Semi-Ebonite. Part 1

1935 ◽  
Vol 8 (4) ◽  
pp. 554-570 ◽  
Author(s):  
P. A. Gibbons
Keyword(s):  
Tensile Strength ◽  
Plastic Flow ◽  
Room Temperature ◽  
Constant Load ◽  
Vulcanized Rubber ◽  
Large Elongation ◽  
Soft Rubber

Abstract Hitherto two products of the reaction between sulfur and rubber have been studied and used commercially, soft rubber and ebonite. Few publications have appeared concerning the products obtained by vulcanization of proportions between 5 and 30 parts of sulfur with 100 parts of rubber. Before the introduction of organic accelerators of vulcanization the coefficient of vulcanization was considered a satisfactory criterion of the quality of soft vulcanized rubber. Mixes of rubber and sulfur vulcanized to a coefficient of more than 3.5 to 4 were usually considered overvulcanized in that experience showed that the optimum properties as regards tensile strength and elongation at rupture occurred at this degree of vulcanization. Semi-ebonites differ from soft rubber and ebonite in as much as they are extremely sensitive to small changes in the time of vulcanization. Their plasticity is such that the velocity of plastic flow just prior to break is relatively great, and thus they may experience a large elongation at constant load. Their plasticity decreases with further vulcanization, in fact, with advance in vulcanization they become almost rigid at room temperature. The decrease in plastic flow is accompanied by an increase in hardness and brittleness and the ultimate stage in the rubber-sulfur reaction, ebonite, is reached.

scholarly journals Tensile Strength and Creep Resistance in Nanocrystalline Cu, Pd and Ag

1990 ◽  
Vol 206 ◽  
Author(s):  
G. W. Nieman ◽  
J. R. Weertman ◽  
R. W. Siegel
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Yield Strength ◽  
Creep Resistance ◽  
Room Temperature ◽  
True Strain ◽  
Constant Load ◽  
Creep Tests ◽  
Grain Sizes

ABSTRACTMeasurements of tensile strength and creep resistance have been made on bulk samples of nanocrystalline Cu, Pd and Ag consolidated from powders by cold compaction. Samples of Cu-Cu2O have also been tested. Yield strength for samples with mean grain sizes of 5–80 nm and bulk densities on the order of 95% of theoretical density are increased 2–5 times over that measured in pure, annealed samples of the same composition with micrometer grain sizes. Ductility in the nanocrystalline Cu has exceeded 6% true strain, however, nanocrystalline Pd samples were much less ductile. Constant load creep tests performed at room temperature at stresses of >100 MPa indicate logarithmic creep. The mechanical properties results are interpreted to be due to grain size-related strengthening and processing flaw-related weakening.

Permanent Set in Vulcanized Rubber

1949 ◽  
Vol 22 (4) ◽  
pp. 1036-1044 ◽  
Author(s):  
L. Mullins
Keyword(s):  
Plastic Flow ◽  
Room Temperature ◽  
Elastic Recovery ◽  
The Other ◽  
Initial Length ◽  
Chain Molecules ◽  
Permanent Set ◽  
Vulcanized Rubber ◽  
Rate Of Recovery ◽  
Long Chain

Abstract The residual extension which remains after a sample of rubber has been stretched for some period, then released and allowed to recover, is popularly called permanent set. This set, however, is far from being permanent since it continuously decreases with the period of recovery; furthermore, after the rate of recovery has become exceedingly slow and is no longer readily observable, an increase in temperature will usually result in a sharp increase in the rate of recovery. It has been usual to identify this set with irreversible plastic flow, but it will be immediately evident that this can rarely be justified for, owing to incomplete high-elastic recovery, the measured value of set is a combination of both plastic flow and high-elastic deformation which has not completely recovered. Thus before any attempt is made to discuss the interpretation of the results of set tests, a study must be made of the significance of set. Treloar has investigated this phenomenon in raw natural rubber and has shown that entanglements or cohesional linkages may form while the rubber is stretched, and these oppose recovery; further, although van der Waals forces between the long-chain molecules largely control the rate and the amount of recovery, the crystallization of rubber produced by stretching may profoundly influence the set. On the other hand Tobolsky has studied the set which results from stretching rubber vulcanizates at high temperatures ; in such cases the amount of set is controlled by two processes which take place while the rubber is stretched; one of these involves the oxidative breaking of network chains, the other the oxidative cross-linking of network chains. Although these ideas are well founded, they do not provide a completely satisfactory basis for the understanding of set, and the purpose of this work is to extend these ideas and to explain the significance of the results of normal set tests ; in these tests rubber samples were extended at room temperatures to moderate elongations for relatively short periods of time. Most of the tests performed in this investigation were made on dumbbell shaped samples, which were extended by 200 per cent of their initial length for fifteen minutes at room temperature and then allowed to recover for one hour at room temperature; the residual extension was then noted and expressed as a percentage of the initial length. These tests will be referred to as normal set tests. In some tests various periods and temperatures of extension and recovery were used.

Vulcanization of Latex. Differences in the Behavior of Fresh, Old, and Purified Latex

1943 ◽  
Vol 16 (2) ◽  
pp. 318-341
Author(s):  
J. W. Van Dalfsen
Keyword(s):  
Tensile Strength ◽  
Room Temperature ◽  
Essential Difference ◽  
Atmospheric Conditions ◽  
Noticeable Effect ◽  
Vulcanized Rubber ◽  
The Difference ◽  
Hydrolysis Of ◽  
Transition Stages ◽  
Free Sulfur

Abstract Patents granted to Schidrowitz show that when latex is vulcanized and then dried at room temperature, the product has the properties of vulcanized rubber. Films produced in this way show tensile strengths and elasticity which correspond to those of latex films vulcanized in the dry state. It is apparent, however, that when fresh latex is vulcanized under certain definite conditions, the product has fair tensile strength and elasticity only at a relative humidity of zero, but which under ordinary atmospheric conditions is brittle, seems to be overcured, and is practically without tensile strength. This tensile strength, however, is increased by additional dry vulcanization, so there can be no question of overcure. Just as soon as vulcanization has proceeded to a point where brittle films without tensile strength are obtained, the latex, when treated with acid, does not coagulate, but merely flocculates. Nor can such vulcanized fresh latex at this stage be made to coagulate coherently by other means. This form of latex is not sticky. The flocculate referred to can be obtained only by vulcanizing fresh latex in the presence of zinc oxide, and under conditions such that hydrolysis of the nonrubber substances is a minimum. It is, therefore, desirable to have recourse to ultra-accelerators and to be sure that the vulcanization temperature is not too high. By keeping fresh latex alkaline, or by purifying it, it will not flocculate. Latex that has been purified or aged may occasionally, under similar conditions, give a brittle and incoherent coagulum, whereas in other cases a normally coherent but somewhat brittle coagulum results. The nature of the coagulum is governed by the degree of purification and hydrolysis of the nonrubber substances; hence all transition stages between a flocculate and a completely coherent coagulum may occur. By adding serum from fresh latex to purified latex, the behavior of such purified latex changes in the sense that it behaves more like fresh latex. In studying experimentally the difference in behavior of fresh latex and purified latex, the first thing considered was the combination of sulfur. It was found that sulfur first dissolves in the serum, after which it dissolves in the rubber itself. Only then does vulcanization take place. This became evident from the definite acceleration of the combination of sulfur in the latex stage, when before vulcanization, latex was heated with sulfur alone. By this preparatory treatment too, dry vulcanization at room temperature was accelerated, but there was no noticeable effect on dry vulcanization at 80° and 110° C. At 30° C, about 1 per cent of the sulfur dissolved in the rubber particles, in the form of free sulfur. From this it was concluded that it is not possible to remove by mechanical means (as by clarification) excess free sulfur from vulcanized latex. No essential difference could be found between the combined sulfur of fresh latex and that of purified old latex.

The Stress-Strain Relationship in Ebonite

1934 ◽  
Vol 7 (1) ◽  
pp. 197-211
Author(s):  
B. L. Davies
Keyword(s):  
Tensile Strength ◽  
Plastic Flow ◽  
Testing Machine ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Tensile Testing Machine ◽  
Hooke’S Law ◽  
Hooke's Law ◽  
Soft Rubber

Abstract 1. A simple “extensometer” has been devised for the more accurate measurement of small elongations in hard rubber samples, thus enabling stress-strain curves to be obtained on a standard tensile testing machine. 2. The form of the curve has been described more fully than heretofore. It shows that hard rubber does not deform exactly in accordance with Hooke's Law, but exhibits plastic flow. 3. Deviations from Hooke's Law shown by the experimental curves depend upon the speed of stretching. Increased speed of elongation has been found to give higher readings of tensile strength. 4. Prolonged mastication of the rubber gives a weaker product, similar effects being obtainable by the use of a neutral softener. 5. The effects of increasing time of vulcanization have been described. The range of curves showing transition from over-cured soft rubber to ebonite indicates that the hard rubber curve is possibly related to the initial portion of the soft rubber curve. The plasticity of the overvulcanized rubber, as indicated by the deviation from Hooke's Law, increased with time of vulcanization until the “semi-ebonite” stage was reached. 6. The leather-like “semi-ebonites” differed from soft and hard rubber inasmuch as they were extremely sensitive to small changes in time of vulcanization, and inasmuch as their plasticity was such that the velocity of plastic flow was comparable with the rate of pulling (1 in. per minute), at a particular point in the test they experienced a large elongation at constant load, i. e., the velocity of flow was equal to the speed of pulling. Their plasticity decreased with further vulcanization. 7. The longest cures in the above-mentioned group gave products which were rigid at room temperature. Since these must be more resistant to shock than vulcanizates in a higher state of cure, it seems that the best technical cure of ebonite for mechanical purposes is that which gives maximum tensile strength combined with the property of undergoing considerable plastic flow (of the order of 5 per cent) at the constant maximum load, and at an arbitrarily fixed rate of stretching, the temperature being commensurate with the thermal conditions of service. Such a cure is clearly indicated by the stress-strain curve. 8. Accelerated ebonite mixings are more sensitive to time of cure than rubber-sulfur stocks without accelerators. An accelerator may produce very little effect on the tensile strength and breaking elongation, but may yield a stock which “scorches” readily. This prevulcanization was detrimental to the mechanical properties of the vulcanizate, even though it was so slight that its presence was not detected during normal processing. 9. Mineral rubber in ebonite stocks has been shown to accelerate the cure as indicated by the stress-strain curve. 10. Stocks containing high loadings of gas black gave vulcanizates which were weak and brittle. The effect of the black on the stiffness was similar to that produced by further cure. 11. The stress-strain curve provides a reliable means whereby stocks containing different accelerators and other compounding ingredients may be compared at equivalent states of vulcanization.

Study on Natural Rubber Quality of Micro-Cut Tapping with Gas-Stimulation

2013 ◽  
Vol 834-836 ◽  
pp. 175-179
Author(s):  
Kai Dian Wang ◽  
Mao Fang Huang ◽  
Chun Liang Yang ◽  
Zong Qiang Zeng ◽  
Zhi Xiong Liang ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Natural Rubber ◽  
Protein Content ◽  
Dynamic Property ◽  
Control Group ◽  
Vulcanized Rubber ◽  
The Difference

The natural rubber samples produced by conventional tapping methods were used as a control, then analyzed the dry rubber property of natural rubber, the dynamic property and Physical & mechanical property of vulcanized rubber using Rubber processing analyzer and Thermogravimetric Analyze the difference between the properties of dry rubber and vulcanized rubber produced by Micro-cut Tapping with Gas-stimulation. The results indicated that the tensile strength, tear strength elastic modulus of dry rubber that produced by Micro-cut Tapping with Gas-stimulation are respectively 20%, 7% lower than the control. The protein content of dry rubber materials produced by Micro-cut Tapping with Gas-stimulation is 16.7% higher than control group.

scholarly journals The Tensile Strength of Rubber and Rubber Molecule

1950 ◽  
Vol 23 (3) ◽  
pp. 581-586
Author(s):  
Chullchai Park ◽  
Usaburo Yoshida
Keyword(s):  
Tensile Strength ◽  
Low Temperature ◽  
Room Temperature ◽  
Chain Molecule ◽  
Chain Molecules ◽  
Vulcanized Rubber ◽  
A Chain

Abstract The tensile strengths of crystallized crude rubber and vulcanized rubber are remarkably different from each other at room temperature, but are found to be almost the same at the temperature of liquid air. By assuming that the tensile strength of crystallized rubber at this low temperature is entirely due to its chain molecules, the forced needed to break a chain molecule of rubber at its weakest point is estimated.

Aging of Rubber in the Oxygen Bomb at Room Temperature

1943 ◽  
Vol 16 (4) ◽  
pp. 924-925
Author(s):  
J. R. Scott
Keyword(s):  
Tensile Strength ◽  
Oxygen Concentration ◽  
Room Temperature ◽  
Accelerated Aging ◽  
Natural Aging ◽  
Tensile Tests ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Accelerated Aging Test ◽  
Aging Test

Abstract The work described below was carried out as a first step in determining whether an oxygen-bomb test at room temperature could be used as an accelerated aging test for unvulcanized rubber compositions, e.g., as used on surgical and adhesive plasters and for combining shoe fabrics, because a high-temperature test is unsatisfactory in such cases, owing to the melting of the compositions. The only infallible way of assessing the value of an accelerated test for such compositions is by comparison with natural aging, but as this is a very lengthy process and as the deterioration is difficult to measure quantitatively, it was decided to make preliminary tests on the effect of high oxygen concentration at room temperature by using vulcanized rubber. Although the results proved to be negative so far as the original purpose of the work was concerned, it is considered of interest to place them on record in view of the prominence given in some papers on aging to the relationship between oxygen concentration and rate of oxidation and deterioration of rubber. A mix composed of rubber 100, sulfur 3, zinc oxide 5, stearic acid 1, and diphenylguanidine 0.75, was vulcanized for 30 minutes at 153° C. Tensile tests, using standard ring-specimens and the Schopper machine, were made on unaged specimens and on specimens that had been aged (1) in an oxygen bomb at 300 lb. per sq. in. oxygen pressure and at room temperature (about 10° C), (2) in a Geer oven at 70° C. Four rings were used for each test, the tensile strength and breaking elongation figures quoted being the average for the two rings giving the highest tensile strength, and the figures for the elongations at constant loads the average of all four rings.

A Rugged Semiautomatic Extensometer for Rubber

1963 ◽  
Vol 36 (1) ◽  
pp. 68-74 ◽  
Author(s):  
P. I. Donnelly
Keyword(s):  
Tensile Strength ◽  
Tensile Properties ◽  
Tensile Testing ◽  
Electrical Circuit ◽  
Optimum Conditions ◽  
Routine Testing ◽  
Vulcanized Rubber ◽  
Poly Vinyl Chloride ◽  
Digital Indication ◽  
Soft Rubber

Abstract The evaluation of an elastomer—new or established—inevitably involves a study of tensile properties. ASTM procedure D 412 is generally used as a guide for the tensile testing of vulcanized rubber. In this method, an operator observes bench marks on the sample and records the modulus at every 100% elongation, the ultimate elongation, and the tensile strength at break. An extensometer has been developed to eliminate operator coordination and judgment factors from rubber tensile testing. It is simple and sufficiently rugged for routine testing. Its features are a counterbalanced guide rod with a sliding electrical contactor, and specimen followers which automatically unlatch to avoid being damaged when specimens break. In addition there is a counter for direct digital indication of elongation, and an electrical circuit which controls a short duration spark to mark the autographic chart. Experience in testing up to 5000 specimens per year has shown that the apparatus makes an inexperienced operator as effective as trained operators working under optimum conditions. The instrument has been used successfully on materials ranging from soft rubber to plasticized and filled poly (vinyl chloride).

scholarly journals The Effect of Seawater on The Compressive Strength and Split Tensile Strength in Self Compacting Geopolymer Concrete

Jurnal CIVILA ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 197
Author(s):  
Herwina Rahayu Putri ◽  
Firman Paledung ◽  
Erniati Bachtiar ◽  
Popy Indrayani
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Room Temperature ◽  
Construction Material ◽  
Geopolymer Concrete ◽  
Split Tensile Strength ◽  
Coarse Aggregates ◽  
Binder Ratio

Fly ash is a kind of trash that may degrade the quality of the air. As a result, it is critical that it be used as an ecologically beneficial material. Although cement is the most often used construction material, its manufacturing generates carbon dioxide, which may degrade air quality. The aim of this research was to evaluate the compressive strength and split tensile strength of self-compacting geopolymer concrete (SCGC) cured in seawater, as well as to compare SCGC with and without saltwater. In this research, a cylindrical specimen with a diameter of 10 cm and a height of 20 cm was utilized as the specimen. Fly ash is used in proportion to fine and coarse aggregates at a ratio of 1: 0.65: 1.5. Using a 0.4 activator to binder ratio. The molarity ranges utilized were 11 M, 12 M, 13 M, 14 M, and 15 M. Compressive strength and split tensile strength tests were conducted on 28-day-old concrete. The findings indicated that when the molarity of SCGC treated with seawater increased from 11 to 15 M, the compressive and split tensile strengths increased. Compressive strength values were greatest in SCGC treated at room temperature when an activator of 13 M was used, and compressive strength values dropped in SCGC treated at room temperature when an activator greater than 13 M was used

Deterioration of Vulcanized Rubber by Copper and Manganese Compounds

1944 ◽  
Vol 17 (1) ◽  
pp. 221-226
Author(s):  
E. C. B. Bott ◽  
L. D. Gill
Keyword(s):  
Tensile Strength ◽  
Room Temperature ◽  
Vulcanized Rubber ◽  
Preliminary Work ◽  
Manganese Compounds

Abstract The deterioration of vulcanized rubber containing increasing percentages of copper and manganese compounds and the extent of the protection given to the stocks by a secondary naphthylamine have been investigated. Jones and Craig showed that the addition of copper stearate made no difference to the type of aging of stocks containing various percentages of antioxidant when measured by decrease in tensile strength, and the results of Taylor and Jones indicate that the decrease is proportional to the time of aging in the Geer oven. Preliminary work.—Experiments were made on the base mix to determine its suitability and its optimum cure. The optimum cures of the base mix plus copper or manganese compounds after storage for six weeks in the dark at normal room temperature and of the base mix plus sym. di-β-naphthyl-p-phenylenediamine also were obtained. The following compounds A, B, C and D were mixed on a laboratory mill having 12 × 6 in. rolls.

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