bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting joint sealant performance of elastomers by computer simulation. II. Results in simple extension and compression
Authors: Catsiff E. H. , Hoffman R. F. , Kowalewski R. T. 
Published: April 2003

AbstractStress computations have been performed by a technique based on the subdivision of a body into many quasi‐homogeneous elements of a material having separable time‐dependent and strain‐dependent mechanical properties. For several sealant materials and joint seal shapes, under simple tension and/or compression movements, results are compared to experimental data on model sealed joints. There is reasonable agreement between the predicted and experimental total stress in joint seals of all the sealants tested up to nominal joint deformations of about 20%–40%. Furthermore it has been shown that the strain distribution in the outer layer of the sealant is nonuniform and the deformed shape is nonparabolic, which disagrees with the assumptions of the joint seal analysis proposed by E. Tons. The nonparabolic deformations have been experimentally confirmed using a resin‐casting technique to “freeze” the deformed joint seal to permit measurement of its shape. The computed stress and strain distributions show that the stresses are highest near the corners of the joint seal and are directed at an acute angle to the substrate, indicating that the peel strength of the sealant plays a major role in determining the overall joint strength. It has been shown how the computational technique can be applied to alternate compression and tension cycles to predict some effects of polymer stress relaxation characteristics on the stress distributions. Although the computational method has only been applied to a few representative isothermal sealed‐joint systems under relatively simple loading conditions, the technique certainly has been shown to be feasible for predicting stresses within a seal over a reasonable range of nominal joint deformations. It is expected that the technique can be extended to more complex joint motions by modification of the computer programs and the input of additional data on actual joint movements. Work is in progress to extend the method in this direction and should lead to a more rational approach to sealant specifications and selection as well as improvements in joint seal designs.
Copolymerization of ethylene oxide and propylene oxide by anhydrous potassium hydroxide
Authors: Rastogi Anil K. , St. Pierre Leon E. 
Published: April 2003

AbstractEthylene oxide and propylene oxide have been copolymerized at low temperatures in the presence of anhydrous potassium hydroxide. The monomer reactivity ratios were found to be r(ethylene oxide) = 6.5 and r(propylene oxide) = 0.5.
The stress birefringence of vulcanizates of polyisoprene–polyethylene blends
Authors: Nishioka A. , Furukawa J. , Yamashita S. , Kotani T. 
Published: April 2003

AbstractAs a model for the vulcanizates of block copolymers, mixtures of polyisoprene and polyethylene vulcanized both with a peroxide and with sulfur were investigated by stress birefringence. It was found that the polyethylene dispersion showed a reinforcing effect only in the peroxide vulcanizates. On the other hand, the stress birefringence was decreased with increased polyethylene content except at high polyethylene content. In the latter case, the slope of the line in the birefringence–stress plot was almost equal to that for the pure polyisoprene vulcanizate at high stress levels. However, at lower stresses significant optical creep was observed, i.e., the stress increased without bire‐fringence. Such an optical creep as this exists also in styrene–butadiene block copolymer. These facts are interpreted by the assumption that polyethylene dispersion, when it is linked chemically with polyisoprene matrix, acts as a reinforcing agent by forming physical crosslinks similar to the hard domains in block copolymers. Such physical crosslinks can slip during elongation, resulting in the observed optical creep. These phenomena disappear at the elevated temperature.
Multiple peak resolution in gel permeation chromatography
Authors: Schrager M. , Ward A. L. 
Published: April 2003

AbstractA new, graphic method of the resolution of a chromatogram into its component peaks is presented. From a mathematical description of the chromatogram of a monodispersed sample, a practical method of peak resolution of a multicomponent sample is derived. From this, the constituents may be characterized as to size and their weight fractions determined. As an example the final product in the synthesis of N,N‐diglycidyl tribromoaniline is analyzed graphically and compared with results obtained using the du Pont 310 Curve Resolver. The agreement appears to be quite satisfactory.
Yielding processes in glassy polymers
Authors: Zitek P. , Zelinger J. 
Published: April 2003

AbstractOur contribution deals with a description of yield in glassy polymers, being treated as an activated process. For description the Eyring equation in simplified form has been selected:

where σy = yield stress, T = absolute temperature, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon = {\rm deformation (strain) rate,}$\end{document} and A, B, C = equation parameters. In the first part the applicability of this equation has been verified by applying data of our own as well as those published elsewhere. For a more comprehensive representation of the results the data were processed in the form of generalized master curves by using the appropriate shift factors derived from eq. (1).
Aminothiol polyalkylene sulfide oligomers
Authors: Woodhams R. T. , Adamek S. 
Published: April 2003

AbstractThe carbonates and oxides of zinc and cadmium polymerize propylene sulfide to elastomeric materials, but with the addition of ammonia low molecular weight polymers are produced. The effect of the ammonia is to react with some of the propylene sulfide to give aminopropanethiol, which will itself polymerize monomer by a stepwise reaction or, after reaction with the metal carbonate, form a metal bis(aminopropanethiolate) which is an active initiator. Chemical and spectroscopic examination of these polymers shows them to be essentially bifunctional, with one NH2 and one SH terminal group. There is, however, evidence to suggest that further reaction of monomer occurs with the terminal amine groupings to give polyfunctional compounds. From the relative proportions of ammonia, zinc carbonate, and monomer, the rate of polymerization, molecular weight, and degree of endgroup coordination with catalyst residue can be controlled as desired. Due to the highly reactive endgroups, the polymers are readily crosslinked with epoxy resins, aziridinyl compounds, and hexamethoxymethylene melamine to give useful products exhibiting high solvent resistance.
Etude par résonance magnétique nucléaire des polychlorures de vinyle polymérisés par les systémes titanate de butyle–alcoyles‐aluminium
Authors: Pham Q. T. , Rocaniere P. , Guyot A. 
Published: April 2003

AbstractNMR analysis of the chain ends of samples of poly(vinyl chloride) prepared using a Ti(OBu)4–alkylaluminum system in CCl4 reveals that the mechanism of the formation of free radicals depends on whether the alkylaluminum used is chlorinated or not. In the first case, some of the radicals are reactive in the initiation step of the polymerization, while in the latter case theses radicals first undergo transfer to CCl4, then the CCl3· formed initiates the polymerization of vinyl chloride. The poly(vinyl chloride) radicals are chiefly stopped by transfer to CCl4 (chlorine abstraction) or to alkylaluminum (hydrogen abstraction). In transfer reactions between growing radicals and alkylaluminum, the radicals formed have to react with CCl4 before reinitiating the polymerization of vinyl chloride.
High flux freeze‐dried cellulose acetate reverse osmosis membranes as microporous barriers in gas permeation and separation
Authors: Agrawal J. P. , Sourirajan S. 
Published: April 2003

AbstractThe permeations of helium, hydrogen, methane, ethylene, nitrogen, and argon, and helium–methane, nitrogen–ethylene, oxygen–nitrogen, and sulfur dioxide–nitrogen mixtures have been studied using freeze‐dried porous cellulose acetate reverse osmosis membranes. The results illustrate the existence of mobile and immobile sorbed layers and the governing influence of surface flow in gas‐phase reverse osmosis separations. Preshrunk freeze‐dried porous cellulose acetate membranes seem to offer a practical means of utilizing the reverse osmosis process for recovering helium from natural gas and separating sulfur dioxide from flue gases.
Crosslinked poly(hydroxyethyl methacrylate) membranes for desalination by reverse osmosis
Authors: Jadwin T. A. , Hoffman A. S. , Vieth W. R. 
Published: April 2003

AbstractA series of crosslinked hydroxyethyl methacrylate (HEMA) membranes for reverse osmosis desalination has been prepared. The crosslinkers used were trimethylol propane trimethacrylate (TPT) or ethylene glycol dimethacrylate (EGD). Membranes were synthesized by polymerizing the monomers as a thin homogeneous film. In addition to reverse osmosis tests, the membranes were also characterized by osmosis experiments and sorption measurements. The reverse osmosis water flux (1500 psi applied pressure, 4% NaCl brine, pH = 5) for these membranes decreases from 0.6 gallonmil/ft2‐day (GMFD) to 0.055 GMFD and salt rejection increase from 78% to a maximum of 94% as the amount of TPT is increased from 0 to 11 mole‐%. Water contents decrease from 42% to 15% over the same range of crosslinker, but the preferential sorption of water to salt does not vary. Thus, rises in reverse‐osmosis semipermeability were found to result from changes in water–salt diffusivity ratios. The mechanism of permselectivity has been interpreted in terms of parallel diffusive fluxes across the membrane of primary H‐bonded water and secondary water plus salt ions.
The dependence of the rate of emulsion polymerization of methyl methacrylate on the soap concentration
Authors: Lee P. I. , Longbottom H. M. 
Published: April 2003

AbstractThe dependence of the rate of emulsion polymerization of methyl methacrylate on the concentration of sodium dodecyl sulfate has been studied using the Mx+–N2H5OH system as initiator (where Mx+ is Cu2+, Fe3+, and Mn3+). It was found that the rate dependence on soap concentration was different for each initiator. The extent of this variation was:

The variation is large enough to show that the dependence of the rate of emulsion polymerization on soap concentration is not simply a function of the solubility of the monomer in water, as had been suggested by Gershberg.
Environmental stress relaxation studies of polymers: Effect of temperature on polyethylene–xylene and polyethylene–toluene systems
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractThe method of stress relaxation has been used to study the effect of temperature on the stress decay behavior in the systems of polyethylene–xylene and polyethylene–toluene. The behavior of stress decay in the polyethylene under xylene or toluene at various temperatures was observed and the activation energies of polyethylene–xylene and polyethylene–toluene were obtained.
Structural characterization of vulcanizates. XI. Network‐bound accelerator residues
Authors: Campbell D. S. 
Published: April 2003

AbstractRadiotracer techniques have been used to determine amounts of accelerator which become bound to the vulcanizate networks during the vulcanization of NR with sulfur and CBS. Three different vulcanization systems have been studied, having different proportions of accelerator to sulfur. The vulcanizates have also been characterized in terms of the numbers and types of chemical crosslinks present and the results of the bound accelerator analyses have been considered in relation to the crosslink levels and distribution.
Dynamic mechanical properties of particulate‐filled composites
Authors: Lewis T. B. , Nielsen L. E. 
Published: April 2003

AbstractThe relative shear moduli of composites containing glass spheres in a rubbery matrix obey the Mooney equation, analogous to the relative viscosity of similar suspensions in Newtonian liquids. However, when the matrix is a rigid epoxy, the relative shear moduli are less than what the Mooney equation predicts but greater than what the Kerner equation predicts. Relative moduli are less for rigid matrices than for rubbery matrices because (1) the modulus of the filler is not extremely greater compared to that of the rigid matrix; (2) Poisson's ratio is less than 0.5 for a rigid matrix; (3) thermal stresses in the matrix surrounding the particles reduce the apparent modulus of the polymer matrix because of the nonlinear stress—strain behavior of the matrix. This latter effect gives rise to a temperature dependence of the relative modulus below the glass transition temperature of the polymer matrix. Formation of strong aggregates increases the shear modulus the same as viscosity is increased by aggregation. Torsion or flexure tests on specimens made by casting or by molding give incorrect low values of moduli because of a surface layer containing an excess of matrix material; this gives rise to a fictitious increase in apparent modulus as particle size decreases. The mechanical damping can be markedly changed by surface treatment of the filler particles without noticeable changes in the modulus. The Kerner equation, which is a lower bound to the shear modulus, is modified and brought into closer aggrement with the experimental data by taking into account the maximum packing fraction of the filler particles.
Combined stress failure tests for a glassy plastic
Authors: Broutman L. J. , Krishnakumar S. M. , Mallick P. K. 
Published: April 2003

AbstractThe development of a unique test method for biaxial stress experiments on brittle material is discussed. Results of biaxial tension‐tension and tension‐compression experiments on poly‐methylmethacrylate (plexiglas) are presented. The strength results compare reasonably well with modified distortion energy theory in the tension‐compression stress quadrant.
Copolymerization of styrene. IV. Copolymerization with esters of benzylidenecyanoacetic acid
Authors: Gilath Arie , Ronel Samuel H. , Shmueli Mirjam , Kohn David H. 
Published: April 2003

AbstractStyrene was copolymerized in bulk with a number of esters of benzylidenecyanoacetic acid. The kinetic scheme of all pairs fitted the improved scheme of copolymerization, taking into account the effect of the penultimate unit. The Alfrey‐Price Q and e values were calculated. Using the modified Taft equation, log (1/r1) = ρ*σ* + δEs, it was found that the relative reactivities of the ester monomers toward the polystyryl radical were correlated by the polar substituent constants σ* of the ester alkyl groups (ρ* = 0.14) and not by their steric substituent constants Es (δ = 0.008).
A dilatometer for measuring compressibilities of polymers in their melting range
Authors: Waldman N. , Beyer G. H. , Griskey R. G. 
Published: April 2003

AbstractA dilatometer was developed for studying the compressibility of polymers in their melting range at pressures to 8500 atm and temperatures to 370°C. Temperature was controlled to ±0.01°C and pressures were maintained and controlled by means of a hydraulic deadweight gauge system. The device was sensitive to volume changes of 1 part in 30,000.
An analytical solution to Tung's axial dispersion equation. Applications in gel permeation chromatography
Authors: Hamielec A. E. 
Published: April 2003

AbstractEquations developed for correcting Mn, Mw, and [μ] for imperfect resolution are generally satisfactory. Choosing the appropriate instrumental spreading function is however a very difcult task. There is need for further research on this problem, in particular with polymer standards for which the DMWD or even Mz is known (in addition to Mn and Mw).A criterion for resolution in GPC which is based on a solution of Tung's axial dispersion equation has been proposed.The operation of GPC in recycle mode appears very promising. Equations have been developed to interpret data obtained in this operational mode. It is probable that a great deal of work will be done in this area in the very near future.
The solubility of poly(vinylidene chloride)
Authors: Wessling Ritchie A. 
Published: April 2003

AbstractThe relative abilities of various solvents to dissolve crystalline polyvinylidene chloride were judged by comparing temperatures at which dilute suspensions became homogeneous. PVDC is not soluble in common solvents at ambient temperatures. It dissolves in solvents of matching solubility parameter only above ∼130°C. An analysis of the data suggests that δ = 10.1 for PVDC. Five classes of specific solvents were observed that could dissolve PVDC at much lower temperatures. These include sulfoxides, dialkyl amides, alkyl lactams, cyclic sulfides, and cyclic ketones. PVDC acts as a weak Lewis acid in these solutions. The best solvents found, in order of decreasing activity, are: hexamethylphosphoramide, tetramethylene sulfoxide, N‐acetylpiperidine, N‐methylpyrrolidone, N‐formylhexamethyleneimine, and trimethylene sulfide.
The diffusion of nonionic penetrants in polyamide
Authors: Shibusawa Takao , Iijima Toshiro 
Published: April 2003

AbstractThe diffusion behavior of nonionic penetrants in aqueous solution into nylon 6 was examined in the temperature range 5°–95°C. The Arrhenius plot of the diffusion coefficients is linear and its slope changes at 30–40°C higher than the glass transition temperature in water, as determined by dilatometry and viscoelastic measurements. The results are discussed in relation to the molecular size of the penetrant and the segmental motion of polymer chains.
ESR study of intramolecular energy transfer in the radiolysis of cellulose furoates
Authors: Singh Sujan , Hinojosa Oscar , Arthur Jett C. 
Published: April 2003

AbstractThe substitution of 2‐furoyl, 5‐methyl‐2‐furoyl, 2‐furanacryloyl, or 5‐bromo‐2‐furoyl groups on fibrous cotton cellulose increased the radiation rsistance of cellulose, as indicated by the retention of strength of the modified fibrous cellulose at high dosages of γ‐radiation compared with that of irradiated, unmodified fibrous cellulose. The presence of electropositive or electronegative substituents on the furan groups did not significantly change their radioprotective effects for cellulose. Electron spin resonance (ESR) spectra of irradiated celluloses indicated that the long‐lived free radical sites were similar, if not the same, in both irradiated, unmodified, and modified celluloses. The radio protective effects of furan groups for cellulose were attributed to absorption of energy from the secondary radiations, primarily the secondary electrons, by the groups due to their π‐electron‐type structures. The absorption of energy by the groups apparently decreased the localization of energy on carbon C1 or C4 on the cellulose molecule which would result in depolymerization and loss in breaking strength of the fibrous cellulose. The radioprotective effects of furan groups for cellulose were similar to those of benzenoid groups.
Studies on melt spinning of nylon 6. I. Cooling and deformation behavior and orientation of nylon 6 threadline
Authors: Ishibashi Tohru , Aoki Kiyoshi , Ishii Tsuneo 
Published: April 2003

AbstractThe melt spinning of nylon 6 filament yarns was studied by measuring the filament tensions at the takeup roll, the filament temperatures θ(x), filament diameters d(x), and birefringence Δn(x) as functions of distance x from the spinneret, and by observing how the molecular orientation was affected by these differences in cooling and thinning. Results were as follows: The thinning of the filament line, d(x), is affected little by the spinning temperature or by the degree of polymerization of the yarns taken up; it however depends heavily on the takeup speed VTu and the rate Q of production. Trouton viscosity β(T) as a temperature function derived from these experiments on nylon 6 is expressed consistently by the equation β ≑ 0.34 exp (3250/T), where T is absolute temperature. Nylon 6 filaments exhibit higher Trouton viscosity values than polyester or polypropylene filaments under the same spinning temperature. Filament temperature θ(x) versus distance x agreed well with theoretical values. The speed of molecular orientation was highest in the temperature range from 120°C to 40°C (the latter being the glass transition temperature of nylon 6). Furthermore, the larger the time rate of polymer deformation and the longer the residence time of polymer in the above temperature range, the higher was the orientation of the filament yarns taken up.
A comparison of some imidazole catalysts as epoxy curing agents
Authors: Dearlove Thomas J. 
Published: April 2003

AbstractSome physical properties of epoxy resins cured with 2‐substituted imidazoles, e.g., 2‐ethyl‐4‐methylimidazole (EMI‐24), and 1‐substituted imidazoles, e.g., 1‐methylimidazole (MI‐1), were studied in order to determine the effect of additional crosslinking that has been proposed to occur with EMI‐24. While these catalysts were found to yield identical physical properties in that system, they were found to behave differently when the epoxy resin was flexibilized with a polysulfide rubber. Evidence from infrared (IR) and nuclear magnetic resonance (NMR) spectra proved that imidazoles unsubstituted in the 2‐position were being deactivated through their conversion to a dihydroimidazole compound in a proportion related to the amount of polysulfide rubber present. Hence, only imidazoles substituted in the 2‐position will cure epoxy–polysulfide rubber systems.
Radiation‐convertible polymers from norbornenyl derivatives. Crosslinking with ionizing radiation
Authors: Colomb H. O. , Trecker D. J. , Osterholtz F. D. 
Published: April 2003

AbstractVinyl polymers with pendant norbornenyl (bicyclo[2.2.1]heptenyl) groups crosslink rapidly on exposure to ionizing radiation. Analysis (according to Charlesby‐Pinner theory) of extraction data from an ethylene–vinyl acetate copolymer and the corresponding ethylene–vinyl norbornenecarboxylate copolymer shows that the unsaturated polymer crosslinks by a chain reaction. At low doses, the kinetic chain length is about 4. Pendant norbornenyl groups accelerate crosslinking of a vinyl alcohol–vinyl acetate–vinyl chloride copolymer and convert poly(vinyl alcohols) and cellulose acetate from degrading to crosslinking polymers. A novel application of the Charlesby‐Pinner plot strongly suggests linear dependence of the extent of crosslinking on the norbornenyl group concentration in a series of modified poly(vinyl alcohols). The greater effectiveness of pendant norbornenyl groups, compared to cyclohexenyl groups, demonstrates the importance of the reactivity of the double bond.
The preparation of some block copolymers
Authors: Black P. E. , Worsfold D. J. 
Published: April 2003

AbstractThe reactivity of the double bonds in p‐divinylbenzene toward anionic reagents is much greater than is the residual double bond in the divinylbenzene unit incorporated in a polymer chain. Thus it is possible to add to a “living” polymer a few divinylbenzene units before appreciable crosslinking occurs. Each of these units will have a vinyl group conjugated with a phenyl ring and will be comparable in reactivity to styrene. If the reaction is stopped at this point by the addition of methanol, the molecular weight of the product is essentially that of the original living polymer. These polymers may then be copolymerized through these active double bonds with any monomer with which styrene may be copolymerized, to form block or graft‐like copolymers. The copolymerizations may be effected by any of the methods applicable to styrene, i.e., free radical, cationic, or anionic. Such copolymerizations have been attempted with methyl methacrylate, butyl acrylate, vinyl chloride, vinylidene chloride, vinyl acetate, butadiene, isobutene, and propene, usually successfully.