Investigations into the Silica/Silane Reaction System

Abstract Silica in combination with organosilanes (e.g. [bis(3-triethoxysilylpropyl)tetrasulfane] = TESPT) has recently become more important in tire applications. Their use in tire treads leads to an improvement in rolling resistance and wet traction. The requirements for the attainment of these properties are, that the triethoxysilyl groups of TESPT react with the silanol groups on the silica surface during compounding, and the polymer active groups react with the polymer during cure. The reaction of precipitated silica with this silane was investigated. The influence of various parameters on the reaction type and the reaction kinetics was considered. The results of the investigation obtained using 29Si-CP/MAS solid state NMR spectroscopy agree well with a horizontal reaction model in which a single siloxane bond is first formed with the silica surface (primary reaction). It is followed by condensation reactions between silanol groups of silane molecules which are already bound to the silica surface (secondary reaction). The kinetic studies data show a clear difference between the fast primary reaction and the slow secondary reaction. Both reactions become more rapid in acidic and alkaline pH ranges. The primary reaction accelerates up to a particular H2O content after which the rate remains constant. The secondary reaction keeps on accelerating with rising H2O content. Modification with different silane concentrations showed a higher rate constant at low concentrations.

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SILICA GRAFTED WITH EPOXIDIZED LIQUID POLYBUTADIENES: EVIDENCE FOR THE MECHANISM OF REINFORCEMENT

Rubber Chemistry and Technology ◽

10.5254/rct.19.81500 ◽

2019 ◽

Vol 92 (3) ◽

pp. 431-444 ◽

Cited By ~ 1

Author(s):

Marcus V. Braum ◽

Marly A. M. Jacobi

Keyword(s):

Close Agreement ◽

Silica Surface ◽

Rolling Resistance ◽

Handling Performance ◽

Precipitated Silica ◽

Low Field ◽

Progressive Loss ◽

Equilibrium Swelling ◽

Coating Matrix

ABSTRACT Precipitated silica with backbone epoxidized liquid polybutadiene grafted onto its surface has recently been presented as a new reinforcement material that requires significantly less energy to disperse in comparison wtih the traditional in situ silanization process. This potentially provides better traction and hard-handling performance in car tire treads, without greatly increasing rolling resistance. The purpose of this study was to seek evidence proving the previously proposed reinforcement mechanism, through solid-state 1H low-field nuclear magnetic resonance and equilibrium swelling experiments. The evidence points to an increase in the amount of epoxidized chain segments chemically bonded to the silica surface and to an increase in coating-matrix entanglements with increases in the degree of epoxidation and cure of the coated silica. Such evidence is consistent with the hypothesis of increasing the number of entanglements and/or their progressive loss of mobility with an increase in the degree of epoxidation and decrease in temperature, which is in close agreement with the proposed mechanism.

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Serum Cholinesterase Variants: Examination of Several Differential Inhibitors, Salts, and Buffers Used to Measure Enzyme Activity

Clinical Chemistry ◽

10.1093/clinchem/17.3.183 ◽

1971 ◽

Vol 17 (3) ◽

pp. 183-191 ◽

Cited By ~ 30

Author(s):

Philip J Garry

Keyword(s):

Enzyme Activity ◽

Sodium Fluoride ◽

Phosphate Buffer ◽

Divalent Cations ◽

Kinetic Studies ◽

Competitive Inhibitor ◽

Serum Cholinesterase ◽

Low Concentrations

Abstract Dibucaine, used as a differential inhibitor with acetyl-, propionyl-, and butyrylthiocholine as substrate, clearly identified the "usual" and "atypical" serum cholinesterases. Succinylcholine was also used successfully as a differential inhibitor with butyrylthiocholine as substrate. Sodium fluoride, used as a differential inhibitor, gave conflicting results, depending on whether Tris or phosphate buffer was used in the assay. Mono- and divalent cations (NaCl, KCl, MgCl2, CaCl2, and BaCl2) activated the "usual" and inhibited the "atypical" enzyme at low concentrations. The "usual" enzyme had the same activity in 0.05 mol of Tris or phosphate buffer per liter, while the heterozygous and "atypical" enzymes showed 12 and 42% inhibition, respectively, when assayed in the phosphate buffer. Kinetic studies showed the phosphate acted as a competitive inhibitor of "atypical" enzyme. Km values, determined for "usual" and "atypical" enzymes, were 0.057 and 0.226 mmol/liter, respectively, with butyrylthiocholine as substrate.

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Kinetic studies on the regulation of rabbit liver pyruvate kinase

Biochemical Journal ◽

10.1042/bj1310287 ◽

1973 ◽

Vol 131 (2) ◽

pp. 287-301 ◽

Cited By ~ 33

Author(s):

M. G. Irving ◽

J. F. Williams

Keyword(s):

Pyruvate Kinase ◽

Specific Activity ◽

Deae Cellulose ◽

Kinetic Studies ◽

Rabbit Liver ◽

Hill Coefficient ◽

Saturation Curve ◽

Low Concentrations ◽

Ammonium Sulphate Fractionation ◽

The Hill

Two kinetically distinct forms of pyruvate kinase (EC 2.7.1.40) were isolated from rabbit liver by using differential ammonium sulphate fractionation. The L or liver form, which is allosterically activated by fructose 1,6-diphosphate, was partially purified by DEAE-cellulose chromatography to give a maximum specific activity of 20 units/mg. The L form was allosterically activated by K+ and optimum activity was recorded with 30mm-K+, 4mm-MgADP-, with a MgADP-/ADP2- ratio of 50:1, but inhibition occurred with K+ concentrations in excess of 60mm. No inhibition occurred with either ATP or GTP when excess of Mg2+ was added to counteract chelation by these ligands. Alanine (2.5mm) caused 50% inhibition at low concentrations of phosphoenolpyruvate (0.15mm). The homotropic effector, phosphoenolpyruvate, exhibited a complex allosteric pattern (nH+2.5), and negative co-operative interactions were observed in the presence of low concentrations of this substrate. The degree of this co-operative interaction was pH-dependent, with the Hill coefficient increasing from 1.1 to 3.2 as the pH was raised from 6.5 to 8.0. Fructose 1,6-diphosphate interfered with the activation by univalent ions, markedly decreased the apparent Km for phosphoenolpyruvate from 1.2mm to 0.2mm, and transformed the phosphoenolpyruvate saturation curve into a hyperbola. Concentrations of fructose 1,6-diphosphate in excess of 0.5mm inhibited this stimulated reaction. The M or muscle-type form of the enzyme was not activated by fructose 1,6-diphosphate and gave a maximum specific activity of 0.3 unit/mg. A Michaelis–Menten response was obtained when phosphoenolpyruvate was the variable substrate (Km+0.125mm), and this form was inhibited by ATP, as well as alanine, even in the presence of excess of Mg2+.

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Peculiarities of Chemisorption of Dimethyl Carbonate on Silica Surface

Фізика і хімія твердого тіла ◽

10.15330/pcss.17.1.88-92 ◽

2016 ◽

Vol 17 (1) ◽

pp. 88-92

Author(s):

I.S. Protsak ◽

E.M. Pakhlov ◽

V.A. Tertykh

Keyword(s):

Ir Spectroscopy ◽

Fumed Silica ◽

Dimethyl Carbonate ◽

Silica Surface ◽

Chemical Interaction ◽

Spectroscopy Method ◽

Silanol Groups

This paper presents the results of studies of dimethyl carbonate interaction with sites of the fumed silica surface. The investigations were performed in a vacuum quartz cuvette using IR spectroscopy method. Chemical interaction of dimethyl carbonate with sites of the dehydrated silica surface was shown to occur at temperature of 200 °C and higher, chemisorption processes take place involving both structural silanol groups and siloxane bridges on the surface.

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Modelling the surface of amorphous dehydroxylated silica: the influence of the potential on the nature and density of defects

New Journal of Chemistry ◽

10.1039/c7nj03922k ◽

2018 ◽

Vol 42 (2) ◽

pp. 1356-1367 ◽

Cited By ~ 4

Author(s):

Stéphanie Halbert ◽

Simona Ispas ◽

Christophe Raynaud ◽

Odile Eisenstein

Keyword(s):

Molecular Dynamics ◽

Silica Surface ◽

Silanol Groups

The nature and density of defects on the amorphous dehydroxylated silica surface are studied by molecular dynamics for information on the silanol groups of pretreated silica.

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The enzymology of short-chain fatty acyl-coenzyme A synthetase from seeds of Pinus radiata. Kinetic studies and a proposed reaction mechanism

Biochemical Journal ◽

10.1042/bj1370435 ◽

1974 ◽

Vol 137 (3) ◽

pp. 435-442 ◽

Cited By ~ 3

Author(s):

Owen A. Young ◽

John W. Anderson

Keyword(s):

Fatty Acid ◽

Pinus Radiata ◽

Kinetic Studies ◽

Single Species ◽

Competitive Inhibitor ◽

Fatty Acyl ◽

Short Chain ◽

Low Concentrations ◽

High Concentrations ◽

Acyl Coenzyme A

1. Short-chain fatty acyl-CoA synthetase from seeds of Pinus radiata was examined by acetate- and propionate-dependent PPi–ATP exchange. Reaction mixtures came to equilibrium almost instantly as judged by rates of exchange and analysis of an incubation mixture. 2. The activity of the enzyme was correlated with the concentration of MgP2O72- but not with the concentration of Mg2+, as judged by PPi–ATP exchange and fatty acyl AMP-dependent synthesis of ATP in the presence of PPi. In PPi–ATP exchange assays, no clear relationship between activity and any single species of ATP was apparent. 3. High concentrations of fatty acid inhibited PPi–ATP exchange. PPi–dATP exchange was less than PPi–ATP exchange at low concentrations of fatty acid, but at higher concentrations PPi–dATP exchange exceeded PPi–ATP exchange. The rate of synthesis of fatty acyl-CoA in the presence of dATP was less than with ATP. 4. ATP and propionate inhibited the synthesis of ATP from propionyl-AMP and PPi. The inhibition by ATP was competitive with respect to propionyl-AMP and non-competitive with respect to PPi. The inhibition by propionate was non-competitive with respect to propionyl-AMP and PPi. 5. AMP was a competitive inhibitor of propionyl-AMP-dependent synthesis of ATP and competitively inhibited propionate-dependent PPi–ATP exchange when ATP was the variable substrate. 6. It was concluded that the first partial reaction catalysed by the enzyme is ordered; ATP is the first substrate to react with the enzyme and PPi is probably the only product released.

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Clean chlorination of silica surfaces by a single-site substitution approach

Dalton Transactions ◽

10.1039/c8dt00186c ◽

2018 ◽

Vol 47 (12) ◽

pp. 4301-4306 ◽

Cited By ~ 7

Author(s):

Niladri Maity ◽

Samir Barman ◽

Edy Abou-Hamad ◽

Valerio D'Elia ◽

Jean-Marie Basset

Keyword(s):

Silica Surface ◽

Single Site ◽

Silanol Groups ◽

Silica Surfaces ◽

Selective Chlorination ◽

Hydrogen Bonded

Unveiling a clean, selective chlorination method for the quantitative substitution of well-defined non-hydrogen bonded silanol groups of the silica surface.

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TOWARD REPLACEMENT OF PETROLEUM OILS BY MODIFIED SOYBEAN OILS IN ELASTOMERS

Rubber Chemistry and Technology ◽

10.5254/rct.16.84830 ◽

2016 ◽

Vol 89 (4) ◽

pp. 608-630 ◽

Cited By ~ 9

Author(s):

Jiaxi Li ◽

Avraam I. Isayev ◽

Xiaofeng Ren ◽

Mark D. Soucek

Keyword(s):

Soybean Oil ◽

Abrasion Resistance ◽

Crosslink Density ◽

Dynamic Properties ◽

Rolling Resistance ◽

Styrene Butadiene Rubber ◽

Butadiene Rubber ◽

Precipitated Silica ◽

Modified Soybean Oil ◽

Tan Δ

ABSTRACT Precipitated silica- and carbon black (CB)-filled styrene-butadiene rubber (SBR) compounds and vulcanizates containing naphthenic oil (NO), soybean oil (SO), and modified soybean oil (MSO) were studied. Gel fraction; crosslink density; bound rubber fraction; curing behavior; and thermal, mechanical, and dynamic properties were compared. Interaction between SO, MSO, and silane coupling agent was also studied. It was shown that the incorporation of SO and MSO had similar effects in both silica- and CB-filled SBR compounds and vulcanizates. SO and MSO were found to consume curatives leading to a lower crosslink density and improved thermal stability of compounds and vulcanizates. In comparison with NO, MSO was found to increase the elongation at break and tensile strength, and the values of tan δ at 10 °C and 60 °C predict an increase of the wet traction performance and the rolling resistance to decrease the modulus and abrasion resistance. After adjusting the recipe, the modulus and abrasion resistance of the silica- and CB-filled SBR/MSO vulcanizates were tremendously increased, and the silica-filled SBR/MSO vulcanizates exhibited a better wet traction performance, a lower rolling resistance, and a better abrasion resistance simultaneously than the silica-filled SBR/NO vulcanizate.

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