bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Construction on Mechanical Behavior of Fabric Reinforced Rubber
Authors: Farboodmanesh S. , Chen J. , Mead J. , White K.
Published: February 2011

Fabrics coated with rubber have wide applications in fields such as medical substrates, protective clothing, and flexible membranes for civil structures, airbags, geotextiles and industrial fabrics. As the market for coated fabrics expands to applications with more complex geometries and loading conditions, a competitive edge can be gained by optimizing the selection of fabric substrate and coating materials. This work includes a detailed experimental study of the effect of various parameters such as weave pattern, yarn size, and coating thickness on rubber coated fabric mechanical response. Nine types of woven PET fabrics were fabricated, consisting of the same warp yarn size and count, but different fill yarns (220, 500, and 1000 denier) and weave patterns (plain weave, 4-harness satin weave, and 8-harness satin weave). The fabrics were coated with neoprene latex using a dip-coating process. The coating penetration was much greater for the two-ply warp yarns than the fill yarns. Both coated and uncoated fabrics were tested. Shear tests and microscopy were used to understand the interaction between the fabric structure and the rubber coating. Results suggest that the shear behavior of the rubber-coated fabric is dominated by the rubber at low shear angles and by the fabric at higher shear angles. These results improve our ability to predict and prevent undesirable behaviors such as wrinkling, distortion and tear.
Assignment of Effective Network Chains in Cured Rubbers Derived from Chemical Crosslinking, Entanglements, Polymer End Linking to Carbon Black and Filler Interaction: VII. Tensile Retraction Measurements
Authors: Hergenrother William L. , Ulmer J. D. , Robertson Christopher G.
Published: February 2011

The individual contributions to effective network chains from chemical cross-links and from trapped polymer chain entanglements were estimated for gum rubber compounds using Tensile Retraction (TR). In addition, the influences of carbon black and of polymers with functional end-groups, on the character of the polymer network in filled compounds were explored. The effective network chain contributions were established for gum vulcanizates through an entanglement model and an independent estimate of the polymer molecular weight between entanglements, Me. It was found that Me was related closely to the extrapolated γ intercepts obtained from the TR of cured gums. The gum compounds were used to further estimate the effects of fillers and functional end-groups on the total number of effective network chains. Comparing an α,ω-difunctional SBR with its non-functional counterpart enabled the assessment of the effects of functional end-groups. The comparison allowed for the determination of the probability, π, that a functional end group reacts with carbon black. The π was seen to increase as the volume fraction of filler increased, and π2 provided an estimate of the fraction of functional polymer chains that react with carbon black at both ends.
Constitutive Equations for Isotropic Rubber-Like Materials Using Phenomenological Approach: A Bibliography (1930–2003)
Authors: Vahapoğlu Vahap , Karadeniz Sami
Published: February 2011

To describe the elastic behavior of rubber-like materials, numerous specific forms of strain energy functions have been proposed in the literature. This bibliography provides a list of references on the strain energy functions for rubber-like materials on isothermal condition using the phenomenological approach. The published works, either containing the strain energy function proposals or the discussions on such proposals, based upon the phenomenological approach, are classified.
Biomedical Applications of Rubbers and Elastomers
Authors: McMillin Carl R.
Published: February 2011

This paper discusses recent topics in the biomedical applications of rubbers and elastomers. It focuses on the current problems obtaining materials for implants from manufacturers due to concern about potential liability by raw materials manufacturers. The many problems and opportunities for development of polyurethane and silicone implants are discussed along with a review of a few other rubbers and elastomers used for implants. Some of the many other rubbers and elastomers available in medical grades and used in non-implant biomedical applications are presented.
Three-Dimensional Morphology of Carbon Black in NR Vulcanizates as Revealed by 3D-Tem and Dielectric Measurements
Authors: Kato Atsushi , Shimanuki Junichi , Kohjiya Shinzo , Ikeda Yuko
Published: February 2011

Usual rubber products are a composite from rubber and nano-filler (e.g. carbon black, silica, etc.), and it is believed that the good dispersion of the nano-filler is the most important issue determining the performance of rubber vulcanizates. So far, transmission electron microscopy (TEM) has been the most useful tool for evaluation of the dispersion. However, it affords images of the sample projected on an x, y-plane, and the information along the thickness (z-axis) direction is missing. Three-dimensional (3D) visualization of nanometer structure of nano-filler dispersion in a rubber matrix is what all rubber technologists have been dreaming of. This dream is at last realized, and described in this paper. Use of TEM combined with computerized tomography (abbreviated as 3D-TEM in this paper, which is sometimes called electron tomography) enabled us to reconstruct 3D images of nano-filler aggregates in rubbery matrix. The 3D-TEM results on carbon black in natural rubber were presented in this paper. The network structure formed by agglomeration of carbon black aggregates was elucidated by combining the 3D images and physical properties of the vulcanizates. Density, electrical resistivity and dielectric relaxation of carbon black loaded natural rubber as an example of physical properties, were measured, and explained by the structure elucidated by 3D-TEM. This technique will prove to be more and more important for the rational design of the nano-composites of rubbery matrix.
A Composition Rule to Predict the Linear Viscoelastic Properties of Polybutadienes with Varying Microstructure
Authors: Robles-Vásquez O. , González-Álvarez A. , Puig J. E. , Manero O.
Published: February 2011

A composition rule is proposed here to predict the glass transition temperature (Tg), the zero shear-rate dynamic viscosity (η0′), the plateau modulus (G0) and the terminal relaxation time (λ) of narrow molecular weight distribution (MWD) polybutadienes with various vinyl contents in solution and in the melt from the knowledge of the vinyl fraction, polymer fraction in solution and average molecular weight. The predictions of the composition rule are compared with data of a variety of narrow MWD polybutadienes with varying microstructure.
Multifunctional Engineering Design of Elastomeric Components
Authors: Reifsnider Kenneth , Huang Xinyu , Zou Yue , Solasi Roham , Feshler Matthew
Published: February 2011

Earlier work has shown that the strength and growth of defects in elastomers is greatly affected by microstructure and mechanical constraint. Current work is focused on ionomeric materials which behave as elastomers under certain conditions of temperature, hydration, and mechanical constraint. These materials are typically characterized by large strains to failure. The present paper will deal with two aspects of their response that is important to design. The first is the creation of nonlinear constitutive equations that are appropriate for the description of their response in commercial codes. And the second is the development of strength concepts that are appropriate for the description of failure of such materials. Finally, the relationship of the material response and failure criteria to complexity of active stress states will be discussed.
Influence of Silica and its Different Surface Treatments on the Vulcanization Process of Silica Filled SBR
Authors: Ramier J. , Chazeau L. , Gauthier C. , Guy L. , Bouchereau M. N.
Published: February 2011

The effect of different silica treatments on the vulcanization of silica filled Styrene Butadiene Rubber (SBR) is investigated. The concentration, the length and the functionality (coupling or non coupling) of the silane used for this treatment are the parameters studied. It is shown that the silane grafting, by covering the silica surface, modifies the adsorption and desorption on this surface of the accelerators used in the vulcanization system, which in turn modifies the crosslinking kinetic and therefore should influence the final crosslinking state of the matrix.
Filler Distribution and Domain Size of Elastomer Compounds by Solid-State NMR and AFM
Authors: Hu Weiguo , Ellul Maria D. , Tsou Andy H. , Datta Sudhin
Published: February 2011

Solid-state NMR methods were used to characterize the filler distribution in rubber blends and domain size of thermoplastic vulcanizates (TPV). Correlation between filler content and magic angle spinning (MAS) 13C and 1H NMR signal linewidth was established, and filler content in each component of the rubber blends was determined. In IIR/BR and BIMS/BR blends, carbon black enriches in BR phase. Comparison of the carbon black enrichment in both blends suggests that BIMS has a slightly stronger interaction with fillers than does IIR. Results obtained from AFM analysis were compared with NMR observations. Spin diffusion NMR was demonstrated to be useful for quantifying the amount of interfacial component in TPV. Its advantages — ease of quantification and high sensitivity for smaller domains — make it a complementary approach to microscopic techniques for elastomer morphology characterization.
Effect of Methacrylate Co-Agents on Peroxide Cured PP/EPDM Thermoplastic Vulcanizates
Authors: de Risi F. R. , Noordermeer J. W. M.
Published: February 2011

Thermoplastic vulcanizates (TPVs) have gained large technical and economic importance. TPVs are characterized by a chemically crosslinked rubber phase, embedded in a thermoplastic matrix, produced by dynamic vulcanization during mixing with the thermoplastic in its molten state. Methacrylate species are investigated as co-agents for peroxide vulcanization of polypropylene/ethylene-propylene-diene-rubber (PP/EPDM) TPVs, whereby the weight fraction of the EPDM is varied from 30, 50 to 70%. Ethylene glycol dimethacrylate (EDMA), trimethylol propane trimethacrylate (TMPTMA, often referred to as TRIM) and zinc dimethacrylate (ZDMA) are tested. A fixed amount of dicumyl peroxide as crosslinker and varying contents of co-agents are employed, the latter to boost EPDM-crosslinking and prevent degradation of the PP by β-scission. Differences observed in mechanical properties point to diverse structures of the crosslink networks of the TPVs. Of the three co-agents, TMPTMA gives the best overall balance of properties by EPDM crosslinking and preventing PP-degradation. This is explained by the positioning of the solubility parameter of this co-agent between those of EPDM and PP, whilst EDMA presents a value far away from either one. ZDMA, although giving very good room temperature properties like tensile strength, shows signs of thermo-reversion of the crosslinks in the compression set measured at 70 °C.
Numerical Simulation of tire Traction on Various Road Conditions
Authors: Nakajima Yukio
Published: February 2011

The tire is the only point of contact between the car and the road and the traction is drastically changed by the road condition. Since the critical functions performed by the tire are determined by a tiny contact interface, the numerical simulation has been pursued to analyze the tire traction on various road conditions. The numerical simulation of tire traction on various road conditions such as ice, snow, water and soil are a very challenging problem, because these involve fluid-structure interaction, tire-road contact analysis and difficulty of tire pattern modeling. In this paper, the study on the numerical simulation of tire traction on various road conditions is reviewed. The tire is analyzed by FEM with Lagrangian formulation and the interfacial material is analyzed by FVM with Eulerian formulation. Since the tire and the interfacial material are modeled separately and their coupling is automatically computed by the coupling element, the tire-interfacial material interaction of the complex geometry, such as the tire with the tread pattern, can be analyzed practically. Since the prediction of tire traction is verified to be in good agreement with experiment, this technology has been started applying the development of tire pattern design. This tool will be one of the key technologies to shorten the period of development. Lastly, future works for this simulation technology are proposed.
Rubber Reinforcement and its Classification
Authors: Hamed G. R.
Published: February 2011

Principles of rubber reinforcement are discussed and new nomenclature is proposed to classify reinforced rubbers. The engineering tensile strength σb of amorphous, gum, non-crystallizable rubbers is only about σb≈3 MPa. These have no commercial use. However, if such rubbers contain enough stiff (hard or rigid) “entities” of density ρ and specific surface area S, such that 600/ρ m2/mL>S>60/ρ m2/mL, then σb>20 20 MPa. These rubbers are considered highly reinforced. The value of S for a stiff “entity” is largely dependent on its characteristic smallest dimension, d. For spheres or rods, d is diameter, and for plates, d is thickness. For all three shapes, the range of d corresponding to the limits of S given previously is approximately 100 nm>d>1 nm. Sometimes, the prefix nano- has been used to designate materials that contain stiff “entities” in this range of d. Other times, the prefix nano- has denoted a smaller range of d, 10 nm>d>1 nm. Thus, the term nano- is ambiguous in the literature. It is proposed to divide the size range, 1 nm<d<100 nm, of stiff “entities” into two ranges with different designations. When 10 nm>d>1 nm, the prefix proposed is nano-, and when 100 nm>d>10 nm, meso- is proposed as the prefix. This division may seem superfluous and arbitrary, but there is scientific merit for it. The way that the stiff “entities” come about provides criteria for further categorization. If the “entities” are (insoluble) particles that have similar d before and after incorporation (i.e., d is largely pre-determined) into an elastomer, then “composite” is the suffix proposed. But, if the stiff “entities” evolve and d depends on the kinetics and thermodynamics of phase separation, then the suffix is “structured.” Nomenclature for four types of rubber are then proposed: meso-composite, meso-structured, nano-structured and nano-composite. Commercial examples of the first three are known: black-filled SBR vulcanizates (meso-composite, σb≈20–30 MPa), SBS triblock copolymers (mesostructured, σb≈20–30 MPa), and elastomeric ionomers (nano-structured, σb≈50–60 MPa). Both meso-rubbers need about 20–25% (by volume) stiff “entity” to attain high reinforcement, whereas, only 2% stiff “entity” (ionic domains) imparts high reinforcement to nano-structured ionomers. Highly reinforced meso-rubber contains a higher concentration of stiff “entity” than that present in highly reinforced nano-rubber. However, in both meso- and nano-rubbers, the average distance between stiff “entities” is about 5 nm. This distance is similar to the spacing of crosslinks in vulcanizates that are optimally crosslinked. To the author's knowledge, no nano-composite rubber that is highly reinforced has been made. Nonetheless, the existence of high strength nano-structured ionomers suggests that highly reinforced nano-composites may be possible.
Comparative Study of Silica-, Nanoclay- and Carbon Black-Filled Ethylene Propylene Diene Monomer (EPDM) Rubbers Treated by Ultrasound
Authors: Tan Haisheng , Isayev A. I.
Published: February 2011

The ultrasonic treatment of unfilled EPDM and silica-, nanoclay- and CB-filled EPDM mixtures was carried out using a coaxial ultrasonic extruder at various ultrasonic amplitudes. Rheological properties, morphology, cure characteristics and mechanical properties were measured. The storage and loss moduli and complex dynamic viscosity of untreated and ultrasonically treated silica-filled EPDM mixtures were significantly higher than those of the nanoclay- and CB-filled EPDM mixtures in the frequency measurement range with the Tan Delta being significantly lower than that of the nanoclay-filled EPDM mixtures. The increase of the tensile strength and elongation at break of silica-, nanoclay- and CB-filled EPDM vulcanizates was observed with increasing ultrasonic amplitude and filler loading with the values being 26.5 MPa and 1070% in treated 30 phr silica-filled vulcanizates. The hardness of all samples was slightly decreased with increasing ultrasonic amplitude with the silica-filled EPDM showing the highest values. The minimum torque of filled EPDM mixtures gradually decreased with increasing ultrasonic amplitude. Depending of filler type and loading the maximum torque showed an increase or a decrease with ultrasonic amplitude. The scorch time of silica- and CB-filled EPDM mixtures slightly increased with increasing ultrasonic amplitude. The optimum cure time of the silica- and nanoclay-filled EPDM mixtures gradually increased and the CB-filled mixtures slightly decreased with filler loading. Ultrasonic treatment of the silica-filled EPDM leads to the formation of a transition layer on the surface of agglomerates into which macromolecular chains penetrate.
Dynamic Properties of Filled Rubber — Part I: Simple Model, Experimental Data and Simulated Results
Authors: Ahmadi H. R. , Kingston J. G. R. , Muhr A. H.
Published: February 2011

A simple “viscoplastic” model is used to capture the stress-strain behavior of a filled SBR vulcanizate; a key objective is to predict dynamic properties, in particular the Fletcher-Gent or Payne effect, from non-cyclic stress-strain data. A simple fitting procedure is described to obtain the parameters of the viscoplastic model from the stress relaxation data and stress-strain loading curves at constant rate. Special attention is given to keeping the numbers of parameters and of characterization tests small. Elastic models are incapable of representing several aspects of the material behavior whereas it is confirmed that the proposed “viscoplastic” approach captures the essence of the behavior.
Atom Transfer Radical Graft Copolymerization on a Poly(Epichlorohydrin-CO-Ethylene Oxide) (ECO) Elastomer
Authors: Manikyaharithus Kalaga , Singha Nikhil K.
Published: February 2011

Graft copolymerization by conventional radical polymerization leads to poor control in molecular weight and quite often gel formation because of several side reactions. In this investigation, PMMA was grafted on poly(epichlorohydrine-co-ethylene oxide) (ECO) elastomer by using ‘grafting from’ technique via atom transfer radical polymerization (ATRP), a very recently developed method of controlled radical polymerization. The pendant —Cl group in ECO rubber was activated by using CuBr catalyst and thus macromolecular chain in ECO rubber acted as macroinitiator. Grafting of PMMA on ECO was confirmed by FT-IR and NMR analyses. DSC traces showed two Tgs in PMMA grafted ECO rubbers indicating microphase separation of hard and glassy PMMA microdomains in the flexible elastomeric ECO matrix. Interestingly, there was large increase in tensile strength and tension set in the ECO-grafted-PMMA materials.
Elastomer Nanocomposites
Authors: Maiti Madhuchhanda , Bhattacharya Mithun , Bhowmick Anil K.
Published: February 2011

Recently, elastomer - nanocomposites reinforced with low volume fraction of nanofillers have attracted great interest due to their fascinating properties. The incorporation of nanofillers such as layered silicate clays, carbon nanotubes, nanofibers, calcium carbonate, metal oxides or silica nanoparticles into elastomers improves significantly their mechanical, thermal, dynamic mechanical, barrier properties, flame retardancy, etc. The properties of nanocomposites depend greatly on the chemistry of polymer matrices, nature of nanofillers, and the method in which they are prepared. The uniform dispersion of nanofillers in elastomer matrices is a general prerequisite for achieving desired mechanical and physical characteristics. In this review article, current developments in the field of elastomer nanocomposites reinforced with layered silicates, silica, carbon nanotubes, nanofibers and various other nanoparticles have been addressed. Attention has been paid to the structure and properties of such high-performance nanocomposites, along with the theories and models existing in this field.
Structural Analysis of Filler in Rubber Composite under Stretch with Time-Resolved Two-Dimensional Ultra-Small-Angle X-Ray Scattering
Authors: Kishimoto Hiroyuki , Shinohara Yuya , Amemiya Yoshiyuki , Inoue Katsuaki , Suzuki Yoshio , Takeuchi Akihisa , Uesugi Kentaro , Yagi Naoto
Published: February 2011

We investigated the hierarchical structure of silica, especially agglomerate structure, in stretched rubber by time-resolved two-dimensional ultra-small-angle X-ray scattering (2D-USAXS). Time-resolved 2D-USAXS measurements give us the in-situ structural information up to 5 μm during sample deformation. The results are summarized as follows: at first, the agglomerate is turned so that the long axis of the agglomerate is parallel to the stretching direction, and the “weakly-bonded agglomerates” weakly bonding between agglomerates is broken down. Second, the distance between agglomerates increases with the small deformation of agglomerate. Finally, the “tightly-bonded agglomerates” strongly bonding between agglomerates start to deform. Existence of silane-coupling agents causes the differences in the manner of agglomerate deformation. These kinds of structural information will be a key to understanding the origin of rubber reinforcement by filler such as carbon black and silica.
Aging with Applied Strain of A Black-Filled Natural Rubber Vulcanizate. Part I: Network Changes
Authors: Ohlemacher Crittenden J. , Hamed Gary R.
Published: February 2011

Black-filled natural rubber, with an inefficient sulfur cure, was aged at 90 °C and 110 °C under nitrogen, with and without applied strain. Samples aged under strain became “double networks” and retained a residual extension ratio. The crosslink density of samples passed through a maximum with increasing severity of aging. Presumably this arises because the thermally labile, polysulfidic crosslinks break, and new crosslinks of lower rank form, resulting in increased crosslink density; but, when aged at 110 °C, this is offset by chain scission and other main-chain modifications. For double networks, it is proposed that a second network, which tends to keep samples extended, is formed at the expense of crosslinks in the original, first network. Unaged and single network samples were isotropic in tensile behavior and only slightly anisotropic in swelling behavior. For double networks, swelling and tensile properties were anisotropic, and there was some evidence that parallel specimens have increased ability to strain-crystallize. The observed anisotropies in double networks are proposed to arise from the chain orientation that persisted after double network formation.
Compatibility Improvement between Chlorinated Thermoplastic Rubber and Polychloroprene Adhesive
Authors: Mercedes Pastor-Blas M. M.
Published: February 2011

Traditionally, it has been believed that there is an incompatibility between the chlorinated rubber surface and polychloroprene adhesives resulting in a lack of adhesion. However, in this study it has been shown that a polychloroprene adhesive (PCP30P) produces similar T-peel strength values when using a polyurethane (PU) adhesive in joints produced between a chlorinated thermoplastic SBS rubber and roughened leather. In both cases a cohesive failure mode within the rubber was obtained. This polychloroprene adhesive (PCP30P) contains a thermoreactive phenolic resin in its formulation. The nature of the resin greatly influences the viscoelastic properties of the polychloroprene adhesive. Thus, polychloroprene adhesive with no resin or with resins of a different nature do not produce suitable adhesive joints between the chlorinated rubber and the leather (Terpene phenolic resin (PCP30TP), a glycerol esther colofony resin (PCP30EC) and an aromatic hydrocarbon resin (PCP30AH) were studied). The interactions produced between the chlorinating agent and the adhesive were studied by ATR-IR on solid films of the polychloroprene adhesives and the tackifier resins previously immersed in the chlorinating solution (0.5 and 3 wt% TCI/MEK). All the polychloroprene adhesives were modified by the chlorinating agent, being capable of producing a good interaction with the chlorinated rubber surface at the interface. Therefore, the good performance of the PCP30P adhesive compared with the other polychloroprene adhesives has been ascribed to rheological behavior more similar to the PU adhesive assessed by DMTA. The PCP30P adhesive is the most elastic material among all the considered polychloroprene adhesives. This increased elasticity and better viscoelastic properties are imparted by the thermoreactive phenolic resin in its formulation.
Goodyear Medalist Lecture. Goodyear Medalist Lecture Towards Understanding of the Rheology of Rubber Compounds and their Processing
Authors: White James L.
Published: February 2011

The problems of the rheological properties of rubber compounds and the understanding of the processing operations that are used to produce rubber products have received relatively little study in the literature compared to thermoplastics. This seems in part due to an almost 200 year old tradition of industrial secrecy and the vertically integrated nature of the synthetic rubber producer — tire manufacturer combines in the USA. Thus while abundant information has always been available from thermoplastics suppliers on processing technology, little has been available on rubber. Because I began my professional career in the rubber industry and became from an early age concerned with its technical problems, I have not been swayed to the same extent by the thermoplastics dominated technical literature as others in the polymer community.
Cure Kinetics Study of Unfilled and Carbon Black Filled Synthetic Isoprene Rubber
Authors: Sun Ximei , Isayev Avraam I.
Published: February 2011

The reversion type cure kinetic and induction time models were successfully utilized to predict the isothermal and nonisothermal evolution of the state of cure in vulcanization of the unfilled and carbon black (CB)-filled IR compounds measured by APA 2000. The rate constants for the reversion reaction and the formation of the stable and unstable crosslinks and the parameters of the induction time function with the Arrhenius temperature dependences were determined from the isothermal cure measurements. The equation was proposed to adequately describe the measured dependence of the difference between the maximum and minimum torques as a function of isothermal curing temperature. The measured induction time as a function of heating rate and step temperature variation was successfully predicted based on parameters of the isothermal induction time model. Isothermal cure modeling at each curing temperature individually or at all the curing temperatures simultaneously showed the excellent agreement with the experimental data for both curing and reversion. More severe reversion in the CB-filled IR in comparison with the unfilled IR was explained by comparing their reversion rate constants.
Cure State by Atomic Force Microscopy (AFM)
Authors: Johnson Lili L. , Jacob Sunny
Published: February 2011

Phase shift angle measurements were made on ethylene propylene diene rubber (EPDM), polypropylene (PP), and thermoplastic elastomers (TPVs) using TappingMode™ phase imaging technique by atomic force microscopy (AFM). In this work, the phase shift angle for rubber or elastomer is independent of penetration depth for setpoint ratio (rsp) below 0.6, which indicates elastic behavior of the materials. Thermoplastic vulcanizates (TPVs) containing different amount of curative show that phase shift angle increases with increasing curative content. Our study shows that phase shift angle measurement can be used to evaluate cure state of elastomer phase for model TPVs.
Structural Arrest and Thermodynamic Scaling in Filler-Reinforced Polymers
Authors: Robertson C. G. , Bogoslovov R. , Roland C. M.
Published: February 2011

The role of small silica particles on the stiffness and glass transition dynamics of polyvinylacetate (PVAc) was examined for filler volume fraction (ϕ) from 0 to 0.28. Whereas the influences of bound polymer and a strain-dependent filler network were clearly noted in the shear properties, the only effect of filler on the bulk modulus was the reduction in deformable polymer. The calorimetric glass transition of PVAc and its dependence on cooling rate were unaltered by the presence of the silica, in agreement with previous dielectric relaxation results. In contrast to the temperature dependence of the segmental dynamics, which was independent of ϕ, the effect of volume on segmental relaxation was amplified by the addition of silica. This resulted in larger values for the thermodynamic scaling exponent (γ), which also increased sharply at the filler concentration corresponding to the development of a percolated filler network.
Investigations on the Extraction and Migration behavior of Polycyclic Aromatic Hydrocarbons (PAHS) from Cured Rubber Formulations Containing Carbon Black as Reinforcing Agent
Authors: Hamm Stephan , Frey Thomas , Weinand Rudolf , Moninot Gilles , Petiniot Nicole
Published: February 2011

Potential release of polycyclic aromatic hydrocarbons (PAHs) from cured rubber materials containing carbon black as reinforcing agent was studied on the basis of seven standard formulations prepared with different loadings of a carbon black grade specifically selected for its high PAH content. A specific test method involving Soxhlet extraction with toluene was developed and validated for quantification of the US-EPA and EU priority PAHs in the rubber materials containing up to 350 ppm of these compounds. PAH migration into aqueous media was assessed by total immersion of rubber sheets into drinking water, artificial sweat, saliva and rainwater for 7 days at 30 °C. GC/MS and internal deuterated standards were applied for PAH determination in all tests. Migration of PAHs from the cured rubber into aqueous media was not detected for the EU PAHs including benzo(a)pyrene and proved to be very low for the combined US-EPA PAHs, not exceeding 1.2 µg/dm2. Migration-derived PAH concentrations for drinking water were at least 105 lower than those in the rubber compounds. This study demonstrates that once incorporated into a rubber matrix, the PAHs originating from carbon black are scarcely available to aqueous media. These results should be considered while developing PAH exposure assessments for rubber articles.
Nitrogen Inflation of Tires
Authors: Waddell Walter H. , Napier R. Christopher , Tracey Donald S.
Published: February 2011

Inflation pressure retention (IPR as a loss rate) is a key predictive parameter to improving tire durability. Improved Tire IPR, manifested as reduced percent pressure loss per month values, has statistically been shown to be a direct result of innerliner compounds made with increasing amounts of halobutyl rubber when used as a direct replacement for natural rubber if other variables are constant. Roadwheel performance of tires is highest when using 100-phr of halobutyl rubber in the innerliner compound. This affords a tire with desirably low IPR loss rate values, desirably low tire intracarcass pressure (ICP) values, and increased tire durability as measured in hours until failure on laboratory roadwheels. The use of nitrogen gas in tires in severe service conditions is known, and a variety of benefits have been claimed for use in passenger car tires. In order to test specific claims, tires with innerliners having a 100-phr bromobutyl rubber, and 80/20 and 60/40 bromobutyl/natural rubber blends were studied using three filling gases: dry, pure nitrogen (99.4%), dry air and a 50/50 mixture of dry nitrogen/oxygen (49.8%). Performance was measured for new and oven-aged tires. It is shown that the direct benefits of using nitrogen are in reducing the Tire IPR loss rate values, and in reducing aging since oxygen gas has been initially excluded. Other claimed benefits are found to be a secondary result of the lower Tire IPR loss rate values. Use of nitrogen as the inflation gas does not benefit the measured cavity gas temperature or tire rolling resistance, both of which are shown to be tire pressure dependent, but not dependent upon the filling gas when measured at equal tire inflation pressures.
Chemical Mapping of Rubbers and Polymers via Confocal Raman Spectroscopic Imaging
Authors: Cherney Daniel P.
Published: February 2011

Confocal Raman Spectroscopic Imaging has been demonstrated as a non-destructive technique to determine the spatial and chemical content of rubbers and polymers. Raman spectroscopy is a particularly useful tool for characterizing chemicals and mixtures because each chemically-distinct species has a unique Raman spectrum. The addition of confocal optics to the microscope greatly improves both the lateral and axial spatial resolution of the instrument. The lateral resolution of the instrument is less than one-third of a micron. The axial resolution, the resolution in the direction of incident light propagation, is as good as two microns with an air objective and on the order of a micron for an oil immersion objective. The vast enhancement of resolution provided by the confocal optical arrangement allows rubber and polymer mixtures to be mapped in multiple dimensions with excellent spatial, chemical, and morphological specificity. Confocal Raman microscopy is a rapid technique that should be considered as an alternative, or in addition, to analysis that requires other microscopic techniques such as atomic force microscopy (AFM) or scanning electron microscopy (SEM).
Novel Polyisobutylene-Based Biocompatible TPE Nanocomposites
Authors: Lim Goy Teck , Foreman-Orlowski Elizabeth A. , Porosky Sara E. , Pavka Paul , Puskas Judit E. , Götz Christian , Altstädt Volker
Published: February 2011

The tensile and thermal properties of linear poly(styrene-b-isobutylene-b-styrene) (L_SIBS) and styrenic copolymers with a dendritic polyisobutylene core (D_SIBS) filled with 10 – 30 wt% of organophilic montmorillonite nanoclays (Cloisite(®)-20A) via solution blending were investigated. D_SIBS polymers were successfully reinforced by the clays without additional compatibilizers to show increase in both modulus and ultimate tensile strength. The clay platelets were well dispersed in the polymer matrix as determined by transmission electron microscopy (TEM). However, L_SIBS composites displayed decreasing tensile strength with increasing clay loading. TEM found clay agglomerates in L_SIBS composites that can act as “hotspots” for premature failure of the material. D_SIBSs loaded with 60 phr (37.5 wt%) carbon black (N234) also showed significant reinforcement. Interestingly, a D_SIBS with 17 wt% hard phase content reinforced with 60 phr carbon black exhibited an increase in the glass transition temperature of the hard phase from 116 °C to 126 °C. This will make steam sterilization of the material possible for biomedical applications.
Quantifying Compound Aging Resistance at Service (Ambient) Temperatures
Authors: Terrill Edward R. , Lewis James T.
Published: February 2011

Oxygen consumption rates were measured on natural rubber compounds with varying levels of a standard antioxidant package. The oxygen consumption rate measurements were performed at temperatures between 20 °C and 80 °C. The results elucidated the mechanism of antioxidants, including their pro-oxidant effects. The pro-oxidant effect dwindled with time. Integrated oxygen uptake results were calculated from repetitive oxygen consumption rate measurements. Integrated oxygen uptake time temperature master curves with empirical shift factors were combined with elongation-tobreak data to monitor the extent of aging. The stability of the compounds at service life temperatures could be quantified by combining the integrated oxygen uptake shift factors with the tensile elongation-to-break data; thereby to produce an elongation-to-break master curve at service life temperatures.
Computed Dependence of Rubber'S Fatigue Behavior on Strain Crystallization
Authors: Mars W. V.
Published: February 2011

This work explores the consequences of strain crystallization on rubber's fatigue crack nucleation behavior over an extensive space of operating conditions, including tension and compression loading states, and relaxing and non-relaxing cycles. The study considers, via computation, how the nonlinear elastic stress-strain behavior, the fatigue crack growth characteristics, and the damage accumulation law combine to produce the Haigh diagram and the Cadwell diagram. Four hypothetical materials are studied, which differ in their crystallization and associated fatigue crack growth behavior. The calculations demonstrate that a relatively simple idealization can credibly predict the unique shape and sensitivities of observed fatigue behavior over a wide range of conditions. They also clarify how features of the Haigh and Cadwell diagrams are linked to the occurrence of crystallization and to parameters such as the power-law slope and the fatigue threshold.
Translucent Thermoplastic Elastomers
Authors: Ellul Maria D. , Hazelton D. R.
Published: February 2011

Thermoplastic elastomer vulcanizates, TPVs, having the property of optical translucence have been prepared by dynamic vulcanization. The new materials are based on a polypropylene homopolymer principally containing propylene units of exactly alternating configuration and having a syndiotactic pentad fraction of at least 0.86. The dispersed elastomer phase consists of a crosslinked ethylene propylene copolymer rubber having an ethylene content of at least 74 weight %. These thermoplastic elastomer compositions have significantly lowered Gardner haze values, while maintaining the desirable properties of low compression set and thermal stability. The compositions have utility in molded mechanical rubber goods as well as extruded articles for fluid delivery applications.
Mapping Work-Related Stress and Health in the Context of the Family Firm
Authors: Dodd Sarah Drakopoulou
Published: February 2011

The family firm organizational form is an important element of even the most modern industrial landscape. The implications of family ownership and management of business enterprises for health and safety at work remain, perhaps surprisingly, unexplored. This study presents and illustrates several key organizational health and safety factors that are likely to be influenced by the family firm form. Special dangers include heightened risk of accident and poor physiological health. Special benefits are found to be higher task control, social support, evolutionary fitness and a richer accumulation of experiences. Additional research is recommended for this relatively unexplored area.
Rigid‐Rod Polymers
Authors: Wang David H. , Jiang Hao , Wade Adams W.
Published: February 2011

Pursuing high strength and high modulus polymer fibers and novel electrooptical properties have motivated much research activity in rigid‐rod polymers in the past 40 years. In this review, we examine the synthesis, structures, and properties of rigid‐rod polymers with emphasis on polybenzobisoxazoles (PBO), polybenzobisthiazoles (PBZT) and polybenzimidazoles (PBI), beginning with their solution properties, especially lyotropic liquid crystallinity. High performance fibers spun from lyotropic liquid crystalline polyphosphoric acid (PPA) solution are described. The characterization of fiber properties including mechanical, thermal, electrical, and optical properties is summarized. PBO (Zylon) and PIPD (M5) fibers were successfully commercialized in high strength applications such as body armor, ropes, cables, and recreational equipment in the last 10 years, and we discuss the possible causes of rapid degradation of some PBO fibers. The concepts of molecular composites and nanocomposites provide new applications in antiballistic materials, fire protection, athletic equipment, cables, strings, ropes, cordage, sails, multilayer circuits, and catalyst supports. Recently, rigid‐rod polymer films have drawn attention in the electrooptical fields, especially for phosphoric acid (PA)‐doped PBI membranes (Celtec MEAs) in the applications of high temperature fuel cells. Computer simulation has been employed as a powerful tool to predict the properties of the rigid‐rod polymers.
Azo Compounds
Authors: Sheppard C. S.
Published: February 2011

Azo compounds are organo‐nitrogen derivatives with the characteristic NN functionality and the general formula RNNR′, where R and R′ can be the same or different organic groups. In the polymer industry, azo compounds are used as dyes, blowing agents, and free‐radical polymerization initiators. This article describes the azo compounds used as free‐radical initiators.
Casein
Authors: Schrieke R. R. , Winter G.
Published: February 2011

Casein is the main protein of milk, constituting approximately 3% of cow's milk. The two types, acid and rennet, are precipitated from skim milk. The term casein usually applies to the acid form; the industrial use of rennet casein is small. Physical and chemical properties, as well as other uses, test methods, and manufacturing are reviewed.
Sheeting
Authors: Mackenzie K. J.
Published: February 2011

Sheeting or sheet is defined as shaped plastic having a large width and length in relation to the thickness, with a thickness greater than 250 µm. Plastic films are differentiated from sheet only in thickness (less than 250 µm). Sheeting is formed from synthetic polymers, including polyolefins, poly(vinyl chloride) (PVC), polyesters, cellulosic esters, polystyrene, poly(methyl methacrylate), and polycarbonate resins. Cross‐linked or thermoset resins, including reinforced composite materials, can be formed into sheet structures; foamed plastic sheeting is also produced. Laminar sheet materials are important, with many market opportunities.
Greater likelihood of remission in rheumatoid arthritis patients treated earlier in the disease course: Results from the Consortium of Rheumatology Researchers of North America registry
Authors: Furst Daniel E. , Pangan Aileen L. , Harrold Leslie R. , Chang Hong , Reed George , Kremer Joel M. , Greenberg Jeffrey D.
Published: February 2011

Objective

To examine whether disease duration is an independent predictor of achieving remission in rheumatoid arthritis (RA) patients initiating therapy.

Methods

RA patients in the Consortium of Rheumatology Researchers of North America registry newly prescribed a nonbiologic disease‐modifying antirheumatic drug (DMARD) or anti–tumor necrosis factor (anti‐TNF) with at least one followup visit were identified. Achievement of remission was defined using the Clinical Disease Activity Index (CDAI; score ≤2.8) and 28‐joint Disease Activity Score (DAS28; score <2.6) at any followup visit within one year; sustained remission was defined as remission during any two successive visits. Likelihood of remission was examined through logistic regression based on 5‐year increments of disease duration, adjusting for baseline covariates.

Results

Among the 1,646 nonbiologic DMARD initiators, CDAI remission occurred in 21.3% of those with ≤5 years of disease duration, 19.6% with 6–10 years, and 13.5% with ≥11 years (P < 0.001); sustained remission occurred in 10.2%, 8.8%, and 2.5%, respectively (P < 0.001). Results were similar among the 3,179 anti‐TNF initiators (CDAI remission in 22.3%, 17.7%, and 12.8%, respectively [P < 0.001]; CDAI sustained remission in 9.7%, 9.5%, and 4.2%, respectively [P < 0.001]). DAS28 results were similar in both groups. In adjusted analyses, an increase of disease duration by 5 years was associated with a reduced likelihood of CDAI remission in nonbiologic DMARD (odds ratio [OR] 0.91, 95% confidence interval [95% CI] 0.83–0.99) and anti‐TNF initiators (OR 0.88, 95% CI 0.83–0.94). A similar result was seen for sustained remission using the CDAI (nonbiologic DMARD: OR 0.61, 95% CI 0.48–0.76; anti‐TNF: OR 0.85, 95% CI 0.75–0.97).

Conclusion

Earlier treatment was associated with a greater likelihood of remission.
Very High Performance Alkali Anion‐Exchange Membrane Fuel Cells
Authors: Matsumoto Kazuya , Fujigaya Tsuyohiko , Yanagi Hiroyuki , Nakashima Naotoshi
Published: February 2011

Anion‐exchange membrane fuel cells (AEMFCs) have emerged as an alter‐native technology to overcome the technical and cost issues of proton‐exchange membrane fuel cells (PEMFCs). In this study, we describe a new electrocatalyst for AEMFCs composed of carbon nanotubes (CNTs), KOH‐doped polybenzimidazole (PBI) and platinum nanoparticles (Pt), in which the CNTs are wrapped by KOH‐doped PBI at a nanometer thickness and Pt is efficiently loaded on the wrapping layer. In the electrocatalyst, it is revealed that the CNTs and the KOH‐doped PBI layer function as electron‐ and hydroxide‐conductive paths, respectively, and the large exposed surface of the Pt allows an effective access of the fuel gas. Quantitative formation of the well‐defined interfacial structure formed by these components leads to an excellent mass transfer in the catalyst interface and realizes a high fuel‐cell performance. Membrane electrode assemblies fabricated with the electrocatalyst show a high power density of 256 mW cm−2. To the best of our knowledge, this is the highest value for AEMFC systems measured in similar experimental conditions.
Compact and Stable Quantum Dots with Positive, Negative, or Zwitterionic Surface: Specific Cell Interactions and Non‐Specific Adsorptions by the Surface Charges
Authors: Park Joonhyuck , Nam Jutaek , Won Nayoun , Jin Ho , Jung Sungho , Jung Sungwook , Cho So‐Hye , Kim Sungjee
Published: February 2011

A new type of quantum dot (QD) ligand chemistry is introduced that can provide positive, negative, or zwitterionic surface QDs. CdSe/CdZnS core‐shell QDs are decorated with ligands, and the non‐specific and specific interactions of the QDs through their surface charge are investigated with the focus on cellular adsorptions and endocytosis. Zwitterionic QDs are compact with a ligand hydrodynamic thickness of less than 2 nm, they are colloidally very stable over a broad pH range and even in saturated NaCl solution, and they show minimal non‐specific adsorptions. Positive and negative QDs show a very different behavior for cellular adsorption and subsequent incorporation, suggesting mostly energy‐independent pathways for positive QDs and exclusively adenosine triphosphate (ATP)‐dependent pathways for negative QDs. The zwitterionic QD surface ligands can also be used in conjunction with other functional groups, which allows simple conjugations for highly specific targeting whereas retaining the advantages of a zwitterionic QD surface. This QD surface chemistry can provide highly specific and very sensitive imaging with very low background level. Using the mixed QD surface ligand system, we demonstrated streptavidin and antibody QD conjugates that show a signal‐to‐noise ratio that is over 4000 times higher than the unconjugated mixture, which was used as a control case. The QD chemistry reported herein can be easily extended to other functional groups, such as alkynes, azides, or other amines, and can be further used in many future applications, including single‐QD level experiments, sensitive assays, or in vivo applications using anti‐fouling QD probes.