bluuebunny/crossref_metadata_2025 huggingface dataset:
Perception and attitude of obstetric fistula patients about their condition: a report from the Regional Hospital Maroua, Cameroon
Authors: Tebeu Pierre Marie , Rochat Charles-Henry , Kasia Jean Marie , Delvaux Thérèse
Published: February 2011

Background. Obstetric fistula results in a continuous leakage of urine or feces through the vagina. The social consequences of obstetric fistula are severe, with affected women often ostracized from the community, divorced, abandoned and remaining childless. Objective. The general objective of this study was to analyze the perception and attitude of obstetric fistula patients treated at the Regional Hospital of Maroua, Cameroon. Design and Methods. This is a case series study of 42 obstetric fistula patients at the Regional Hospital of Maroua, Cameroon. After confirmation of the diagnosis of obstetric fistula, the patients were invited to participate to a survey prior to the surgical procedure, from May 2005 to August 2007. Results. Thirty-two percent of patients (13/41) said that they used to isolate themselves. Fifteen percent of patients (6/41) cited suicide as a solution for their fistula problem. Among the 29 patients who had never been operated before, 12 (41%) declared that this was due to a lack of financing means; eight (28%) cited the lack of fistula treatment services; seven (24%) said that this fistula was recent and 2 (7%) declared that they did not consult before. Conclusion. Obstetric fistula patients have a very negative perception about their condition. It is strongly recommended to improve the accessibility to maternal health program in order to prevent and manage the obstetric fistula in Far North Cameroon.
Imaging pockmarks and ring-like features in Hudson Bay from multibeam bathymetry data
Authors: Roger J , Duchesne M J , Lajeunesse P , St-Onge G , Pinet N
Published: February 2011

Multibeam bathymetry data collected in Hudson Bay in 2004, 2005, 2007 and 2010 during an ArcticNet cruises onboard the CCGS Amundsen show two sectors characterized by a high density of pockmarks and peculiar ring structures. The first sector is situated in
northern Hudson Bay close to Mansel Island and is characterised by a ± 2 km long depression in which pockmarks with an average diameter of 100 m and an average depth of 10 m are present. The second sector is divided into two distinct parts; a northern domain characterized by a significant
number of pockmarks and a southern one dominated by abundant circular ring-like features. The ring structures are < 200 m in diameter and 10 m deep and have a central peak. The occurrence of these features could be explained by salt doming that fractured bedrock. The occurrence of the
ring structures and the pockmarks within the same area suggests that they might be process-related and that fluid escape may be an important characteristic for both types of morphological features. The very good state of preservation of both the pockmarks and the ring structures and the fact that
they attenuate iceberg scours suggest that they have been formed recently (after deglaciation, i.e., after ~8500 years).
An algorithm for operational flood mapping from Synthetic Aperture Radar (SAR) data using fuzzy logic
Authors: Pulvirenti L. , Pierdicca N. , Chini M. , Guerriero L.
Published: February 2011

Abstract. An algorithm developed to map flooded areas from synthetic aperture radar imagery is presented in this paper. It is conceived to be inserted in the operational flood management system of the Italian Civil Protection and can be used in an almost automatic mode or in an interactive mode, depending on the user's needs. The approach is based on the fuzzy logic that is used to integrate theoretical knowledge about the radar return from inundated areas taken into account by means of three electromagnetic scattering models, with simple hydraulic considerations and contextual information. This integration aims at allowing a user to cope with situations, such as the presence of vegetation in the flooded area, in which inundation mapping from satellite radars represents a difficult task. The algorithm is designed to work with radar data at L, C, and X frequency bands and employs also ancillary data, such as a land cover map and a digital elevation model. The flood mapping procedure is tested on an inundation that occurred in Albania on January 2010 using COSMO-SkyMed very high resolution X-band SAR data.
Mechanochemical Reactions in Black-Filled SBR Vulcanizates under Large Deformation
Authors: Ahagon Asahiro , Kirino Yoshiaki
Published: February 2011

Mechanochemical degradation of black-filled SBR's at large deformation was studied in relation to abrasion. Deformation of rubbers caused bond scission and reduced the crosslink density; however, subsequent free radical reactions reconstructed the network structure in a short time to some extents depending on the strain. The extent of crosslink recovery was larger with larger strains. As a consequence, the loss in crosslink density showed a peak when plotted against the strain. When rubber was deformed by repeatedly passing through a narrow gap of a two-roll mill, the crosslink density was raised appreciably above the original level after a small number of passes. Surprisingly, the rubber could become plastic-like while the crosslink density was maintained high. All of these results matched well with the characteristic phenomena observed in abrasion of rubbers, e.g., the varying appearance of wear with severity, the worn surface and debris prone to be oxidized, and the bimodal size distribution of debris. It was strongly suggested that mechanochemical degradation participated in abrasion in a wide range of severity.
High-Resolution Latex-State 13C-NMR Spectroscopy for Natural Rubber Vulcanizates
Authors: Kawahara Seiichi , Ukawa Jinta , Sakai Junichiro , Yamamoto Yoshimasa , Isono Yoshinobu
Published: February 2011

Crosslinking junctions of natural rubber vulcanizates were characterized by high-resolution latex-state 13C-NMR spectroscopy. Vulcanized natural rubber latex was prepared by two methods: i.e., vulcanization of the rubber latex and cryogenic crushing of a rubber sheet vulcanized on a hot press. High-resolution latex-state 13C-NMR spectroscopy was attained even after vulcanization of the rubber latex, as is evident from no background in spectrum and narrow half width of signals independent of vulcanization time. Small signals at 44 ppm and 57 ppm in the aliphatic carbon region were assigned by measurements of both Distortionless Enhancement by Polarization Transfer (DEPT) and Attached Proton Test (APT) to secondary and tertiary carbons of crosslinking points. The assignment was proved by high-resolution solution-state NMR spectroscopy of vulcanized liquid cis-1,4-polyisoprene as a model, in which DEPT, APT, 2-dimensional 1H-1H correlation (H-H COSY), 2-dimensional 1H-13C correlation (H-C COSY) and 2-dimensional heteronuclear multiple bond correlation (HMBC) measurements were applied.
Investigations on Initial Stage of Aging of Tire Rubbers by Chemiluminescence Spectroscopy
Authors: Santoso M. , Giese U. , Schuster R. H.
Published: February 2011

The initial stage of the thermal oxidation aging process of polydienes (NR, BR, and SBRs) and polyolefins (EPDM) was investigated using the chemiluminescence (CL) method, which detects the low-intensity light emitted by the polymer oxidation reaction as a function of time. It thus quantitatively characterizes the kinetics of the polymer oxidation reaction and the aspect of the polymer microstructure during the thermal oxidation condition, the influence of the rubber mixture's ingredients or vulcanizates, and the role of the anti-aging agent. The oxidation induction time (OIT) — defined as the time at which the oxidation reaction starts — is introduced as the analytical result of CL analysis, with a standard deviation of 5–6%. The OIT from CL analysis indicates the resistance of the polymer against the thermal oxidation condition. The polydiene microstructure is found to play a significant role in the aging behavior of polymers. In the case of polydienes with higher double-bond concentration in the main chain (1,4 units) — NR or BR, for example — the OIT occurs after a relatively brief exposure to thermal influences and oxygen, depending on the temperature. SBR, with a high vinyl (1,2-butadiene units) or styrene content, is relatively more resistant than NR or BR to radical attack by oxidation reaction. EPDM with no double bonds in the main polymer chain exhibits, moreover, the strongest aging resistance. After extraction of the polymers to remove the stabilizer commonly added to the polymer, OIT values are as much as 400% shorter than for raw polymers. The OIT values of polymers processed (mixed, milled, and pressed) prior to thermal aging analysis are found to be between the OIT values of raw polymers and those of extracted ones. The temperature at which analysis was carried out has an influence on the polymer's OIT. OIT's are shorter at higher temperatures, increasing the maximum intensity of the CL curve and also the CL reaction rate. The activation energy (Ea) of polydienes is calculated on the basis of temperature dependency analysis. NR and BR have slightly similar Ea values of about 55 kJ/mol, while the group of SBRs, with varied vinyl or styrene content, also has similar Ea values of about 80–90 kJ/mol. PPD derivatives are anti-aging substances used to evaluate the role of antioxidants in the polymer. The consumption of antioxidant in the initial stage of the CL reaction is clearly indicated in the CL curve. Antioxidants prolong the durability of the polymer by a factor of about 3.5 to 20. DTPD is the most effective antioxidant, followed by 6PPD, IPPD, and 77PD. Thermal oxidation characterization of vulcanizates by the CL method is more complicated due to various ingredients in the mixture and to the fact that some species are fixed as pendant group in the polymer chain. This results in more than one peak in the CL curves. It is highly likely that this effect depends strongly on the type of accelerator used in the vulcanization system.
The Study of Adsorption of Iodine on Carbon Black by Inverse Liquid Chromatography
Authors: Maafa D. , Balard H. , Donnet J. B.
Published: February 2011

The study of iodine adsorption on carbon black samples was made using inverse liquid chromatographic frontal analysis (ILC). Unlike HPLC supports, the efficiency of the chromatographic column filled with a carbon black designed for rubber applications is low. Then the front boundaries of a non-adsorbed molecule, like heavy water (D2O) or acetone, was taken as reference for the calculation of the desorption isotherms. The monolayer capacity of adsorption, Langmuir's and Henry's constants were determined from the desorption isotherms. It was observed that 40% of the surface of the studied carbon black corresponds to a phenomenon of irreversible adsorption of the probe, and that the ILC also highlighted the heterogeneity of the studied carbon black. The adsorption energy distribution functions of iodine obtained by this method are similar to those which were already determined by IGC-FC with the heptane -like probe. The differences in behaviors between two families of carbon black could be attributed to the surface roughness.
Use of Benzene-1,3-Bis(Sulfonyl)Azide as Crosslinking Agent of TPVs Based on EPDM Rubber—Polyolefin Blends
Authors: López Manchado Miguel A. , Kenny† José M.
Published: February 2011

The use of innovative crosslinking agents for the preparation of thermoplastic vulcanizates (TPVs) is investigated. In this preliminary study, the most common TPV systems, based on polypropylene (iPP) and ethylene—propylene—diene terpolymer rubber (EPDM) blends, are studied. Among typical vulcanization agents, only the peroxides are able to crosslink saturated elastomers, however, they present the disadvantage that give rise to chain scission of the thermoplastic matrix. For this reason, the main goal of the present study is to investigate a new vulcanization agent for elastomeric matrices, which also permit the dynamic vulcanization process in their blends with polyolefins. This agent is based on a diazide derivative, benzene-1,3-bis(sulfonyl)azide that, for the specific behavior of the sulfonyl azide group, allows its interaction with the carbon—hydrogen bonds of the elastomeric phase and of the polyolefin. The study includes the dynamic vulcanization of PP—EPDM blends and their rheological, mechanical and thermal characterization. A comparison with traditional TPVs prepared with sulfur as vulcanization agent is also presented.
Effect of Aluminum Powder on Filled Natural Rubber Composites
Authors: Vinod V. S. , Varghese Siby , Alex Rosamma , Kuriakose Baby
Published: February 2011

The effect of aluminum powder on the properties of natural rubber composites containing high abrasion furnace black (HAF), general purpose furnace black (GPF), acetylene black, china clay and precipitated silica was studied. In all cases the total filler content including aluminum powder is fixed at 40 parts per hundred rubber (phr). Gradual replacement of these fillers by aluminum powder showed a marked increase in thermal conductivity. This increased thermal conductivity of aluminum powder filled composites decreased the vulcanization time and led to uniform curing throughout the material, especially for thick articles. Mechanical properties like tensile strength, tear strength, rebound resilience, heat build-up, hardness, compression set, etc., are comparatively better for these composites. Aluminum powder incorporated vulcanizates also showed good resistance against thermal aging and oxidative degradation. Thus, use of aluminum powder in rubber compounds can lead to energy saving in the vulcanization of thick rubber articles and enhance the service life of such rubber products.
Filler Dispersion, Network Density, and Tire Rolling Resistance
Authors: Nikiel Leszek , Gerspacher Michel , Yang Henry , O'Farrell Charles P.
Published: February 2011

The filler dispersion is an essential rubber compound characteristic. Traction, treadwear, and rolling resistance are affected by filler dispersion. The quantification of dispersion is a length scale phenomenon. The existing experimental tools, which are capable of measuring dispersion, for example transmission electron microscopy (TEM), mechanical scanning microscopy (MSM), optical microscopy, and reflectometry, have limitations and the information they provide may not probe the relevant scale length. The recent advance in instrumentation allows one to include electrical measurements in the arsenal of tools available to quantify the dispersion. This paper reviews the range of dispersion measurements and the correlation with compound dynamic properties is presented.
Coupled Response Model for Elastomeric Bushings
Authors: Kadlowec Jennifer , Wineman Alan , Hulbert Gregory
Published: February 2011

Elastomeric bushings are essential components in tuning vehicle suspension systems. A nonlinear viscoelastic force—deformation relation, which is computationally convenient for use in multibody dynamics simulations of automotive suspensions, is presented. This force—deformation relation extends a single mode force—deformation relation to include coupling effects due to combined radial—torsional deformations. The relation contains a force relaxation function, which is dependent upon the radial displacements and angular rotations imposed on the bushing. The relaxation function is constructed using experimental results from bushing tests under radial, torsional and coupled radial—torsional deformation modes. It is shown that the predictions of the proposed relation are in good agreement with experimental results.
Micromechanical Testing of Polyisobutylene—Polystyrene Block-Type Thermoplastic Elastomers
Authors: St. Lawrence S. , Shinozaki D. M. , Gerchcovich M. , Myler U. , Puskas J. E. , Kaszas Gabor
Published: February 2011

The mechanical properties of a variety of linear triblock copolymers (polysytrene-polyisobutylene-polystyrene, PS-PIB-PS) have been measured. The molecules were synthesized using living carbocationic polymerization of isobutylene, followed by the sequential addition of the second monomer, styrene. The microstructure of the resulting materials was examined as a function of mass fraction of PS using transmission electron microscopy of stained thin films. At small mass fractions, the reinforcing phase (PS) was distributed within the rubbery PIB phase, and the composite could be considered micromechanically using the Bard and Chung model. The comparison of experiment to theory revealed a strong mechanical dependence on Langley-Graessley intermolecular entanglement in the PIB phase. At higher mass fractions the microstructure was seen to consist of interpenetrating networks similar to the double gyroid morphology reported for block copolymers. The experimental approach involved the preparation of solution cast transmission electron microscopy specimens from which the undistorted size, distribution and arrangement of phases could be measured, and the similar preparation of thicker tensile specimens from which the accurate mechanical response could be measured. In this way the correlation between the microstructure and deformation was made accurately. The unique mechanical testing methods and instrumentation to measure tensile properties of thin samples were described.
A Fundamental Approach of the Cord Calendering Process
Authors: Nijman Gerard
Published: February 2011

Calendering is one of the oldest rubber processing technologies. It is known that coating of fabrics has been done for almost 200 years. Steel cord and fabric cord topping is one of the processes in tire manufacturing. Specifications and tolerances for calendered cords are very tough. It is especially difficult to fulfill the thickness variation across the calendered ply and the cord density (end count). Modern calender lines are very complicated in order to fulfill these requirements. Despite that there is rather little research work done in the field of rubber calendering. The level of research was reduced when extruders started to become more common in the 1970s. The purpose of this paper is to present a calender model based on the flow in the nip of two rolls. The pressure build-up in the clearance explains the influence of roll deflection on geometrical parameters. It is also related to roll wear and therefore on long term consistency of the quality of calendered cord. Roll deflection compensating methods and their influence on quality are presented from the point of view of the presented model. Roll crowning specifications are explained and a discussion of why cord tension is needed to keep the end count constant is also given.
Effects of Time and Temperature on the Reaction of Tespt Silane Coupling Agent During Mixing with Silica Filler and Tire Rubber
Authors: Reuvekamp L. A. E. M. , ten Brinke J. W. , van Swaaij P. J. , Noordermeer J. W. M.
Published: February 2011

The addition of a coupling agent to silica-rubber compounds enhances the filler-matrix compatibility. Under certain mixing conditions the surface of the filler may be only partly activated, which may have an adverse effect on the properties in the final product. Some coupling agents may also act as sulfur donor. The dump temperature employed during mixing and the length of time the compound is exposed to that temperature govern the reaction mechanisms of the coupling agent and determine whether the agent leads to the formation of a silica-rubber bond or acts as a curing agent. A temperature of at least 130 °C is necessary to ensure that the reaction between the coupling agent and the silica proceeds, whereas the coupling agent starts to react with the rubber or to donate sulfur, resulting in scorching, at temperatures above 160 °C. An increase in the 300% modulus and/or G' at 100% strain above 150 °C is an indication of scorching caused by the sulfur in the coupling agent. No scorching is observed when a coupling agent without sulfur is used. Another important parameter is the mixing time. It was observed that the coupling agent must be mixed with the silica for at least 10 minutes at 150 °C to obtain a sufficient degree of coupling.
Study of Rubber-Brass Adhesion Mechanism by Secondary Ion Mass Spectrometry
Authors: Kim Jong Myoung , van Ooij Wim J.
Published: February 2011

The sulfidization reaction of brass was studied in a squalene model system by Time-of-Flight Secondary Ion Mass Spectrometry, TOF-SIMS. Fragments of the accelerator were observed on the surface of the brass and their concentration changed with reaction time. Copper sulfide formation in the brass panels was confirmed from the TOF-SIMS spectra. The composition of the brass panels could be studied by varying the analysis depth. TOF-SIMS spectra of copper sulfide layer showed a pattern of cluster formation. Cobalt was observed to exist in the sulfide film partly in combination with carbon. Evidence was found of covalent bonding between copper sulfides and squalene.
Sensitivities in the Production and Design of EPDM Rubber Springs
Authors: Naveh N. , Vittoser J. , Glikman Z. , Putter S.
Published: February 2011

Modeling and robustness are two major concerns in the design and fabrication of rubber springs. This work is part of an extended program to investigate the relationships between rubber formulation, spring design, production variables, and spring performance throughout their useful life. The robustness of an EPDM compound to variations in composition or process parameters has been evaluated. The effect of crosslinker content, source of carbon black and mixing, was assessed in terms of standard mechanical properties. The elastic moduli were measured on lab size specimens and used to successfully model the behavior of a large toroidal rubber spring. Modeling included tailoring the cross-sectional shape and chamfering the corners to reduce strain levels, thus enabling spring compression up to 25% of its height with moderate strain. The spring behavior is unaffected by the scatter in friction at assembly stage or during service. The cross-sectional shape is shown to be a major factor in the spring behavior.
Synthesis and Rheological Characterization of Branched Versus Linear Solution Styrene-Butadiene Rubber
Authors: Kerns Michael L. , Henning Steven K.
Published: February 2011

By mediating the reactivity of the initiator/modifier system toward metallation of the polymer backbone, we have developed synthetic strategies that effectively control the relative level of branching and polydispersity in SSBR. This development has allowed for the optimization of both the microstructure and macrostructure of solution elastomers to meet the demands of a given application. In this study, we have taken the approach of controlling the polymer macrostructure by adjusting our initiator/modifier system so as to mediate the propensity for backbone metallation to occur. Understanding it is from the metallated sites along the polymer backbone that branches tend to propagate, we have demonstrated the ability to produce varying degrees of branching. Several synthetic strategies were employed in order to impose control over the levels of branching in solution SBRs. The macrostructure is the independent variable in this study and subtle differences can have profound effects on the rheology and, thus, mixing, extruding and even physical properties of the resultant compound. Polymer samples were characterized by light scattering and several rheological tests to determine the relative levels of branching in order to verify the proposed synthetic mechanisms that underlie branching control.
Thermal Properties of Tire Cords and their Effects on Post-Curing Inflation of Tires
Authors: Lim Won Woo
Published: February 2011

We simulated tensile properties of several heat-treated tire cords in a laboratory in order to know the carcass cords' properties in post-curing and non-post-curing inflated tires. We also compared the tensile properties of the simulated cords with those of carcass cords in tires and examined an optimum post-curing inflation condition. After curing tires, EASL (Elongation At Specified Load) of carcass cords in tires was higher than that of raw cords. Following the curing, the EASL decreased orderly depending on post-curing inflation time. Tensile properties of carcass cords in non-post-curing inflated tires were almost the same as compared to those of fully relaxed cords by heating at a curing temperature. Post-curing inflation had an effect on increasing modulus of carcass cords in tires. The effect can also be significant when tires are cooled down to glass transition temperature of the carcass cords.
Increase of Frictional Force of Rubber Block by Uniform Contact Pressure Distribution and its Application to Tire
Authors: Nakajima Y. , Takahashi F.
Published: February 2011

The theorem on the relationship between pressure distribution and the frictional force was derived: “The frictional force is maximized when the pressure distribution is uniform, if μ(P)P is convex with respect to P where μ(P) and P are friction coefficient and pressure.” In order to verify this theorem, the surface shape of the rubber block with the uniform pressure distribution was designed by the optimization technique. The surface shape of the optimized block was dependent on the friction coefficient of contact surface. The optimized block for dry surface increased the frictional force two to ten percent on dry steel and the optimized block for ice surface increased eight percent on ice. The technology of optimized block for dry surface was applied to a tire and verified to be effective for traction on dry asphalt road, maneuverability, comfort and wear.
Ultrasonically Treated Polypropylene/Ground Tire Rubber Blends
Authors: Oh Jeong Seok , Isayev A. I.
Published: February 2011

Compounding ground tire rubber (GRT) with commercial polyolefins such as polypropylene (PP) is a possible way of recycling GRT. These new blends can provide low cost materials. The present study describes new materials which are obtained by the ultrasonically treated PP/GRT blends. In order to improve the efficiency of the treatment process, a new ultrasonic reactor was built. In this reactor, two horns were placed in a slit die which is attached to a plastic extruder. PP/GRT blends mixed by using a twin screw extruder were passed through the reactor to devulcanize GRT. Then the blends were dynamically revulcanized using an internal mixer. Mechanical properties, rheology and morphology of the obtained blends were studied. Under optimal conditions of ultrasonic treatment, the mechanical properties of the blends were improved in comparison with our earlier experiments.
Contributions of Time Dependent and Cyclic Crack Growth to the Crack Growth Behavior of Non Strain-Crystallizing Elastomers
Authors: Busfield J. J. C. , Tsunoda K. , Davies C. K. L. , Thomas A. G.
Published: February 2011

Engineering components are observed to fail more rapidly under cyclic loading than under static loading. This reflects features of the underlying crack growth behavior. This behavior is characterized by the relation between the tearing energy, T, and the crack growth per cycle, dc/dn. The increment of crack growth during each cycle is shown here to result from the sum of time dependent and cyclic crack growth components. The time dependent component represents the crack growth behavior that would be present in a conventional constant T crack growth test. Under repeated stressing additional crack growth, termed the cyclic crack growth component, occurs. For a non-crystallizing elastomer, significant effects of frequency have been found on the cyclic crack growth behavior, reflecting the presence of this cyclic element of crack growth. The cyclic crack growth behavior over a wide range of frequencies was investigated for unfilled and swollen SBR materials. The time dependent crack growth component was calculated from constant T crack growth tests and the cyclic contribution derived from comparison with the observed cyclic growth. It is shown that decreasing the frequency or increasing the maximum tearing energy during a cycle results in the cyclic crack growth behavior being dominated by time dependent crack growth. Conversely at high frequency and at low tearing energy, cyclic crack growth is dominated by the cyclic crack growth component. A large effect of frequency on cyclic crack growth behavior was observed for highly swollen SBR. The cyclic crack growth behavior was dominated by the time dependent crack growth component over the entire range of tearing energy and/or crack growth rate. The origin of the cyclic component may be the formation/melting of quasi crystals at the crack tip, which is absent at fast crack growth rates in the unswollen SBR and is absent at all rates in the swollen SBR.
Effect of MAH Modified Carbon Black Prepared by Solid State Grafting in situ on the Adhesion Between Nylon 66 Cords and Natural Rubber and Dynamic Mechanical Properties of the Vulcanizates
Authors: Jia Demin , Zhang Xiliang
Published: February 2011

Effect of maleic anhydride (MAH) modified carbon black prepared by solid state grafting in situ on the adhesion between nylon 66 cords and natural rubber was investigated by H pull out and flat belts-determination of ply adhesion test, and scanning electron microscopy (SEM). The results, which are cords bulk failure and rubber bulk failure in the two tests for unaged and aged samples employing MAH modified carbon black respectively, shown that good adhesion between cords and rubber interfaces is formed for the samples and kept in the two tests. This indicates that MAH modified carbon black can effectively enhance RFL dipped nylon 66 cords to natural rubber adhesion. In our viewpoint, the reason of the results is that active reaction groups introduced onto the carbon black surface by modification reacted with RFL; hence, integration effect was formed between dipped RFL nylon 66 cords and natural rubber interfaces. DMA results show that the modification of carbon black with MAH can effectively lower the rolling resistance of natural rubber vulcanizates. Mechanical property studies indicate carbon black modified with MAH is beneficial to keep higher tensile strength and elongation, especially for the aged vulcanizates.
The Modification of Butadiene-Acrylonitrile Rubber with Vinylcyclohexyl Ketone
Authors: Resulov Niyazi Şahidoğlu , Sari Bekir , Talu Muzaffer
Published: February 2011

Butadiene-acrylonitrile-vinylcyclohexyl ketone (BD-AN-VCHK) terpolymer was synthesized by radical polymerization. The structure of the synthesized terpolymer was elucidated by IR spectroscopy and physical and mechanical tests. BD-AN-VCHK terpolymer was stable at lower temperatures and exhibited good adhesive properties. It was also observed that the yield of terpolymer was dependent upon the initial concentration of VCHK and pH of the media. The percentage of conversion increased by increasing the initial concentration of VCHK. With addition of 10.8% VCHK to the BD-AN mixture, the glass transition temperature (Tg) value of the polymers decreased from −40 °C to −57 °C. However further increase of VCHK ratio (20.4%) resulted in the formation of the polymers with Tg value of −48 °C. It was shown that this was due to the fact that VCHK, entering the structure during polymerization process, converted the trans structure of butadiene sequences into the cis form.
Surface Morphology of Thermal, Furnace and Pyrolytic Carbon Blacks by Nitrogen Adsorption - Relation to the Electrical Conductivity
Authors: Pantea Dana , Darmstadt Hans , Kaliaguine Serge , Blacher Silvia , Roy Christian
Published: February 2011

The surface morphology of various carbon blacks was studied by low-pressure nitrogen adsorption. The shape of their low-pressure nitrogen isotherm depends on the concentration of surface defects. This defect concentration on the surface is different for thermal blacks, even for those of the same grade. Different surface morphologies were also observed for carbon blacks obtained by pyrolysis of truck tires. The concentration of defects increased with pyrolysis pressure. For the various furnace blacks, however, similar surface morphologies were observed. The electrical conductivity of thermal and pyrolytic carbon blacks decreases with increasing defect concentration. However, in spite of a similar surface morphology, different conductivities were observed for furnace blacks. The carbon black surface morphology is therefore not a determining factor for the electrical conductivity. Furthermore, the graphitic character of the carbon black surface was studied by secondary ion mass spectroscopy (SIMS). For thermal, furnace and pyrolytic carbon blacks, the conductivity increased with increasing graphitic character of the carbon black surface, thus underlining the importance of this parameter.
Insulation Materials for Wire and Cable Applications
Authors: Mead J. L. , Tao Z. , Liu H. S.
Published: February 2011

A wide range of polymers has been used for wire and cable insulation. Older materials include natural, butyl, and styrene-butadiene rubber. Newer materials include crosslinked polyethylene, silicone rubber, ethylene-propylene elastomers, and thermoplastic elastomers. Properties of importance to electrical insulation ability include dielectric constant, resistivity, dielectric loss, and dielectric strength. Flame resistance is also important in certain applications. This paper reviews the different polymeric materials used in cable constructions and the important electrical properties for material selection.
Thermoreversible Crosslinking Rubber Using Supramolecular Hydrogen Bonding Networks
Authors: Chino Keisuke , Ashiura Makoto , Natori Junichiro , Ikawa Masahiro , Kawazura Tetsuji
Published: February 2011

Thermoreversible crosslinking rubber (TRC-IR) was easily synthesized by modification of isoprene rubber (IR) with maleic anhydride followed by the addition of 3-amino-1,2,4-triazole (ATA), in solid phase. The mechanical properties of the resulting rubber were more similar to the sulfur-vulcanized rubber than general thermoplastic elastomers (ex. SEBS). Although the tensile strength and elongation at break were lower than those of a corresponding sulfur-vulcanized rubber, the moduli were as high as those of sulfur-cured rubber. Re-molding of TRC-IR could be repeated more than 10 times without significantly changing its mechanical properties. Differential scanning calorimetry (DSC) and infrared analyses revealed that the superior mechanical properties and good recyclability are attributable to the strong hydrogen bonding. The TRC-IR showed an endothermic transition peak at around 185 °C on the DSC chart, indicating cleavage of the hydrogen bonding. Infrared analyses also revealed that the absorption peaks of carboxylic acid were shifted to a lower region by the strong hydrogen bonding. The thermoreversible crosslinking system was also applied to EPM, EBM (ethylene-butene rubber), and IIR. These rubbers also showed superior mechanical properties as well as excellent recyclability.
The Interaction between Rubber and Liquids. V. the Osmotic Pressures of Polymer Solutions in Mixed Solvents
Authors: Gee Geoffrey
Published: February 2011

An expression is obtained for the free energy of dilution of a ternary mixture of polymers + two liquids by one of the liquids. This is used to consider the osmotic equilibrium between a solution of a polymer in a mixture of two liquids, and a second phase containing only the two liquids. It is shown that the osmotic behavior of the ternary solution is very similar to that of a polymer in a single liquid, and in particular that van't Hoff's law holds at infinite dilution. The distribution of the two liquids between solvent and solution is also calculated. The experimental difficulties involved in the use of mixed solvents are discussed.
The Interaction between Rubber and Liquids. VI. Swelling and Solubility in Mixed Liquids
Authors: Gee Geoffrey
Published: February 2011

The equations derived in the previous paper for the osmotic equilibrium between a ternary mixture of polymer + two liquids and a mixture of the two liquids are applied to the swelling of cross-linked polymers in mixed liquids and to the solubility of linear polymers in mixed liquids. A mixed liquid has solvent properties intermediate between those of its components only when these mix ideally. The larger the heat of mixing of the liquids, the greater is the solvent power of the mixture relative to those of the components. This conclusion forms the basis of an explanation of the enhanced swelling of rubbers in pairs of dissimilar liquids and of the fact that a mixture of two nonsolvents may be a solvent over a certain range of concentration. Experimental results are given for the swelling of vulcanized rubbers and the critical solubility limits of unvulcanized rubbers. It is shown that these can be explained qualitatively from the cohesive energy densities of the three components, and semiquantitatively from the measured heats of mixing of the three binary mixtures. The work described in these two papers forms a part of the program of fundamental research on rubber undertaken by the Board of the British Rubber Producers' Research Association.
The Melting of Crystalline Polymers
Authors: Frith Elizabeth M. , Tuckett R. F.
Published: February 2011

The thermodynamic equilibrium which exists between crystalline and amorphous polymeric phases is discussed in terms of a fringed micelle model, as indicated by x-ray data. An expression derived for the melting point of a crystalline polymer is found to depend on the proportion θ of amorphous material in the structure: this unsharp melting point depends ultimately on a nonlinear relationship between θ and the free energy of the system. Calculated values of the crystalline amorphous equilibrium ratio over a range of temperature are in good agreement with experimental data. An attempt has been made to extend the calculations to the case of stretched polymers and a qualitative agreement has been found. This work has been carried out in the Department of Colloid Science, Cambridge, and we should like to thank Professor E. K. Rideal for much stimulating criticism. This paper arose out of discussions with Professor Sir R. H. Fowler: his advice and encouragement during its development have been invaluable to us, and we should like to record here our grateful thanks to him.
The Structure of Polyisoprenes. II. The Structure of β-Gutta-Percha
Authors: Jeffrey G. A.
Published: February 2011

The x-ray diffraction data at present available from β-gutta-percha are shown to be insufficient to distinguish fine details of molecular structure. Since a qualitative estimate of the intensities on the fibre diagram can be adequately satisfied by a model having normal interatomic distances and valency angles, no evidence exists for the improbable distortion of the methyl group out of the plane of the double bond previously ascribed to the molecule.
Limiting Law of the Reinforcement of Rubber
Authors: Smallwood Hugh M.
Published: February 2011

1. Analysis shows that, subject to certain limitations, the modulus of a loaded stock (M*) depends on the modulus of the rubber matrix (M), according to the equation: M*=M(1+2.5ϕ) where 100ϕ is the volume percentage of filler. When these limitations are fulfilled, the effect of compounding on modulus is, therefore, independent of the particle size of the filler. The assumptions on which this equation is founded are as follows: (1) the filler particles are spherical; (2) there is complete adhesion between rubber and filler; (3) the elongation is small; (4) the filler is completely dispersed; (5) the volume loading is small; (6) the filler particles are sufficiently large that the molecular structure of the rubber may be neglected. 2. The stresses about a filler particle have been derived mathematically. 3. Experimental data check the calculations for the following fillers: P-33, Thermax, and whiting. Catalpo clay presents some anomalies because of its acicular particles. 4. Carbon black does not conform to the calculations. This is attributed to the fact that it is strongly flocculated in rubber. 5. Zinc oxide (Kadox or XX zinc oxide), which should conform, because it is well dispersed in rubber, causes abnormally large increases in modulus, presumably because of alteration of the type of cure and consequent alteration of the modulus of the rubber matrix.
Some Low Temperature Properties of Elastomers
Authors: Conant F. S. , Liska J. W.
Published: February 2011

The low-temperature Young's modulus of copolymers of the butadieneacrylonitrile (B/A) type was found to be lowered by a reduction in the acrylonitrile content of the copolymer. Mass- and emulsion-polymerized butadiene were found to possess considerably different low temperature physical characteristics. Certain plasticizers (employed to improve low-temperature properties) imparted a time-stiffening effect to compounds which, in the absence of the given plasticizer, showed no time effect. An experimental method for the measurement of primary creep of elastomers at low temperatures is described. Calculation of a creep constant, as defined, appears to yield a critical temperature which may be useful as a serviceability index.
Electrostatic Properties of Rubber and GR-S
Authors: Havenhill R. S. , O'Brien H. C. , Rankin J. J.
Published: February 2011

A new electrostatic modulator has been described for measuring the electrostatic charges on rubber, synthetic rubber, and various materials. In this apparatus the electrostatic lines of force established between the charged specimen and a stationary electrode plate connected to the grid of an audiofrequency amplifier are cut or modulated at audiofrequency by a small four-bladed, motor-driven fan. This produces in effect an alternating current voltage which can be readily amplified by the audio amplifier and quantitatively measured on a meter in the output circuit. This device, in conjunction with a mirror-surfaced metal plunger system for contacting the rubber samples, has been used to measure the contact potential of various rubber and GR-S compounds. Electrostatic contact potential data are shown for both rubber and GR-S compounds with and without organic and inorganic reinforcing agents, and these data bear out the formulation of an electrostatic contact potential theory of reinforcement in which the reinforcement of rubber and GR-S is explained on the basis of contact potentials and resultant electrostatic attractive forces which exist between the rubber and the reinforcing agents. By the application of this theory, organic materials which have a highly positive electrostatic charge, such as polymerized trimethyldihydroquinoline and Flectol-H (an acetone-aniline condensation product), have been found to increase the tensile strength of the pure-gum type of GR-S compounds as much as fivefold and nearly to double the tensile strength of high zinc oxide loaded GR-S compounds.
Some Relations between Stress, Strain, and Temperature in a Pure-Gum Vulcanizate of Gr-S Synthetic Rubber
Authors: Roth Frank L. , Wood Lawrence A.
Published: February 2011

Some relations between stress, strain and temperature have been investigated for a pure-gum vulcanizate of GR-S to furnish experimental information for use in theoretical consideration of its elastic behavior. The results of the work also yield some practical information about the tensile properties at high and low temperatures. In this work stress was studied as a function of temperature, with the elongation, or sometimes the length, constant. In this way effects of friction and flow accompanying changes in length of specimens were minimized. The general methods employed in this study were first outlined by Meyer and Ferri, who in common with other observers applied them to natural rubber. Peterson, Anthony, and Guth, in the only studies of this sort dealing with synthetic rubber, did not include GR-S or other butadienestyrene copolymers.
Speed of Retraction of Rubber
Authors: Stambaugh R. B. , Rohner Margaret , Gehman S. D.
Published: February 2011

The results obtained with this apparatus show that interesting information can be obtained by making measurements of the speed of retraction under various conditions and by comparing different compounds and polymers. This information should be of value both for a better understanding of the molecular structure and the forces involved and also as a practical means for properly qualifying the material as to its elastic properties. The device appears to have an immediate practical application as an aid to the compounder in determining the “best” cure. The apparatus is quite simple to use and if properly designed is sturdy and dependable. Reliable measurements could be made at the rate of about fifty per hour without requiring much skill. Thus, the speed of retraction measurement would be practical for a routine, standard test.
Comparison of Abrasion Resistance with Other Physical Properties
Authors: Upham F. N.
Published: February 2011

The measure of the curing rate of rubber stocks has, for many years, been based on tensile strength values or factors involving tensile strength. From these data, a number of rubber stocks have been termed flat-curing, but if the rate of cure be related to the resistance to abrasion, the stocks would not be regarded as possessing that property. It appears that the abrasion test is more sensitive to changes in the state of cure than the tensile strength test, and it is therefore suggested that curing rates should be based on abrasion test data.
Fatigue Failure of GR-S Tread Stocks
Authors: Winn Hugh , Shelton J. Reid
Published: February 2011

The fundamental nature of fatigue failure in rubber during flexing has been widely studied and is known to be complex. Among the more important factors involved (aside from variations in compounding) are state of cure, temperature of test, and oxidation. The object of this paper is to review and extend these studies as they apply to GR-S. Several investigators have studied the effect of time of cure on the flex cracking resistance of rubber. Busse found that, as the degree of cure was advanced, the flex resistance reached a maximum and then decreased. Similar studies on GR-S show that undercures flex better than either normal cures or overcures. Prettyman, using a different type of machine, showed a maximum near the optimum cure. Cadwell, Merrill, Sloman and Yost and Rainier and Gerke report that the rate of cracking of rubber increased with the temperature of flexing. Similar results have been demonstrated with GR-S by Breckley and by Carlton and Reinbold. Neal and Northam flexed rubber in air, oxygen, and nitrogen on a du Pont type flexing machine. They report no difference between the flexing behavior in air and oxygen. In nitrogen, however, an uninhibited stock flexed five times longer than in air before any failure was evident. The presence of an antioxidant did not change the behavior in nitrogen, but doubled the normal flex-life in air. These workers concluded that the failure of rubber on flexing is due to oxidation rather than to mechanical fatigue. No comparable work on GR-S has yet been reported. The present authors previously showed that oxygen plays an important part in the hardening of GR-S vulcanizates during accelerated aging tests in the 100° C air oven. Since high temperatures are developed during flexing, which might well result in a similar hardening by oxidation, it seemed desirable to determine whether oxygen plays a part in the flex-cracking of GR-S. For this purpose a typical tread stock was selected and flexed in air and in nitrogen which contained various small percentages of oxygen. The effect of state of cure and testing temperatures on the resistance of GR-S to flex-cracking was included in the study.