Vulcanization Chemistry

1985 ◽  
Vol 58 (2) ◽  
pp. 284-294 ◽  
Author(s):  
E. Morita ◽  
A. B. Sullivan ◽  
A. Y. Coran
Keyword(s):  
Weight Basis ◽  
Equal Weight ◽  
Amino Group ◽  
Triazine Ring ◽  
Equivalent Weight ◽  
Hydrogen Atoms ◽  
Sulfur Vulcanization ◽  
Diene Rubbers ◽  
The Ideal

Abstract Prevulcanization inhibitors based on triazines can be prepared. In each case the triazine ring is amino-substituted such that one or two of the amino hydrogen atoms per amino-group are alkylthio- or arylthio-substituted. The new triazine-derived prevulcanization inhibitors are extremely active in accelerated sulfur vulcanization of diene rubbers (e.g., NR or SBR). Differing accelerators or accelerator systems may require different triazine-derived prevulcanization inhibitors for best results. Provided that the reactivity of the inhibitor is sufficiently near the ideal, its weight-basis activity is greatest when its equivalent weight per S—N bond is least. Overall, hexakis(cyclohexylthio)melamine and especially hexakis(isopropylthio)melamine are the most effective premature vulcanization inhibitors tested, on an equal-weight basis.

Quest for the ideal olefin metathesis catalyst

2008 ◽  
Vol 80 (1) ◽  
pp. 31-43 ◽  
Author(s):  
Anna Michrowska ◽  
Karol Grela
Keyword(s):  
Oxygen Atom ◽  
Quaternary Ammonium ◽  
Olefin Metathesis ◽  
Amino Group ◽  
Sulfonated Polystyrene ◽  
Grubbs Catalyst ◽  
Metathesis Catalyst ◽  
Metathesis Catalysts ◽  
Novel Strategy ◽  
The Ideal

Attempts were made to create a catalyst that approaches Gladysz's vision of an "ideal catalyst". Modifications of the Hoveyda-Grubbs catalyst were carried out with the aim to increase its activity and broaden the scope of its applicability to challenging metathesis reactions. This was done by introduction of an electron-withdrawing substituent on the isopropoxybenzylidene group in order to diminish the donor properties of the oxygen atom. The resulting stable and easily accessible nitro-substituted Hoveyda-Grubbs catalyst has found a number of successful applications in various research and industrial laboratories. Also, a new concept for noncovalent immobilization of a ruthenium olefin metathesis catalyst is presented. The 2-isopropoxybenzylidene ligand of Hoveyda-Grubbs carbene is further modified by an additional amino group, and immobilization is achieved by treatment with sulfonated polystyrene, forming the corresponding ammonium salt. In this novel strategy for the immobilization of ruthenium-based metathesis catalysts, the amino group plays a dual role, being first an active anchor for immobilization and secondly, after protonation, activating the catalysts by electron-donating to -withdrawing switch. The same concept has been used in the preparation of a quaternary ammonium catalyst for aqueous olefin metathesis.

A comparative study of the feeding value of dried sugar-beet pulp for milk production

1972 ◽  
Vol 78 (3) ◽  
pp. 371-377 ◽  
Author(s):  
M. E. Castle
Keyword(s):  
Sugar Beet ◽  
Milk Production ◽  
Dry Matter ◽  
Daily Intake ◽  
Weight Basis ◽  
Sugar Beet Pulp ◽  
Equal Weight ◽  
Beet Pulp ◽  
Feeding Value ◽  
Matter Basis

SUMMARYTwo 16-week experiments with lactating Ayrshire cows were conducted to study the effect on milk production of replacing barley with dried molassed sugar-beet pulp on an equal dry-matter basis. The cows on all treatments received equal weights of hay, groundnut cake and minerals but the contents of barley and of sugar-beet pulp each varied from 0 to 80% in the different concentrate mixtures. The total daily intake of dry matter expressed as a percentage of live weight averaged 2·64 and 2·72 in the two experiments.The average yield of milk in the two experiments was 18·8 kg/cow per day, and, within each experiment, the mean yields of milk and the contents of solids-not-fat and crude protein were not significantly different on the contrasting feeding treatments. The intake of water was significantly increased as the dried beet pulp replaced the barley but no major changes occurred in the proportions of V.F.A.S in the rumen liquor.It is concluded that barley and dried molassed sugar-beet pulp had the same feeding value on a dry-matter basis when used in the production ration of milking cows. It is suggested that for most purposes barley and dried sugar-beet pulp are interchangeable on an equal weight basis, but for more precise feeding the two feeds should replace each other on an equal dry-weight basis.

PREPARATION AND PROPERTIES OF CRYSTALLINE CANDIDIN

1956 ◽  
Vol 34 (9) ◽  
pp. 1163-1167 ◽  
Author(s):  
L. C. Vining ◽  
W. A. Taber
Keyword(s):  
Absorption Maximum ◽  
Visible Region ◽  
Crystalline Form ◽  
Molecular Formula ◽  
Amino Group ◽  
Equivalent Weight ◽  
Conjugated Diene ◽  
Antifungal Antibiotic ◽  
Infrared Spectral ◽  
Best Fit

Candidin, the antifungal antibiotic produced by Streptomycesviridoflavus, has been isolated in crystalline form. Analyses and equivalent weight values best fit a molecular formula C46H75NO17. The substance is amphoteric and probably contains one carboxyl and one amino group. Infrared spectral evidence also indicates a polyhydroxylated structure, and the absorption in the visible region shows the presence of a conjugated heptaene chromophore. An additional conjugated diene elsewhere in the molecule is suggested by hydrogenation values and the absorption maximum at 228 mμ.

Lewis-Base Adducts of Group 11 Metal(I) Compounds. XLII. [Cu4X4L4] 'Cubane' Clusters, L = Hindered N-Base Ligand: Synthesis and Structure of the L = 2-(Diphenylmethyl)pyridine Complexes (X = Cl, Br, I)

1989 ◽  
Vol 42 (1) ◽  
pp. 107 ◽  
Author(s):  
LM Engelhardt ◽  
PC Healy ◽  
JD Kildea ◽  
AH White
Keyword(s):  
Bond Distance ◽  
Lewis Base ◽  
Structure Characterization ◽  
Hydrogen Atoms ◽  
X Ray ◽  
The Core ◽  
C 30 ◽  
The Ideal ◽  
Cubane Clusters

The synthesis and single-crystal X-ray structure characterization of tetrameric cubane clusters of copper(1) halides with the hindered N-base ligand 2-(diphenylmethy1)pyridine are reported. The chloride, bromide and iodide structures are isomorphous , crystallizing in the tetragonal space group 141/a, a ≈ 23, c ≈ 12 � , Z = 4 tetramers, the tetramer having crystallographically imposed 4 symmetry, well removed from the ideal 43m. In terms of each X3CuN fragment of the core, this distortion results in one of the N-Cu-X angles being enlarged by c. 30� with respect to the other two and one Cu-X bond distance shortened. Cu-N is also shorter than is usual in a four-coordinate environment and the cluster can be envisaged as being constructed from four quasi-linear monomers. The distortions may be attributed to interaction between the 6- and 2-α-substituent-hydrogen atoms and the halide atoms of the core. The effect diminishes with increasing halide size and increasing volume of the Cu4X4 core.

scholarly journals Intrinsic reconstruction of ice-I surfaces

2020 ◽  
Vol 6 (37) ◽  
pp. eabb7986
Author(s):  
N. Kawakami ◽  
K. Iwata ◽  
A. Shiotari ◽  
Y. Sugimoto
Keyword(s):  
Short Range ◽  
Ice Thickness ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Force Microscopy ◽  
Atomic Structures ◽  
Atomic Force ◽  
Physical And Chemical ◽  
The Ideal

Understanding the precise atomic structure of ice surfaces is critical for revealing the mechanisms of physical and chemical phenomena at the surfaces, such as ice growth, melting, and chemical reactions. Nevertheless, no conclusive structure has been established. In this study, noncontact atomic force microscopy was used to address the characterization of the atomic structures of ice Ih(0001) and Ic(111) surfaces. The topmost hydrogen atoms are arranged with a short-range (2 × 2) order, independent of the ice thickness and growth substrates used. The electrostatic repulsion between non–hydrogen-bonded water molecules at the surface causes a reduction in the number of the topmost hydrogen atoms together with a distortion of the ideal honeycomb arrangement of water molecules, leading to a short-range–ordered surface reconstruction.

Cannonite [Bi2O(SO4)(OH)2] from Alfenza (Crodo, Italy): crystal structure and morphology

2013 ◽  
Vol 77 (8) ◽  
pp. 3067-3079 ◽  
Author(s):  
G. C. Capitani ◽  
T. Catelani ◽  
P. Gentile ◽  
A. Lucotti ◽  
M. Zema
Keyword(s):  
Crystal Structure ◽  
Cleavage Plane ◽  
Structure Refinement ◽  
Molecular Water ◽  
Hydrogen Atoms ◽  
Oh Groups ◽  
Cell Parameters ◽  
Difference Fourier ◽  
Raman And Ir Spectroscopy ◽  
The Ideal

AbstractCanonite from Alfenza grows as crowded, radiating, acicular aggregates covering bismuthinite crystals. Individual crystals have a lozenge-shaped habit on {010}, the presumed cleavage plane of cannonite. Crystal structure refinements in the P21/c space group of two single crystals led to the following cell parameters: a = 7.7196(5) Å, b = 13.8856(9), c = 5.6980(4), b = 109.174(1)º (R1 = 0.0424); and a = 7.7100(8), b = 13.8717(14), c = 5.6939(6), b = 109.155(2)º (R1 = 0.0438). Hydrogen atoms were also localized in the density-difference Fourier map and refined with soft restraints on the bond distances. Raman and IR spectroscopy confirm the presence of OH groups and the absence of molecular water, and deliver OH···O geometry wholly comparable with the structure refinement. Electron microprobe analyses revealed no significant levels of elements other than those expected in the ideal formula except fluorine which was present up to 0.14 a.p.f.u. The crystal structure can be described in terms of anion-centred OBi4 edge-sharing tetrahedra forming chains running parallel to z and strongly cemented along x by isolated SO4 tetrahedra. Each OBi4 tetrahedron is further connected along y by OH groups, making walls of composition Bi4O2(SO4)2(OH)4 parallel to (010). These walls are tied to each other along y by fewer Bi–O–S bridges and weaker OH···O bonds.

Numerical Simulation of Ampacity in Advanced Electrical Conductors

2020 ◽  
Author(s):  
Pouria Khanbolouki ◽  
Mehran Tehrani
Keyword(s):  
Weight Basis ◽  
Low Density ◽  
Equivalent Weight ◽  
One Dimensional ◽  
Temperature Performance ◽  
Elevated Temperature Performance ◽  
Heating Model ◽  
Development And Validation ◽  
Electrical Conductors ◽  
Copper Nanocomposites

Abstract Elevated temperature performance of advanced conductors are investigated with a one-dimensional joule heating model. Step-by-step development and validation of the ampacity prediction model are discussed and results from case studies are provided. A potential advantage of advanced electrical conductors is their relatively low density. Copper — as reference — is compared with carbon-based conductors and copper nanocomposites, on the basis of equivalent volume and equivalent weight. It is shown that while doped carbon nanotube (CNT) conductors may potentially result in an improved conductor compared with copper on a weight basis, ultra-conductive copper (UCC) can outperform copper on both volume and weight bases.

Preliminary Studies on New Anti-Reversion Agents for the Sulfur Vulcanization of Diene Rubbers

2000 ◽  
Vol 73 (1) ◽  
pp. 114-120 ◽  
Author(s):  
E. J. Blok ◽  
M. L. Kralevich ◽  
J. E. Varner
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Crosslink Density ◽  
New Materials ◽  
Sulfur Vulcanization ◽  
Diene Rubbers ◽  
Temperature Applications

Abstract Recently, new materials have been introduced that minimize the loss of crosslink density and properties caused by over-cure and/or high temperature applications. One of these new anti-reversion agents, 1,3-bis(citraconimidomethyl)benzene, compensates for the loss in crosslink density through the formation of new crosslinks. This paper evaluates various multifunctional acrylates to determine if they will function like 1,3-bis(citraconimidomethyl)benzene and reduce reversion through the formation of new crosslinks. The experimental data suggests that some of these acrylates form new crosslinks during overcure conditions and therefore are very effective at maintaining the modulus and tan delta values upon overcure.

scholarly journals Атомная и электронная структура реконструкций поверхности (111) в кристаллах ZnSe и CdSe

2018 ◽  
Vol 60 (1) ◽  
pp. 187
Author(s):  
В.Л. Бекенев ◽  
С.М. Зубкова
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
A Charge ◽  
Quantum Espresso ◽  
First Time ◽  
Vacuum Gap ◽  
The Ideal

AbstractThe atomic and electron structure of four variants of polar (111)-(2 × 2) surfaces in ZnSe and CdSe terminated by a cation, namely, the ideal, relaxed, reconstructed, and relaxed after reconstruction surfaces, are calculated for the first time from the first principles. The surface is simulated by a film with a thickness of 12 atomic layers and a vacuum gap of ~16 Å in the layered superlattice approximation. Four fictitious hydrogen atoms with a charge of 0.5 electrons each are added for closing dangling Se bonds on the opposite side of the film. Ab initio calculations are performed using the QUANTUM ESPRESSO software based on the density functional theory. It is shown that relaxation results in splitting of atomic layers. We calculate and analyze the band structures and total and layer-wise densities of electron states for four variants of the surface.

Labortory Bioassays for Evaluating Sweet Corn Antibiosis on European Corn Borer (Lepidoptera: Pyralidae) Larval Development

1997 ◽  
Vol 32 (3) ◽  
pp. 342-357 ◽  
Author(s):  
Daniel F. Warnock ◽  
William D. Hutchison ◽  
Timothy J. Kurtti ◽  
David W. Davis
Keyword(s):  
Larval Development ◽  
European Corn Borer ◽  
Sweet Corn ◽  
Weight Basis ◽  
Equal Weight ◽  
Plant Tolerance ◽  
Larval Weight ◽  
Isolation And Identification ◽  
Corn Borer ◽  
Contaminant Control

European corn borer (Ostrinia nubilalis Hübner) can severely affect commercial sweet corn quality during years of heavy infestation. The isolation and identification of allelochemicals in sweet corn which detrimentally affect O. nubilalis may enhance breeder selection for greater ear feeding resistance, thus reducing the need for insecticide application. Field selection techniques for improving plant resistance to O. nubilalis cannot easily distinguish between plant tolerance or antibiosis. A laboratory bioassay incorporating ear tissues from field resistant and susceptible sweet corn genotypes into a nutritionally complete O. nubilalis larval diet was developed as an initial step to facilitate the isolation and identification of potential chemical resistance factors in sweet corn. Neonates reared for 7 d on a meridic diet with limited fungal and bacterial contaminant control agents weighed more than larvae grown on a comparable diet with high levels of contaminant control (5.96 and 2.46 mg, respectively). Silk tissue from several sweet corn genotypes significantly reduced larval weight and increased total larval development time compared with kernel tissue. Silk tissues incorporated on a weight basis had volumes about 3 × that of an equal weight of kernel tissues. However, tissues incorporated into a specific diet volume on a weight or volume basis usually did not alter larval weight or time to pupation within a genotype. Incorporation on a weight basis was most time efficient. Future bioassays screening for antibiotic effects of sweet corn tissue on O. nubilalis development should utilize a diet with limited contaminant control agents, incorporate tissue on a weight basis, and focus on silk tissue.

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