Vulcanization. Part II. Fate of Curing System during Sulfur Curing of Nr Accelerated by MBT Derivatives and Activated by Zinc Stearate

1964 ◽  
Vol 37 (3) ◽  
pp. 650-667 ◽  
Author(s):  
R. H. Campbell ◽  
R. W. Wise
Keyword(s):  
Zinc Oxide ◽  
Analytical Techniques ◽  
Zinc Stearate ◽  
Supporting Evidence ◽  
Reaction Products ◽  
Curing Characteristics ◽  
Vulcanization Process ◽  
Difficult Part ◽  
Curing Systems

Abstract As discussed in Part I it was generally believed that during the sulfur vulcanization of rubber, important vulcanization intermediates are formed as a result of reactions between components of the various curing systems, e.g., sulfur, accelerator, zinc oxide and elastomer. A variety of reaction products have been postulated, however, actual supporting evidence for most of these postulations is limited. This is not surprising considering that the complexity of the system makes the identification and quantitative determination of these intermediates by conventional analytical techniques difficult. Part I of this paper described some analytical methods and the application of procedures for determining the fate of the curing system throughout the vulcanization of natural rubber in the presence of sulfur and various benzothiazole type accelerators. This study confirmed that important vulcanization intermediates are formed during the vulcanization process and that they play decisive roles in delay action acceleration. However, in most practical cases zinc oxide and stearate are also required to obtain satisfactory vulcanization and curing characteristics. It was therefore desirable to extend the studies to curing systems which include zinc and stearate ion.

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.

Acceleration by Thiourea and Related Compounds of the Tetramethylthiuram Disulfide Vulcanization of Natural Rubber

1961 ◽  
Vol 34 (3) ◽  
pp. 795-797 ◽  
Author(s):  
C. G. Moore ◽  
B. Saville ◽  
A. A. Watson
Keyword(s):  
Zinc Oxide ◽  
Natural Rubber ◽  
Tetramethylthiuram Disulfide ◽  
Reasonable Explanation ◽  
Vulcanization Process ◽  
Related Compounds ◽  
Curing Systems

Abstract It has recently been discovered that thiourea and certain of its N-derivatives and chemically related compounds, accelerate the vulcanization of natural rubber (NR) by tetramethylthiuram disulfide (TMTD)-zinc oxide combinations to such an extent that excellent vulcanizates can be produced at 100° C or lower. A reasonable explanation of this acceleration is now offered, based on a theory of vulcanization by TMTI) and related “sulfurless” curing systems currently being developed here. This theory recognizes the importance of polysulfidic intermediates (I, m>2), formed during the vulcanization process, which subsequently react with the polyisoprene to yield further intermediates (II) which finally react to yield sulfurated crosslinks. The process is broadly schematized as follows:

Polarographic Determination of Accelerators, Antioxidants, and Other Rubber Chemicals. I.

1959 ◽  
Vol 32 (4) ◽  
pp. 1254-1268
Author(s):  
F. Mocker
Keyword(s):  
Zinc Oxide ◽  
Quantitative Determination ◽  
Raw Materials ◽  
Zinc Stearate ◽  
Zinc Salt ◽  
Polarographic Method ◽  
Experimental Conditions ◽  
Methanolic Extracts ◽  
Rubber Compounds

Abstract The present paper shows that the Polarographic method for the determination of rubber additives (rubber chemicals) delivers fully usable results. The following points are discussed : 1. The method is qualified for a rapid quantitative determination of MBT and 2-mercaptobenzimidazole in raw materials control. 2. The zinc salt of MBT can be indirectly determined after its decomposition with acid. 3. MBT and 2-mercaptobenzimidazole can be determined directly in the methanolic extracts of masterbatches. 4. As with the masterbatches, MBT can be determined directly in the extracts of rubber stocks and vulcanizates when zinc oxide is absent. Magnesium oxide or zinc stearate do not interfere. 5. Experimental conditions are given which permit quantitative determinations of MBT in the presence of zinc oxide in uncured and cured rubber compounds. 6. The experiments have shown that the method is applicable to complex recipes containing MBT as the only accelerator. Of course, the limit of error is higher, that is, around −5%. The investigations are being continued and the results will be presented at a later date.

Decomposition of peroxobenzoic acid in benzene catalyzed by transition metal 2,4-pentanedionates

1984 ◽  
Vol 49 (3) ◽  
pp. 673-679 ◽  
Author(s):  
Pavel Lederer ◽  
Eva Mácová ◽  
Josef Vepřek-Šiška
Keyword(s):  
Transition Metal ◽  
Reaction Rate ◽  
Reaction Products ◽  
Acid Decomposition ◽  
Analogous Experiment ◽  
Catalytic Effects

The decomposition of peroxobenzoic acid in benzene was studied, and catalytic effects of Fe(III), Mn(III), Co(II), Co(III), and Cr(III) on the reaction rate and the composition of the reaction mixture were investigated. An analogous experiment carried out in perdeuterobenzene and determination of the distribution of deuterium in the reaction products provided evidence for the participation of the solvent in peroxobenzoic acid decomposition.

scholarly journals Electroanalytical Techniques for the Detection of Selenium as a Biologically and Environmentally Significant Analyte—A Short Review

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1768
Author(s):  
Miroslav Rievaj ◽  
Eva Culková ◽  
Damiána Šandorová ◽  
Zuzana Lukáčová-Chomisteková ◽  
Renata Bellová ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Essential Element ◽  
Analytical Techniques ◽  
High Sensitivity ◽  
Stripping Voltammetry ◽  
Short Review ◽  
Electroanalytical Methods ◽  
High Concentrations ◽  
Speed Of Analysis

This short review deals with the properties and significance of the determination of selenium, which is in trace amounts an essential element for animals and humans, but toxic at high concentrations. It may cause oxidative stress in cells, which leads to the chronic disease called selenosis. Several analytical techniques have been developed for its detection, but electroanalytical methods are advantageous due to simple sample preparation, speed of analysis and high sensitivity of measurements, especially in the case of stripping voltammetry very low detection limits even in picomoles per liter can be reached. A variety of working electrodes based on mercury, carbon, silver, platinum and gold materials were applied to the analysis of selenium in various samples. Only selenium in oxidation state + IV is electroactive therefore the most of voltammetric determinations are devoted to it. However, it is possible to detect also other forms of selenium by indirect electrochemistry approach.

scholarly journals Scolicidal activity of biosynthesized zinc oxide nanoparticles by Mentha longifolia L. leaves against Echinococcus granulosus protoscolices

2021 ◽  
Author(s):  
Bushra H. Shnawa ◽  
Samir M. Hamad ◽  
Azeez A. Barzinjy ◽  
Payman A. Kareem ◽  
Mukhtar H. Ahmed
Keyword(s):  
Zinc Oxide ◽  
Zinc Oxide Nanoparticles ◽  
Public Health Problem ◽  
Analytical Techniques ◽  
Oxide Nanoparticles ◽  
Zno Nps ◽  
Leaf Extracts ◽  
X Ray ◽  
Morphological Alterations ◽  
Mentha Longifolia

AbstractCystic echinococcosis is a public health problem in developing countries that practice sheep breeding extensively. In the current study, the protoscolicidal activity of biosynthesized zinc oxide nanoparticles (ZnO NPs) derived from Mentha longifolia L. leaf extracts was investigated. The resultant ZnO NPs were characterized by means of various analytical techniques, such as ultraviolet–visible (UV–Vis) spectrometry, Fourier transform infrared (FT-IR) spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analysis. The results showed that the ZnO NP had the highest scolicidal activity at 400 ppm concentration after 150 min of exposure time, showing 100% mortality rate. The treated protoscolices exhibited loss of viability with several morphological alterations. Hence, an easy and effective green synthesis of ZnO NPs, with efficient scolicidal potential, is reported in this study.

scholarly journals Determination of amino acids in human biological fluids by high-performance liquid chromatography: critical review

Amino Acids ◽  
2021 ◽  
Author(s):  
Grażyna Gałęzowska ◽  
Joanna Ratajczyk ◽  
Lidia Wolska
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
High Performance ◽  
Hplc Analysis ◽  
Limit Of Detection ◽  
Biological Fluids ◽  
Analytical Techniques ◽  
Epidemiological Studies ◽  
Preparation Conditions

AbstractThe quantitation and qualification of amino acids are most commonly used in clinical and epidemiological studies, and provide an excellent way of monitoring compounds in human fluids which have not been monitored previously, to prevent some diseases. Because of this, it is not surprising that scientific interest in evaluating these compounds has resurfaced in recent years and has precipitated the development of a multitude of new analytical techniques. This review considers recent developments in HPLC analytics on the basis of publications from the last few years. It helps to update and systematize knowledge in this area. Particular attention is paid to the progress of analytical methods, pointing out the advantages and drawbacks of the various techniques used for the preparation, separation and determination of amino acids. Depending on the type of sample, the preparation conditions for HPLC analysis change. For this reason, the review has focused on three types of samples, namely urine, blood and cerebrospinal fluid. Despite time-consuming sample preparation before HPLC analysis, an additional derivatization technique should be used, depending on the detection technique used. There are proposals for columns that are specially modified for amino acid separation without derivatization, but the limit of detection of the substance is less beneficial. In view of the fact that amino acid analyses have been performed for years and new solutions may generate increased costs, it may turn out that older proposals are much more advantageous.

scholarly journals Comparison of Elemental Analysis Techniques for the Characterization of Commercial Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 736
Author(s):  
Peter Seidel ◽  
Doreen Ebert ◽  
Robert Schinke ◽  
Robert Möckel ◽  
Simone Raatz ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Analytical Techniques ◽  
Optical Emission ◽  
Breakdown Spectroscopy ◽  
General Evaluation ◽  
Sample Composition ◽  
Laser Induced Breakdown ◽  
Copper Aluminum

Better quality control for alloy manufacturing and sorting of post-consumer scraps relies heavily on the accurate determination of their chemical composition. In recent decades, analytical techniques, such as X-ray fluorescence spectroscopy (XRF), laser-induced breakdown spectroscopy (LIBS), and spark optical emission spectroscopy (spark-OES), found widespread use in the metal industry, though only a few studies were published about the comparison of these techniques for commercially available alloys. Hence, we conducted a study on the evaluation of four analytical techniques (energy-dispersive XRF, wavelength-dispersive XRF, LIBS, and spark-OES) for the determination of metal sample composition. It focuses on the quantitative analysis of nine commercial alloys, representing the three most important alloy classes: copper, aluminum, and steel. First, spark-OES is proven to serve as a validation technique in the use of certified alloy reference samples. Following an examination of the lateral homogeneity by XRF, the results of the techniques are compared, and reasons for deviations are discussed. Finally, a more general evaluation of each technique with its capabilities and limitations is given, taking operation-relevant parameters, such as measurement speed and calibration effort, into account. This study shall serve as a guide for the routine use of these methods in metal producing and recycling industries.

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