Determination of Zinc in Rubber Compounds. A New Internal Indicator Method

1942 ◽  
Vol 15 (2) ◽  
pp. 382-390
Author(s):  
Willard P. Tyler
Keyword(s):  
Indicator System ◽  
Uranyl Acetate ◽  
Indicator Method ◽  
General Application ◽  
Oxidation Reduction ◽  
Rubber Compounds ◽  
Internal Indicator ◽  
External Indicator ◽  
Slight Advantage

Abstract Two internal indicator volumetric methods for the determination of zinc in rubber compounds have been devised and investigated. The first method is a wet-oxidation method employing nitric acid, bromine, and perchloric acid as oxidants, and p-ethoxychrysoidine, a new oxidation-reduction indicator for this use, as indicator. It is of general application to all types of rubber compounds. The second method, less generally applicable to rubber compounds, utilizes either the new indicator or the well-known indicator, diphenylbenzidine. This method depends on ashing of the sample, and cannot be used for the analysis of zinc in rubber compounds containing lead or silicates, since it has been found that no method in which the sample is ashed yields accurate results if these substances are present. Both methods use potassium ferrocyanide as the volumetric precipitant and potassium ferricyanide as an integral part of the indicator system. Both methods are applicable to other organic and inorganic zinc-containing materials. The first method appears to have a slight advantage in ease of manipulation, total time of determination, and range of applicability. There is little choice between the methods or indicators as regards precision, accuracy, or the actual time used by the analyst for a determination, providing each method and indicator is used only under the proper conditions. Both methods are superior to the external indicator method using uranyl acetate, the method now in common use in rubber laboratories.

Ultrastructural changes in sciatic nerve tissue: Effects of passive maternal smoking

1983 ◽  
Vol 41 ◽  
pp. 650-651
Author(s):  
Amankwah K.S. ◽  
A.D. Weberg ◽  
R.C. Kaufmann
Keyword(s):  
Sciatic Nerve ◽  
Maternal Smoking ◽  
Ultrastructural Level ◽  
Uranyl Acetate ◽  
Nerve Tissue ◽  
Ultrastructural Changes ◽  
Cacodylate Buffer ◽  
And Control ◽  
Spontaneous Delivery

Previous research has revealed that passive (involuntary inhalation) tobacco smoking during gestation can have adverse effects upon the developing fetus. These prior investigations did not concentrate on changes in fetal morphology. This study was undertaken to delineate fetal neural abnormalities at the ultrastructural level in mice pups exposed in utero to passive maternal smoking.Pregnant study animals, housed in a special chamber, were subjected to cigarette smoke daily from conception until delivery. Blood tests for determination of carbon monoxide levels were run at 15-18 days gestation. Sciatic nerve tissue from experimental and control animals were obtained following spontaneous delivery and fixed in 2.5% gluteraldehyde in 0.1M cacodylate buffer pH 7.3. The samples were post-fixed in osmium ferrocyanide (1:1 mixture of 1.5% aqueous OSO4 and 2.5% K4 Fe(CN)6). Following dehydration, the tissues were infiltrated with and embedded in Spurr. Sections were stained with uranyl acetate and lead citrate.

Determination of Combined and Second Order Factor Effects for Simultaneous Optimization of Physical and Mechanical Properties of NR/BR Blend System

2014 ◽  
Vol 42 (4) ◽  
pp. 290-304
Author(s):  
Rajarajan Aiyengar ◽  
Jyoti Divecha
Keyword(s):  
Physical And Mechanical Properties ◽  
Second Order ◽  
Simultaneous Optimization ◽  
Order Effects ◽  
Elongation At Break ◽  
Five Factors ◽  
Rubber Compounds ◽  
Polybutadiene Rubber ◽  
Contour Plots

ABSTRACT The blends of natural rubber (NR), polybutadiene rubber (BR), and other forms of rubbers are widely used for enhancing the mechanical and physical properties of rubber compounds. Lots of work has been done in conditioning and mixing of NR/BR blends to improve the properties of its rubber compounds and end products such as tire tread. This article employs response surface methodology designed experiments in five factors; high abrasion furnace carbon black (N 330), aromatic oil, NR/BR ratio, sulfur, and N-oxydiethylene-2-benzothiazole sulfenamide for determination of combined and second order effects of the significant factors leading to simultaneous optimization of the NR/BR blend system. One of the overall optimum of eight properties existed at carbon 44 phr, oil 6.1 phr, NR/BR 78/22 phr with the following values of properties: tensile strength (22 MPa), elongation at break (528%), tear resistance (30 kg/mm), rebound resilience (67%), moderate hardness (68 International rubber hardness degrees) with low heat buildup (17 °C), permanent set (12%), and abrasion loss (57 mm3). More optimum combinations can easily be determined from the NR/BR blend system models contour plots.

Applications of Thermal Analytical Procedures in the Study of Elastomers and Elastomer Systems

1980 ◽  
Vol 53 (3) ◽  
pp. 437-511 ◽  
Author(s):  
D. W. Brazier
Keyword(s):  
Thermal Analysis ◽  
Dynamic Properties ◽  
Evolved Gas Analysis ◽  
Gas Analysis ◽  
International Standards ◽  
New Technique ◽  
Heating Rates ◽  
Single Experiment ◽  
Rubber Compounds

Abstract An attempt has been made to review the development of thermoanalytical procedures as they have been applied to elastomers and elastomer systems over the past 10 years. For all rubber industry products, temperature and its effects, either alone or in conjunction with the chemical environment, play an important role from the production stage through to the final failure of the product in the field. It is thus not surprising that thermal analysis, in which temperature is the prime variable, has found such diverse applications in elastomer studies. The identification and quantitative analysis of rubber formulations have received most attention. Such formulations produce characteristic “fingerprints” when studied in DTA, DSC, TG, or TMA. In DSC, the determination of the glass transition characteristics, the observation and determination of crystallinity, the detection of cyclization reactions, and the monitoring of thermal and oxidative degradation characteristics can all be observed in a single experiment covering the temperature range from −150 to +600°C. At normal heating rates, e.g., 20°C/min, such information is available in 40 min. TG/DTG analysis can yield the elastomer or elastomers content, oil and plasticizer, carbon black (level and often type), and inorganic ash in less than 60 min. Processing and curing can also be studied. Blend compatibility can be assessed on the basis of both Tg and crystallinity measurements and the data used to determine optimum mixing times. Sulfur vulcanization and peroxide curing of elastomers is readily monitored by DSC and can be used for confirmation analysis of the presence of curatives. Limitations in such analysis exist, but as understanding and ability to interpret cure exotherms increase, valuable information about the mechanism and the nature of the cured network will be obtained. The testing of rubber compounds involves many hours of labor by current procedures. The rapidity of thermal analysis promises to offer some relief. In addition to DSC and TG, TMA, a relatively new technique, offers a rapid approach to low-temperature testing. Dynamic mechanical analysis (DMA) offers a rapid route to determining dynamic properties, but as yet, relatively little has been published on the application of this new technique to elastomers. As environmental concern increases, techniques such as evolved gas analysis (EGA) and combined techniques such as TG/gas chromatography are predicted to play an important role. As for the future, it is readily apparent that the principles of the methods have been established and, in several cases, it now remains to reduce them to a practical level. In some areas, such as vulcanization studies, much remains to be undertaken to improve our interpretive skills. Although there is some indication that certain industries have produced “in-house” standards for the analysis of rubber compounds by DSC and TG/DTG, it will only be when national and international standards organizations study and produce standard procedures, that the techniques will be generally adopted. Maurer's prediction in 1969 of increased applications of DTA and TG in elastomer studies has undoubtedly proved correct, and with the proliferation of reliable commercial instrumentation, significant developments can be anticipated in the next decade.

Evaluation of the Development Level of Information and Communications Technology in Education Based on the Entire-Array-Polygon Indicator Method: Taking the Questionnaire Survey Data of 13 Cities in Province W as an Example

2021 ◽  
Vol 7 (2) ◽  
pp. 987-997
Author(s):  
Danxia Xing ◽  
Chun Lu
Keyword(s):  
Survey Data ◽  
Questionnaire Survey ◽  
Objective Assessment ◽  
Indicator System ◽  
Information And Communications Technology ◽  
Communications Technology ◽  
Ict In Education ◽  
Indicator Method ◽  
Development Level ◽  
Entire Array

The objective assessment of the development level of information and communications technology (ICT) in education can support the government in formulating and implement ICT policies. The article first introduced the Entire-Array-Polygon (EAP) indicator method and then designed an evaluation indicator system which containing five first indicators and 31 secondary indicators. Finally, using the questionnaire survey data of 13 cities in Province W as an example, the EAP indicator method was used to carry out on the evaluation of ICT development level. The study drew the following conclusions: EAP indicator method can objectively assess the development level of ICT; the overall development level of ICT in the 13 cities in Province W is average and above, and most of them are level II. When using the EAP indicator method to assess the development level of ICT, experts do not need to determine the indicator's weight. Also, this method presents the evaluation results more concisely and intuitively, so it can be promoted as an essential method of evaluating on the development level of ICT in education.

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