Pre-Vulcanization Inhibition of a N-t-Butyl-2-Benzothiazole Sulfenamide Cure by N-(Cyclohexylthio)Phthalimide

2004 ◽  
Vol 77 (5) ◽  
pp. 931-946 ◽  
Author(s):  
M. H. S. Gradwell ◽  
N. R. Stephenson
Keyword(s):  
Zinc Oxide ◽  
Crosslink Density ◽  
Decomposition Product ◽  
Crosslinking Reaction ◽  
Rapid Rise ◽  
Reaction Products ◽  
Presence And Absence

Abstract The reactions of N-(cyclohexylthio)phthalimide (CTP), in the absence of zinc oxide, leading to the inhibition of vulcanization in a N-t-butyl-2-benzothiazole sulfenamide (TBBS) accelerated sulfur cure were studied in the presence and absence of rubber. Mixtures of CTP, TBBS and sulfur were heated in a DSC and the reaction products and residual curatives analyzed by HPLC. Cyclohexanethiol, a decomposition product of CTP, reacted with TBBS producing 2-mercaptobenzothiazole (MBT) and t-butylamine, both of which reacted with CTP. In a polyisoprene compound, the addition of CTP did not delay the formation of the initial crosslinks, however the crosslink density did not increase substantially until the CTP had been consumed. MBT, a product of the crosslinking reaction, reacted preferentially with the CTP and not the TBBS. In the absence of CTP, the MBT was shown to accelerate the rate of TBBS polysulfide formation leading to a rapid rise in crosslink density.

The Chemistry of the Zinc Oxide Cure of Halobutyl

1984 ◽  
Vol 57 (4) ◽  
pp. 813-825 ◽  
Author(s):  
I. Kuntz ◽  
R. L. Zapp ◽  
R. J. Pancirov
Keyword(s):  
Zinc Oxide ◽  
Zinc Chloride ◽  
Reaction Pathway ◽  
Diels Alder ◽  
Crosslinking Reaction ◽  
Conjugated Diene ◽  
Carbon Carbon Bonds ◽  
Carbon Bonds ◽  
Chloride Catalyst ◽  
Major Reaction

Abstract The studies described in this papier lead to certain conclusions. The crosslinking reaction of halobutyl with zinc oxide does not give rise to ether crosslinks. All the evidence indicates that the chemistry involves the formation of carbon-carbon bonds by an alkylation type chemistry. The dehydrohalogenation of the halobutyl to form a zinc chloride catalyst is a key feature of the crosslinking chemistry. But conjugated diene butyl and Diels-Alder reactions are not the major reaction pathway for the zinc oxide crosslinking reaction. These conclusions have significance for the zinc oxide cure of CR which has an active allylic halide structure formed by 1,2-monomer enchainment.

Crosslinking Reaction of Rubber with Aldehydes

1970 ◽  
Vol 43 (2) ◽  
pp. 188-209
Author(s):  
Y. Minoura ◽  
M. Tsukasa
Keyword(s):  
Solid State ◽  
Organic Acids ◽  
Physical Properties ◽  
Lewis Acids ◽  
Solid State Reactions ◽  
Crosslinking Reaction ◽  
Reaction Products ◽  
Toluenesulfonic Acid ◽  
Ionic Reaction ◽  
Acidic Catalysts

Abstract The reactions of rubber with aldehydes have previously been studied in latex or in solutions and the reaction products formed by cyclization, condensation, or addition, have been reported. In the present study, solid-state reactions of rubber with aldehydes were carried out. It was found that crosslinked rubbers may be obtained by press curing in the presence of aldehydes with acidic catalysts. Poly-chloroprene and Hypalon especially undergo these reactions without a catalyst or with a small amount of catalyst. In the experiments using various aldehydes, some improvements in the properties of the crosslinked rubber were observed when aldehydes such as paraformaldehyde or α-polyoxymethylene were used. Some Lewis acids such as SnCl2·2H2O were found to be more effective catalysts than the above, and it was found that organic acids such as p-toluenesulfonic acid could also be used. The curing seemed to be an ionic reaction. The physical properties of the crosslinked rubber are similar to those of sulfur-cured rubbers.

Studies on Dicumyl Peroxide Vulcanization of Styrene—Butadiene Rubber in Presence of Sulfur and 2-Mercaptobenzothiazole

1974 ◽  
Vol 47 (2) ◽  
pp. 266-281 ◽  
Author(s):  
C. K. Das ◽  
S. Banerjee
Keyword(s):  
Zinc Oxide ◽  
Stearic Acid ◽  
Crosslink Density ◽  
Addition Reaction ◽  
Styrene Butadiene Rubber ◽  
Methyl Groups ◽  
Butadiene Rubber ◽  
First Order ◽  
First Order Kinetics ◽  
Styrene Butadiene

Abstract The effect of sulfur, MBT, zinc oxide, and stearic acid on the DCP vulcanization of SBR has been studied. DCP decomposition obeys first order kinetics in all cases, but its rate constant is higher in presence of MBT. Sulfur and MBT reduce the crosslink density due to DCP. In the mixes containing sulfur, MBT, zinc oxide, and stearic acid in presence of DCP the crosslink density is initially additive. Here oxidation of some pendent vinyl groups are effected by DCP, and these groups also take part in thiol addition reaction with MBT. The thiazole accelerated sulfuration of SBR proceeds fundamentally by the same mechanism as reported for NR, but the details show slight difference chiefly due to the presence of pendent vinyl groups and styrene units in the chain and due to the absence of pendent methyl groups in SBR.

Reversion during TMTD Vulcanization

1960 ◽  
Vol 33 (4) ◽  
pp. 1068-1071 ◽  
Author(s):  
B. A. Dogadkin ◽  
V. A. Shershnev ◽  
A. V. Dobromislova
Keyword(s):  
Zinc Oxide ◽  
Metal Oxides ◽  
Carbon Disulfide ◽  
Crosslink Density ◽  
Argon Atmosphere ◽  
Oxidative Destruction ◽  
Destructive Processes

Abstract 1) Reduction of crosslink density of vulcanizates (reversion of vulcanization) is observed during vulcanization of a mixture prepared in air of NR and SKI with TMTD without metal oxides and with magnesium and calcium oxides. In these cases the dimethyldithiocarbamic acid formed during vulcanization decomposes into carbon disulfide and dimethylamine. 2) During mixing and curing of these mixtures in an argon atmosphere reversion is absent although evolution of carbon disulfide and dimethylamine is observed. 3) During vulcanization of the mixtures containing zinc oxide no reversion occurs as a result of preparation of the mixtures either in air or in argon. Dimethyldithiocarbamic acid in this case is bound in the form of the stable zinc dimethyldithiocarbamate. 4) Reversion of rubber by TMTD is explained by oxidative destructive processes which are intensified by the products of decomposition of dimethyldithiocarbamic acid, i.e., by carbon disulfide and dimethylamine, and are suppressed by reaction of it to form zinc dimethyldithiocarbamate which serves as an inhibitor of the oxidative destruction of the vulcanizate.

The Determination of Zinc Oxide in Rubber Vulcanizates by X-Ray Diffraction

1960 ◽  
Vol 33 (3) ◽  
pp. 890-898
Author(s):  
Stephen H. Laning ◽  
Melvin P. Wagner ◽  
John W. Sellers
Keyword(s):  
Zinc Oxide ◽  
Quantitative Analysis ◽  
Analytical Method ◽  
Direct Determination ◽  
Zinc Stearate ◽  
Photographic Film ◽  
Reaction Products ◽  
X Ray

Abstract Zinc oxide is a necessary component in most accelerator-sulfur vulcanization systems. While it is not an accelerator, its presence leads to increased modulus, i.e., tighter cures. The manner in which it can effect this better cure is not completely clear. Some insight into the role of zinc oxide has been gained through the analysis of the vulcanizate for reaction products of zinc, such as zinc stearate, the zinc salts of the accelerators, and zinc sulfide. However, these products may not account for all of the zinc oxide which has reacted. An analytical method for the direct determination of unreacted zinc oxide in vulcanizates was therefore needed. The determination of zinc oxide in rubber vulcanizates has received scant attention. Wet-chemical techniques for analysis of the sample after ashing provide only the total amount of zinc from which the amount of unreacted zinc oxide cannot be determined. Endter has reported the use of the Debye-Scherrer x-ray technique for the identification of zinc oxide in rubber samples. While similar to the method developed in this laboratory, Endter employed photographic film for recording the diffraction pattern, and special sample preparation was required to accommodate the photographic technique. This method was satisfactory for qualitative identification of zinc oxide, but was difficult to use for quantitative analysis. Subsequent to this investigation Hagino et al. described the use of x-ray diffractometry for the determination of the mixing ratio of ingredients compounded in rubber. This method was also suggested for the quantitative analysis of zinc oxide, but no studies were reported. During a study in this laboratory to determine the role of zinc oxide in the vulcanization of rubber, a new analytical method, based on x-ray diffractometry, was developed. The method was rapid, nondestructive, and simple. The data were reliable and accurate.

Synergistic Effects of Zinc Oxide on Intumescent Flame-Retarded Polypropylene Composites

2010 ◽  
Vol 178 ◽  
pp. 279-284 ◽  
Author(s):  
Shan Hu ◽  
Hui Zheng ◽  
Shang Yue Shen ◽  
Hong Chang Han ◽  
Hui Jing ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Oxygen Index ◽  
Synergistic Effects ◽  
Synthesis Process ◽  
Reaction Products ◽  
Limiting Oxygen Index ◽  
Polypropylene Composites ◽  
Melamine Phosphate ◽  
Flame Retarded ◽  
Synergistic Agent

The melamine phosphate (MP) was synthesized from melamine and phosphate acid. Zinc oxide (ZnO) was used as a synergistic agent by adding into the MP during the synthesis process. The reaction products were characterized by Fourier transform infrared spectroscopy (FTIR). The properties of polypropylene (PP) composites containing intumescent flame retardant (IFR) additives of melamine phosphate and pentaerythritol (PER) were investigated by the limiting oxygen index (LOI), UL-94 vertical burning test, thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The results indicated that the LOI value of the composites could be enhanced obviously with suitable content of ZnO. When the ZnO content was 6 wt% in MP, the LOI value reached 34.1%, which showed 10% higher than that of the composites without ZnO.

A High-Performance Curing System for Halobutyl Elastomers

1987 ◽  
Vol 60 (1) ◽  
pp. 62-77 ◽  
Author(s):  
D. C. Edwards
Keyword(s):  
Thermal Stability ◽  
Zinc Oxide ◽  
Elastic Properties ◽  
Aromatic Amine ◽  
High Performance ◽  
Storage Stability ◽  
Rapid Rise ◽  
Excellent Thermal Stability ◽  
Compression Set ◽  
Ozone Resistance

Abstract 1. In halobutyl elastomers, zinc oxide interacts synergistically with aromatic amine antioxidants such as APDA 86, DPPD, or DNPD, to produce fast, tight cures. 2. In the case of DNPD, compound storage stability appears to be satisfactory, and the resistance to scorch at processing temperatures is ample. 3. The cure behavior of these systems, particularly in bromobutyl, is exceptionally favorable: a rapid rise to a remarkably flat plateau. 4. The vulcanizates exhibit excellent thermal stability (compression set) and excellent ozone resistance. Measurable elastic properties are retained following 72 h air aging at 200°C.

Efficiency of TMTD Vulcanization

1958 ◽  
Vol 31 (3) ◽  
pp. 559-561
Author(s):  
E. M. Bevilacqua
Keyword(s):  
Zinc Oxide ◽  
Recent Work ◽  
Crosslink Density ◽  
Tetramethylthiuram Disulfide ◽  
Wide Range ◽  
Series Of Experiments

Abstract Tetramethylthiuram disulfide (TMTD), together with a sufficient amount of zinc oxide, is the simplest and most efficient vulcanizing agent known for introduction of sulfur crosslinks into rubber. No other combination approaches it in efficiency over a wide range of temperatures, although under limited conditions sulfur cures can be obtained with approximately as high a crosslink density per mole of vulcanizing agent. The stoichiometry of vulcanization with this curative has been explored in some detail in recent work of Scheele and coworkers. They have confirmed the observation by Jarrijon that during vulcanization dithiocarbamate is formed equivalent to close to two-thirds of the TMTD taken. The generality of this result was established in an exhaustive series of experiments, covering a range of structures of thiuram disulfide and of polyolefin, of temperature, and of concentration of reactants.

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