bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functionally Terminated Butadiene Polymers
Authors: French David M. 
Published: February 2011

Abstract
Prepolymer technology is a relatively new science in which polymer structures of any desired type are built from partially polymerized liquid resins containing reactive functional groups. Well over one hundred low molecular weight polymers and crosslinking agents are currently available commercially. The first examples were the liquid phenolic casting resins which appeared in the mid 1930's. Unsaturated polyester-styrene mixtures were available by 1945 followed shortly by the epoxide resins and the liquid polysulfides. Today the chemist or engineer can chose among a wide assortment of liquid polymers: Polymer chain : Polyester, polyether, polyamide, polysulfide, polybutadiene, polyisobutylene Reactive group: Carboxyl, hydroxyl, sulfhydryl, amine, epoxide, isocyanate, olefin These liquid polymers may be separated into two types: those in which the reactive groups are randomly distributed along the backbone chain and those in which the functional groups are located at the ends of the chains. It is the latter with which this discussion is concerned, in particular with the functionally terminated polybutadienes. Uraneck, Hsieh, and Buck have coined the word “telechelic” for polymer molecules having two reactive terminal groups and we will use this term. The word derives from the Greek tele, far off, and chele, claw.
Course of the Terpolymerization of Ethylene, Propylene, and Dicyclopentadiene. II. Two-Step Addition of Dicyclopentadiene
Authors: Cunningham Robert E. 
Published: February 2011

Abstract
Terpolymerizations of ethylene, propylene, and dicyclopentadiene were carried out in which the dicyclopentadiene was added to the reaction system in two equal portions at the beginning and midpoint of each run, while the monoolefins were added continuously. In the resultant elastomers, unsaturation remains much more constant throughout the course of the polymerization than for terpolymers obtained when all dicyclopentadiene is added at the start of the reaction. Yield and molecular weight of the terpolymers produced by either technique are quite comparable, however. With VCl4 catalyst (with Al2Et3Cl3 cocatalyst) in heptane solvent, the two-step addition of the diene gave terpolymers with little gel, in contrast to the high gel in terpolymers formed with the single initial addition of the diene. This system also produced terpolymer with the highest final unsaturation and molecular weight Catalysts of VCl4, VOCl3, or V(C5H7O2)3 (with Al2Et3Cl3) in benzene gave terpolymers of moderate unsaturations and molecular weights.
Some Factors Affecting the Interpretation of the Plasticity Retention Index—P.R.I.
Authors: Smith M. G. 
Published: February 2011

Abstract
The implications of the PRI test are examined, in order to demonstrate how the values may be interpreted by the rubber goods manufacturer. It is shown that consistency of PRI is desirable, to enable product uniformity through control of processing, in particular high temperature mastication. It is demonstrated that PRI cannot be used to assess the quality of natural rubber, in terms of dynamic properties and vulcanizate aging.
The Curing of Polychloroprene Coating Materials with Polyisocyanates
Authors: Hoehne K. 
Published: February 2011

Abstract
Polychloroprene is an unsaturated chlorine-containing polymer and therefore it does not appear at first sight to have reactive positions. Nevertheless it can be proved to react with isocyanates. Although the chemistry of the reaction has not yet been fully explained, it is possible to determine an isocyanate equivalent weight. Recently a polychloroprene modification which was developed specifically for coating purposes, and which has been attracting more and more attention owing to its special properties, became commercially available under the name Plastifix PC®. This polychloroprene modification is crosslinked exclusively with polyisocyanate (e.g., Desmodur L). Used in this way, the product has already been applied to various practical purposes with favorable results. These applications and the properties of the polychloroprene have already been described elsewhere. The contents of that publication can be briefly summarized as follows: The polymer, which is supplied in the form of granules, is dissolved in solvents like any other resin for surface coating materials—preferably in a mixture of aromatics and esters. After the solution has been pigmented with inert carbon black, the composition is ground with normal grinding equipment. In general an antioxidant, usually an aromatic amine, is added as well. The polyisocyanate is added shortly before processing, though, even after it has been incorporated, the composition generally has a potlife of at least three days. Finishes applied with a brush, roller, or spray dry very fast and adhere very well. They are highly extensible and have long-lasting resistance to water, aqueous solutions of inorganic chemicals, and to petroleum, mineral oils, aliphatic hydrocarbons, and alcohol.
EV Systems for NR. II. Further Development of Curing Systems and Vulcanizate Properties
Authors: Russell R. M. , Skinner T. D. , Watson A. A. 
Published: February 2011

Abstract
It was shown in Part I that the use of EV systems in NR provides a simple network in which the crosslinks are mainly monosulfidic. Part II describes in some detail the properties of vulcanizates obtained by the use of EV systems and their relationship to conventional and TMTD-zinc oxide cured vulcanizates. The disadvantages of short scorch time and heavy bloom which accompany the TMTD-zinc oxide system are overcome by the new EV systems. The monosulfidic network obtained by the use of EV systems confers on NR good overall physical properties together with much improved resistance towards thermal and thermal oxidative aging. The thermal stability of this type of network is reflected in the outstanding resistance of the vulcanizates to set and reversion, and their good resistance to heat build-up under dynamic conditions. Vulcanizates derived from EV systems have increased resistance to thermal oxidative aging due to the inherent thermal stability of the networks and good response to antioxidant protection. This increased resistance results in much better retention of tensile properties, tear resistance and fatigue cracking resistance on aging, relative to that of conventionally cured vulcanizates.
Compatibility of Copolymers with Corresponding Homopolymers
Authors: Riess G. , Kohler J. , Tournut C. , Banderet A. 
Published: February 2011

Abstract
Since incompatibility of two homopolymers is the rule, it was of interest to see if mixing a corresponding copolymer (graft, block, or random) with a mixture of two incompatible homopolymers would bring about compatibility. For this study we limited ourselves to two systems of atactic polymers: polystyrene/poly (methyl methacrylate), and polystyrene/cis-l,4-polyisoprene since, in these systems, no crystallization occurs at normal temperatures. Investigation of these systems in the solid state—i.e., as films, prepared from polymer solutions by evaporation, enabled us to establish compatibility limits with considerable accuracy. The most important parameters for compatibility of homopolymer-copolymer mixtures seem to be, among other things: composition, molecular weight, and structure of the copolymers. Ternary diagrams for a mixture of two homopolymers and a copolymer show quite plainly that only block copolymers induce a certain compatibility. This is especially true when the polymer proportion in the block copolymers is approximately 50/50, and molecular weight of the homopolymers is substantially lower than that of the copolymer. Graft and random copolymers have little or no effect at all, upon compatibility. We also examined the relation between compatibility and impact strength for the system: polystyrene/polyisoprene/block copolymer.
Practical Evaluation of the [η]-M Relationship II. Estimation of Kθ Values of Polymer Solutions
Authors: van Krevelen D. W. , Hoftyzer P. J. 
Published: February 2011

Abstract
A method is proposed for the prediction of the intrinsic viscosity of θ-solutions, based on the constitution of the dissolved polymer. The method makes use of additive values for constitutional groups to calculate a quantity that represents the specific chain stiffness per main chain atom.
Temperature Dependence of Orientation Birefringence in Rubber and Semicrystalline Polymers
Authors: Hammack T. J. , Andrews R. D. 
Published: February 2011

Abstract
Results are presented for temperature dependence of orientation birefringence, Δn(T), from −195° to 150° C for the following crosslinked polymers: polydimethyl siloxane, polyethylene, ethylene/propylene copolymers (84/16, 75/25, 48/52 mole ratio) and ethylene/vinyl acetate copolymers (96/4, 82/18). On cooling from the rubbery state under a small constant load, the birefringence magnitude shows an abrupt increase when crystallization takes place, reaching a maximum value (Δnc) when crystallization is complete; Δnc is determined principally by degree of orientation in the rubbery state. In the rigid semicrystalline state, below Tg, magnitude of orientation birefringence decreases with decreasing temperature. The transition temperature for the ethylene/propylene copolymers is lowered by increasing the propylene content; nature of the transition changes progressively from a crystallization in polyethylene to a glass transition in the copolymer having 52 mole % propylene. The observed difference in optical parameters for polyethylene and its copolymers suggests a difference in physical structure which strongly affects the optical properties. We believe that the structure of the copolymers is microcrystalline, contrasting to spherulitic crystallinity of polyethylene (and polydimethyl siloxane).
Properties of Random and Block Copolymers of Butadiene and Styrene. I. Dynamic Properties and Glassy Transition Temperatures
Authors: Kraus G. , Childers C. W. , Gruver J. T. 
Published: February 2011

Abstract
The effect of monomer sequence on physical properties was investigated for butadiene—styrene solution copolymers made by organolithium initiation. The polymers varied from random copolymers of uniform composition along the polymer chain to ideal block polymers of specific block sequence arrangement and included rubbers of intermediate degrees of randomness. Uniform composition random copolymers exhibit a single glass transition temperature and a very narrow dynamic loss peak corresponding to this transition. The glass transition can be predicted from the styrene content and the microstructure of the butadiene portion of the rubber. Random copolymers in which composition varies along the polymer chain, and to some extent between molecules, exhibit a single glass transition, but the dynamic loss peak is broadened. The extent of this broadening is shown to be compatible with the sequence distribution, polymer segments of various compositions losing mobility at different temperatures. This indicates a tendency for association between segments of different chains which are similar in composition. Block copolymers display two transitions, corresponding to Tg for each type of block. The position and width of the dynamic loss peaks are related to block length and compositional purity of the blocks.
Strain-Wave Propagation in Strips of Natural Rubber Subjected to High-Velocity Transverse Impact
Authors: Smith Jack C. , Fenstermaker Carl A. 
Published: February 2011

Abstract
If a flexible filament marked at intervals along its length is struck transversely by a flying projectile, high-speed photography reveals a shifting of the marks caused by passage of a strain wave. Analysis of these shifts provides data on the strain and average strain velocity in the wave. Tests were performed on strips of lightly vulcanized natural rubber at transverse impact velocities up to 65 m/sec, and the resulting strain-velocity distributions analyzed for viscoelastic effects. Analysis showed that although creep effects were small in the observation time interval of 1–8 msec after impact, significant creep must have occurred at the point of impact within the first millisecond, and additional significant creep occurred at times greater than 8 msec. Strain-wave-front velocity calculated from the quasistatic stress—strain curve was 35.2 m/sec, but a value of approximately 60 m/sec was observed. Strain at the wave front, however, tended to attenuate as the wave propagated causing progressive decrease in the strain-wave-front velocity.
Stress-Strain Behavior of Swollen Polymeric Networks
Authors: Rijke A. M. , Taylor G. L. 
Published: February 2011

Abstract
The network parameters of swollen, solution-crosslinked polymer filaments can be collected from deswelling measurements in solutions of nonpermeating polymer or, as shown in this paper, from the stress—strain relation when in equilibrium with the surrounding solvent. The degree of swelling, at which the partial molar free energy of elasticity equals zero, is found to vary with solvent power in agreement with earlier findings on other systems. Comparison with results of studies on rubber networks crosslinked in the absence of diluent, show that previously observed discrepancies between theory and experiment can be attributed to the deficiency of the single term involving the one-third power of the volume fraction of polymer in the swollen network to describe the contribution of the partial elastic free energy.
Micromethod for Estimation of the Degree of Crosslinking in Elastomers from Compression Modulus of Swollen Vulcanizates
Authors: Smith Derek A. 
Published: February 2011

Abstract
The method uses small specimens (of volume less than 0.1 cc) which swell to diffusion equilibrium in hydrocarbon solvents within 8 hr. Measurements of deflection to better than one μ are made with a modified Wallace microhardness tester, which is described. The name “reticulometer” is proposed for this instrument. Using peroxide-crosslinked natural rubbers swollen to equilibrium νr values of about 0.23 in n-decane or in benzene, values for the concentration of physically active network chains determined by the present method were not greatly different from those determined by conventional “equilibrium” stress—strain measurements in tension on the same samples. Detailed differences are discussed. The chief advantages of the microcompression method are: (a) the use of small samples of shape and size convenient for carrying out other conventional measurements of network chain density; (b) the rapid attainment of diffusion equilibrium encouraging the use of fully swollen specimens and minimizing the risk of inhomogeneous distribution of swelling agent; and (c) the rapidity of testing compared with tension measurements.
A Universal Calibration for Gel Permeation Chromatography
Authors: Grubisic Z. , Rempp P. , Benoit H. 
Published: February 2011

Abstract
Gel permeation chromatography is one of the most powerful techniques for characterizing the polydispersity of polymeric materials. A versatile commercial apparatus has been used successfully in numerous laboratories on various problems of molecular weight distributions. But one of the difficulties still unsolved is the problem of calibration, i.e., the relation between elution volume and molecular weight. Some authors have assumed that retention time depends on the contour length of the molecular chain. Others think that it is more reasonable to use the radius of gyration or some average volume of the polymer molecule as the calibration parameter. In a recent paper we have reported GPC retention times of a series of polystyrenes exhibiting different molecular structures: linear, star-shaped, and comb-like. All were of known molecular weight and of low polydispersity. Obviously the conventional calibration method, where the logarithm of molecular weight is plotted against elution volume, does not yield a universal curve for all the samples. Retention times for branched samples were always larger than those for the linear homologs of the same molecular weight. We therefore tried using the hydrodynamic volume as the calibration parameter.
Thermal Stability of Polyester vs. Polyether-Based Urethans
Authors: Singh A. , Weissbein L. , Mollica J. C. 
Published: February 2011

Abstract
It has been shown, by means of continuous and intermittent stress relaxation measurements and oven aging studies, that polyester-based urethans are more resistant to thermal degradation than the corresponding polyether-based urethans at temperatures in the range of 50° to 150° C. It has also been shown that this difference in thermal stability is due to irreversible, oxidative cleavage of polyether chain segments. Addition of representative antioxidants of the hindered phenolic and amine types to the polyether-based prepolymers prior to curing was found to be ineffective in improving the thermal stability of the resultant polyurethan elastomer. And, finally, the practical significance of these thermal stability studies has been demonstrated through heat buildup measurements.
Network Chain Distribution and Strength of Vulcanizates
Authors: Gehman S. D. 
Published: February 2011

Abstract
Physical characteristics of rubber network structures usually enumerated and discussed are network chain density, crosslink functionality, average chain length between crosslinks, entanglements which act somewhat like crosslinks, and free chain ends which are network defects. Chemical factors include structure of the chain molecules, type of crosslinks, whether monosulfide, disulfide or polysulfide, or direct carbon-to-carbon bonds. Side effects of vulcanization reactions such as chain scission or combination of minor quantities of chemical fragments from the vulcanizing system are also recognized. One might think that these variables would be adequate to account for physical properties of elastomers but explanations of strength aspects of vulcanizates are still unsatisfactory. Something is missing in these considerations, that is, the distribution of crosslinks along a main chain or the length sequences of monomer units in network chains. Usually a random distribution is implicitly assumed. If the distribution is always random and nothing can be done about it and it cannot be measured anyway, there may seem to be little point in writing about it. However, an ideally random distribution for all crosslinking systems and polymers seems very improbable. The importance of network chain length distribution for physical properties has been, of course, well recognized in theory. Bueche's calculations showed that viscoelastic resistance to deformation increased markedly with increased crosslink functionality, that is, as more chains are involved in the displacement of a crosslink. His molecular theory of tensile strength was based on the concept of short, overloaded network chains which snapped and transferred their loads to neighboring chains. An alternate point of view is that short chains are detrimental because they do not stress orient as well as longer chains.
Extrusion of Polymer Melts and Melt Flow Instabilities. II. Site of Initiation and Mechanism of Melt Flow Instability
Authors: Bialas Gene A. , White James L. 
Published: February 2011

Abstract
In the second part of this paper we will make a critical survey of experimental studies on the site of initiation, the structure of the unstable flow regime, criteria for the inception of the instability and mechanisms for initiation of the unstable flow regime. Some new experimental data will be cited in the discussion of criteria.
Performance of SBR and BR Tread Compounds as a Function of Carbon Black Dispersion, Surface Chemistry, and Structure
Authors: Scott C. E. , Chirico V. 
Published: February 2011

Abstract
A study has been made of the effect of carbon black dispersion, oxygen volatile, and extremes in chain structure development on vulcanizate properties and treadwear. The effect of poorly dispersed carbon black is to reduce wear resistance, tensile strength, strain energy, and groove cracking resistance. Other vulcanizate properties are not as noticeably affected. The role of oxygen functionality in reinforcement was investigated in a series of oxidation and devolatilization experiments. Added oxygen functionality of a critical amount reduces modulus, strain energy and treadwear resistance. Attempts to raise these properties through added acceleration results in greatly reduced treadwear. Carbon black-elastomer adhesion is indicated once again as the sine qua non of wear resistance. Carbon blacks possessing an unusually high level of reticulate chain structure require a lower level of chemical crosslinking than carbons of normal structure level for maximum treadwear resistance. This finding is consistent with a reinforcement theory involving stress dissipation by transfer to the carbon-elastomer interface, where relief occurs by slippage over the friction surface.
Studies on Dicumylperoxide Vulcanization of Natural Rubber in Presence of Sulfur and Accelerators
Authors: Manik S. P. , Banerjee S. 
Published: February 2011

Abstract
The effect of sulfur, MBT, zinc oxide and stearic acid, either singly or in mixtures, on the DCP vulcanization of NR has been studied. In all cases DCP decomposes by a first order law, but the rate constant is higher in presence of MBT. Sulfur and MBT, separately or together reduce the crosslink density, each mole of Sx or MBT destroying one mole of DCP. In mixes containing DCP together with sulfur, MBT, zinc oxide and stearic acid the crosslink density is initially additive. The mechanical properties and the aging characteristics of the vulcanizates have also been reported.
Studies on Blended Polymers. VIII. Blending of Carboxy SBR and Vinylpyridine SBR
Authors: Iino H. , Tsukasa M. , Nagafune T. , Sekaicho K. K. , Minoura Y. 
Published: February 2011

Abstract
Blends of carboxy-SBR and vinylpyridine-SBR, in which interactions were expected to occur between the two types of polymer molecules, were prepared by different blending methods and with different vulcanizing systems, and the variation of their properties with varying mixing ratio was studied. Latex blending was compared with blending on the mill. Investigations were carried out for each blend type with (1) a common curing agent for both polymers, (2) curing agents that affect only one of the polymers, and (3) a combination of curing agents, each of which affects one of the polymers. To examine the state of mixing, the blends were dyed and observed under the microscope. It was found that latex blending gave sufficiently good mixing to enable the interactions between the two polymers to influence the properties strongly, the blending being better than that achieved on the mill. However, when a combination of curing agents that affected the polymers singly was used, the effects of the interactions was no longer observed.
Rheological Behavior of Elastomers. I. Melt Viscosity Characteristics of Uncured Epichlorohydrin Rubber
Authors: Collins Edward A. , Oetzel John T. 
Published: February 2011

Abstract
The data presented indicates that: Mooney viscosity does not give an accurate indication of the viscosity or heat build-up for the polymers under the shear rates and temperatures experienced in factory operations. A new ane more reliable test is needed. The Brabender plasticorder as well as the Instron have the potential of filling this need. Hydrin 200, a 100 Mooney polymer, has a viscosity similar to Neoprene W and lower than or equal to Hycar 1052 under the conditions of shear and temperature found in usual elastomer processing operations. Hydrin 100, a 56 Mooney polymer, has a viscosity which is lower than either Hycar 1052 or Neoprene W. Both Hydrin 100 and Hydrin 200 exhibit lower heat build-up due to shear induced heating than either Hycar 1052 or Neoprene W. This lower shear heat build-up reduces the danger of scorching during processing. Basic rheological data has been presented for four elastomers: Hycar 1052, Hydrin 100, Hydrin 200 and Neoprene W. This data can be used to obtain a better understanding of the processing characteristics of elastomers.