bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solid State NMR Characterization of Crosslinked Brominated Poly(Isobutylene-co-4-Methylstyrene)
Authors: Eckman R. R. , Gardner I. J. , Wang H-C. 
Published: February 2011

Abstract
The curing of brominated poly(isobutylene-co-4-methylstyrene) was studied using solid-state magic-angle-spinning NMR, a technique which is uniquely suited to investigate cured or crosslinked polymers. This brominated copolymer contains 4-bromomethylstyryl and 4-methylstyryl functional groups and was compression cured with pure ZnO. It was proposed that a precomplex is formed between zinc and the 4-bromomethylstyryl group, which generates a benzylic carbocationic intermediate. Crosslinking predominantly occurs by alkylation of the phenyl ring of another 4-bromomethylstyryl group by the benzylic intermediate. The ZnO brings the two bromides of these groups into proximity. The dependence of the cure chemistry on the concentration of 4-bromomethylstyryl functional groups was studied. Conversion of some 4-bromomethylstyryl groups to oxygenated species upon curing was also observed.
Basic Studies of Extrusion of Rubber Compounds in a Pin Barrel Extruder
Authors: Shin Kyung-Chul , White James L. 
Published: February 2011

Abstract
An experimental study of the flow, pumping, and mixing characteristics of three different rubber-carbon black compounds in a model pin barrel extruder is presented. These are a model SBR/BR passenger tire compound, a NR truck tire compound, and a NBR mechanical goods compound. Comparisons are made of the initial extruder without pins or slices/grooves in the screw flights, an extruder containing slices or grooves in its flights, and a pin barrel extruder. It is found for each compound that introducing slices in screw flights improves mixing/homogenization and decreases pumping ability. Introduction of pins improves mixing/homogenization and has little effect on pumping. The homogenization is best for the passenger tire tread compound and worst for the NBR mechanical good compound.
Polystyrene-Natural-Rubber Mixtures: Preparation and Properties
Authors: Valić S. , Topić M. , Andreis M. , Ranogajec F. , Veksli Z. , Šincek-Pećanić V. 
Published: February 2011

Abstract
Thermoplastic elastomers were prepared from mixtures of polystyrene and natural-rubber latexes. The mechanical measurements, thermally stimulated depolarization current measurements, and NMR spin-spin relaxation measurements have shown that the properties of prepared thermoplastic elastomers depend on the composition and the interface created by changing the size of the accessible polystyrene surface.
Influence of Some Parameters on the Solution of a Thermal Model of Vulcanization
Authors: Burger Jacques , Burger Nicole , Pogu Marc 
Published: February 2011

Abstract
The thermal behavior of a piece of rubber during a vulcanization process is modelized by a set of two coupled differential equations. The first one is a classical nonlinear heat equation while the second is a reaction equation. The aim of this article is first to solve numerically the two equations using a finite element procedure for the partial differential equation and a Runge-Kutta like scheme for the reaction equation, and then to study the sensitivity of the solution to variations in some parameters.
Solid State Carbon-13 NMR Studies of Elastomers. XL N-t-Butyl Benzothiazole Sulfenimide Accelerated Sulfur Vulcanization of cis-Polyisoprene at 75 MHz
Authors: Krejsa M. R. , Koenig J. L. 
Published: February 2011

Abstract
The network structure of TBSI-accelerated vulcanization of cis-polyisoprene was studied using C-13 solid-state NMR. The initial crosslink products consisted of A1c (cis) and A2c (cis) polysulfides. As the percent cure is increased, the A1c and A2c structures reduce in rank to monosulfides, and polysulfidic B1c (cis) and B1t (trans) structures are formed. During the maturation period C1c (cis) polysulfidic structures are also formed. The percent of sulfurization was shown to vary directly with sulfur concentration, while the efficiency of sulfurization (crosslink/cyclic-structure ratio) was shown to vary with accelerator content. TBSI-accelerated vulcanization was found to be more inefficient (lower crosslink/cyclic-structure ratio) than TBBS-accelerated vulcanization during the initial cure region. However, this results in shorter sulfur chains, which decreases the reactivity of TBSI vulcanizates as compared to TBBS vulcanizates during the reversion regime.
Electrophilic Addition of Brominated Poly(Isobutylene-co-4-Methylstyrene) to Olefins Catalyzed by Zinc Salts: A Model Study
Authors: Fréchet J. M. J. , Bielski R. , Wang H-C. , Fusco J. V. , Powers K. W. 
Published: February 2011

Abstract
The chemical reactivity of a new elastomer based on brominated poly(isobutylene-co-4-methylstyrene) in electrophilic additions to olefins has been investigated using model compounds as well as appropriate polymers. The reactions catalyzed by zinc salts are influenced by the solubility as well as the composition of the catalyst. While the reactivity of zinc bromide is limited by its low solubility in nonpolar medium, zinc oxide and zinc stearate can afford excellent results once an induction period has elapsed. The induction period likely corresponds to the formation of more reactive zinc based moieties through interchange reactions with the benzylic bromide groups. The mechanism of the addition process involves initial formation of carbocationic complexes with the zinc salts, followed by addition to the double bonds of the olefins. The products resulting from these additions have been characterized by NMR as well as gas chromatography-mass spectrometry. A comparison of potential crosslinking processes involving olefin addition or electrophilic aromatic substitution reactions shows that the former process is preferred. The findings of this study are directly applicable to the co-curing of elastomers based on brominated poly-(isobutylene-co-4-methylstyrene) with polyolefins.
Filler-Elastomer Interactions. Part VIII. The Role of the Distance between Filler Aggregates in the Dynamic Properties of Filled Vulcanizates
Authors: Wang Meng-Jiao , Wolff Siegfried , Tan Ewe-Hong 
Published: February 2011

Abstract
Based on the concepts of the occlusion of rubber and random packing of spheres whose volume is equivalent to that permeated by individual aggregates, an equation was deduced to estimate the distance between carbon-black aggregates in filled rubber. It was found that when the interaggregate distance reaches a critical point which is approximately identical for all carbon blacks investigated (furnace blacks), the elastic modulus measured at very low strain deviates from the modified Guth-Gold equation. Tan δ and resilience are mainly determined by the distance between aggregates. These phenomena are related to filler networking which is determined by the attractive potential and the distance between individual aggregates. Since the factor Sf, used to characterize the strength of secondary filler networks in hydrocarbon rubbers and measured by means of inverse gas chromatography, is approximately the same for all furnace blacks, the interaggregate distance seems to determine filler networking. A comparison of fillers with different Sf (graphitized vs. nongraphitized carbon blacks, carbon black vs. silica) shows that at the same interaggregate distance, a lower Sf leads to higher tan δ of the filled vulcanizates.
FT-IR Spectroscopy, a Major Tool for the Analysis of Peroxide Vulcanization Processes in the Presence of Coagents. I. Mechanism of EPM Peroxide Vulcanization with Aromatic bis(Allyl)Esters as Coagents
Authors: Dikland H. G. , van der Does L. , Bantjes A. 
Published: February 2011

Abstract
In this paper the results of investigations on the mechanism of EPM peroxide vulcanizations in the presence of various bis(allyl)esters of aromatic diacids—as coagents—are presented. These coagents are commonly used in the rubber industry to increase the crosslinking efficiency, however, until now the mechanism of this process remained unclear. In our studies it is demonstrated that when using FT-IR spectroscopy in combination with equilibrium swelling techniques and atomic force scanning microscopy, the role of the coagents can be elucidated.
Improved Quantitative Determination of Elastomers in Tire Rubber by Kinetic Simulation of DTG Curves
Authors: Yang J. , Kaliaguine S. , Roy C. 
Published: February 2011

Abstract
A method of identifying and quantifying elastomers and processing oil in tire rubber, called DTG curve simulation method, is proposed. This method is based on DTG (derivative thermogravimetry) analysis of the straight elastomers NR, BR and SBR, which produces a series of decomposition rate data and pairs of kinetic constants. DTG curves of binary elastomer systems NR/SBR, NR/BR and BR/SBR are measured. The samples are qualitatively identified following the shape of their DTG curves. Quantitative determination is achieved by DTG curve simulation using a least squares method. When correct elastomers and proper compound ratio are chosen, minimum simulation error is achieved leading to effective identification. Satisfactory results were obtained when applying the method to elastomer mixtures of known composition and to tire rubbers of unknown composition. The study advanced the capability of the TG-DTG technique for quantitative determination of elastomers and blends.
FTIR and NMR Studies on Crosslinking Reaction between Chlorosulfonated Polyethylene and Epoxidized Natural Rubber
Authors: Roychoudhury A. , De P. P. , Dutta N. K. , Roychoudhury N. , Haidar B. , Vidal A. 
Published: February 2011

Abstract
A blend of chlorosulfonated polyethylene and epoxidized natural rubber undergoes a self-crosslinking reaction at elevated temperatures. Sulfonyl chloride groups of chlorosulfonated polyethylene react with epoxy groups of epoxidized natural rubber to give ether crosslinks between the two polymers. In addition to the self-crosslinking reaction, these two polymers undergo a number of side reactions as evidenced by spectroscopic studies.
Comparison of Four-Flighted and Two-Flighted Internal Mixer Rotors Using Cylindrical Coordinate Hydrodynamic Lubrication Theory
Authors: Hu Benfei , White James L. 
Published: February 2011

Abstract
Internal mixers have played a key role in the polymer industry. Internal mixers with four-flighted rotors are attracting more and more attention today. In this paper, we apply a new model based on cylindrical coordinate hydrodynamic lubrication theory for internal mixers to various rotor designs. Numerical techniques were used to carry out the calculations of the pressure field, mean flux field, and various mixing characteristic parameters. Comparisons were made for both four-flighted and two-flighted rotor designs. This was done assuming a fully filled mixing chamber. The simulation effort is important for the understanding of mixing mechanisms in internal mixers and to provide a basis for the rational design of internal mixers.
Blends of Crystallizable Polybutadiene Isomers
Authors: Nir Moira Marx , Cohen Robert E. 
Published: February 2011

Abstract
Precipitated blends of two crystallizable polybutadiene (PBD) isomers were characterized in terms of crystallization and phase behavior, morphology, and tensile mechanical properties. The isomers are syndiotactic 1,2 PBD (Mv=32.5 kg/mol) and trans 1,4 PBD (Mv=425 kg/mol). The blends exhibit heterogeneous behavior over the full range of composition. Using a solvent precipitation method, blends are obtained with heterogeneity on the order of 1 µm. Tensile properties of these semicrystalline blends are generally intermediate between those of the corresponding semicrystalline homopolymers, with some enhancement at approximately 10% 1,2 PBD content. Comparisons are made with previously reported data on amorphous PBD blends.
Analysis of Fatigue Crack Propagation in NR/BR Rubber Blend
Authors: Lee M-P. , Moet A. 
Published: February 2011

Abstract
Fatigue behavior in a blend of natural rubber (NR) and polybutadiene rubber (BR) has been investigated. The energy release rates measured from load-displacement curves recorded during the fatigue test could be used to characterize the fatigue crack propagation (FCP) history of NR/BR blend. Crack propagation kinetics showed an initial low slope “ozone crack regime” with an S-shaped “mechanico-oxidative cut growth regime”. The blend has a mechanical fatigue limit of 2.4 kJ/m2. The crack initiation constituted 25% of the total fatigue life and the low slope stage comprised 40% of the crack propagation life. Examination of the fracture profile and the fracture surface revealed that microcracks and crack tip roughening were two damage mechanisms controlling the resistance to crack propagation in the “mechanico-oxidative cut growth regime”, while the reverse herringbone pattern near the notch corresponded to the “ozone crack regime”.
States of Carbon Black Dispersion and Extensibility of Rubbers
Authors: Ahagon Asahiro 
Published: February 2011

Abstract
Analysis is made for the origin of the mixing-induced tensile property variation of a filled rubber. Attention is paid to the hydrodynamic effect f(ϕe) of the filler, defined here as the factor to adjust the deviation of 100% modulus from the theory of rubber elasticity. For the rubbers mixed under variety of conditions, the f(ϕe)'s are calculated from the observed values of the modulus, at 25°C and 100°C, and the crosslink density. The variation of the f(ϕe) is considered to be governed by the mobility of the polymer confined in agglomerates of the filler. The mobility variation due to mixing seems to be mainly influenced by agglomerate size at 25°C, and by agglomerate size and chemical constraints at 100°C. Therefore, the f(ϕe)'s at the two temperatures are suggested to be useful measures of the state of carbon-black micro-dispersion. The extensibility of the rubbers is closely related f(ϕe). This indicates that the failure property is also governed by the mobility of the confined polymer.
A Review of Sulfur Crosslinking Fundamentals for Accelerated and Unaccelerated Vulcanization
Authors: Krejsa M. R. , Koenig J. L. 
Published: February 2011

Abstract
This work has reviewed and summarized the present understanding of the fundamental science and chemistry of rubber vulcanization. The future of this area holds much potential. Recent studies have begun to fully elucidate the accelerator and accelerator complex chemistry, and definitively answer questions that have been open for debate for many years. Additionally, the understanding of the network structure is rapidly progressing through advances in analytical techniques. The largest area of future research will be the use of multiple experimental techniques to fully elucidate and understand the relationship between accelerator chemistry and the formation of specific network structures. With this knowledge, it will then be possible to molecularly engineer vulcanizates with specific properties.
Reactive Processing of Rubbers
Authors: Burlett Donald J. , Lindt J. Thomas 
Published: February 2011

Abstract
Although alluded to occasionally during the previous discussions of chemistries used for reactive processing, the physical nature of the product probably has a significant effect on its useful properties. At the same time, the chemistries used often are dominant in the preparation of the final product. This is also one of the least well characterized aspects of reactive processing. The type of matrix formed during alloying, blending, modification, graft polymerizing, etc. (dispersion, co-continuous network or interpenetrating network) and the domains (characterized by various sizes and shapes) depend both on the chemistry being utilized and the mixing produced by the equipment used. A fine balance is maintained between the chemistry being used—its time and temperature requirements—and the physical aspects of mixing and dispersion. The design of the mixing operations must consider the interplay of these two aspects to control the physical properties of the products generated. The area of reactive processing of rubbers will continue to grow and many of the factors that control the physical properties of the product will be controlled by variations in the mixing and chemical processes developed.
129Xe NMR in Polymers
Authors: Miller J. B. 
Published: February 2011

Abstract
Through the efforts of many researchers, 129Xe NMR has shown to be a sensitive probe of phase morphology in polymers, providing a unique means of investigating the amorphous phase of bulk polymers. Recently developed models of the 129Xe chemical shift in polymers open the possibility of measuring van der Waals' interaction energies and chain dimensions from xenon spectra. In most cases, the information obtained from 129Xe NMR pertains only to the amorphous phase of the polymer, even in semicrystalline systems. The use of spin-polarized xenon has opened the possibility of probing the surface and near surface regions of polymers.
A Study of Thiocarbamyl Sulfenamide/Zinc Oxide and TMTD/Zinc Oxide Sulfurless Cure Systems
Authors: Layer Robert W. 
Published: February 2011

Abstract
In sulfurless cures of NR, soluble thiocarbamyl sulfenamides are found to produce the same state of cure as thiuram disulfides when compared on an equivalent dithiocarbamyl group basis. The addition of MBTS or benzothiazole sulfenamides to thiocarbamyl sulfenamides, or to thiurams, increases the modulus in proportion to the amount added. Adding sufficient benzothiazole sulfenamide appears to double the amount of sulfur donated by these thiocarbamyl accelerators and simultaneously increases monosulfide crosslink formation. The addition of zinc dibutyldithiocarbamate to thiocarbamyl sulfenamides significantly increases the modulus but has no effect on TMTD. Thiuram disulfides are generally reported to donate one sulfur per mole for crosslink formation. However, critical analysis of the literature and the above data indicates that two moles of TMTD are required to form one crosslink, i.e. donate one sulfur.
Thermally Induced Crosslinking in Blends of Poly(Vinyl Chloride) and Hydrogenated Acrylonitrile—Butadiene Rubber
Authors: Manoj N. R. , De S. K. , De P. P. 
Published: February 2011

Abstract
A blend of Poly(vinyl chloride) (PVC) and hydrogenated acrylonitrile—butadiene rubber (HNBR) undergoes crosslinking at high molding temperatures in the absence of any external curing agents. This is evident from Monsanto rheometric, solvent swelling, and infrared spectroscopic studies. The reaction proceeds through the interaction of allylic and tertiary chlorine in PVC, with amide and acid groups in HNBR formed during molding. The network structure is believed to consist of amide and ester crosslinks. Dynamic mechanical analysis and differential scanning calorimetry show that the blend components are miscible Variation in molding time and temperature has no effect on the miscibility.
Fracture Toughness of PVC/NBR Blends Evaluated by the J-Integral
Authors: Nakajima N. , Liu J. L. 
Published: February 2011

Abstract
The effect of gel on the fracture toughness of four PVC/NBR (50/50) blends was characterized by two different J- integral methods. Three of these blends are compatible blends with 33% acrylonitrile in NBRs, and the fourth with 21% acrylonitrile content, is an incompatible blend. Two types of gel are involved in this study microgels and macrogels. The J-integral methods are (1) conventional method proposed by Bagley and Landes and (2) crack initiation locus method proposed by Kim and Joe. The same load-displacement curves are used in both methods. However, the latter eliminates the energy dissipation away from the crack tip in the determination of Jc, while the former does not. Both methods produced almost the same results indicating that the energy dissipation away from the crack tip is negligible in these samples. The fracture toughness of a macrogel-containing blend is much greater than that of a microgel-containing blend, which, in turn, is only slightly greater than that of a gel-free blend. This implies that the two gel-containing blends have different fracture processes. The incompatible blend has the lowest fracture toughness due to weak interaction at the boundaries of the two phases.
An Experimental Study of Failure in Circumferentially Notched Elastomer Cylinders
Authors: Quigley Claudia J. , Dooley Robert , Parks David M. 
Published: February 2011

Abstract
Cylindrical dumbbell specimens containing deep circumferential cracks were loaded in tension until failure to investigate the fracture process in thick carbon black filled elastomers. Failure occurred at large deformations and was characterized by material tearing and small amounts of slow stable crack extension until rupture. The tearing process itself consisted of two distinct phenomena, delamination and crack extension. Upon load application, parabolic and asymmetric blunting of the crack tip was observed followed by a visible separation of the fabricated crack surfaces into upper and lower crack surfaces connected by an inner core of elastomer material. Localized material failure, identified as delamination, occurred along the outer surface of this inner core between the fabricated crack surfaces. Crack extension in the load direction was found above and below the fabricated crack surfaces. Both qualitative and quantitative aspects of failure were studied. Load and crack mouth opening displacement (CMOD) histories were examined, and the stretch ratio and tearing energy at rupture were measured. Finally, a model describing the tearing process was discussed.
Ground Rubber Tire / Thermoplastic Composites: Effect of Different Ground Rubber Tires
Authors: Rajalingam P. , Sharpe J. , Baker W. E. 
Published: February 2011

Abstract
Thermoplastic composites containing different Ground Rubber Tire (GRT) materials, Linear Low Density Polyethylene (LLDPE) and, in some case, a coupling agent (IB‘E’, an ethylene glycidyl methacrylate copolymer) were prepared by melt blending. The impact energies of all the thermoplastic composites (normally containing 40 wt % GRT) were evaluated using an instrumented impact tester. The effects of the GRT particle-size, particle size distribution and shape, the mode of grinding, and the oxygen surface concentration were analyzed. The wet-ambient-ground GRT based composites show higher surface oxidation and give better impact energy than cryo-ground and normal air-ground GRT based composites. Smaller GRT particle size results in a small increase in the impact property of the composite and a greater influence on the melt processability of the composites. Of the different GRT surface modification techniques studied for improved composite interfacial adhesion and impact properties the composites from electron beam radiation treated GRT yield higher increases in impact energy in comparison to corona and plasma treated GRT based composites.