Vibration Properties of Rubberlike Materials Dependence on Temperature

1943 ◽  
Vol 16 (2) ◽  
pp. 400-416 ◽  
Author(s):  
R. B. Stambaugh
Keyword(s):  
Internal Friction ◽  
Natural Rubber ◽  
Critical Temperatures ◽  
Cohesive Forces ◽  
Exponential Law ◽  
Vibration Properties ◽  
Inverse Effect ◽  
Similar Materials ◽  
Straight Lines ◽  
Rubberlike Materials

Abstract 1. The vibration modulus and resilience are independent of the frequency of vibration if the temperature is constant. 2. The internal friction is approximately inversely proportional to the frequency. 3. The modulus decreases as temperature increases. Curves for synthetic stocks at high temperatures are not very different from those of rubber at low temperatures. 4. Resilience rises linearly with temperature. Rubber shows a transition from one slope to another at about 25° C. 5. The dependence of the internal friction of rubber and similar materials on temperature follows the same exponential law as the viscosity of liquids. At certain critical temperatures sudden changes occur in the cohesive forces, which cause a transition from one curve to another. For the natural rubber sample this occurs at about 17° C. 6. The amplitude of vibration has a large inverse effect on the modulus and friction, which cannot be explained by the temperature rise of the sample due to heat generated in it. The effect may be due to nonlinearity of the stress-strain curves. 7. Modulus and friction are affected by temperature in the same way, indicating the dependence of both on some fundamental characteristic of the molecular structure. Natural rubber requires two straight lines for representation on the modulus-friction plot, the junction occurring at about 25° C.

The Variation with Temperature of the Dynamic Properties of Rubber and Synthetic Rubberlike Materials

1945 ◽  
Vol 18 (2) ◽  
pp. 306-317
Author(s):  
W. P. Fletcher ◽  
J. R. Schofield
Keyword(s):  
Natural Rubber ◽  
Freezing Point ◽  
Dynamic Properties ◽  
Dynamic Compression ◽  
Smooth Curves ◽  
The Subject ◽  
Region 10 ◽  
Increasing Temperature ◽  
Straight Lines ◽  
Rubberlike Materials

Abstract (1) Over the range from 5° to 40° C, the temperature coefficients of the dynamic compression moduli of all the rubber and rubberlike materials studied are negative and fall numerically with increasing temperature. (2) The highest numerical value of this coefficient for natural rubber is −2.7×10−3 per ° C. Neoprene-Gn has a coefficient 3 to 4 times this value and Buna-S about 5 times. Hycar OR-15 shows the highest coefficient of −1.3×10−1 per ° C from 10 to 20° C, the value changing sharply at 20.2° C to −0.14×10−1, which is maintained up to 40° C. (3) Results for Neoprene-E were not reproducible, owing to a type of slow freezing effect. (4) In all cases but Thiokol-RD resilience tended to increase with increasing temperature throughout the range. (5) Resilience-temperature curves for natural rubber, Neoprene-GN, Neoprene-YD, and Buna-S take the form of straight lines intersecting at 20° to 22.5° C. Neoprene-Z shows a similar effect with intersection at 30.5° C. and Hycar OR-15 similarly at 31.5° C. (6) Copolymers of butadiene and acrylonitrile show increasing modulustemperature coefficient, and in the region 10° to 20° C decreasing resilience with increasing acrylonitrile content. The resilience-temperature diagrams for these polymers, except Hycar OR-15, are smooth curves which appear to reach steady values towards the upper end of the temperature range. (7) Thiokol-RD appears to have a freezing-point, under the dynamic conditions employed, somewhere in the region of 15–20° C; there is evidence that Hycar OR-15 shows a similar effect between 0° and 10° C. (8) The relationships enumerated above refer to basic compounds of the various materials. How far the temperature effects may be reduced or modified by suitable compounding is the subject of continuing investigation.

Anelastic Behavior due to Interstitial Oxygen in SmBa2Cu3O7-δ

2006 ◽  
Vol 530-531 ◽  
pp. 557-561
Author(s):  
Rubens Maribondo Nascimento ◽  
Juliana Maria de Albuquerque Gimenez ◽  
Carlos Roberto Grandini ◽  
Alfredo Gonçalves da Cunha
Keyword(s):  
Internal Friction ◽  
Oscillation Frequency ◽  
Orthorhombic Phase ◽  
Precise Determination ◽  
Relaxation Processes ◽  
Interstitial Oxygen ◽  
X Ray Diffraction ◽  
Critical Temperatures ◽  
Thermally Activated ◽  
Relaxation Structure

The composite SmBa2Cu3O7-δ (Sm-123), obtained by the substitution of the ion Y for Sm in the very well known and studied YBa2Cu3O7-δ (Y-123), is potentially attractive for better understanding superconductivity mechanisms and for its applications as electronic devices. Sm-123 samples show higher critical temperatures than Y-123 ones do and a larger solubility of Sm in Ba-Cu-O solvent, which makes their growth process faster. When oxygen is present interstitially, it strongly affects the physical properties of the material. The dynamics of oxygen can be investigated by anelastic spectroscopy measurements, a powerful technique for the precise determination of the oscillation frequency and the internal friction when atomic jumps are possible. Anelastic spectroscopy allows determining the elasticity modulus (related to the oscillation frequency) and the elastic energy loss (related to the internal friction) as a function of the temperature. The sample was also investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), and electric resistivity. The results obtained show a thermally activated relaxation structure composed by at least 3 relaxation processes. These processes may be attributed to the jumps of oxygen atoms present of the Cu-O plane in the orthorhombic phase.

The Effect of Softeners in Rubber

1953 ◽  
Vol 26 (1) ◽  
pp. 152-155
Author(s):  
Ira Williams
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
High Modulus ◽  
Mineral Oils ◽  
Cohesive Forces ◽  
Commercial Use ◽  
Effect Of Solvents ◽  
Vulcanized Rubber ◽  
Unfavorable Effect ◽  
The Cost

Abstract The use of oils and liquid softeners to assist in the mastication and processing of rubber or to produce softer vulcanized stocks has been standard practice since the early commercial use of rubber. More recently certain synthetic rubbers, polymerized under special conditions, have been treated with rather large amounts of mineral oils, with a resulting decrease in the cost of the rubber and apparently with no unfavorable effect on the rubber in most instances. A number of investigators have reported the effect of swelling agents on the properties of vulcanized rubber. Busse discusses the effect of solvents in a general way. Tiltman and Porritt conclude that the decrease in modulus caused by swelling in benzene is caused by a “loosening of cohesive forces.” Tire treads of natural rubber containing such softeners as pine tar and mineral rubber decrease in wear resistance in proportion to the softener content. Well vulcanized rubber of high modulus is most resistant to swelling in oils. Naunton, Jones, and Smith find that unaccelerated stocks lose the most tensile strength after being swollen, that milling of the raw rubber increases swelling, and that the presence of softeners in the rubber during vulcanization reduces the oil resistance. A limited amount of swelling has been reported to have little effect on the tensile strength of vulcanized natural rubber. Bourbon points out that separating the rubber molecules with solvent decreases the rate of vulcanization.

Time and Stress Effects in the Behavior of Rubber at Low Temperature

1950 ◽  
Vol 23 (1) ◽  
pp. 54-66 ◽  
Author(s):  
J. R. Beatty ◽  
J. M. Davies
Keyword(s):  
Shear Stress ◽  
Low Temperature ◽  
Natural Rubber ◽  
Applied Stress ◽  
Dynamic Modulus ◽  
Rate Of Change ◽  
Rate Process ◽  
X Ray ◽  
Stress Effects ◽  
Rubberlike Materials

Abstract The stiffening of rubberlike materials at low temperature involves several different phenomena, sometimes with their effects superimposed. One of these is crystallization. This is a rate process which is generally very fast at high stresses and very slow at zero stress. In these experiments at temperatures near −25° C and under a shear stress of about 148 lb. per sq. in. the dynamic modulus of the rubber increased at a rate convenient to study. Correlation with x-ray data showed that crystallization was very likely responsible for the increase in stiffness. The rate of change of stiffness increased rapidly with increase in applied stress, and there was no optimum rate at −25° C, as has been found for unstressed rubber. The degree of vulcanization influenced the rate of change, tighter cures giving smaller changes. Neoprene-FR, GR-S, and polybutadiene, which ordinarily show little evidence of crystallization, showed very definite, but small increases in stiffness. Mixing GR-S with natural rubber seems to limit the crystallization of the natural rubber rather effectively, but apparently Neoprene-FR does not mix intimately enough with natural rubber to affect the crystallization of the latter appreciably.

Stress-Temperature Relations in a Pure-Gum Vulcanizate of Natural Rubber

1945 ◽  
Vol 18 (2) ◽  
pp. 367-379 ◽  
Author(s):  
Lawrence A. Wood ◽  
Frank L. Roth
Keyword(s):  
Natural Rubber ◽  
Constant Temperature ◽  
Considerable Importance ◽  
Tabular Form ◽  
Stress Strain ◽  
Time Relaxation ◽  
Relaxation Temperature ◽  
Straight Lines ◽  
Short Time

Abstract Stress-temperature relations at constant elongation have been investigated for a pure-gum vulcanizate of natural rubber. The rubber was first allowed to relax for about two hours at constant elongation and constant temperature to minimize the effects of short time relaxation of stress. The stress, except under special conditions, was changing very little at the end of this time. The stress-temperature relations for temperatures below the relaxation temperature could be represented by straight lines. The values of the slopes and intercepts of these lines are presented in tabular form. The stresses at the end of the relaxations were used as the basis of stress-strain curves. Crystallization was found to be an easily-recognized factor of considerable importance in the interpretation of the results.

Unsaturation of Synthetic Rubberlike Materials

1943 ◽  
Vol 16 (2) ◽  
pp. 280-285
Author(s):  
La Verne E. Cheyney ◽  
Everett J. Kelley
Keyword(s):  
Natural Rubber ◽  
Negative Influence ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Iodine Chloride ◽  
Cross Linkage ◽  
History Of ◽  
Interesting Correlation ◽  
Rubberlike Materials

Abstract The quantitative determination of rubber unsaturation has concerned numerous investigators. The use of iodine chloride as a reagent for this purpose (the well-known Wijs method) has achieved favor in recent years. Under the proper experimental conditions, addition has been shown to be quantitative, and substitution reactions can be kept at a minimum. This procedure has likewise been rather extensively employed as a measure of the residual unsaturation of various rubber derivatives. This reagent does not, however, add quantitatively to all unsaturated compounds, regardless of structure. The presence of a negative substituent on one or more of the unsaturated carbon atoms inhibits the reaction; in fact, it may entirely prevent it, as in the cases of maleic or fumaric acids or dichloroethylene. In other compounds extensive substitution may occur along with addition, as in the case of the unsaturated terpenes. The unsaturation of the polymerized diolefins should be of considerable interest, especially in comparison with natural rubber. It should be of special interest to study the comparative reactions with iodine chloride, which has become practically a standard reagent for rubber. Kemp and Mueller mention that polychloroprene, to which they erroneously refer as polyvinyl chloride, adds iodine chloride to only 30 per cent of theory. This could be due to two causes—the negative influence of the chlorine attached to an unsaturated carbon, and/or possible cross-linkage between chains (cyclization). It is well established that polychloroprene is much less reactive chemically toward other reagents than is natural rubber. It is unfortunate that Kemp and Mueller did not state with more detail the history of the sample studied, as such a result might have shown some interesting correlation with the experiments reported in this paper.

Determination of Tensile Strength of Natural Rubber and GR-S. Effect of Specimen Size

1949 ◽  
Vol 22 (4) ◽  
pp. 1125-1133 ◽  
Author(s):  
Takeru Higuchi ◽  
H. M. Leeper ◽  
D. S. Davis
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Specimen Size ◽  
Specimen Length ◽  
Tenfold Increase ◽  
Specimen Volume ◽  
Numerical Magnitudes ◽  
Rubberlike Material ◽  
Straight Lines

Abstract Peirce's equation, which relates observed tensile strength of textile fibers with their length, was found to be applicable to rubberlike material if specimen volume is used in place of specimen length. Experiments in which the tensile strengths of GR-S and natural rubber compositions were determined for a range of specimen volumes yielded results in close accord with theory. A tenfold increase in the volume of the material resulted in a decrease of 308 and 339 and of 204 pounds per square inch in the observed tensile strength of GR-S and comparable natural rubber stocks, respectively. The numerical magnitudes of the slopes of the straight lines obtained when tensile strengths were plotted against the logarithms of the relative specimen volumes are shown to bear direct relationships to the homogeneity of the stocks under test. The use of a dumbbell sample with a constricted center should result in a relatively simple means of measuring quantitatively the degree of homogeneity of rubber compositions.

DETERMINING MATERIAL PROPERTIES OF NATURAL RUBBER USING FEWER MATERIAL MODULI IN VIRTUE OF A NOVEL CONSTITUTIVE APPROACH FOR ELASTIC BODIES

2018 ◽  
Vol 91 (2) ◽  
pp. 375-389 ◽  
Author(s):  
A. Muliana ◽  
K. R. Rajagopal ◽  
D. Tscharnuter ◽  
B. Schrittesser ◽  
G. Saccomandi
Keyword(s):  
Experimental Data ◽  
Natural Rubber ◽  
Material Properties ◽  
Biaxial Loading ◽  
Uniaxial Stretching ◽  
Insignificant Change ◽  
Elastic Bodies ◽  
In Virtue Of ◽  
Rubberlike Materials

ABSTRACT We discuss the development of a method for the determination of the material properties of rubber and rubberlike materials within the context of a novel constitutive framework that has been put into place recently. The new constitutive framework leads to fewer material moduli than the models that are currently in vogue. We corroborate the predictions of our model against the experimental data of Treloar as well as Jones and Treloar for uniaxial and biaxial loadings and also with regard to new experimental results that have been generated by us for uniaxial stretching of natural rubber. We record both the axial and lateral responses of the specimens. This allows us to also examine the compressibility of the natural rubber specimens. Finally, we also characterize the response of compressible elastic bodies both under the assumption that the motion is isochoric, as the experiments suggest insignificant change in volume, as well as without resorting to such an assumption, when subjected to biaxial loading.

The Weber Color Test for the Identification of Natural Rubber

1945 ◽  
Vol 18 (4) ◽  
pp. 902-904 ◽  
Author(s):  
I. F. C. Parker ◽  
W. C. Wake
Keyword(s):  
Organic Chemistry ◽  
Positive Result ◽  
Natural Rubber ◽  
Natural Product ◽  
Color Test ◽  
Gutta Percha ◽  
Synthetic Rubber ◽  
Violet Color ◽  
Color Reactions ◽  
Rubberlike Materials

Abstract The Weber color reaction, mentioned in a recent note, has become of importance in detecting natural rubber in mixtures in which it may be considerably diluted with synthetic rubber or nonrubber materials. The detailed instructions for carrying out the test are given elsewhere, and Stern has published a table which shows also the colors obtained when the test is applied to rubbers other than the natural product. It is clear from this table, and is confirmed by our experience, that the strong violet color developed is distinctive for natural rubber and gutta-percha, provided that the material has been extracted with acetone. However, color reactions in organic chemistry are rarely found to be as specific as earlier workers have claimed, and work is being carried out in these laboratories to establish the limitations of the reaction when applied to rubberlike materials. With very few exceptions, synthetic rubbers and rubberlike materials available at present do not give a positive result with this test, although very faint violet colors, which cannot be confused with a positive result, are sometimes obtained. Those giving any violet color are listed in Table I.

Sign in / Sign up

Export Citation Format

Share Document