Ozone Resistance of Natural Rubber Vulcanizates. Part II. Influence of Fillers and Waxes

1958 ◽  
Vol 31 (4) ◽  
pp. 874-881 ◽  
Author(s):  
B. I. C. F. van Pul
Keyword(s):  
Natural Rubber ◽  
Side Chains ◽  
Melting Points ◽  
Dynamic Conditions ◽  
Static Conditions ◽  
Natural Rubber Vulcanizates ◽  
Ozone Resistance

Abstract Commerical waxes whose melting points, refractive indexes and numbers of side chains are within the ranges described seem likely to give good ozone protection under static conditions. All waxes lead to worse cracking under dynamic conditions than if none had been included and it is clearly better to use no wax if the rubber is likely to be submitted to intermittent stretching.

Ozone Resistance of Natural Rubber Vulcanizates. Part III. Influence of Accelerators and Antioxidants

1958 ◽  
Vol 31 (4) ◽  
pp. 882-895 ◽  
Author(s):  
B. I. C. F. van Pul
Keyword(s):  
Natural Rubber ◽  
Ozone Concentration ◽  
Static Conditions ◽  
Natural Rubber Vulcanizates ◽  
Ozone Resistance ◽  
Phenylene Diamine

Abstract An investigation of the ozone protection given to natural rubber vulcanizates by different accelerators and antioxidants has shown that, of the accelerators investigated, the thiuram derivatives appear to be the best antioxidants, when they are used as vulcanizing agents; of the large number of antioxidants examined. NN′-di-sec-octyl p-phenylene diamine appears to be the best antiozonant. Vulcanizates containing this material showed no cracks after being exposed for 400 hours to an ozone concentration of 25×10−8 ml/ml under static conditions; it was far superior to all other materials examined.

Ozone Resistance of Natural Rubber Vulcanizates. Part I. Apparatus for Exposure at Low Ozone Concentration

1958 ◽  
Vol 31 (4) ◽  
pp. 866-873
Author(s):  
B. I. C. F. van Pul
Keyword(s):  
Natural Rubber ◽  
Ozone Concentration ◽  
Cracking Resistance ◽  
Dynamic Conditions ◽  
Ozone Concentrations ◽  
Natural Rubber Vulcanizates ◽  
Ozone Resistance

Abstract An apparatus is described for evaluating the cracking resistance of rubber specimens exposed under static or dynamic conditions to ozone concentrations between 5 and 50×10−8 ml/ml of air. Ozone concentration is kept constant automatically however much is destroyed at the walls of the cabinet or at the surfaces of the rubber testpieces. Temperature can be regulated between 20° and 100° C.

Factors Influencing the Ozone Resistance of Neoprene Vulcanizates under Flexure

1959 ◽  
Vol 32 (4) ◽  
pp. 1117-1133 ◽  
Author(s):  
R. M. Murray
Keyword(s):  
Dynamic Testing ◽  
Constant Stress ◽  
Ozone Exposure ◽  
Surface Barrier ◽  
Limiting Factor ◽  
Surface Films ◽  
Protective Film ◽  
Dynamic Conditions ◽  
Static Conditions ◽  
Ozone Resistance

Abstract The need for dynamic testing conditions, such as mild flexing, to study the attack of ozone on elastomeric vulcanizates, has become increasingly apparent. Many rubber goods, such as belts, tire sidewalls, and hose, are subjected to intermittent or continuously fluctuating strains in service and to evaluate their ozone resistance under constant stress or strain conditions is unrealistic and often leads to entirely erroneous conclusions. For example, it is well known that under static strain a vulcanizate's ozone resistance is enhanced by compounding with a wax which migrates to its surface and forms a protective film. However, numerous investigators have reported that when a wax film is continuously ruptured by dynamic testing, the vulcanizate is even more vulnerable to ozone attack than if no wax were present. Other surface films also may act detrimentally under dynamic conditions. One such film may form under static exposure by the migration of antiozonants to the surface of a sample where they or their ozone reaction products provide a shield against ozone. Also, diene elastomers, even when not under stress, react with ozone without cracking and it has been postulated that the thin films formed as a result of this reaction are less extensible and consequently more subject to rupture on flexing than the unreacted rubber beneath them. It may well be found that the resistance of any surface barrier to dynamic stresses is the limiting factor for many products in service. Consequently, techniques for testing under dynamic conditions are needed at least to supplement testing under constant stress or strain in ozone. Ozone exposure under dynamic conditions may prove to have analytical advantages over the static method. First, because dynamic tests accelerate ozone attack over that obtained statically even though no increased strain is impressed. This permits the more ozone resistant elastomers to be tested at lower concentrations of ozone than would be possible statically. By testing in more dilute ozone, the correlation between results obtained under atmospheric exposure and the ozone cabinet should be better. Also, it seems likely that compounding ingredients which improve ozone resistance under dynamic conditions should provide improvement under static conditions as well, even though the converse is not necessarily true.

Aging of Natural Rubber Vulcanizates in the Presence of Dithiocarbamates

1959 ◽  
Vol 32 (3) ◽  
pp. 739-747 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Protective Action ◽  
Dicumyl Peroxide ◽  
Vulcanized Rubber ◽  
Aging Properties ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The thermal and photochemical aging of extracted dicumyl peroxide-, TMTD (sulfurless)- and santocure-vulcanized rubber, in presence of a number of metal and alkylammonium dithiocarbamates, has been investigated by measurements of stress relaxation. The dithiocarbamates have a considerable protective action upon the degradation of peroxide- and TMTD-vulcanizates, but they accelerate stress decay in santocure-accelerated vulcanizates. The reasons for this behavior are discussed. It is suggested that the excellent aging properties of unextracted TMTD vulcanizates are due to the presence of zinc dimethyldithiocarbamate formed during vulcanization.

scholarly journals The Effect of Various Hydroxide and Salt Additives on the Reduction of Fluoride Ion Mobility in Industrial Waste

2021 ◽  
Vol 13 (3) ◽  
pp. 1554
Author(s):  
Tadas Dambrauskas ◽  
Kestutis Baltakys ◽  
Agne Grineviciene ◽  
Valdas Rudelis
Keyword(s):  
Liquid Medium ◽  
Silica Gel ◽  
Ion Mobility ◽  
Fluoride Removal ◽  
Dynamic Conditions ◽  
Treatment Conditions ◽  
Medium Flow ◽  
Silica Gel Waste ◽  
Fluorine Ions ◽  
Static Conditions

In this work, the influence of various hydroxide and salt additives on the removal of F− ions from silica gel waste, which is obtained during the production of AlF3, was examined. The leaching of the mentioned ions from silica gel waste to the liquid medium was achieved by the application of different techniques: (1) leaching under static conditions; (2) leaching under dynamic conditions by the use of continuous liquid medium flow; and (3) leaching in cycles under dynamic conditions. It was determined that the efficiency of the fluoride removal from this waste depends on the w/s ratio, the leaching conditions, and the additives used. It was proven that it is possible to reduce the concentration of fluorine ions from 10% to <5% by changing the treatment conditions and by adding alkaline compounds. The silica gel obtained after the leaching is a promising silicon dioxide source.

A New Technical Standard Procedure to Measure Stimulation and Gravel-pack Fluid Leak-off under Dynamic Conditions

2015 ◽  
Author(s):  
Mahmoud Asadi ◽  
Brain Ainley ◽  
David Archacki ◽  
Eric Aubry ◽  
Harold Brannon ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Standard Procedure ◽  
Oil And Gas Industry ◽  
Testing Procedure ◽  
Technical Standard ◽  
Gas Wells ◽  
Dynamic Conditions ◽  
Oil And Gas Wells ◽  
Static Conditions ◽  
Gravel Pack

Abstract Historically, leak-off analyses of stimulation fluids have been performed using in-house laboratory procedures. The lack of industry standard procedures to perform leak-off and wall building coefficient analyses of stimulation fluids has introduced inconsistency in both results and reporting for many years. A technical standard adopted in 2006 by both API and ISO for static conditions has provided the oil and gas industry with the first standardized procedure to measure and report leak-off1. However, the more complex testing under dynamic conditions was not addressed. As a result, a group of industry experts have compiled their years of experiences in developing a new technical standard to measure the leak-off characteristics of stimulation and gravel-pack fluids under dynamic flow conditions. Stimulation and gravel-pack fluids are defined, for the purpose of this technical standard, as fluids used to enhance production from oil and gas wells by fracturing and fluids used to place filtration media to control formation sand production from oil and gas wells. Leak-off is the amount of fluid lost to porous media during these operations. The leak-off procedure was developed through the colaberation of several industry companies by evaluating numerous in-house laboratory techniques and conducting round robin testing to ensure that any modifications to these procedures were reliable and repeatable. The new standard provides a step-by-step procedure that includes fluid preparation, experimental equipment design, testing procedure and data analyses for fluids exhibiting viscosity controlled leak-off or wall building characteristics. Example calculations are reviewed within this paper.

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