Vulcanization of Elastomers. 26. Vulcanization of Natural and Synthetic Rubbers by Sulfur in the Presence of Organic Bases

1960 ◽  
Vol 33 (3) ◽  
pp. 834-845
Author(s):  
Walter Scheele ◽  
Wolfgang Redetzky
Keyword(s):  
Initial Rate ◽  
Reaction Order ◽  
Research Work ◽  
Intermediate Compound ◽  
Sulfur Concentration ◽  
Kcal Mole ◽  
Initial Concentration ◽  
Organic Bases ◽  
Single Power ◽  
Theory And Experiment

Abstract In connection with earlier research work, we have carefully studied the decrease of sulfur during the vulcanization of Perbunan N 2818 in the presence of DPG, at various temperatures and with varied molar concentrations of sulfur and accelerator. We found : 1. The sulfur concentration decreases at all temperatures according to a time law of order 0.8. An activation energy of about 28 kcal/mole is derived from the temperature dependence of the rate constant. 2. The reaction order is independent of the initial concentration of reactants. 3. A discrepancy is found in the order of the reaction with respect to time and with respect to concentration, and it is clearly shown that the dependence of the initial rate on the initial concentration can not be expressed by a single power law. 4. The attempt is made to explain the discrepancy by postulating catalysis by an intermediate compound. The consequences from this consideration are compared with the experimental results, and, on the whole, agreement is found between theory and experiment.

Vulcanization of Elastomers. 25. Natural Rubber and Synthetic Elastomers with Sulfur and Sulfenamides. I

1960 ◽  
Vol 33 (3) ◽  
pp. 846-856 ◽  
Author(s):  
Walter Scheele ◽  
Horst-Eckart Toussaint ◽  
Yoan-Kun Chai
Keyword(s):  
Reaction Order ◽  
Molar Ratio ◽  
Reactive Intermediate ◽  
Sulfur Concentration ◽  
Kcal Mole ◽  
Experimental Conditions ◽  
Sulfur Vulcanization ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Time Plot

Abstract The sulfur vulcanization of Perbunan N 2818 (acrylonitrile-butadiene) was investigated in the presence of N-cyclohexyl-2-benzothiazolylsulfenamide (CZ) at different temperatures and various concentrations of reactants. The following were found : 1. The decreasing sulfur concentration vs. time plot followed the 0.8th order under all experimental conditions and an activation energy of 28.2 kcal/mole was calculated. 2. When using the cyclohexylammonium salt of MBT as accelerator, sulfur decrease proceeds at the same rate as with CZ. 3. It was concluded from 1 and 2 that even in the presence of CZ, the ammonium salt was the actual accelerator, which forms during the scorch or induction period through reaction of CZ with the rubber. 4. In view of the discrepancy found in the relation of reaction order with respect to time and concentration of reactants, the formation of a reactive intermediate is postulated; the analogy between the kinetics of sulfenamide accelerated sulfur vulcanization, and those accelerated with MBT as well as DPG is pointed out. 5. In connection with 3 the dependence of starting rate as well as rate constant of 0.8th order of the decreasing sulfur concentration on the molar ratio of CZ/S8 and on the sulfur starting concentration is discussed.

scholarly journals Metal Ions and Hydrogen Peroxide. XXV

1972 ◽  
Vol 27 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Peter Waldmeier ◽  
Bernhard Prijs ◽  
Helmut Sigel
Keyword(s):  
Hydrogen Peroxide ◽  
Ionic Strength ◽  
Metal Ions ◽  
Experimental Evidence ◽  
Initial Rate ◽  
Reaction Order ◽  
Ph Dependence ◽  
Initial Concentration ◽  
Ph Dependent ◽  
Ph Range

The decomposition of H2O2, catalyzed by the Co2® complex of 4,4′,4″,4″′-tetrasulfophthalocyanine (CoIIPTS), was investigated in the pH range 3.8 through 10 by measuring the initial rate, v0=d(O2)/dt, of the increasing formation of O2 (25°; I=0.1). In this pH range v0 is proportional to the initial concentration of H2O2 (determined at pH 5.0 and 9.2). Due to the dimerization (log KD=5.47 ±0.09 at natural ionic strength and about 7.63 ±0.16 in 0.1 M NaClO4; 25°) and polymerization of CoIIPTS the catalyst and its reaction order are difficult to establish: Based on the experimental evidence it is suggested that v0 is proportional to the concentration of monomer CoIIPTS. Additionally, there is evidence that the experimentally determined v0 contains the contributions of a pH-independent and a pH-dependent reaction course. These results are analog to those obtained earlier with FeIIIPTS as catalyst. A mechanism for the catalyzed disproportionation of H2O2 by CoIIPTS is proposed. The catalase-like activity of CoIIIPTS (OH) is smaller than that of CoIIPTS and the pH-dependence is different.

The effect of electrondonors on the polymerization kinetics of isoprene

1980 ◽  
Vol 45 (12) ◽  
pp. 3338-3346
Author(s):  
Miroslav Kašpar ◽  
Jiří Trekoval
Keyword(s):  
Induction Period ◽  
Ethyl Ether ◽  
Reaction Order ◽  
Propagation Rate ◽  
Reaction Scheme ◽  
Polymerization Kinetics ◽  
Polymerization Rate ◽  
Constant Concentration ◽  
Initial Concentration ◽  
Kinetics Of

The effect of small additions of 1-octene, butyl ethyl ether and triethylamine on the polymerization kinetics of isoprene (2-methyl-1,3-butadiene) in benzene initiated with butyllithium was investigated by employing the GLC analysis. The addition of 1-octane was reflected only in a shorter induction period of the reaction; the effect on the propagation rate was insignificant. With the increasing amount of butyl ethyl ether, the polymerization rate increases linearly, while the reaction order with respect to the concentration of triethylamine is variable and increases from 0.33 to 0.66 with the increasing concentration of the initiator. For a constant concentration of triethylamine, the reaction order with respect to the initial concentration of the initiator was found to vary considerably, reaching even negative values. A reaction scheme was suggested, taking into account the competition between two different solvates of alkyllithium.

scholarly journals Visible Light Induced Enhanced Photocatalytic Degradation of Industrial Effluents (Rhodamine B) in Aqueous Media Using TiO2Nanoparticles

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
J. O. Carneiro ◽  
A. P. Samantilleke ◽  
P. Parpot ◽  
F. Fernandes ◽  
M. Pastor ◽  
...  
Keyword(s):  
Visible Light ◽  
Rhodamine B ◽  
Colloidal Stability ◽  
Titanium Dioxide Nanoparticles ◽  
Aqueous Media ◽  
Research Work ◽  
Industrial Effluents ◽  
Intermediate Compound ◽  
X Ray Diffraction ◽  
Textile Materials

In recent years, new textile materials have been developed through the use of nanotechnology-based tools. The development of textile surfaces with self-cleaning properties has a large combined potential to reduce the environmental impact related to pollution. In this research work, three types of textiles substrates (cotton, Entretela, and polylactic acid (PLA)) were functionalized with titanium dioxide nanoparticles (TiO2) using chemical and mechanical processes (padding). During the functionalization process, two different methods were used, both of which allowed a good fixation of nanoparticles of TiO2on textile substrates. The samples were examined for morphology and for photocatalytic properties under visible light irradiation. A study aimed at evaluating the effect of pH of the aqueous solution of TiO2nanoparticles was performed in order to promote interaction between TiO2and the dye solution rhodamine B (Rh-B). The TiO2nanoparticles were characterized by X-ray diffraction (XRD). The measurement of the zeta potential of the TiO2nanoparticle solution proved to be always positive and have low colloidal stability. Chromatography (HPLC and GC-MS) analyses confirm that oxalic acid is the intermediate compound formed during the photodegradation process.

The Vulcanization of Elastomers. 20. Sulfur Vulcanization Accelerated with Thiuram Compounds. I

1959 ◽  
Vol 32 (1) ◽  
pp. 139-149 ◽  
Author(s):  
Walter Scheele ◽  
Adolf Franck
Keyword(s):  
Reaction Order ◽  
Accurate Determination ◽  
Sulfur Concentration ◽  
Quantitative Investigation ◽  
Tetramethylthiuram Disulfide ◽  
First Order ◽  
Sulfur Vulcanization ◽  
Complicated Course ◽  
Peak Value

Abstract The present paper deals with the results of an orientating, quantitative investigation of sulfur vulcanization accelerated by thiuram disulfide, with tetramethylthiuram disulfide as the representative example. It was found: In the sulfur cure of natural rubber with tetramethylthiuram disulfide at different TMTD:S ratios, the rates of TMTD decrease and dithiocarbamate formation increase with increasing sulfur concentration, the TMTD content being kept constant. The rates practically do not change any further when the compounds contain 6 gram atoms of sulfur per mole of thiuram disulfide. The peak value of dithiocarbamate formation increases with the increase of sulfur concentration and reaches a constant end value of about 90 mole per cent based on the amount of original thiuram disulfide, when the stocks contain 4 gram atoms of sulfur per mole thiuram disulfide. This end value is identical to the end value of dithiocarbamate formation in the reaction of thiuram disulfide with zinc oxide (in the absence of rubber). The crosslinking, as measured by the change of reciprocal equilibrium swelling per time unit is also a reaction whose rate increases with the sulfur concentration to the point where the compounds contain 6 gram atoms of sulfur per mole of thiuram disulfide. The optimum degrees of crosslinking are roughly proportional to the sulfur concentration; at high sulfur levels the vulcanizates tend to revert. As in the pure TMTD vulcanization, the TMTD decrease as well as the dithiocarbamate formation are always first order reactions. The reversion at higher sulfur levels as well as the complicated course of the increase of combined sulfur during vulcanization render all but impossible an accurate determination of the reaction order for the crosslinking at higher sulfur levels. Nevertheless, in vulcanizations with 1 mole TMTD per 1 or 2 gram atoms of sulfur the crosslinking is a first order reaction.

Vulcanization of Elastomers. 40. Vulcanization of Natural Rubber and Synthetic Rubber with Sulfur in Presence of Sulfenamides. III

1965 ◽  
Vol 38 (1) ◽  
pp. 189-203 ◽  
Author(s):  
W. Scheele ◽  
J. Helberg
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Natural Rubber ◽  
Rate Constants ◽  
Sulfur Concentration ◽  
Kcal Mole ◽  
Synthetic Rubber ◽  
Chemical Constitution ◽  
Induction Times ◽  
Kinetics Of

Abstract Vulcanization of natural rubber with sulfur was studied in presence of six sulfenamides, to determine the effect of the chemical constitution of the sulfenamide on sulfur decrease and on crosslinking. The results can be condensed as follows: (1) The kinetics of sulfur disappearance is in every respect qualitatively independent of the chemical constitution of the sulfenamide. (2) For the sulfenamides investigated, the smallest and largest rate constants for sulfur decrease differed only by a factor of two. (3) Greater differences are encountered in the induction times for sulfur decrease and for crosslinking. The latter are notably longer than those for sulfur disappearance. (4) The same activation energy, 23 kcal/mole, is derived from the temperature dependence of the induction times for all the sulfenamides. (5) The dissociation of sulfenamides in solution and their reaction with mercaptobenzothiazole were investigated further. The results provide the basis for a proposed reaction mechanism, which is presented in detail and can account for a number of the features typical of sulfenamide-accelerated vulcanization. (6) The drop in sulfur concentration goes at practically the same rate, if one introduces, instead of N, N-dicyclohexyl-2-benzothiazolesulfenamide, the corresponding ammonium mercaptide in equimolar concentration.

The Reaction of Ozone with SBR Rubbers

1959 ◽  
Vol 32 (4) ◽  
pp. 1062-1079 ◽  
Author(s):  
E. R. Erickson ◽  
R. A. Berntsen ◽  
E. L. Hill ◽  
Paul Kusy
Keyword(s):  
Initial Rate ◽  
Protective Action ◽  
Rate Data ◽  
High Solubility ◽  
Initial Concentration ◽  
Degree Of Protection ◽  
Effective Barrier ◽  
Gaseous Ozone ◽  
Low Concentrations ◽  
Oxidized Products

Abstract All SBR vulcanizates, when tested in a relaxed state, reacted with ozone of low concentrations to form a film of oxidized products which provided an effective barrier against further attack by gaseous ozone. SBR vulcanizates that were under stress, but which contained no effective antiozonant in their formulation, were readily attacked by ozone. The absorption of ozone appeared to begin with an initial rate of zero which was followed by rapidly increasing rates until a maximum had been reached, when ozone cracks were visible on the surface of the rubber. SBR vulcanizates that were under stress, but which contained an antiozonant, were protected from an attack by ozone to a degree that ranged from poor to excellent. The degree of protection depended (a) on the differential in the rates of reaction of the antiozonant and the rubber hydrocarbon with ozone, (b) on the initial concentration of the antiozonant on the surface of the vulcanizate which reacted with ozone to form a barrier of oxidized residues, and (c) on the rate of effusion of fresh antiozonant from within the rubber to the outer surface of the barrier. SBR vulcanizates containing a naphthenic processing oil as an extender were not so resistant to ozone as standard SBR vulcanizates. It is probable that the effectiveness of the antiozonants tested in these vulcanizates was reduced by their high solubility in the oil phase. SBR vulcanizates containing trioctyl phosphate as a plasticizer were vigorously attacked by ozone. It is possible that the gaseous ozone dissolved to some extent into the plasticizer phase, increasing the concentration of ozone in the area causing a more severe oxidation of the rubber. SBR vulcanizates that had been coated with an antiozonant by dipping the specimen several times into a solution of the antiozonant in a solvent were found to contain a higher concentration of the antioxonant directly on the surface of the vulcanizate than in the case where three parts of the antiozonant were added during vulcanization. A mechanism for the ozonization of SBR vulcanizates has been proposed which includes a possible mechanism for the protective action of antiozonants. A rate equation has been derived from this mechanism which was consistent with the experimental rate data.

scholarly journals Vertical In-Vessel Composter for Stabilization of Market Vegetable Waste

2020 ◽  
Vol 9 (3) ◽  
pp. 486-490
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Organic Waste ◽  
Research Work ◽  
Chemical Characteristics ◽  
Vegetable Waste ◽  
Initial Concentration ◽  
Mix Proportion ◽  
Physico Chemical ◽  
Seeding Material

Composting can be one of the solutions to tackle the issue of handling solid waste. In the present research work, a bench-scale vertical in-vessel aerobic composter was designed to stabilize the Devaraja market vegetable waste, Mysore using horse dung and plantain leaves as seeding material and bulking agent respectively. On average, Devaraja market generate 4.8-5.6 ton per day. Mix proportion of organic waste, bulking and seeding materials fed into composter was in the ratio of 5: 1: 0.5. Initial and variation in physico-chemical characteristics of waste were monitored during the composting period. The initial concentration of total nitrogen, phosphorous, total organic carbon and C/N ratio which was found to be 1.67%, 0.78%, 1.93%, 43.5% and 26 showed a variation of 2.4%, 1.1%, 2% 29% and 15 respectively at the end of 21 days of composting.

scholarly journals Studi Kinetika Efektifitas Minyak Daun Cengkeh (Syzigium aromaticum) Sebagai Antifungi Candida albicans

2019 ◽  
Vol 6 (2) ◽  
pp. 107-114
Author(s):  
Rustam Musta ◽  
Laily Nurliana
Keyword(s):  
Candida Albicans ◽  
Reaction Order ◽  
Kinetic Studies ◽  
Order Reaction ◽  
Minimum Concentration ◽  
Initial Concentration ◽  
Fungal Activity ◽  
Reaction Constants ◽  
Anti Fungal

Kinetic studies effectiveness clove leaf (Syzigium aromaticum) oil as antifungal Candida albicans have been done. The study have purpose to determine the reaction order, reaction constants (k) and relationship the concentration of clove leaf (Syzigium aromaticum) oil every time (At) with the initial concentration of of clove (Syzigium aromaticum) oil (Ao) and time (t) and equipped determination of the minimum concentration of clove leaf (Syzigium aromaticum)oil effective anti-fungus Candida albicans. The results shows the anti-fungal activity clove leaf (Syzigium aromaticum) oil on Candida albicans for each variation of the concentration 100%, 75%, 50% and 25% are 14.2 mm, 12.2 mm, 10.8 mm and 10.4 mm respectively. Reaction order as antifungal of the clove leaf (Syzigium aromaticum) oil on Candida albicans is 0.2112 with k = 5.0594. The minimum concentration of clove leaf (Syzigium aromaticum) oil as anti-fungal Candida albicans is 17.86%.

Degradation of safranin by heterogeneous Fenton processes using peanut shell ash based catalyst

2019 ◽  
Vol 79 (7) ◽  
pp. 1367-1375
Author(s):  
Amir Ikhlaq ◽  
Hafiza Zara Anwar ◽  
Farhan Javed ◽  
Saba Gull
Keyword(s):  
Research Work ◽  
Agitation Speed ◽  
Peanut Shell ◽  
H2o2 Concentration ◽  
Fenton Process ◽  
Heterogeneous Fenton ◽  
Initial Concentration ◽  
Industrial Sectors ◽  
Efficient Performance ◽  
Maximum Decolorization

Abstract Today, dyes are one of the major problematic pollutants in the environment and are broadly used in several industrial sectors. In the current research work, decolorization of safranin (basic dye) from aqueous solution was investigated using iron-impregnated peanut shell ash (Fe-PSA) as a catalyst in the UV-assisted heterogeneous Fenton process (Fe-PSA/H2O2/UV). The effect of parameters such as H2O2 concentration, catalyst dose, pH, initial dye concentration, temperature, and agitation speed was studied. The maximum decolorization of safranin was achieved at optimum parametric values of reagent dose = 8 mM, catalyst dose = 0.5 g, pH = 3, initial concentration of safranin = 50 ppm, temperature = 25 °C, and agitation speed = 200 rpm. The results revealed the efficient performance of Fe-PSA as catalyst in the Fe-PSA/H2O2/UV process for safranin treatment.

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