Studies on the Kinetics of Vulcanization of Rubber

1964 ◽  
Vol 37 (2) ◽  
pp. 557-562
Author(s):  
H. L. Taneja ◽  
S. Banerjee
Keyword(s):  
Zinc Oxide ◽  
Steady State ◽  
Natural Rubber ◽  
Square Root ◽  
Initiator Concentration ◽  
Appreciable Increase ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Free Sulfur

Abstract The dependence of the rate of accelerated vulcanization of natural rubber (smoked sheet) on the concentration of mercaptobenzothiazole accelerator has been reported on in this paper. The rate of decrease of free sulfur at the steady state has been found to be proportional to the square root of the initiator concentration expressed as grams/100 grams of rubber. The rate has also been found to be enhanced by the addition of 1% of zinc oxide. Higher amounts of zinc oxide does not lead to a further appreciable increase in the rate.

Vulcanization of Elastomers. 18. Vulcanization of Natural Rubber with Sulfur in the Presence of Mercaptobenzothiazole. III

1958 ◽  
Vol 31 (3) ◽  
pp. 548-558 ◽  
Author(s):  
Otto Lorenz ◽  
Elisabeth Echte
Keyword(s):  
Zinc Oxide ◽  
Natural Rubber ◽  
Zinc Stearate ◽  
Oxide Content ◽  
Square Root ◽  
Initial Concentration ◽  
Velocity Constant ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Limiting Value

Abstract The present work is concerned with the influence of the concentration of sulfur and the zinc oxide content on the kinetics of the vulcanization of natural rubber with sulfur in the presence of mercaptobenzothiazole, zinc stearate and zinc oxide. The following results were obtained. 1. The velocity constant of the sulfur decrease, kSI, is inversely proportional to the initial concentration of sulfur. 2. The velocity constant of the change with time of the reciprocal equilibrium swelling, kQI, is inversely proportional to the square root of the initial concentration of sulfur. 3. The limiting value of the reciprocal equilibrium swelling, 1/Q∞ (degree of crosslinking), at constant stearate content, is proportional to the square root of the initial concentration of sulfur. 4. The amount of accelerator consumed during vulcanization increases with increase in the initial amount of sulfur. The decrease in the accelerator is a first order reaction having approximately the same rate as the decrease of sulfur. 5. The velocity constants of the sulfur decrease and the change with time of the reciprocal equilibrium swelling are practically independent of the amount of zinc oxide. Other situations exist, of course, for compounds without zinc oxide. 6. Empirical equations were derived to express the dependence of the constants kSI, kQI and 1/Q∞ on the composition of the mixture.

SERINOL DERIVATIVES FOR THE SUSTAINABLE VULCANIZATION OF DIENE ELASTOMERS

2018 ◽  
Vol 91 (4) ◽  
pp. 701-718 ◽  
Author(s):  
Vincenzina Barbera ◽  
Sara Musto ◽  
Giuseppe Infortuna ◽  
Valeria Cipolletti ◽  
Attilio Citterio ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Building Block ◽  
Induction Time ◽  
High Selectivity ◽  
Rubber Compounds ◽  
Aldehydes And Ketones ◽  
Diene Rubbers ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Kinetics Of Vulcanization

ABSTRACT 2-amino-1,3-propandiol (serinol) was used as the starting building block of synthetic pathways that led to the preparation of innovative chemicals suitable as ingredients for rubber compounds. Serinol based reactions were performed in the frame of a sustainable process, in the absence of any solvent and catalyst, with aldehydes and ketones, such as acetone, cinnamaldehyde and camphor. The synthesis of either imines or oxazolidines was obtained with high selectivity. Serinol, imine and oxazolidine derivatives of serinol were used as accelerator for the vulcanization of diene rubbers. They were proved to be efficient secondary accelerators in silica based compounds based on poly(styrene-co-butadiene) in place of diphenyl guanidine. The kinetics of vulcanization was investigated for natural rubber based compounds in the absence of any filler. With respect to serinol, the imine derivatives were able to enhance the induction time of vulcanization and to afford a similar vulcanization rate.

Studies of the Vulcanization of Rubber. III. Kinetics of Change of Tensile Strength of Natural Rubber during Vulcanization

1954 ◽  
Vol 27 (3) ◽  
pp. 615-621 ◽  
Author(s):  
B. Dogadkin ◽  
B. Karmin ◽  
I. Golberg
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Structure Formation ◽  
Linear Function ◽  
General Equation ◽  
Original Material ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Butadiene Styrene

Abstract 1. It is shown that the tensile strength of vulcanized butadiene-styrene rubber is a linear function of the plasticity of the original material. 2. Proceeding from concepts of the presence during vulcanization of a number of opposing processes of structure formation and destruction, both of which influence the molecular weight of the rubber, a general equation is derived which expresses the kinetics of the change of tensile strength of a vulcanizate. 3. Experimental material is offered which proves the applicability of the proposed equation to the representation of the kinetics of vulcanization of mixtures of natural rubber containing relatively small sulfur contents, i.e., up to 3 per cent.

The Vulcanization of Elastomers. VII. The Vulcanization of Natural Rubber with Thiuram Disulfides. Part IV

1957 ◽  
Vol 30 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Walter Scheele ◽  
Peter Stange
Keyword(s):  
Zinc Oxide ◽  
Natural Rubber ◽  
Constant Temperature ◽  
Rate Constants ◽  
Experimental Error ◽  
Oxide Content ◽  
Oxide Crystals ◽  
Kinetics Of ◽  
Limiting Value

Abstract The present paper deals with the kinetics of the thiuram vulcanization at varying thiuram disulfide concentrations as well as with the influence of the zinc oxide content upon vulcanization at constant temperature (120° C). It was found : 1. The limiting value of dithiocarbamate formation of 66 mole per cent relative to the amount of thiuram disulfide used is—within wide limits—independent of the initial thiuram disulfide concentration. 2. At constant thiuram disulfide concentration the limiting value of dithiocarbamate formation is unchanged when the zinc oxide content is successively increased. 3. Changing the zinc oxide content while the thiuram disulfide concentration is kept constant exerts an influence on the kinetics of the decrease of thiuram as well as on the increase of dithiocarbamate. The rate constants of both reactions increase. 4. It is concluded from these results that in all probability vulcanization is initiated on the surface of the zinc oxide crystals. 5. Even in stocks containing as much as 40 g. zinc oxide per hundred g. of compounds, the limiting value of dithiocarbamate formation remains unchanged. This was verified by the analysis of vulcanizates after extremely long cure times. The average limiting value of two experiments after 24 hours of cure was 65 mole per cent which corresponds to a two-thirds reaction within the experimental error.

Vulcanization. Part VII. Kinetics of Sulfur Vulcanization of Natural Rubber in Presence of Delayed-Action Accelerators

1965 ◽  
Vol 38 (1) ◽  
pp. 1-14 ◽  
Author(s):  
A. Y. Coran
Keyword(s):  
Positive Integer ◽  
Stearic Acid ◽  
Natural Rubber ◽  
Zinc Ion ◽  
Square Root ◽  
Reaction Products ◽  
Sulfur Concentration ◽  
Sulfur Vulcanization ◽  
Delayed Action ◽  
Kinetics Of

Abstract The scheme and treatment of the kinetics of scorch-delay vulcanization proposed in a previous paper were applied to natural rubber sulfur vulcanization accelerated by 2,2′-thiobisbenzothiazole (MBTS), 2-(N-cyclohexyl)benzothizaolesulfenamide (CBS), 2-(N-morpholinothio)benzothiazole (MOR), or 2-(N,N-diisopropyl)benzothiazolesulfenamide (DPBS). According to the scheme (see PDF for diagram) where the subscript x = a positive integer. The specific rates k1 and k2 and the ratiok4/k3′ were related to starting concentrations of accelerator, sulfur, and stearic acid. In general, an increase in stearic acid concentration or a decrease in accelerator concentration induces an increase in k1 or k4/k3′ but a decrease in k2. An exception to this is that, when the highly hindered sulfenamide DPBS is used as the accelerator, k1 does not change with changes in starting concentrations. It is interesting that k2 does not respond appreciably to changes in sulfur concentration when sulfenamides are used, unless the sulfur concentrations are extremely low. In contrast to this, k2 increases linearly with the square root of the sulfur concentration when MBTS is used. The changes in rates which occur with changes in the starting concentrations were attributed to the formation of chelates between zinc ion (brought into solution by stearic acid) and accelerator, intermediate reaction products, or crosslink precursors. The differences noted between the rates obtained with the three sulfenamides were attributed to differences in steric hindrance and stability.

Vulcanization of Elastomers. 39. Vulcanization of Natural and Synthetic Rubbers by Sulfur and Sulfenamides. II

1965 ◽  
Vol 38 (1) ◽  
pp. 176-188 ◽  
Author(s):  
W. Scheele ◽  
G. Kerrutt
Keyword(s):  
Natural Rubber ◽  
Concentration Dependence ◽  
Intermediate Compound ◽  
Kcal Mole ◽  
Experimental Conditions ◽  
Molar Ratios ◽  
Induction Periods ◽  
Induction Times ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization

Abstract The dependence of the kinetics of vulcanization of natural rubber by sulfur in presence of N-cyclohexyl-benzothiazolylsulfenamide (CHBS) on temperature and for varied molar ratios of accelerator and sulfur was more exactly investigated. 1. Although the vulcanization of natural rubber accelerated with N-cyclohexyl-benzothiazolylsulfenamide with conventional experimental conditions is characterized by very long induction times, nevertheless—as also for other accelerated vulcanization reactions—sulfur decrease follows a time law with nt<1 and the activation energy, as in other cases, is calculated to be 29 kcal/mole. 2. The value nt=0.6 is found for the exponent of the time law, independent of temperature and concentration of reactants. 3. The concentration dependence of the rate of sulfur decrease under conditions of constant sulfur content and increasing sulfenamide concentration is found to be consistent with catalysis by an intermediate compound. 4. The actual accelerator may be essentially cyclohexylammonium-benzothiazoylmercaptide. 5. The temperature and concentration dependence of the induction periods for sulfur decrease and crosslinking were investigated. The course of crosslinking with reaction time, which is characterized by strong reversion, is discussed.

Study of UV Curing Kinetics for Coating Containing Siloxane Modified Polyurethane-Acrylate

2013 ◽  
Vol 791-793 ◽  
pp. 175-178 ◽  
Author(s):  
Yu Song Qi ◽  
Jian Wen Yang ◽  
Zhao Hua Zeng ◽  
Yong Lie Chen
Keyword(s):  
Steady State ◽  
Incident Light ◽  
Uv Curing ◽  
Curing Kinetics ◽  
Initiator Concentration ◽  
Incident Light Intensity ◽  
Polyurethane Acrylate ◽  
Steady State Kinetics ◽  
Curing Kinetic ◽  
Kinetics Of

The UV curing kinetics of coating containing siloxane modified polyurethane-acrylate were studied using photo-DSC (DPC). The effects of some factors such as incident light intensity, initiator concentration, reaction temperature on the curing kinetics have been analysized from DPC data. The curing kinetic parameters (kp and kt) for prepolymers have also been determinedv by combining steady state and non-steady state kinetics.

Extraction and identification of fillers and pigments from pyrolyzed rubber and tire samples

1996 ◽  
Vol 54 ◽  
pp. 174-175
Author(s):  
P. Sadhukhan ◽  
J. B. Zimmerman
Keyword(s):  
Zinc Oxide ◽  
Electron Microscope ◽  
Carbon Black ◽  
Natural Rubber ◽  
Transmission Electron Microscope ◽  
Rolling Resistance ◽  
Synthetic Polymers ◽  
Nitrogen Atmosphere ◽  
Transmission Electron ◽  
Curing Agents

Rubber stocks, specially tires, are composed of natural rubber and synthetic polymers and also of several compounding ingredients, such as carbon black, silica, zinc oxide etc. These are generally mixed and vulcanized with additional curing agents, mainly organic in nature, to achieve certain “designing properties” including wear, traction, rolling resistance and handling of tires. Considerable importance is, therefore, attached both by the manufacturers and their competitors to be able to extract, identify and characterize various types of fillers and pigments. Several analytical procedures have been in use to extract, preferentially, these fillers and pigments and subsequently identify and characterize them under a transmission electron microscope.Rubber stocks and tire sections are subjected to heat under nitrogen atmosphere to 550°C for one hour and then cooled under nitrogen to remove polymers, leaving behind carbon black, silica and zinc oxide and 650°C to eliminate carbon blacks, leaving only silica and zinc oxide.

Kinetic analysis of mechanism of intestinal Na+-dependent sugar transport

1985 ◽  
Vol 248 (5) ◽  
pp. C498-C509 ◽  
Author(s):  
D. Restrepo ◽  
G. A. Kimmich
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Sugar Transport ◽  
Enzyme Kinetic ◽  
Steady State Distribution ◽  
State Distribution ◽  
Least Squares Fit ◽  
Coupling Stoichiometry ◽  
Rate Limiting ◽  
Kinetics Of

Zero-trans kinetics of Na+-sugar cotransport were investigated. Sugar influx was measured at various sodium and sugar concentrations in K+-loaded cells treated with rotenone and valinomycin. Sugar influx follows Michaelis-Menten kinetics as a function of sugar concentration but not as a function of Na+ concentration. Nine models with 1:1 or 2:1 sodium:sugar stoichiometry were considered. The flux equations for these models were solved assuming steady-state distribution of carrier forms and that translocation across the membrane is rate limiting. Classical enzyme kinetic methods and a least-squares fit of flux equations to the experimental data were used to assess the fit of the different models. Four models can be discarded on this basis. Of the remaining models, we discard two on the basis of the trans sodium dependence and the coupling stoichiometry [G. A. Kimmich and J. Randles, Am. J. Physiol. 247 (Cell Physiol. 16): C74-C82, 1984]. The remaining models are terter ordered mechanisms with sodium debinding first at the trans side. If transfer across the membrane is rate limiting, the binding order can be determined to be sodium:sugar:sodium.

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