMA) formation in a range of TMTD-accelerated, black-filled rubber formulations encompassing EPDM, SBR, NR, and NBR rubbers. Two levels of TMTD and carbon black were variables in this study as was the type of carbon black used (N330 and N550). The use of statistical experimental design has shown how reliable data on nitrosamine formation in vulcanizates can be obtained by paying strict attention to process history, and has revealed, for the SBR, NR, and NBR rubbers studied, a correlation between the temperatures reached on mixing with the level of nitrosamine generated on subsequent vulcanization. For these rubbers the effect of this process history outweighs that of any ingredient variable. While allowing new insights to be gained on nitrosamine formation in rubber, these findings allow the development of a self-consistent mechanism for nitrosation processes where the reactions in diene rubbers mirror those in air.
Power Transmission Belt Performance and Failure
Authors: Dalgarno Kenneth W. 
Published: February 2011

Abstract
The performance and life of power transmission belts has been investigated by a number of research groups over the past decade or so. Most studies have been directed at a particular problem with or application of belting technology, with synchronous and V-ribbed belts generating the most research activity. This paper reviews contemporary studies on the performance and failure of synchronous and V-ribbed belts to develop an overall picture of how the understanding of belt materials, mechanics, and failure mechanisms has progressed in recent years. The studies which have moved the understanding of belt behavior furthest forward have been those which sought, through an improved understanding of how a belt acts as a composite, to integrate the various strands of materials, mechanics and failure analysis knowledge available to give a clear and coherent picture of how a belt works and fails, although none of the studies seen so far can claim to have accomplished this completely.
Hysteresis Contributions in Carbon Black-Filled Rubbers Containing Conventional and Tin End-Modified Polymers
Authors: Ulmer J. D. , Hergenrother W. L. , Lawson D. F. 
Published: February 2011

Abstract
A methodology was developed to estimate individual hysteresis contributions arising from the carbon black network, polymer free chain ends and effective polymer network chains. The estimation technique was applied to rubber compounds formulated with linear polymers of varied number-average molecular weight (Mn) from each of three different series. The three series corresponded to polymers modified with either zero, one or two tin ends per chain. In general, the relative hysteresis contributions depend on strain amplitude and Mn. For unmodified polymers at strain amplitudes from 0.02 to 0.07, and with Mn in the neighborhood of 150 kg/mole, each of the three hysteresis sources contributes about one-third of the total tan δ. With respect to shear loss modulus (G″), the carbon black network contributes about 60%, while free chain ends and the effective polymer network chains each contribute about 20%. At the same Mn and strain conditions, tin end-modified polymers reduce G″ and tan δ by as much as 60%, in comparison to their unmodified counterparts. The benefit is achieved primarily through reductions of up to 85% in the carbon black network contribution to hysteresis. Since the hysteresis contribution from free chain ends is not reduced so much by tin end-modification, the greatest potential for additional tan δ benefits lies in further free chain end reduction. In addition, it was found that tin end-modification has no measurable effect on the hysteresis contribution from effective network chains. Further, the analysis showed that an ineffective polymer network chain provides approximately ten times the hysteresis and one-half the elasticity of an effective network chain, at the test conditions of the current study. In general, the quantitative results, and some qualitative results as well, will change with compound composition and with temperature. Consequently, the development of a methodology, one that allows estimation of individual hysteresis contributions from different sources, is a major component of the present study.
Distributive Mixing in Variable Intermeshing Clearance Mixers: Simulation and Experiments
Authors: Yao Chih-Hsiang , Manas-Zloczower Ica , Regalia Roberto , Pomini Luigi 
Published: February 2011

Abstract
Distributive mixing performance in Variable Intermeshing Clearance (VIC) mixers was studied numerically and verified experimentally. A fluid dynamics analysis package (FIDAP), based on the finite element method, was employed to simulate the flow patterns in the original lab size mixer (VIC1) and a new design with an enlarged mixing chamber (VIC2). Distributive mixing was studied numerically by means of tracking the evolution of particles originally gathered as clusters. The results of numerical simulations were checked against experimental data to verify the validity of the model. Both the numerical simulations and the experimental data indicate that the VIC2 design, with an enlarged mixing chamber, shows consistently better distributive mixing results in comparison with the traditional VIC1. In both mixers, increasing the inter-rotor clearance improves distributive mixing. However, enlarging the gap size too much in the bridge region, in the VIC2 mixer, becomes detrimental for mixing. The initial position of the clusters is also important in distributive mixing. Clusters located in the middle of the bridge region are better distributed than the ones located on the sides, particularly at small inter-rotor clearances.
Novel Thermoplastic Elastomers: Star-Blocks Consisting of Eight Poly(Styrene-b-Isobutylene) Arms Radiating from a Calix[8]Arene Core
Authors: Jacob Sunny , Majoros Istvan , Kennedy Joseph P. 
Published: February 2011

Abstract
The first synthesis by a core-first strategy of novel star-block copolymers consisting of eight poly(styrene-b-isobutylene) (PSt-b-PIB) arms radiating from a calix[8]arene core is described. An octafunctional methoxy calix[8]arene derivative was used to initiate the living polymerization of isobutylene (IB) to desirable molecular weights, then styrene (St) was added to obtain the sought star-blocks. Molecular weights and PSt contents were determined by triple-detector GPC and 1H NMR spectroscopy. Star-block thermoplastic elastomers containing 17–32% PSt showed high strength and elongation (up to ∼26 MPa and &gt;500%) and relatively low melt viscosities. The mechanical and rheological properties of these star-blocks are superior to those of linear PSt-b-PIB-b-PSt triblocks. PIB-based thermoplastic elastomers may be of use as novel biomaterials.
Experimental Investigations and Numerical Modeling of Incompressible Elastomers during Non-Homogeneous Deformations
Authors: Przybylo P. A. , Arruda E. M. 
Published: February 2011

Abstract
Three hyperelastic constitutive models, the Arruda and Boyce model, the Yeoh model, and the Ogden model, are used to simulate the response of vinyl elastomers in large, non-homogeneous deformation states. A single uniaxial compression test is used to characterize the elastomers to obtain model constants. Drucker stability is enforced by restriction of the coefficients for the Yeoh and Ogden models to produce physically feasible uniaxial results. The ability of the models to predict the global force versus deformation responses and deformed shapes for large deformation shear, tensile deformation of a long bar with fixed grips, and inflation of a thin disk is examined. The experiments used in this study are designed to provide known boundary conditions to eliminate ambiguity in the modeling. We demonstrate for the first time that each of these models may be sufficiently characterized via a simple, homogeneous compression test to allow accurate predictions of large, non-homogeneous deformations involving rotations of the principal stretch directions.
Novel Method for Preparation of Low Molecular Weight Natural Rubber Latex
Authors: Tangpakdee Jitladda , Mizokoshi Megumi , Endo Akiko , Tanaka Yasuyuki 
Published: February 2011

Abstract
Low molecular-weight natural rubber (LNR) and LNR latex was prepared by oxidative degradation of de-proteinized natural rubber (DPNR) latex in the presence of 1 phr of K2S2O8 and 15 phr of propanal, by shaking at 60 °C. The intrinsic viscosity [η] of DPNR with only K2S2O8 decreased from 7.2 to 5.5 after 2 h and then increased to 6.5 after 3 h. By the addition of propanal, DPNR showed a significant decrease in the [η] value of LNR with [η] of about 0.5 after 5 h of the reaction, while rubber from high-ammonia natural rubber (HANR) latex showed a slight decrease in [η]. The concentration of latex and the kind of surfactant used for stabilizing the latex had little effect on the degradation rate of DPNR latex. The LNR latex is stable as the latex form and the dried rubber coagulated from latex is transparent and colorless. The LNR was a telechelic polymer containing aldehyde and ketone groups at both terminals as determined by NMR and molecular weight analyses.
Injection Molding of a Natural Rubber Compound: Simulation and Experimental Studies
Authors: Isayev A. I. , Wan M. 
Published: February 2011

Abstract
Experimental and theoretical results are obtained for the cavity filling of a natural rubber (NR) compound. The shear rate and temperature dependent viscosity function based on the modified Cross model is fitted to experimentally measured viscosity data. A nonisothermal vulcanization model with nonisothermal induction time is fitted to the nonisothermal curing kinetic data obtained by differential scanning calorimetry (DSC). These data are utilized in the simulation of the cavity filling and curing stages. The pressure traces at various locations in the mold during cavity filling are obtained at different inlet and mold temperatures. The predicted results for the pressure traces are in good agreement with those measured in the cavity, but significantly lower than those measured in the nozzle. Evolution of the state of cure in the post-filling stage is predicted and compared with experimental data measured in moldings obtained at various cycle times. The measured states of cure in the moldings are in good agreement with their predicted values. Based on earlier flow studies of SBR compounds, it is shown that the discrepancy between the experimental and predicted pressure traces in the nozzle for the NR compound is due to high local pressure drops arising during the flow in juncture regions of the delivery system and the possibility of flow-induced crystallization. The importance of taking into account the entry pressure losses, viscoelastic effects and flow-induced crystallization in the injection molding process is strongly emphasized. The complexity of the issues related to this subject is discussed.
Tensile Behavior of an SBR Vulcanizate Containing a Single Rubber Particle
Authors: Gibala D. , Hamed G. R. , Zhao J. 
Published: February 2011

Abstract
The effect of a single, embedded rubber particle on the tensile strength of an SBR vulcanizate has been determined. For a given size, a particle taken from an ambient grind resulted in higher strength compared to a sample containing a particle prepared by hand-cutting with a blade. In the former case, fracture initiated within the particle while, in the latter, fracture was interfacial between the particle and matrix. For both types of particles, strength decreased with increased particle size.
The Evolution of Morphology in NR/HDPE Blends. Part I. Microscopy for Unvulcanized Blends
Authors: Laokijcharoen Pasaree , Coran A. Y. 
Published: February 2011

Abstract
Phase morphology is an important factor in the determination of properties of polymer blends. In this work, methods for determining phase morphology of unvulcanized natural rubber (NR)/high-density polyethylene (HDPE) blends were investigated. Small, quick-quenched samples were taken from the internal mixer for examination under scanning electron microscopy (SEM). There was almost no interruption of the mixing because the sampling device was designed for preventing the coalescence of dispersed particles. Three specimen-preparation methods for SEM were considered: (i) OsO4 vapor staining, followed by carbon coating; (ii) toluene etching of NR phase at room temperature, followed by coating of the surface with a platinum alloy; (iii) crosslinking of NR phase by S2Cl2 vapor and then etching of HDPE phase by using boiling xylene. Method (i), OsO4 staining of cryogenic microtomed samples, was selected for the work on the kinetics of dispersion during the mixing process. Vast differences in phase morphology were observed among the types of samples: quick quenched, cold pressed, and compression molded. We considered the quick-quenched samples to have the phase morphology, which was the most similar to that of the blend during its mixing.
The Chain End Distributions and Crosslink Characteristics in Black-Filled Rubbers
Authors: Ahagon Asahiro 
Published: February 2011

Abstract
A black-filled rubber compound consists of two phases: the free polymer phase, where no particle exists, and the carbon black agglomerate phase, where highly concentrated particles are bound by a small amount of the polymer—so called bound rubber. The Charlesby—Pinner virtual linear number-average molecular weight Mn1 of the polymer in each phase is determined for black-filled compounds to obtain information about the chain end distribution in the compounds. The nominal crosslink density of the bound rubber is also measured by means of the swelling measurement of the “carbon gel” to characterize the crosslink variation in the vulcanizates. The results indicate that the chain end density is much higher in the agglomerate phase than in the free polymer phase due to enhanced chain scission during mixing. The enhancement of scission is considered due to the free radical crosslinking which imposes restriction to chain slippage in the flow field. This together with the previous findings suggests the features of the phase construction in the filled vulcanizates: tightly crosslinked free polymer phase with fewer chain ends, and loosely crosslinked agglomerate phase with more chain ends but, with rather suppressed chain mobility due to the dense nano-scale particles. The features match well with the energy dissipating and the toughened nature of the filled vulcanizates.