Ozone Resistance of Rubber Insulations

1959 ◽  
Vol 32 (4) ◽  
pp. 1104-1116
Author(s):  
W. H. Couch ◽  
G. H. Hunt ◽  
O. S. Pratt
Keyword(s):  
Natural Rubber ◽  
Corona Discharge ◽  
Atomic Oxygen ◽  
Constant Load ◽  
Butyl Rubber ◽  
Surface Coatings ◽  
High Voltage Insulation ◽  
High Concentrations ◽  
Low Pressures ◽  
Ozone Resistance

Abstract The results of experiments on the ozone and corona cutting of rubber high voltage insulation show that the relaxation of mechanical stress in the insulation plays an important role. Studies were made to establish the stress decay characteristics of various formulations based on natural rubber, SBR and butly rubber. A method was developed for correlating the stress decay and ozone resistance characteristics which permits the performance of bent samples of any formulation to be predicted at ozone concentrations up to 0.2%. Comparisons were made between the cutting in an intense corona discharge and that in high concentrations of ozone outside of the discharge. These comparisons show that the results of ozone tests at constant load together with stress relaxation tests may be used to predict the performance of rubber insulation in corona discharge. Tests were carried out in the products of corona discharge at pressures less than atomospheric. These tests lead to the conclusion that at very low pressures (ca. 1 mm Hg) cutting is caused not by ozone but by atomic oxygen. Compounds based on a variety of polymers were exposed to atomic oxygen and it was found that butyl rubber cuts rapidly in atomic oxygen while natural rubber, SBR, neoprene, and Hypalon do not. Antioxidants do not protect butyl rubber against cutting in atomic oxygen, but surface coatings were found to offer protection.

The Effect of Pile Bombardment on Uncured Elastomers

1949 ◽  
Vol 22 (1) ◽  
pp. 138-147 ◽  
Author(s):  
W. L. Davidson ◽  
I. G. Geib
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Mineral Content ◽  
Control Sample ◽  
Butyl Rubber ◽  
Alpha Particles ◽  
High Concentrations ◽  
Ionizing Radiations ◽  
Rubber Stock

Abstract Previous work on the effects of ionizing radiations on hydrocarbons has established that four competitive processes are usually operative: (1) dehydrogenation, (2) condensation or polymerization, (3) hydrogenation (action of nascent hydrogen on any unsaturated matter present), (4) decomposition (C—C cleavage). The chain reacting nuclear pile offers an ideal means for subjecting relatively thick samples of matter (such as rubber) to uniformly high concentrations of radiation. Such studies on natural rubber, Butyl rubber, and polyisobutylene allow one to draw the following conclusions. 1. Uncured natural rubber undergoes a slight curing action when exposed to pile radiations. 2. Polyisobutylene samples are appreciably degraded by pile radiations. 3. The same effects as noted in (1) and (2) are greatly enhanced by secondary alpha particles, produced by an (n, α) reaction on boron (milled into the elastomer). However, even a 2-hour bombardment of natural rubber yields a product greatly inferior to sulfur vulcanizates. 4. Pile bombardment does not introduce measurable unsaturation in polyisobutylene and decreases the unsaturation in natural rubber but slightly. 5. A typical Butyl rubber stock is permanently degraded by pile irradiation, showing on cure reduced tensile strength compared to that of a control sample. 6. Natural rubber shows a weak but measurable radioactivity days after bombardment, probably because of its mineral content. Polyisobutylene is not appreciably active.

Vulcanization Reactions in Butyl Rubber. Action of Dinitroso, Dioxime, and Related Compounds

1946 ◽  
Vol 19 (4) ◽  
pp. 900-914 ◽  
Author(s):  
John Rehner ◽  
Paul J. Flory
Keyword(s):  
Natural Rubber ◽  
Chemical Reactions ◽  
Active Agent ◽  
Butyl Rubber ◽  
Nitroso Compounds ◽  
Cross Linking ◽  
Oxidizing Agent ◽  
Nitroso Group ◽  
Oxidizing Agents ◽  
Related Compounds

Abstract Experiments have been carried out to determine the chemical reactions that occur when Butyl rubber is vulcanized by quinone dioxime or related compounds. Observations have been made of the reactions of these substances with simple olefins, and of the effect of oxidizing agents on the dioxime-type of vulcanization of Butyl in solution. The theory is proposed that, in the vulcanization of Butyl by quinone dioxime or its esters, in presence of oxidizing agents, the active agent is p-dinitrosobenzene formed by oxidation of the dioxime. Chemical reactions are suggested for the subsequent cross-linking or vulcanizing steps, and the results of confirmatory experiments are presented. p-Dinitrosobenzene and other polynitroso compounds are active vulcanizing agents for Butyl, natural rubber, Buna-S, Buna-N, and Neoprene, and do not require the addition of an oxidizing agent. It is suggested that vulcanization of natural rubber by polynitro compounds involves their reduction to corresponding nitroso compounds as the first step, and that the nitroso group adds to rubber to produce cross-linkages.

Choice of Resilient Materials for Anti-Vibration Mountings

1959 ◽  
Vol 32 (4) ◽  
pp. 1209-1227 ◽  
Author(s):  
J. C. Snowdon
Keyword(s):  
Resonant Frequency ◽  
Natural Rubber ◽  
Dynamic Modulus ◽  
Vibration Reduction ◽  
Butyl Rubber ◽  
Damping Factor ◽  
High Frequencies ◽  
The Poor ◽  
Major Increase

Abstract This article attempts to determine, solely from the aspect of vibration reduction, the criteria which define a good antivibration mount material. It concludes firstly that such a material should possess a high damping factor which does not increase greatly with frequency, and secondly, that it should be free from any major increase in dynamic modulus with frequency. Results of transmissibility measurements on a variety of resilient materials indicate that high damping synthetic rubbers normally possess a dynamic modulus which increases rapidly with frequency. It is shown that this modulus increase is responsible for the poor isolation afforded by these rubbers at frequencies above the resonant frequency of the mounting system, and not their inherent high damping as commonly supposed. Filled butyl rubber is an exception, affording an isolation at high frequencies not greatly inferior to that of natural rubber, yet at the same time possessing much higher damping.

scholarly journals High concentrations of natural rubber latex allergens in gloves used by laboratory health personnel in South Africa

2014 ◽  
Vol 105 (1) ◽  
pp. 43 ◽  
Author(s):  
Muofhe Edith Ratshikhopha ◽  
Tanusha Soogreem Singh ◽  
David Jones ◽  
Mohamed Fareed Jeebhay ◽  
Andreas L Lopata
Keyword(s):  
South Africa ◽  
Natural Rubber ◽  
Health Personnel ◽  
Natural Rubber Latex ◽  
Rubber Latex ◽  
High Concentrations

The photolysis of ozone by ultraviolet radiation III. The photolysis of dry ozone/oxygen mixtures at low pressures in a flow system

1970 ◽  
Vol 316 (1526) ◽  
pp. 431-439 ◽  
Keyword(s):  
Quantum Yield ◽  
Atomic Oxygen ◽  
Flow System ◽  
Reaction Scheme ◽  
Oxygen Mixture ◽  
Quantum Yields ◽  
Ozone Decomposition ◽  
Partial Pressures ◽  
Low Pressures ◽  
Hypothetical Reaction

The photolysis at λ = 254 nm of dry ozone + oxygen mixtures (90, 50 and 10% O 3 ) has been studied for partial pressures of ozone between 5 x 10 -2 and 2 Torr. A flow technique was employed, and the extent of ozone decomposition was followed absorptiometrically. Over the pressure range investigated, the quantum yield was virtually independent of ozone pressure for any ozone + oxygen mixture, and increasing dilution of the mixture from 90 to 10% ozone only slightly reduced the observed quantum yield. All quantum yields were near 4. The results are interpreted in terms of the formation of singlet molecular and atomic oxygen in the primary photochemical step; kinetic analysis of a hypothetical reaction scheme predicts quantum yields consistent with those observed.

Heats of Vulcanization of Synthetic Rubbers

1944 ◽  
Vol 17 (2) ◽  
pp. 404-411 ◽  
Author(s):  
P. L. Bruce ◽  
R. Lyle ◽  
J. T. Blake
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Chemical Reactions ◽  
Side Reaction ◽  
Heat Evolution ◽  
Butyl Rubber ◽  
Vulcanized Rubber ◽  
Principal Reaction ◽  
Low Sulfur ◽  
Quantity Of Heat

Abstract 1. The heats of vulcanization for natural rubber and Buna-S are nearly equal. The data for both materials indicate two different chemical reactions during vulcanization. At low sulfur percentages, the principal reaction forms soft vulcanized rubber and is accompanied by little or no heat evolution. Above the 2 per cent sulfur region, a second reaction predominates, forming hard rubber and producing a relatively large quantity of heat. 2. The presence of an accelerator (Santocure) in Buna-S has little, if any, effect on heat of vulcanization. 3. The addition of carbon black to Buna-S lowers the heat of vulcanization in the region above 4 per cent sulfur. The calories evolved in a 10 per cent sulfur compound decrease linearly with percentage of carbon black. 4. The heats of vulcanization of Buna-N (Hycar OR-15) indicate the presence of two chemical reactions. Unlike natural rubber and Buna-S, the ebonite reaction does not predominate until the sulfur concentration is raised above 10 per cent. 5. The heat of vulcanization of Butyl rubber with sulfur is equal to the heat evolved with natural rubber containing 0.6 per cent sulfur. If one sulfur atom reacts per double bond, the maximum amount combining would be 0.72 per cent sulfur. During the vulcanization of Butyl rubber with p-quinone dioxime and lead peroxide, a large amount of heat is evolved by a side reaction between the vulcanizing agents. The reaction involving the Butyl rubber produces about 6 calories per gram, a considerably higher value than the 1 calorie produced by sulfur vulcanization. 6. The heat of vulcanization of Neoprene-GN without added agents corresponds to a value for smoked sheet rubber containing 4.5 per cent sulfur. The addition of zinc oxide and magnesia decreases the heat of vulcanization.

scholarly journals Study the impact of A nanomixture of carbon black and clay on the mechanical properties of A series of irradiated natural rubber/ butyl rubber blend

2021 ◽  
Author(s):  
Dalal Alshangiti
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Carbon Black ◽  
Natural Rubber ◽  
Theoretical Models ◽  
Butyl Rubber ◽  
Nano Particles ◽  
Vinyl Silane ◽  
Link Density ◽  
The Impact

Abstract A series of natural rubber/ butyl rubber NR/IIR blend loaded with N660 carbon black CB and triethoxy vinyl silane treated clay nano particles (TCNP) were prepared using gamma irradiation in the presence of polyfunctional monomer, trimethylolpropane triacrylate (TMPTA). The effect of incorporating different content of N660 carbon black and 5 part per hundred of rubber (phr) of treated clay on the mechanical properties of the prepared nano composites have been investigated. The additions of TCNP into CB/ rubber composites markedly increase their tensile strength due to the increase of the cross-link density. These results indicated that the TCNP may be enclosed or trapped in the occluded structure of CB. The effect of CB and TCNP content on the tensile strength (σ), elongation at break (εb %) and modulus of elasticity (E, MPa) of natural rubber/ butyl rubber NR/IIR blend have been investigated. The incorporation of 5 phr of TCNP into 30 phr carbon black loaded NR/ IIR composites results in the increased tensile strength value by about 60%. Finally, theoretical models were used to interpret the experimental results.

Joining sheath to plasma in electronegative gases at low pressures using matched asymptotic approximations

1999 ◽  
Vol 62 (5) ◽  
pp. 541-559 ◽  
Author(s):  
M. S. BENILOV ◽  
R. N. FRANKLIN
Keyword(s):  
Fluid Model ◽  
Complex Structure ◽  
Density Ratio ◽  
Debye Length ◽  
Plasma Sheath ◽  
Negative Ion ◽  
Ion Temperature ◽  
Ion Motion ◽  
High Concentrations ◽  
Low Pressures

The method of matched asymptotic expansions is used to examine the structure of the plasma sheath of the positive column at low pressure in electronegative gases using the fluid model to describe the positive-ion motion. It is shown that at low negative-ion concentrations, and at high concentrations, the structure is that of a plasma joined to a thin sheath, but that for the electron/negative-ion temperature ratio Te/Tn ≡ ε > 5 + √24, and for a well-defined range of A ≡ nn0/ne0 (the central negative ion to electron density ratio) and for small Debye length, there is a more complex structure with a central negative-ion-dominated plasma surrounded by a quasiplasma in which density oscillations may occur before joining to a sheath. This is in agreement with recent computations using the same model.

Ozonolysis by High Voltage Power Supply to the Melt-Extrudates of Admicelled Rubber and Natural Rubber

2013 ◽  
Vol 747 ◽  
pp. 459-462
Author(s):  
Angkana Pongpilaipruet ◽  
Rathanawan Magaraphan
Keyword(s):  
Natural Rubber ◽  
High Voltage ◽  
Power Supply ◽  
Chain Scission ◽  
Flow Rate Measurement ◽  
High Voltage Power Supply ◽  
Electrical Field ◽  
Melt Flow Rate ◽  
Admicellar Polymerization ◽  
Ozone Resistance

Ozone (O3) is created when diatomic oxygen (O2) is exposed to an electrical field or ultraviolet light. The reaction occurring between double bonds in the unsaturated elastomer chain of natural rubber (NR) and O3 is known as ozonolysis which in turn results in a variety of products. The end result of these reactions is polymer chain scission. In this study, NR was employed as a core substrate for admicellar polymerization of pyrrole (Py) and methyl methacrylate (MMA). Ozonolysis that was studied by using a high voltage power supply connected to a capillary rheometer. These melt extrudates were then subjected to the ozonolysis at a voltage of 9 kV. The effect of ozonolysis at extrude conditions on the chain scission of both extrudates was investigated by melt flow rate measurement (MFR) and Fourier transform infrared spectroscopy. The admicelled rubber showed smaller in percent change of MFR and intensity of changed structure from ozonolysis which suggesting better ozone resistance of the admicelled rubber. Moreover, PMMA-NR showed better ozone stability than PPy-NR.

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