bluuebunny/crossref_metadata_2025 huggingface dataset:
The Odyssey of an Invention Charles Goodyear Medal Address—1975
Authors: Bayer Otto
Published: February 2011

It is a special honor for me to receive the internationally acclaimed Charles Goodyear Medal for my work in the field of polyurethane chemistry. The least I can do is to express my gratitude with an acceptance speech about this subject, but this is not so easy for me as I have not mastered the English language well enough to formulate and translate my thoughts at the same time. Therefore, I must ask for your understanding while I read my English manuscript. The selection of a subject caused me a few headaches because, for many in the audience, a survey of polyurethane chemistry would just mean a repetition of well-known facts. Also, many monographs have been published in the meantime—by experts and by those who like to think they are. Furthermore, having retired seven years ago from active research, I do not want to report on the latest research developments of my former colleagues. Today, the refinement of formulations for various end uses and the development of new applications are of primary interest. For example, I am thinking of the integral-skin foam technology which makes it possible to produce parts with a completely smooth or textured surface using temperature-controlled metal molds. Such foams exhibit a density gradient across the foam which shows a transition from the noncellular skin to a low-density core. Today I would like to tell you how the discovery of polyurethane came about, a most dramatic story. You will find that here—as with many important discoveries—a new idea was not sufficient in itself. What was also needed was an enterprising and optimistic spirit, tempered by controlled self-criticism, in order to succeed in a venture which in the beginning seemed hopeless, both technically and economically. In the early years of my career I was entrusted with the management of organic research in the Leverkusen plant of the former I. G. Farben. My main fields were dyestuffs, organic intermediates, and the pertinent basic research. Although dyestuff chemistry is still my first love, I always knew that an unusual increase in demand could not be expected. New dyestuffs and dye processes could only succeed at the expense of the olders ones. I tried, therefore, to place the research emphasis in my laboratory on two subjects, namely, plant-protection chemistry and macromolecular chemistry. We succeeded in both fields. In 1935 we discovered the phosphorus insecticides (G. Schrader), which are today among the most important insecticides in the world.
Optimal Curing of Rubber Compounds with Reversion Type Cure Behavior
Authors: Han In-Su , Chung Chang-Bock , Lee Jae-Woo
Published: February 2011

A systematic procedure is presented for the optimal curing of rubber compounds showing reversion type cure behavior. First, a cure kinetic model is proposed that can explain the reversion and the induction period commonly found in the vulcanization of rubber compounds. The state of cure behavior is analyzed as a function of cure temperature and time on the basis of the derived kinetic model. Then, the problem of determining optimal cure temperature profile for a rubber slab in a simple cure press is addressed and formulated into a constrained dynamic optimization problem. Finally, numerical algorithms and simulation results are presented to demonstrate the proposed cure optimization procedure.
Surface Modification of Textile Tire Cords by Plasma Polymerization for Improvement of Rubber Adhesion
Authors: Luo Shijian , van Ooij Wim J. , Mäder Edith , Mai Karsten
Published: February 2011

Aramid cords and fibers and polyester tire cords were treated by means of plasma polymerization techniques. Coatings of plasma-polymerized pyrrole or acetylene were deposited on the surface of cords and fibers in a custom-built semi-continuous reactor operated on a pulsed DC glow discharge. The deposition conditions of the plasma-polymer coatings were varied within wide limits. The cords were tested for adhesion in rubber in a industrial pull-out test. It was found that the plasma polymer coating can significantly increase pull-out forces. Coatings deposited under low power and high pressure conditions performed better than the coatings prepared under high power and low pressure conditions. The plasma-polymerized coatings were characterized by a range of analytical techniques and the performance results are explained in a tentative model based on the molecular structure of the films. The structure was found to be strongly dependent on the deposition conditions.
Multiaxial Cyclic Response of Filled Rubber
Authors: Li C. G. , Steif P. S.
Published: February 2011

Cyclic response of filled rubber to simultaneous combinations of shear and extension is studied experimentally. Both in-phase (elastic) and out-of-phase (dissipative) portions of the response are measured for simple shear, uniaxial tension, and combinations of the two. As noted by other researchers, the response is nonlinear, with a strong dependence on strain amplitude. However, it is shown that the response to tension and to combinations of strains can be approximately related to the response to simple shear. Such correlations are useful in predicting the response of rubber-based components subjected to complex strain cycles when only experimental data on shear is available.
Sliding Resistance on a Constrained Rubber Layer Due to Rubber Hysteresis
Authors: Li C. G. , Steif P. S.
Published: February 2011

Sliding resistance of a rigid cylinder over a thin rubber layer due to rubber hysteresis is investigated. This problem underlies a model being developed for quantitatively accurate predictions of the performance of a new class of damping devices. As a full multiaxial constitutive law reflecting the amplitude-dependent behavior of filled rubbers is not available, this paper sets forth an approximate method of analysis which indirectly accounts for the material nonlinearity. Results of extensive finite element calculations are then reduced to compact material-independent forms which can be used as a universal design tool. Measurements of rolling resistance are also compared with theoretical predictions.
Methods for Predicting More Confident Lifetimes of Seals in Air Environments
Authors: Gillen Kenneth T. , Celina Mathias , Keenan Michael R.
Published: February 2011

We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress—relaxation (CSR) techniques in combination with conventional oven aging exposures. The results initially indicated important synergistic effects when mechanical strain is combined with oven aging, as well as complex, non-Arrhenius behavior of the CSR results. By combining modeling and experiments, we show that diffusion-limited oxidation (DLO) anomalies dominate traditional CSR experiments. A new CSR approach allows us to eliminate DLO effects and recover Arrhenius behavior. Furthermore, the resulting CSR activation energy (Ea) from 125 to 70 °C is identical to the activation energies for the tensile elongation and for the oxygen consumption rate of unstrained material over similar temperature ranges. This strongly suggests that the same underlying oxidation reactions determine both the unstrained and strained degradation rates. We therefore utilize our ultrasensitive oxygen consumption rate approach down to 23 °C to show that the CSR Ea likely remains unchanged when extrapolated below 70 °C, allowing more confident room temperature lifetime predictions for the butyl seal.
History of Rubber Research
Authors: Morawetz Herbert
Published: February 2011

After the discovery of the tapping of Hevea rubber trees in the middle of the eighteenth century and early technological applications of Hevea rubber, efforts to discover the chemical nature of rubber started with the determination of its elemental composition in 1826. Later it was shown that rubber pyrolysis yields low molecular weight chemicals with the identical elemental composition. It was long believed that these add to each other by “secondary valence bonds.” However Staudinger's work starting in 1920 proved that Hevea (H.) rubber consists of chains linked by covalent bonds. The utility of rubber increased dramatically with the discovery of vulcanization by Goodyear in 1844. However the nature of this process remained for many years controversial due to the influence of the “colloid school” of chemistry. The first observations on the nature of rubber elasticity date back to 1805, but more than a century passed before it was shown that the retractive force of stretched rubber is entropic. X-ray crystallographic studies not only provided the ultimate proof that natural rubber consists of covalently bonded chain molecules, but also gave evidence for its chemical structure. A century ago it was found that polymeric products other than H. rubber exhibited similar elastic properties. The race to produce synthetic rubbers was largely stimulated by the two World Wars. The availability of 14C labeled precursors led to the detailed description of the biosynthetic pathway by which rubber is produced in the Hevea plant.
Cutaneous Reactions to Rubber
Authors: Taylor James S. , Leow Yung-Hian
Published: February 2011

The three major adverse cutaneous reactions to rubber include natural rubber latex allergy, irritant contact dermatitis and allergic contact dermatitis. An overview of relevant aspects of the types of natural and synthetic rubber, rubber production, and specific chemicals used in compounding and vulcanization, as well as latex proteins is essential to an understanding of these reactions. Natural rubber latex allergy is a type I, IgE mediated, immediate hypersensitivity reaction to one or more proteins present in natural rubber latex with clinical manifestations ranging from contact urticaria to allergic rhinitis, asthma, and anaphylaxis. Over the past decade, natural rubber latex allergy has become a major medical, occupational health, and medicolegal problem. Individuals at highest risk are patients with spina bifida and health care workers. Diagnosis is based largely on clinical history and examination, and serologic and intracutaneous testing. Irritant contact dermatitis is non-immunologic and is the most common cutaneous reaction to rubber. Cumulative exposure to low-grade irritants impairs the barrier function of the skin and allows penetration of potential irritants and allergens. Diagnosis is based on history of exposure to known irritants, cutaneous examination, and exclusion of allergy. Allergic contact dermatitis is a type IV cell mediated, delayed hypersensitivity reaction which occurs primarily from exposure to rubber chemicals either directly or from residual amounts present in rubber products. Most cases present with an eczematous dermatitis, but purpura, lichenoid dermatitis, and depigmentation occasionally occur. Diagnosis is made on the basis of history, examination, and epicutaneous patch testing with rubber chemicals and rubber products. Treatment is with allergen and irritant avoidance and substitution, environmental control, personal protective equipment and topical and systemic pharmacologic therapy. A unified approach is needed in the diagnosis and treatment of adverse cutaneous reactions to rubber and it is important to remember that some patients may have both contact dermatitis and natural latex allergy. Determining the bioavailability and elicitation threshold of rubber allergens may be helpful in reducing allergic reactions from consumer and industrial rubber products.
A Historical Perspective and Review of Elastomeric Stick—Slip
Authors: Rorrer Ronald A. L.
Published: February 2011

Stick—slip sliding of elastomers is an important subtopic to the general topic of the sliding friction of elastomers. This paper provides a review of the experimental and analytical work that has occurred over the last 50 years on stick—slip sliding. Both dry and lubricated sliding of elastomers are reviewed. Stick—slip of elastomers is traced from the early experimental work on friction of the 1950–1960s through the more recent experimental and modeling results of the 1980–1990s. From the literature the common driving mechanism for both wet and dry sliding is most often attributed to a negative slope for friction as a function of velocity.
Rubber Friction on Self-Affine Road Tracks
Authors: Klüppel Manfred , Heinrich Gert
Published: February 2011

A basic theoretical concept of rubber friction on rough surfaces is presented that relates the frictional force to the dissipated energy of the rubber during sliding stochastic excitations on a broad frequency scale. It is shown that this is of high relevance for tire traction and allows for a prediction of the likely level of friction of tread compounds on the basis of viscoelastic data. The impact of both, the frequency dependent loss- and storage modulus on the frictional force during sliding of tires on rough tracks, is demonstrated quantitatively for different sliding velocities. The effect of the surface roughness of road tracks is described by three characteristic surface descriptors, i.e., the fractal dimension and the correlation lengths parallel and normal to the surface. These descriptors can be obtained from a fractal analysis of the road texture via stylus- or laser measurements. In particular, it is shown that the applied model of rubber friction is in agreement with the classical friction data of Grosch, who found a broad maximum for the friction coefficient with increasing sliding speed. The broadness of the friction maximum is shown to be directly related to the broadness of the roughness scale of the surface.
Evaluating the Durability of Silicone Duplex Coatings Using a Scratch Tester
Authors: Kohl J. G. , Singer I. L. , Griffith J. R.
Published: February 2011

Scratch tests were used to evaluate the durability of duplex elastomeric coatings under single pass, continuous loading, low speed sliding contact. The coatings consisted of a softer elastomer top layer (effective modulus = 3 MPa) on a stiffer elastomer bond layer (effective modulus = 23 MPa) on epoxy-coated steel. Duplex coating thicknesses ranged from 0.1 to 1 mm. Two different scratch styli were used: a 1.6 mm radius steel ball and a conical pin with a 0.8 mm radius diamond tip. The tangential force increased monotonically with normal force, then dropped suddenly; the onset of this drop is defined as the critical tangential force, Tc. Tc increased linearly with increases in both bond and top coat thicknesses, but the thickness dependence of the bond coat was 2 to 3 times more than that of the top coat. Optical and Raman microscopy of scratch tracks associated the damage at Tc with either tearing of the top coat behind the slider or debonding of the bond coat ahead of the slider or a combination of both. The thickness dependence of Tc is discussed qualitatively in terms of both stress and fracture mechanics models that account for damage to elastomer-coated substrates.
Stiffness of Rubber Bush Mountings Subjected to Tilting Deflection
Authors: Horton J. M. , Gover M. J. C. , Tupholme G. E.
Published: February 2011

An exact explicit expression is derived for the reduced tilting stiffness of a cylindrical rubber bush mounting of finite length. Close agreement is found between the calculated numerical values and the available experimental data.
Thermal Degradation Studies of a Polyurethane Propellant Binder
Authors: Celina M. , Graham A. C. , Gillen K. T. , Assink R. A. , Minier L. M.
Published: February 2011

The thermal oxidative aging of a crosslinked hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) based polyurethane rubber, used as a polymeric binder in solid propellant grain, was investigated at temperatures from 25 to 125 °C. The changes in tensile elongation, polymer network properties and chain dynamics, mechanical hardening and density were determined with a range of techniques including modulus profiling, solvent swelling, NMR relaxation and O2 permeability measurements. We critically evaluated the Arrhenius methodology that is commonly used with a linear extrapolation of high temperature aging data using extensive data superposition and highly sensitive oxygen consumption experiments. The effects of other constituents in the propellant formulation on aging were also investigated. We conclude that crosslinking is the dominant process at higher temperatures and that the degradation involves only limited hardening in the bulk of the material. Significant curvature in the Arrhenius diagram of the oxidation rates was observed. This is similar to results for other rubber materials.
On the Reason that Passenger Tire Sidewalls are Based on Blends of Natural Rubber and cis-Polybutadiene
Authors: Kim H. J. , Hamed G. R.
Published: February 2011

A tire sidewall must have good resistance to fracture over a range of conditions covering rapid as well as slow crack growth. A vulcanizate based on a 50/50 natural rubber (NR)/cis-butadiene rubber (cis-BR) blend seems to meet this requirement. It retains the ability for longitudinal crack branching and has catastrophic rupture resistance near that of a corresponding NR vulcanizate. At the same time, the blend has good resistance to slow fatigue crack growth, much like that of a cis-BR vulcanizate. The combination of desired properties in the blend may result from co-continuity of its NR and BR phases.
Energy Release Rate for a Crack in a Tilted Block
Authors: Gent A. N. , Razzaghi-Kashani M.
Published: February 2011

Approximate relations were obtained previously for the tilting stiffness of a rubber block bonded between two rigid plates, assuming linear elastic behavior.1 They take into account restrictions placed on the deformation by the bonded surfaces, a feature that becomes extremely important for thin blocks of an incompressible material. Results are reviewed here for two special cases: an infinitely wide or a relatively narrow block. In both cases the length and width are assumed to be large compared to the block thickness. Approximate values are then derived for the energy release rate G for a relatively deep crack running into the block on the tension side, parallel to the bonded surface. Values for tilting stiffness and energy release rate have also been calculated by finite element analysis (FEA) for slightly compressible rubber blocks, with Poisson's ratio in the range: 0.49 to 0.5, and for blocks of various thicknesses. Good agreement is obtained with the approximate theory for deep cracks, when the assumptions on which the theory is based are more likely to be valid. Application of repeated tilting deformations to a bonded rubber block appears to be a simple way of measuring crack growth rates under mechanical fatigue. Moreover, a wide range of energy release rates can be employed using a single specimen.
Chemical Interaction and Phase Morphology Development of Carboxy Terminated Butadiene-co-Acrylonitrile Rubber Toughened Epoxy Blends
Authors: Vineeta Nigam , Setua D. K. , Mathur G. N.
Published: February 2011

The nature of chemical interaction between carboxy terminated butadiene-co-acrylonitrile (CTBN), a reactive liquid rubber, and epoxy cresol novolac (ECN) resin during curing with diamino diphenyl methane (DDM) as hardener has been studied by Fourier transform infrared spectroscopy (FTIR). Blends of CTBN and ECN were withdrawn at a regular interval of 15 min for 2 h and the FTIR spectra were recorded in each case. Variations of the positions of the characteristic peaks of the oxirane group of epoxy and carboxyl group of CTBN as well as formation of several new peaks with the progress of the curing were observed. Scanning electron microscopy (SEM) was conducted in each of the above samples to study the evolution of phase morphology through growth of the rubber phase while the continuous epoxy matrix underwent curing by the hardener. The surface topography and microstructure of impact-failed toughened epoxies have also been studied with the help of atomic force microscopy (AFM).
Carbon Black and Fullerenes: New Discoveries in Early Formation Mechanisms and Nucleation
Authors: Johnson M. Pontier , Locke R. W. , Donnet J. B. , Wang T. K. , Wang C. C. , Bertrand P.
Published: February 2011

Recent studies on the formation of carbon black have resulted in the previously unreported finding of buckminster-fullerene, C60, in trace quantities in the toluene extractable materials. High-resolution transmission electron microscopy (HRTEM) experiments indicate the molecule may be functioning as a nucleation site in the formation of primary particles of carbon black. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) provided the surface chemical analysis of conventional and experimental carbon blacks. The toluene extracts represented the precursor compounds present in the gaseous phase at the time of quench. The extracts were analyzed by Fourier transform infrared (FTIR) spectroscopy, liquid chromatography (LC)/mass spectroscopy (MS) and elemental composition. The data, taken as a whole, have led to a more clear understanding of the competitive chemical pathways occurring during the inception and nucleation of a primary particle of carbon black. Direct observation of nucleation sites and types are possible with HRTEM analysis.
Characterization of Ground Rubber Tire and its Effect on Natural Rubber Compound
Authors: Naskar Amit K. , De S. K. , Bhowmick A. K. , Pramanik P. K. , Mukhopadhyay R.
Published: February 2011

Ground rubber tire (GRT) particles of different sizes were characterized and the effect of these particles in a natural rubber (NR) compound was studied. It is found that smaller particles contain less polymer, but have higher amounts of fillers and metals with respect to polymer. NR compound containing smaller GRT particles shows better physical properties, but poorer aging characteristics.
Use of Atomic Force Microscope as a Nanoindenter to Characterize Elastomers
Authors: Mareanukroh Methporn , Eby R. K. , Scavuzzo R. J. , Hamed Gary R. , Preuschen Judith
Published: February 2011

The atomic force microscope (AFM) in the force mode has been used as a nanoindenter for determining the crosslink density and modulus of rubber on a fine scale. The force—distance curves obtained as the sample is moved against the tip can render information about mechanical properties of the sample. The technique for this purpose has been established. Several instrumental and technical difficulties encountered during the development of the technique have been identified and solved. The difficulties include surface roughness, thickness variation of the sample, hysteresis of the scanner, determining the stiffness of the cantilever, determining the geometry of the tip, converting the sensor output to force and determining the penetration depth of the tip. The determination of the effective tip geometry requires use of a calibration material. Force—distance measurements were made on a series of styrene-butadiene rubbers (SBR) with different crosslink densities. The modulus determined by AFM agreed with the modulus measured with dynamic mechanical analysis. The results of force/penetration depth show a linear relationship with crosslink density. The AFM results are shown to correlate with those from NMR. The effects of rubber oxidation in air were examined. The results show that both homogeneous and heterogeneous oxidation can be detected by this method.
Prediction of Rheometric Properties of Compounds by Using Artificial Neural Networks
Authors: Schwartz Gustavo Ariel
Published: February 2011

The ability of an Artificial Neural Network (ANN) to evaluate the variability of rheometric properties of rubber compounds from their formulation is presented. Because of the complexity and non-linearity of mixing processes, an exact mathematical treatment of the problem is extremely difficult, or even impossible. The use of artificial neural networks (ANNs) might be very useful to analyze these processes, since they have the ability to map nonlinear relationships without prior information about process or system models. In this work a three-layer ANN is used and the optimum parameters are determined. The results are compared with theoretical and experimental published data. The dependence of the rheometric properties as a function of compound components is also analyzed. Finally, the sensibility matrix concept is introduced. The sensibility matrix allows us to calculate the minimum expected variability, for a given compound, due to the weight tolerances of its components.
The Action of N-(Cyclohexylthio)Phthalimide as a Prevulcanization Inhibitor of 2-Bisbenzothiazole-2,2′-Disulfide Accelerated Sulfur Vulcanization
Authors: Gradwell Michael H. S. , Stephenson Nigel R.
Published: February 2011

Prevulcanization inhibitors (PVI) provide an important delay in the curing reactions that occur in accelerated sulfur vulcanization. In this study, the reactions of N-(cyclohexylthio)phthalimide (CTP) with other curatives (excluding zinc oxide) were investigated in the presence and absence of rubber. The CTP has been shown to react very readily with 2-mercaptobenzothiazole (MBT) and this reaction has previously been credited with the delay observed. However, recent studies have shown that MBT is not formed until crosslinking has started. In a 2-bisbenzothiazole-2,2′-disulfide (MBTS) accelerated sulfur cure, CTP was shown not to delay the onset of crosslinking, but once crosslinking began, with the concurrent formation of MBT, the CTP reacted with the MBT inhibiting further polysulfide formation, pendent group formation and thus crosslinking. Crosslinking continues after the CTP has been consumed.
Swelling of Constrained Rubber Layers: Effect on Free Energy of Detachment
Authors: Gent A. N. , Hung W. J. , Tse M. F.
Published: February 2011

The degree of swelling of a rubber layer by a compatible liquid has been calculated for cases when the layer is constrained, for example when it is bonded to a rigid substrate. The stored energy residing in swollen layers is also computed. From these results the amount of energy is determined that becomes available if a bonded layer separates from a substrate and then becomes free to swell further. The released energy is shown to be quite high, of the order of 10 MJ/m3 in a representative case. Attention is drawn to the importance of the layer thickness when this energy is applied to bond rupture. For layers having a thickness of the order of 1 mm or greater, the available energy is greater than the intrinsic strength of the bond or of the swollen elastomer itself. In accord with this conclusion, soft rubber layers, sandwiched between and bonded to flexible but inextensible backings, are observed to separate spontaneously and then tear away from the backing when swollen by a compatible liquid. And layers that are still attached to the backing become sharply curved before tearing loose, in rough agreement with the theoretical predictions.
Synthesis, Bromination and Cure of Isobutylene/Isoprene/P-Methylstyrene and Isobutylene/Isoprene/Styrene Terpolymers
Authors: Kaszas Gabor , Tran Binh
Published: February 2011

High molecular weight isobutylene/isoprene/p-methylstyrene and isobutylene/isoprene/styrene terpolymers containing up to 10.6 mol% p-methylstyrene and 3.6 mol% styrene were synthesized using “H2O”/AlCl3 as an initiator/coinitiator system in methylchloride at -95 °C. p-Methylstyrene was found to be uniformly distributed in the chains due to its similar reactivity to isobutylene. In contrast, styrene had a lower reactivity than isobutylene or even isoprene, resulting in low conversion of the styrene monomer. The reactivity ratios obtained were in good agreement with the published values. Up to about 3 mol% styrenic monomer content, the Tg of the terpolymers showed no significant increase. The isoprene units of the terpolymers were brominated by the conventional bromination technique. During bromination, some of the aromatic rings also underwent bromination. The extent of this reaction was found to be much lower in the case of p-methylstyrene than in the case of styrene. The brominated terpolymers were cured using ZnO. The brominated terpolymers displayed much faster cure, higher maximum torque and modulus at the same brominated isoprene concentration than brominated copolymers of isobutylene and isoprene, indicating that the aromatic rings participate in the cure. The brominated terpolymers showed an increased resistance to hot air aging, compared to brominated polymers containing no styrenic termonomer.
The Friction and Wear of Rubber Part 1: Effects of Dynamically Changing Slip Direction and the Damage Orientation Distribution Function
Authors: Gerrard David P. , Padovan Joe
Published: February 2011

In Part 1, results of an experimental and analytical study are offered which examined the effects of a dynamically changing slip direction on a rubber surface's friction and wear performance and on the properties of an industrial abrasive. For a filled SBR compound, it was found that a dynamically changing slip direction had a small effect on the friction/traction performance, but a substantial beneficial effect on the surface's wear performance. The abrasive's ability to generate wear was found to be strongly dependent on the accumulation of side slip over the life of the abrasive. Conceptualization of the Damage Orientation Distribution Function is offered to describe the statistical nature of the oriented damage generated on a slipping rubber surface. The experimental results are shown to be in excellent agreement with model predictions based on several simple assumptions regarding the effects that changing slip orientation has on the response of the Distribution Function.
Influence of Novel Electron Beam Modified Surface Treated Dual Phase Filler on Rheometric and Mechanical Properties of Styrene Butadiene Rubber Vulcanizates
Authors: Shanmugharaj A. M. , Bhowmick Anil K.
Published: February 2011

Rheometric and mechanical properties, hysteresis and swelling behavior of the Styrene-Butadiene Rubber vulcanizates (SBR) filled with unmodified and novel electron beam modified surface treated dual phase fillers were investigated. Scorch time increases for these modified filler loaded vulcanizates due to introduction of quinone type oxygen on the surface. Electron beam modification of dual phase filler in the absence of trimethylol propanetriacrylate (TMPTA) or triethoxysilylpropyltetrasulphide (Si-69) significantly improves the modulus of the SBR vulcanizates, whereas the values of tensile strength and elongation at break drop. However, presence of TMPTA or silane slightly increases the modulus with significant improvement in tensile strength. This effect is more pronounced at higher loading of these modified fillers in SBR vulcanizates. These variations in modulus and tensile strength are explained by the equilibrium swelling data, Kraus plot and a new mathematical model interpreting the polymer-filler interaction. Hysteresis loss ratio of SBR vulcanizates loaded with irradiated fillers in absence and presence of TMPTA or silane increases due to highly aggregated structure of the filler.
Effects of Thermal Aging on The Mechanical Properties of Natural Rubber
Authors: South Joseph T. , Case Scott W. , Reifsnider Kenneth L.
Published: February 2011

The focus of this research was to investigate the effect of thermal degradation upon the mechanical properties of a natural rubber compound. We examined both the quasi-static and dynamic mechanical properties of a natural rubber vulcanizate which had been subjected to isothermal, anaerobic aging. The thermal aging was conducted between the temperatures of 80 °C and 120 °C for times ranging from 3 to 24 days. The effect of thermal degradation was measured using the changes in the crosslink distribution of the vulcanizates as functions of time at temperature. A master curve relationship between the crosslink distribution of the vulcanizates due to thermal degradation and the static and dynamic mechanical properties has been developed. It was found that the both the quasi-static and dynamic mechanical properties correlated with the percentage of poly and monosulfidic crosslinks, where in general higher levels of polysulfidic crosslink gave rise to the highest mechanical properties.
Novel Thermoplastic Elastomers Based on Acrylonitrile-Butadiene-Styrene Terpolymer (ABS) from Waste Computer Equipment and Nitrile Rubber
Authors: Anandhan S. , De P. P. , De S. K. , Bhowmick Anil K. , Bandyopadhyay S.
Published: February 2011

Acrylonitrile-butadiene-styrene terpolymer (ABS) is one of the engineering plastics most frequently used as outer casings for computer equipment such as monitors, keyboards and other similar components. In an attempt to recycle, blends of scrap computer plastics (SCP) based on ABS with nitrile rubber (NBR) were prepared and mechanical properties and morphology were studied. Effect of dynamic vulcanization on the properties of 60/40, 70/30, and 80/20 NBR/SCP blends was assessed. These blends show the thermoplastic elastomeric behavior. Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) studies show that the dynamically vulcanized NBR particles are dispersed in the ABS matrix. The thermoplastic elastomeric blends show excellent swelling resistance in IRM # 93 oil.
Reinforcing Effect of Silica and Silane Fillers on the Properties of Some Natural Rubber Vulcanizates
Authors: Ansarifar A. , Nijhawan R. , Nanapoolsin T. , Song M.
Published: February 2011

The reinforcing effect of up to 6 parts per hundred rubber by weight (phr) bis- (3-triethoxysilylpropyl) tetrasulfide (TESPT), a bifunctional organosilane, on the crosslink density, bound rubber, and technical properties of some conventional accelerator/sulfur compounds of natural rubber, containing 30 phr precipitated amorphous white silica was studied. The crosslink density and bound rubber improved as a function of TESPT loading. The tensile strength, elongation at break, stored energy density at rupture, and cohesive tear strength deteriorated at low loading of TESPT, but they subsequently increased after the full amount of TESPT was introduced into the compound. The improved properties of the vulcanizate was due to the better dispersion of the filler in the rubber matrix. However, the cyclic fatigue life was adversely affected, and the hardness hardly changed as a result of adding TESPT to the rubber.
Thermomechanical Degradation of SBR During Ultrasonic Treatment under the Static Conditions
Authors: Yashin V. V. , Hong C. K. , Isayev A. I.
Published: February 2011

The paper presents the results of experimental and theoretical studies of the ultrasonic treatment of ground vulcanized unfilled styrene-butadiene rubber (SBR) in a static device (no flow). Degradation of the rubber network took place during the treatment. Crosslink density and gel fraction were measured in the samples ultrasonically treated at various pressures, ultrasonic amplitudes and exposure times. Consumption of the ultrasonic energy was also monitored. The structural characteristics of SBR ultrasonically treated under static conditions have been found to be significantly different from those reported previously for the continuous process. Theoretical calculations have demonstrated that the observed differences could be attributed to a partial depolymerization of broken rubber chains caused by a significant temperature rise in the course of ultrasonic treatment under static conditions. It has also been shown that the non-linearity of compressibility of a thin ground rubber layer has to be taken into account in the calculations of ultrasonic power consumption.
Fatigue of Cord-Rubber Composites: V. Cord Reinforcement Effect
Authors: Song J. H. , Costanzo F. , Lee B. L.
Published: February 2011

Fatigue behavior of cord-rubber composite materials forming the belt region of radial pneumatic tires has been characterized to assess their dependence on stress, strain and temperature history as well as materials composition and construction. Estimated at various levels of stress amplitude were the fatigue life, the extent and rate of resultant strain increase (“dynamic creep”), cyclic strains at failure, and specimen temperature. Reflecting their matrix-dominated failure modes, such as cord-matrix debonding and delamination, composite laminates with different cord reinforcements showed the same S-N relationship as long as they were constructed with the same rubber matrix, the same cord angle, similar cord volume, and the same ply lay-up. The interply shear strain of 2-ply ‘tire belt’ composite laminate under circumferential tension was affected by twisting of specimen due to tension-bending coupling. However, a critical level of interply shear strain, which governs the gross failure of composite laminate due to the delamination, appeared to be independent of different lay-up of 2-ply vs symmetric 4-ply configuration. Because of much lower values of single cycle strength (in terms of gross fracture load per unit width), the composite laminates with larger cord angle and the 2-ply laminates exhibited exponentially shorter fatigue lifetime, at a given stress amplitude, than the composite laminates with smaller cord angle and 4-ply symmetric laminates, respectively. Maximum cyclic strain of composite laminates at failure, which measures the total strain accumulation for gross failure, was independent of stress amplitude and close to the level of static failure strain. For all composite laminates under study, a linear correlation could be established between the temperature rise rate and dynamic creep rate which was, in turn, inversely proportional to the fatigue lifetime.
Dependence of Physical Properties and Processing Behavior of Blends of Silicone Rubber and Fluororubber on Blend Morphology
Authors: Ghosh Arun , De† S. K.
Published: February 2011

The paper reports that the processing behavior and physical properties of the blends of silicone rubber and fluororubber based on tetrafluoroethylene/propylene/vinylidene terpolymer. The processing behavior of the fluororubber can be improved on blending with low viscous silicone rubber. The results indicate that the processing behavior, mechanical properties, surface energies, and flammability of the blends are controlled by the blend morphology. Surface morphology of the blends show that blends of two rubbers are microheterogeneous and biphasic structure, wherein silicone rubber acts as a continuous matrix with the fluororubber as a dispersed phase.
Gum and Black-Filled Double Networks of cis-1,4-Polyisoprene Crosslinked with Sulfur Donors: Part I. Tensile Properties
Authors: Hamed G. R. , Umetsu K.
Published: February 2011

Gum and black-filled double networks of cis-1,4 polyisoprene, crosslinked with sulfur donors, have been prepared by first partially curing sheets, then stretching them and completing cure. Double networks are anisotropic and exhibit a residual extension ratio λr, which is higher for filled compared to gum samples. Additionally, double networks of filled specimens have higher anisotropy than gum counterparts, presumably because carbon black promotes chain alignment and strain-crystallization. Tensile specimens cut parallel to the stretch direction are stiffer, less extensible, and sometimes stronger than simple isotropic networks, while perpendicular specimens have stress-strain responses much like that of the isotropic control.
Mechanism of Improved Aged Rubber-to-Brass Adhesion Using One-Component Resins
Authors: Patil Pankaj Y. , van Ooij William J.
Published: February 2011

Using a squalene liquid rubber modeling approach, we have shown recently that the role of an adhesion promoting one-component resin system is similar to the conventional resorcinol based two-component resin system1. However, to further study the effect of resins in real natural rubber based formulations, eight similar formulations were mixed to make compounds in natural rubber. These rubber compounds were characterized and tested for their mechanical properties viz. stress at break, stress at 300% strain, elongation %, initial, heat and humidity aged wire adhesion pull-out test, tensile tear strength test. Furthermore, to confirm our proposed theory of the migration of resins from the rubber matrix towards the surface, the surfaces of the rubber compounds were studied using ATR-FTIR spectroscopy. NMR spectroscopy was performed on the rubber compounds to study the sulfur crosslink density distribution. Based on our new findings relating to improved corrosion performance of sulfidized brass cords a theory has been put forward that loss of rubber-to-brass adhesion is in fact due to the aging of the brass cord. This aging of brass cord is found to be due to the dissolution of iron from the steel cord. It was observed that the use of different formulations affected the corrosion performance of the sulfidized brass cords in a different manner. The use of resins, particularly one-component resins, seemed to inhibit this iron dissolution thus resulting in durable rubber-to-brass adhesion even in the humidity aged adhesion blocks.
Investigation of the Payne Effect and its Temperature Dependence on Silica-Filled Polydimethylsiloxane Networks. Part II: Test of Quantitative Models
Authors: Clément F. , Bokobza L. , Monnerie L.
Published: February 2011

The results obtained in Part I, on Polydimethylsiloxane (PDMS) networks filled with treated Aerosil A300 silica at variable temperature and various loadings, have been used to test the quantitative models of the Payne effect proposed by Kraus, Huber-Vilgis, and Maier-Göritz. Each model is able to account only for a part of the experimental results: Kraus and Maier-Vilgis for the variation of the Payne effect with filler volume fraction, Maier-Göritz for the influence of temperature on the Payne effect. But neither of these quantitative models is able to fit the whole set of experimental results on G′ and G″ with a unique set of parameters.
Reinforcement and Nonlinear Viscoelasticity of Polymer Melts Containing Mixtures of Nanofillers
Authors: Sternstein S. S. , Ramorino G. , Jiang B. , Zhu Ai-Jun
Published: February 2011

The reinforcement and concomitant nonlinear viscoelastic behavior have been investigated for several composites of linear polymer melt with various binary mixtures of nanofillers having different surface chemistries and particle sizes. The dependence of storage modulus and loss factor on dynamic shear strain amplitude has been obtained for several compositions of each binary filler pair. Composites with mixed fillers display nonlinear interactions that are filler pair/matrix specific. Total filler concentration appears to be a major factor, suggesting that nearest neighbor particle spacing is crucial even if the neighbors are of a different filler type. The results are consistent with the theory recently proposed by Sternstein and Zhu in which the high reinforcement by nanofillers is due to the trapping of entanglements and the resultant effects on matrix chain mobility and entropic elasticity. At high strain amplitudes, the storage modulus and loss factor of the composites with binary filler mixtures are found to be nearly independent of the filler mixture ratio, and dependent only on the total filler concentration. A “partial molar” storage modulus for mixed filler composites is defined for future considerations, and specific interactions are presented for two binary filler systems.
The Reinforcement and Crosslinking of Styrene Butadiene Rubber with Silanized Precipitated Silica Nanofiller
Authors: Ansarifar A. , Wang L. , Ellis R. J. , Kirtley S. P.
Published: February 2011

Synthetic precipitated amorphous white silica nanofiller was used to reinforce and crosslink styrene-butadiene rubber (SBR). The silica surfaces were pre-treated with bis[3-triethoxysilylpropyl-)tetrasulfide (TESPT) bifunctional organosilane. TESPT chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur-cure. The silica particles were fully dispersed in the rubber, which was cured primarily by using sulfur in TESPT, or, by adding elemental sulfur to the cure system. The cure was also optimized by incorporating different accelerators and activators in the rubber. This study showed that the silica particles could be used both as crosslinking and reinforcing filler in the rubber.
Study on Crosslinking in Diimide Reduction of Nitrile Butadiene Rubber
Authors: Zhou Shuqin , Li Shaoyi , Bai Huadong
Published: February 2011

Acrylonitrile-butadiene rubber (NBR) in latex form was selectively hydrogenated by redox system consisting of hydrazine hydrate and hydrogen peroxide, with boric acid as catalyst. Soluble hydrogenated NBR latex was obtained; but the coagulated products were gelled on drying. This problem becomes the major obstacle for the hydrogenation technique to be commercialized. It is important to study the crosslinking reaction in the system and to solve the problem. The cause for the crosslink was investigated in three possibilities: (i) crosslinking caused by the hydrogenation of CN group; (ii) by the oxidation of C=C double bonds and (iii) by radicals in the system. The control of the crosslink was also studied. The oil resistant nitrile group —CN on the polymer chain had no change during drying process. There were no signs of carbonyl group C=O formed by oxidation and amine like groups -NH- formed by the hydrogenation of CN in HNBR gel fraction. The newly formed alkoxyl radicals were detected by ESR spectroscopy analysis in the hydrogenation system after specific reaction time. Crosslinking reaction was controlled to a large extent by using hydroquinone as gel inhibitor.
Protein Levels Affect the Cure Efficiency and Allergenic Potential of Polyisoprene Latices
Authors: Schloman W. W. , Teetor V. H. , Ray D. T.
Published: February 2011

Commercial NR latex has a higher total protein content than guayule (GR) latex. Some NR proteins are allergens bound to the rubber particle surface. Washing NR latex with a non-ionic surfactant displaced these particle-bound proteins and reduced allergens by more than 95%. The cost of such deproteination was reduced vulcanization efficiency, as determined by crosslink density. The extent of vulcanization correlated well with both total protein and allergen levels. Compared with films prepared from untreated NR latex, films from both surfactant-treated NR latex and GR latex had lower states of cure. Where particle-bound proteins were still present, as they are in GR latex, crosslink development could be completed by heat aging. In contrast, crosslink development in the film from surfactant-treated NR was complete after dipping and drying. The resulting films yielded high levels of extractable protein allergens.