Showing papers by "ExxonMobil published in 1992"

Phase transitions and universal dynamics in confined films.

Abstract: We describe molecular dynamics simulations of fluid films confined between two solid walls. The films consist of spherical molecules, or flexible linear chains with up to twenty monomers. When the wall separation is only a few molecular diameters, crystalline or glassy order is induced across the film. The onset of the glassy phase is characterized by rapidly increasing relaxation times. These manifest themselves through changes in the diffusion constant and in the response to shear. The viscosity exhibits the same power-law scaling with shear rate that was observed in recent experiments. Our study suggests that this response is a universal property of lubricants near a glass transition.

Heat sealable polyolefin films containing very low density ethylene copolymers.

Abstract: The invention provides laminar polyolefin film materials having a base film layer comprising a blend of an olefin polymer and up to about 30% by weight of at least one very low density copolymer of ethylene and a C 3 to C 20 alpha olefin comonomer copolymerizable with ethylene, said base layer having a heat sealable film layer present on one or both surfaces thereof comprising a very low density copolymer of ethylene and a copolymerizable C 5 to C 12 alpha olefin comonomer. The ethylene copolymer constituents of the film are characterized as having a density in the range of about 0.88 g/cm 3 to abut 0.915 g/cm 3 , a melt index in the range of about 0.5 dg/min to about 7.5 dg/min, a molecular weight distribution (M w /M n ) of about 1.5 to about 3.5 and an essentially single melting point in the range of about 60° C. to about 115° C., measured as a DSC peak T m . Films of this invention exhibit extremely good hot tack seal strength at temperatures in the range of from about 200° to 290° F. thereby rendering them extremely useful as packaging materials in high speed packaging operations.

Heat sealable blend of very low density polyethylene or plastomer with polypropylene based polymers and heat sealable film and articles made thereof

Abstract: Heat sealable compositions suitable for film and film structures comprise: (a) from 30 to 70 weight percent of a low melting polymer comprising an ethylene based copolymer having a density of from 0.88 g/cm3 to 0.915 g/cm3, a melt index of from 1.5 dg/min to 7.5 dg/min, a molecular weight distribution no greater than 3.5, and a composition distribution breath index greater than 70 percent; and, (b), being different from (a), from 70 to 30 weight percent of a propylene based polymer having from 88 mole percent to 100 mole percent propylene and from 12 mole percent to 0 mole percent of an alpha-olefin other than propylene.

Coordination Compounds of Polyoxovanadates with a Hexametalate Core. Chemical and Structural Characterization of [VV6O13{(OCH2)3CR}2]2−, [VV6O11(OH)2{(OCH2)3CR}2], [VIV4VV2O9(OH)4{(OCH2)3CR}2]2−, and [VIV6O7(OH)6{(OCH2)3CR}2]2−

Abstract: Reactions of the tris(hydroxymethyl)methane-derived ligands, (HOCH 2 ) 3 Cr, R=NO 2 , CH 2 OH, and CH 3 , with [(C 4 H 9 ) 4 N] 3 [H 3 V 10 O 28 ] in CH 3 CN yield the polyoxovanadate coordination complexes [(C 4 H 9 ) 4 N] 2 [V 6 O 13 {(OCH 2 ) 3 Cr} 2 ].

Nonergodicity and light scattering from polymer gels

Abstract: Dynamic light scattering from polymer gels is complicated by the fact that the scattering intensity and its time correlation function change as different parts of a sample are explored. This results from the nonergodicity of the sample---time averages are not the same as ensemble averages, the result of a finite rigidity that leads to constrained inhomogeneities. We demonstrate a direct technique for ensemble averaging (by moving the sample), present the experimental correlation function containing correlations that do not decay with time, and show that the light scattering results from a superposition of static scattering from immobile inhomogeneities and dynamic density fluctuations from ``gel modes.''

Quantitative Determination of the Mechanical Properties of Shales

Abstract: Shales make up more than 75% of drilled formations and cause at least 90% of wellbore-stability problems. Physical measurements of shale properties are required to develop realistic constitutive relationships and to understand and define shale strength and behavior under downhole conditions. Quantitative shale-strength data are needed to improve wellbore-stability model predictions. This paper describes a research test program to determine the mechanical properties of different classes of shales and to build a database on their characteristics and mechanical behavior. Shale samples from undisturbed block samples were prepared under controlled conditions. Mechanical test techniques were developed to measure effective-stress/strain properties accurately for shales. The tests require a heavy-duty, triaxial test load frame and other specially designed equipment to obtain precise pore pressure measurements. During the tests, pore pressure, stresses, and strains were monitored accurately by an automatic data-acquisition system. The test techniques described can be used to test shales with different characteristics: soft, hard, brittle, plastic, etc. On the basis on results of several shale tests, high-quality, effective-stress/strain data and failure criteria (shale strength relationships) can be obtained routinely.

Elastic articles having improved unload power and a process for their production

Abstract: Disclosed is a process for improving the unload power of a precursor elastic film comprising orienting the film to a draw ratio in the range of about 2:1 to about 20:1 followed by annealing. Further disclosed is an elastic film oriented to a draw ratio in the range of about 2:1 to about 20:1 and comprising a copolymer of ethylene polymerized with at least one comonomer selected from the group consisting of C3 to C20 alpha-olefins and C3 to C20 polyenes, wherein the copolymer has a density in the range of about 0.855 g/cm3 to about 0.9 g/cm3, a melt index in the range of about 0.5 to about 50, with a composition distribution index at least about 45 percent.

Immiscible-fluid displacement: Contact-line dynamics and the velocity-dependent capillary pressure

Abstract: The dynamics of immiscible-fluid displacement is studied in the simple geometry of a capillary tube. Here the interesting physics lies in the breakdown of the no-slip boundary condition near the contact line, defined as the intersection of the fluid-fluid interface with the solid wall. Through numerical hydrodynamic calculations, we link macroscopic-flow behavior to the microscopic parameters governing the contact-line region. It is shown that the moving contact line generates two types of frictional forces. One, the viscous stress, is responsible for the observed deformation of the fluid-fluid interface as the flow velocity U increases. Our calculation is in excellent agreement with prior analytic works on this aspect. In particular, our results reproduce Hoffman's scaling relation as well as the logarithmic dependence of the viscous friction on slipping length. Identical macroscopic-flow behaviors are also found to result from three different slipping models provided that their slipping lengths are each renormalized by a model-dependent constant. Besides the viscous stress, however, comparison with experiments revealed a second frictional force that varies as ${\mathit{U}}^{\mathit{x}}$, with 0x\ensuremath{\le}0.5, which is dominant at capillary numbers ${10}^{\mathrm{\ensuremath{-}}3}$. We propose that the source of this new friction is the excitation of damped capillary waves at the fluid-fluid interface due to contact-line motion over wall roughness. Consideration of this mechanism yields not only the correct range of x values, but also good agreement with the measured magnitude of the second frictional force. The paper concludes with an analysis of the frequency-dependent pressure response to an imposed ac velocity perturbation. An expression is derived for the critical frequency that separates the low-frequency behavior from that of the high-frequency regime.

A niche for enhanced oil recovery in the 1990s

Abstract: Aging oil fields and shrinking reserves are making new demands for enhanced oil recovery. New understanding of reservoir dynamics is enhancing the efficiency of the three main Enhanced Oil Recovery (EOR) methods: thermal, miscible and chemical recovery methods, describing which situations favor the techniques and which rule them out. 9 figs., 14 refs.

Breaker chemical encapsulated with a crosslinked elastomer coating

Abstract: An encapsulated breaker chemical composition used in an oil or gas stimulation operation which comprises: a breaker chemical; and a pinhole free coating of an ionically and covalently crosslinked neutralized sulfonated elastomeric polymer of about 2 to about 80 microns thick deposited onto the surface of the breaker chemical, wherein said polymer encapsulates the breaker chemical, wherein the polymer is permeable to the breaker chemical and the polymer is non-reactive to the breaker chemical.

Microstructural simulation of dynamic recrystallization

Abstract: A Monte Carlo model for dynamic recrystallization has been developed from earlier models used to simulate static recrystallization and grain growth. The model simulates dynamic recrystallization by adding recrystallization nuclei and stored energy continuously with time. The simulations reproduce many of the essential features of dynamic recrystallization. The stored energy of the system, which may be interpreted as a measure of the flow stress, goes through a maximum and then decays, monotonically under some conditions and in an oscillatory manner under others. The principle parameters that were studied were the rate of adding stored energy, AH, and the rate of adding nuclei, AN. As AH increases, for fixed AN, the oscillations decay more rapidly and the asymptotic energy rises. As AN increases, again the oscillations decay more rapidly but the asymptotic stored energy decreases. The mean grain size of the system also oscillates in a similar manner to the stored energy but out of phase by 90 °. The flow stress oscillations occurred for conditions which lead to both coarsening and refinement of the initial grain size. Necklacing of the prior grain structure by new grains were observed for low AH and high AN; it is, however, not an invariable feature of grain refinement. The initial grain size has a profound influence on the microstructure that evolves during the first cycle of recrystallization but at long times, a mean grain size is established which depends on the values of AH and AN alone. Comparison of the relationships between the energy storage rate, maximum and asymptotic stored energy and the grain size suggest that in physical systems the energy storage rate and the nucleation rate are coupled. Comparison of the simulation results with experimental trends suggests that the dependence of nucleation rate on storage should be positive but weak. All of these results were obtained without the addition of special parameters to the model.

Homogeneous catalytic hydrogenation. 6. Synthetic and mechanistic aspects of the regioselective reductions of model coal nitrogen, sulfur, and oxygen heteroaromatic compounds using the (.eta.5-pentamethylcyclopentadienyl)rhodium tris(acetonitrile) dication complex as the catalyst precursor

Abstract: The synthetic and mechanistic aspects of the regioselective hydrogenation of representative mono and polynuclear heteroaromatic nitrogen, sulfur, and oxygen model coal compounds such as 2-methylpyridine (1), N-methylindole (2), benzofuran (3), benzothiophene (4), quinoline (5), 2-methylquinoline (6), 5,6- and 7,8-benzoquinolines (7 and 8), and acridine (9) were studied with a (η 5 -pentamethylcuclopentadienyl)rhodium tris(acetonitrile) dicationic complex, [Cp*Rh(CH 3 CN) 3 ] 2+ , as the catalyst precursor. The order of relative rates as a function of structure was found to be 8>>>9>5>7>6>4>>1-3

Plastomer compatibilized polyethylene/polypropylene blends

Abstract: Compatibilized blends of polypropylene, linear low density polyethylene and a low molecular weight plastomer are disclosed. The blend preferably contains at least about 50 percent by weight of crystalline polypropylene, from about 10 to about 50 percent by weight of LLDPE dispersed in a matrix of the polypropylene, and a compatibilizing amount of an ethylene/alpha-olefin plastomer having a weight average molecular weight between about 5,000 to about 50,000, a density of less than about 0.90 g/cm3, and a melt index of at least about 50 dg/min. The blend is useful in the formation of melt spun and melt blown fibers. Also disclosed are spun bonded-melt blown-spun bonded fabrics made from the blends.

Decoupling of time scales of motion in polybutadiene close to the glass transition.

Abstract: Studying the dynamic structure factor of polybutadiene in the first valley of S(Q) we observed a decoupling of microscopic and macroscopic time scales about 40\ifmmode^\circ\else\textdegree\fi{} above ${\mathit{T}}_{\mathit{g}}$. At higher temperatures the time scale set by the viscosity scales with the microscopic scale, while at lower T strong decoupling effects occur. We present evidence that the decoupled low-temperature relaxation is distinctly different from the high-frequency ``\ensuremath{\beta} process.'' The decoupling temperature coincides with the critical temperature of the mode coupling theory.

Birefringence detection of the order-to-disorder transition in block copolymer liquids

Abstract: The order-to-disorder transition (ODT) in a concentrated solution of a polystyrene-polyiso- prene diblock copolymer (molecular weights of the polystyrene and polyisoprene blocks are 1.2 X l(r and 1.9 x lo4, respectively) in bis(2-ethylhexyl) phthalate is identified by a discontinuous decrease in the static birefringence of the sample upon heating. The location of the ODTis confirmed by rheologicalmeasurements; both the storage and loss moduli of the solution show a sharp decrease at the same temperature. Solutions with concentrations ranging from 48 to 61 wt 95 polymer were examined with the birefringence technique. The measured ODT temperatures for these solutions range from 27 to 178 "C. Small-angle X-ray scattering measurements at temperatures well below the ODT indicate that the ordered solutions have a lamellar microstructure.

Unification of the ferritin family of proteins.

Abstract: Ferritin is the iron-storage protein of eukaryotic organisms. The nucleotide sequence encoding Azotobacter vinelandii bacterioferritin, a hemoprotein, was determined. The deduced amino acid sequence reveals a high degree of identity with Escherichia coli bacterioferritin and a striking similarity to eukaryotic ferritins. Moreover, derivation of a global alignment shows that virtually all key residues specifying the unique structural motifs of eukaryotic ferritin are conserved or conservatively substituted in the A. vinelandii sequence. The alignment suggests specific methionine residues as heme-binding ligands in bacterioferritins. The overall sequence similarity with conservation of key structural residues implies that all ferritins form a unified family of proteins. The results implicate ferritins as proteins potentially common to all aerobic organisms and as such useful in taxonomic classification, evolutionary analysis, and environmental monitoring.

Catalyst and method of broadening polymer molecular weight distribution and increasing polymer tensile impact strength and products made thereof

Abstract: A catalyst and method of producing polyolefins having broadened molecular weight distributions and enhanced tensile impact strengths utilizing a silica supported metallocene-alumoxane catalyst system, wherein at least one of the metallocenes has at least one cyclopentadienyl ring being substituted by at least one optionally substituted hydrocarbon substituent having a 2° or 3° carbon atom with which it is covalently bonded to the cyclopentadienyl ring.

Scaling of transient hydrodynamic interactions in concentrated suspensions

Abstract: The mean-square displacemenf (Δr 2 (τ)) of particles in concentrated suspensions is measured at times sufficiently short to observe the transient nature of hydrodynamic interactions. For all volume fractions O, the velocity autocorrelation function decays as a power law R(τ)∼τ -3/2 . A remarkable scaling with O is observed for the time-dependent self-diffusion coefficient D s (τ)=(Δr 2 (τ))/6τ: If D s (τ) is scaled by its asymptotic value and if time is scaled by a viscous time inversely proportional to the shear viscosity of the suspension

Ethylene alpha-olefin polymer substituted mono- and dicarboxylic acid dispersant additives (PT-920)

Abstract: The present invention is directed to an oil-soluble fuel and lubricating oil additive comprising at least one terminally unsaturated ethylene alpha-olefin polymer of 300 to 20,000 number average molecular weight substituted with mono- or dicarboxylic acid producing moieties (preferably dicarboxylic acid or anhydride moieties), wherein the terminal unsaturation comprises terminal ethenylidene unsaturation. The mono- and dicarboxylic acid or anhydride substituted polymers of this invention are useful per se as additives to lubricating oils, and can also be reacted with a nucleophilic reagent, such as amines, alcohols, amino alcohols and reactive metal compounds, to form products which are also useful fuel and lubricating oil additives, e.g., as dispersants.

Diffusion, dispersion, and settling of hard spheres.

Abstract: Using a multiple light scattering technique and a stabilizing counterflow (i.e., a fluidized bed), we measured the average sedimentation velocity, its variance, and the short-time self-diffusion coefficient in a concentrated hard-sphere suspension. Many-body hydrodynamic interactions slow both the Brownian diffusion and mean sedimentation and provide a novel mechanism for long time dispersion.

Surfactant flood process design for Loudon

Abstract: In this paper laboratory steps required to design a successful surfactant flooding process for the high-quality Loudon oil field are described. These steps involved phase-behavior tests to identify two synthetic surfactant components; Berea coreflood tests to establish the desirability of incorporating polymer in the microemulsion and to optimize blend ratio, microemulsion salinity, drive-water salinity, and bank size; and Loudon rock corefloods to provide a final check in reservoir core material. The process recovered significant quantities of residual oil in two 1-acre pilot tests without the use of a cosurfactant, a cosolvent alcohol, or a low-salinity preflush.