bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyurethane Reaction Injection Molding: Process, Materials, and Properties
Authors: Lee L. J. 
Published: February 2011

Abstract
Reaction injection molding includes aspects of polymerization reactor analysis as well as melt injection molding. Processing can be broken down into several unit operations: metering and machine performance, impingement mixing, mold filling, curing and mold design. Commercial RIM machines have been used successfully for non-filler systems. The results are generally satisfactory. Reactants are usually allowed to circulate through the mixhead, or even through impingement nozzles, such that uniform temperature control and appropriate agitation of reactants can be obtained. Most heads can switch from the recycle to injection mode under high pressure operation, to minimize the lead/lag problem. The mixing chamber is self-cleaned at the end of each shot by a hydraulically driven piston which pushes out all the residue mixture from the mixhead after mold filling. Flow rate/flow area can be adjusted externally by the nozzle size adjuster. Flow rate also can be controlled by the pressure setting. Two or four streams impingement mixing is the common mixing technology used in the present RIM machines. Static or impingement type after-mixers have been used extensively to improve the mixing. Mold filling seems not to be a problem for conventional RIM operation if mold design is appropriate. The typical pressure inside the mold cavity during filling is less than 350 kPa. With the help of slight foaming during curing, RIM polyurethanes usually have excellent, depression-free surfaces. A number of qualitative descriptions of automotive type RIM have appeared, and some basic studies of the process are being carried out. However, as yet there does not appear to be a complete understanding of how the process influences the structure and properties of the polymer formed. The majority of RIM parts have been made in the 140–300 MPa flexural modulus range for fascia applications, where appearance, weight-reduction, and impact resistance are the most important criteria. A representative formulation used to produce automotive fascia by reaction injection molding consists of a polyether/polyester polyol with molecular weight in the range of 1000–3000, a short chain extender like ethylene glycol, 1,4-butane diol or a diamine and a modified derivative of 1,4-diphenylmethane diisocyanate, MDI. The need for further weight reduction to meet government mileage requirements, and for improved corrosion and impact resistance, makes the extension of RIM materials to other external automotive body components increasingly attractive. For these applications, there will be several new requirements: flexural moduli in the 700–4000 MPa range to provide dimensional stability, but still with the desirable impact strength; a low thermal coefficient of linear expansion to allow satisfactory mating with sheet metal surfaces. An increased thermal stability would also be required for parts that would be painted and baked on the car, or for applications such as hoods with higher in-use thermal exposure.
The Rolling Loss of Pneumatic Tires
Authors: Schuring D. J. 
Published: February 2011

Abstract
Tire energy loss has long been neglected as an area of scientific concern, in favor of other performance characteristics such as traction and wear. With the advent of federally mandated fuel economy goals, however, priorities have been shifted, and tire energy loss has now become a prime concern. Tires are responsible for a rather large fraction of the total energy expended by a passenger car or truck. For a typical passenger car driven steadily within the legal speed limit, the energy dissipated by the tires ranges between 3 and 7% of the total energy consumed by the vehicle. For a typical truck (18 wheels), these percentages can be about twice as high (see Section 7). Any reduction in tire rolling loss would therefore yield tangible fuel savings. In the past 5 years or so, the tire industry has reduced rolling loss by more than 25% (Hill and Moore). This is partly due to the rapidly increasing use of radial tires, lower loads, higher inflation pressures and less hysteretic materials. However, it is also partly due to the substantial efforts made by tire researchers to understand the general principles governing the loss of energy in tires. These principles are not intuitively apparent. Energy loss of tires is a very complex phenomenon, and there is little hope that it will ever be fully understood to the extent that energy efficient tires can be designed on the drawing board. But substantial progress has been made, as attested by a recent SAE Conference on Tire Rolling Losses in Boston, the first of its kind, organized to review the state-of-the-art and to stimulate further improvements. These are greatly needed. To meet the fuel economy target of 1980, a reduction of 15% of the present average rolling loss of radial tires is required (Tarpinian, Nybakken, and Mishory), and further improvements are necessary to meet the goals of 1985. Vigorous, and costly, efforts are being made—by industry and academic institutions alike—to come to grips with the rolling loss phenomenon. These efforts include mapping the interacting relations between rolling loss and the many tire parameters, building analytical models that would provide insight into these relations, and developing testing methods that would permit testing them with accuracy. This review is an attempt to organize the present knowledge into these categories and to suggest new avenues for further progress.
Elastomeric Block Polymers
Authors: Dreypuss P. , Fetters L. J. , Hansen D. R. 
Published: February 2011

Abstract
Development of new thermoplastic elastomers is a challenge for future years. It is a difficult challenge because existing thermoplastic elastomers offer a wide variety of prices and properties with good performance price ratios. Most advancements will probably be accomplished by blending or compounding or by slight molecular modifications of existing products. However, a new thermoplastic elastomer can not be ruled out if new technology is developed. With new applications yet to be discovered, and as existing markets mature, the growth of new and existing thermoplastic elastomers should be exciting in the years ahead.
Determination of Free Soap in Styrene Butadiene Latex
Authors: Lake M. , Rappaport G. 
Published: February 2011

Abstract
This method may find application in the determination of dialyzable substances in mixtures where the direct determination of such substances cannot be made. If the analyte of interest is a substance that dialyzes through without interferences, then a determination of the amount that dialyzes through in two separate dialysis times will allow for the calculation of the amount originally present. The cmc of a surfactant may readily be determined.
Rubber-Thermoplastic Compositions. Part II. NBR-Nylon Thermoplastic Elastomeric Compositions
Authors: Coran A. Y. , Patel R. 
Published: February 2011

Abstract
Thermoplastic elaslomeric compositions based on crosslinked NBR and nylon can be produced. A variety of nylons of differing melting points and NBR's of differing AN contents can be used in a broad range of proportions. The compositions can be further altered by the incorporation of fillers and plasticizers. The work indicates that a number of types of nylon-NBR based clastomeric materials, fabricable as thermoplastics and exhibiting good strength and excellent hot oil resistance, can be produced in a range of hardnesses.
An ESR Study of Oxidation in Uniaxially Deformed Polybutadiene and Polyisoprene
Authors: Mead W. T. , Porter Roger S. , Reed P. E. 
Published: February 2011

Abstract
The ESR spectra obtained from diene rubbers following mechanical deformation at cryogenic temperatures in a commercial purity nitrogen atmosphere are composite spectra arising from two or more radicals. The two radicals are thought to be an allyl radical resulting from main-chain rupture and a peroxy radical. The majority of the peroxy radicals observed in the composite spectra are formed as a result of oxygen in the test environment reacting with the allyl radicals formed shortly as chain rupture occurs. However, it appears that a small proportion of the peroxy radicals arise from oxygen incorporated into the rubber network during the processing stage before mechanical testing commences. Only if oxygen is rigorously excluded at all stages of processing and testing is the true spectrum of the primary allyl radical observed following mechanical degradation, showing that the chain rupture site is at the weakest bond, between the α- methylene groups. Oxygenated radical species incorporated during processing can be removed by heat treatment, provided the heat treatment is carried out in an oxygen-free atmosphere. The radical stability vs. temperature tests have shown that the peroxy radical decays at a temperature approximately 20 K lower than the allyl radical, which in turn decays rapidly in the vicinity of the Tg of the rubber. It appears that the anomalous increase in radical concentration near Tg, particularly noticeable in the case of mechanically deformed polymers, possibly arises from stored energy release on warming assisted by the presence of oxygen, oxygen being the major contributor to the process. However, the anomalous effect appears to be complex and other factors may contribute to it. It is generally concluded that the ESR technique offers a sensitive method of observing the oxidation of polybutadiene and other diene rubbers.
Changes in the Dynamic Modulus during Thermal Degradation of Polyisoprene Vulcanizates
Authors: Yano Shoichiro 
Published: February 2011

Abstract
Thermal degradation of IR is investigated in air and in N2 by dynamic mechanical measurements. In this dynamic method, the change in the relative dynamic modulus is found to be frequency dependent, but the data at various frequencies can be superimposed upon each other by shifting along the time axis. Changes in relative modulus as a function of time in air and in N2 can be expressed by Equation (1), which contains two exponential terms. The activation energies for k1 and k2 are 84 and 57 kj/mol in air, and 61 and 57 kJ/mol in N2, respectively.
Effect of Curing Temperature and Curing System on Structure-Property Relations of Rubber Blends
Authors: Bhowmick A. K. , De S. K. 
Published: February 2011

Abstract
In the present paper we have studied the effects of curing temperature (150° and 180°C) and curing system (conventional and efficient vulcanization) on 1) the technical properties, 2) polymer-filler interaction and 3) network structure of NR-BR, NR-SBR-BR, NR-SBR blends. On the basis of cure rate and interphase crosslinking, it has been suggested that the tendency to form mechanically compatible blends follows the order NR-BR &gt; NR-SBR-BR &gt; NR-SBR. It is the interplay of the network structure and polymer-filler interaction which controls the properties of the blend vulcanizates. The resilience, heat build-up and set properties depend more on the network structure, while the tensile, tear and fatigue resistance are influenced more by the polymer-filler interaction.
The Effects of Cross-Linking and Strain on the Glass Transition Temperature of a Polymer Network
Authors: Sharaf M. A. , Mark J. E. 
Published: February 2011

Abstract
The glass transition temperature Tg of an elastomer is of great importance with regard to its utilization since at this temperature and below, the material can no longer exhibit rubberlike behavior. In the present study, networks were prepared from atactic poly(vinyl acetate) and poly(isobutyl methacrylate), both types of networks being inherently non-crystallizable and therefore immune from complications associated with strain-induced crystallization. The values of Tg were obtained by dilatometry, differential scanning Calorimetry, the measurement of viscoelastic losses, and irreversible thermal shrinkage. For both types of networks, Tg was found to increase with increase in degree of crosslinking and with increase in elongation. These results suggest that the most important effect of crosslinking and network elongation is a decrease in the mobility or entropy of the network chains.
The Effect of Chain Length Distribution on Elastomeric Properties. III. Non-Random Networks Prepared with a Partially Vinyl-Selective Bis(Alkylperoxy)Diisopropylbenzene
Authors: Llorente M. A. , Mark J. E. 
Published: February 2011

Abstract
The reactant α,α′-bis(t-butylperoxy)diisopropylbenzene was used to crosslink PDMS polymers containing vinyl side groups with varying degrees of segregation along the chains. On the basis of the elongation moduli of the resulting networks, this reactant was found to be moderately selective for vinyl groups, falling approximately midway between the essentially non-selective benzoyl peroxide and γ-radiation and a highly selective silicon hydride crosslinking agent. As expected, a significant amount of the selectivity was lost at longer reaction time. Placing crosslinks in close proximity decreases the effective degree of crosslinking, and may affect the swelling response more than the modulus in elongation.
Modified Bitumens Containing Thermoplastic Polymers
Authors: Piazza S. , Arcozzi A. , Verga C. 
Published: February 2011

Abstract
The mechanical and viscoelastic behaviour of bitumen, both at high and low temperature, is noticeably improved by addition of thermoplastic polymers such as thermoplastic SBS rubbers and atactic polypropylene. These polymers can be used complementary to each other. Atactic polypropylene decreases the flow of bitumen at room temperature, thus reducing creep. The SBS block copolymer, instead, prevents excessive stiffening of bitumen at low temperature, reducing the brittleness. Characteristics of bitumen-polymer blends depend heavily upon bitumen quality, particularly upon its aromatic content and mixing process.
Numerical Evaluation of the State of Cure in a Vulcanizing Rubber Article
Authors: Prentice G. A. , Williams M. C. 
Published: February 2011

Abstract
In its present state this model should be effective as an aid in analyzing and optimizing cure cycles for vulcanizing articles. It is clearly necessary to have accurate thermo-physical data when simulating the SOC in thick articles. Additional improvements could be realized by more careful treatment of the heat transmitted into the rubber through the blades.
Vibration Isolation: Use and Characterization
Authors: Snowdon J. C. 
Published: February 2011

Abstract
This article is concerned with vibration isolation, with antivibration mountings (resilient isolators), and with the static and dynamic properties of rubberlike materials that are suited for use in antivibration mountings. The design of practical antivibration mounts incorporating rubber or coiled-steel springs is described in Refs. 1–27; pneumatic isolators (air mounts, etc.) are described in Refs. 5, 28–35. Throughout the literature, as here, attention is focussed predominantly on the translational (vertical) effectiveness of antivibration mountings. However, the two- and three-dimensional vibration of one- or two-stage mounting systems is addressed in Refs. 4, 10, 12, 36–56. Following a description of the static and dynamic properties of rubberlike materials, the performance of the simple or one-stage mounting system is analyzed, account being taken of the occurrence of second-order resonances in the isolator and in the mounted item. In the latter case, as likely in practice, the bulk of the mounted item is assumed to remain masslike, whereas the feet of the item are assumed to be nonrigid (multiresonant). Discussion is then given to the two-stage or compound mounting system, which affords superior vibration isolation at high frequencies. Subsequently, the powerful four-pole parameter technique is employed to analyze, in general terms, the performance of an antivibration mounting with second-order resonances (wave effects) when both the foundation that supports the mounting system and the machine are nonrigid. The universally adopted method of measuring mount transmissibility is then described, followed by an explanation of how transmissibility can also be determined by four-pole parameter techniques based on an apparatus used by Schloss. The four-pole measurement approach has not been exploited hitherto, but it is apparently feasible and valuable because it enables mounts to be tested under compressive loads equal to those routinely encountered in service.
Physical Characterization of Pivalolactone-Grafted Elastomers. I. General Morphology
Authors: Buck W. H. 
Published: February 2011

Abstract
The pivalolactone graft copolymers represent a new type of thermoplastic elastomer, and their morphology appears to be unique. A comparison of some of the properties of the three principal types of thermoplastic elastomer is given in Table III. Over a fairly wide composition range (10–40% polyPVL), the general morphology of the polyPVL graft copolymers remains the same: discrete crystallites in a continuous elastomeric phase. The poly(ethyl acrylate)-based grafts, having much higher values of HSL and SSL, tend to form spherulitic structures. These spherulites are composed, however, of discrete polyPVL crystallites. Clean phase separation, as indicated by invariance of Tg with composition, is partly due to the relative compatibility of the backbone and grafted side-chain polymers. Nevertheless, the extent of phase separation between hard and soft phases should always be greater for ABA block and polyPVL graft copolymers than for segmented copolymers because of the free end possessed by each hard segment in the first two cases. The melting temperature of the hard segments in polyPVL grafts depends primarily on the HSL, which can be varied easily during synthesis. The melting temperature of segmented and triblock copolymers cannot easily be changed without large changes in physical properties. The low initial (Young's) modulus of the polyPVL graft copolymers and some ABA triblock polymers is a consequence of a continuous elastomeric phase and a discrete hard segment phase. When the hard phase becomes cocontinuous with the soft phase, a high initial modulus more like that of a plastic than of an elastomer may result. Annealing of crystalline segmented and polyPVL graft copolymers causes improvement in such physical properties as compression set, creep resistance, and tensile strength. This is attributed tc relaxation of molded-in stress, accompanied by recrystallization of the hard segments. Since the glassy hard segments in ABA triblock polymers lack crystalline order, similar improvement in properties would not be expected. PolyPVL crystallites act as both crosslinks and reinforcing filler in these copolymers. The size of the crystallites depends upon both the length of the grafted chain (HSL) and the separation of chains along the elastomer backbone (SSL). Generally, large values of HSL and small values of SSL cause the largest crystallites to form. Based on experimental evidence from transmission electron microscopy, x-ray diffraction, thermal analysis, and solvent swelling, a morphological model has been developed.
Processability of Rubber and Rheological Behavior
Authors: White J. L. 
Published: February 2011

Abstract
The rheological and ultimate properties of unvulcanized rubber and compounds are described. Unfilled elastomers may be represented by the theory of viscoelastic fluids. Various experimental studies are described and interpreted. Filled polymer melts exhibit more complex behavior including yield values, reduced elastic memory, and thixotropy. The influence of these properties on several processing operations including milling/mixing and extrusion is critically discussed.
Temperature Buildup in Bonded Rubber Blocks Due to Hysteresis
Authors: Holownia B. P. 
Published: February 2011

Abstract
The comparison between theoretical and experimental results of the temperature distribution in bonded cyclindrical rubber blocks due to compressive cyclic loading was largely dependent on the value of Poisson's ratio. It was found that, for thin rubber blocks (D/h&gt;6), the third significant figure in the value of v appreciably altered the temperature distribution, while for thick blocks (D/h&lt;4), the same change in v had much smaller effect on the temperature distribution within the rubber block. The theoretical analysis used in the paper can easily be adapted for blocks of different geometries, and hence the temperature distribution within a desirable limit can be achieved by changing the geometry of the rubber block.
Another Look at S-Type Carbon Blacks
Authors: Haws J. R. , Cooper W. T. , Ross E. F. 
Published: February 2011

Abstract
Oxidized carbon blacks impart unique properties to rubber compounds. The most interesting aspects include modified curing characteristics, good resistance to tear, and the potential to promote good adhesion of rubber compounds to brass-plated metal. When these improvements are considered in conjunction with the wide range of surface area and structure available in carbon black, it is evident that oxidized furnace blacks provide combinations of properties not previously available.
Compatibilization of Rubber Blends through Phase Interaction
Authors: Bauer R. F. , Dudley E. A. 
Published: February 2011

Abstract
It can thus be concluded that phase heterogeneity in rubber blends almost always prevails and can be shown by means of microscopy. Compatibilization of these blends, as judged by the emergence of intermediate dynamic loss peaks, can be achieved through a vulcanization process which promotes crosslinks between the heterogeneous polymer phases. Such compatibilization through interphase crosslinking can occur even with polymers of significantly different solubility parameters. Interphase crosslinking can be recognized from swelling restriction in the differential swelling test but also from the development of intermediate dynamic loss peaks. The development of interphase crosslinks, therefore, results in the formation of a new copolymer system from the two mixed components which has new and unique properties. The requirements of cure systems which promote cocuring of polymer phases are not fully understood. Important factors to be considered are curative migration; however, a discussion of this subject would be beyond the scope of this presentation.
Determination of Functionality Distributions in Telechelic Prepolymers by Thin-Layer Chromatography
Authors: Min T. I. , Miyamoto T. , Inagaki H. 
Published: February 2011

Abstract
Functionality distributions of telechelic prepolymers have been determined by thin layer chromatography (TLC). Commercially available 1,2-polybutadienes having either carboxyl or hydroxyl groups were examined. TLC with p-xylene as the developer made it possible to separate the sample into a nonfunctional component and a mixture of mono- and difunctional components. Complete separation of the sample into the three components was achieved by selecting the developer and development procedure appropriately. Quantification of the chromatograms was performed successfully in a TLC apparatus equipped with a flame ionisation detector. A simple method for the determination of the functionality distribution was proposed.
Identification of Natural and Synthetic Polyisoprene Vulcanizates by Thermal Analysis
Authors: Sircar A. K. 
Published: February 2011

Abstract
1. NR and IR vulcanizates can be distinguished from one another by their DSC and DTG curves. 2. Thermal curves remain more or less unaffected by recipe changes. 3. Identification of blends of NR and IR is complicated since different IR's have different exotherm areas. 4. Natural and synthetic trans-polyisoprenes can be distinguished from one another, as well as from their cis counterparts, by their DSC and DTG curves. 5. Differences observed in the natural and synthetic polyisoprenes seem to be due to a higher amount of cyclized product, formed as a result of catalysis by the residual inorganic material in the synthetic product.