Dynamic Properties Of Elastomers Research Articles

Predictive model of dynamic properties of elastomers in thermal degradation environment

In dynamic systems, numerous structural components, such as mounts, bushings, and tires, deteriorate over time due to environmental conditions. In these elastomers, the typical environmental factor of aging is manifested by the oxidation of polymer chains due to exposure to air. The amount of oxidation in elastomers heavily depends on temperature. Elastomer components under thermal degradation show different dynamic characteristics over time. Predicting the mechanical properties of aged elastomers is crucial in structural design for enduring high-quality noise and vibration. In this work, we propose a procedure for predicting the dynamic properties of elastomers undergoing thermal degradation. This process is divided into 1) an inter-variability analysis in specific degradation states caused by uncertainties in the operational temperature environment, variation in the manufacturing process, and error of the material property model and 2) an analysis of the degradation variability caused by uncertainties in the degradation environment and the degradation model. The degradation variability includes the inter-variability and thus becomes a distribution of distributions. Therefore, the double-loop eigenvector dimension reduction method is proposed to predict degradation variability. The time–temperature superposition principle and an equivalent degradation time are introduced to accumulate the degradation states in case of thermal degradation at various temperatures. The proposed method is applied to a circular mount problem. The numerical results illustrate that the proposed method effectively predicts the aging of the dynamic elastomer properties that is due to the thermal environment.

The influence of a fluoroorganic modifier—stillage residues of alcohol-telomeres—on properties of filled poldienurethanes

The results of an investigation of the influence of stillage residues of polyfluorinated alcoholtelomeres on the properties of polydienurethane compositions and elastomers based on them are presented. It is shown that such modification allows one to raise the sedimentation stability of the compositions and increase the characteristics of physicochemical and dynamic properties of elastomers.

Dynamic properties of elastomers after water immersion

AbstractVulcanized bromobutyl, natural and nitrile rubbers were immersed in distilled water, or seawater, at 20, 40 or 60°C for up to 32 weeks and the resulting changes in weight and dynamic mechanical properties were monitored. Larger weight increases were observed for the specimens immersed in distilled water than for the equivalent specimens in seawater, and there was no sign of an equilibrium weight uptake being reached for the specimens immersed in distilled water at 60°C. Bromobutyl rubber showed increases in the magnitude of the loss tangent peak which could be related to the weight increases in both distilled water and seawater but the decreases in peak height observed for natural rubber and nitrile rubber were not well correlated with weight increases.

Materials Characterization in the Design of Castable Polyurethane Parts

Some of the important static and dynamic properties of elastomers will be examined and some examples will be given to show how they were prioritized in the development of specific applications

Distribution functions in elasticity

AbstractThe formation of a gel or elastomer entails the linking together of molecules to form a contiguous random network that has macroscopic dimensions. Forces are propagated in networks along polymer chains and through junctions to other chains. It is important to understand the structure of the force constant matrix that describes a system as complicated as this, even in the case where the potential energy is approximated by a simple harmonic function. This force constant matrix was first formulated by James, but because it is a large random matrix, very little progress can be made in the analysis of its properties. We have opted to approach this problem with the use of large scale computations that are based upon simulations of the formation of networks. Subsequent evaluation of the eigenvalue spectrum of the matrix lends considerable insight into the equilibrium and dynamic properties of elastomers. For present purposes this analysis is couched in terms of the calculation of the probability distribution of the gyration tensor for a phantom network in which non‐bonded interactions are not considered.

Dynamic properties of elastomers containing a random distribution of nonspherical inclusions

A self‐consistent multiple scattering theory will be employed to study the frequency‐dependent complex material properties of elastomers containing a random distribution of nonspherical inclusions. It has been found that “superviscous” damping can be achieved by exciting resonances of the inclusions by a judicious choice of matrix and filler properties, filler size, geometry, and frequency of the wave. Numerical results will be presented for various shapes, material properties and orientations of the inclusions and compared with some available experimental results.

Determination of dynamic properties of elastomers over broad frequency range

Support excitation of a small spring-mass system, consisting of a massm and two thin wafers in shear, is used as a simple and reliable method to determine the dynamic properties (storage-modulus and complex-modulus loss factor) of elastomeric materials over a fairly broad frequency range. No special equipment or instrumentation is required since ordinary vibration equipment is used. Microminiature accelerometers are used to monitor the support and mass accelerations which eliminates the measurement of small forces and displacements. The frequency range of interest over which experimental data can be obtained fromone specimen can be varied by the thicknessh of the elastomeric waters and/or the size of the massm. The method discussed has been used to determine the dynamic properties of a wide variety of elastomers with frequencies as high as 6000 Hz. Typical results demonstrating repeatability of the method are shown for a carboxyl-terminated butadiene acrylonitrile (CTBN) specimen over the frequency range of 500–3000 Hz. The small test setup is easily adaptable for use in small temprature-controlled chambers for temperature/frequency studies of elastomers. The mathematical model developed for reduction of experimental data is based on the complex shear modulus for the damping model of the elastomer where the spring-mass system is subjected to support excitation.

The Effects of Strain and Temperature on the Dynamic Properties of Elastomers

This paper presents the results of a program of analysis and tests to determine the dynamic, properties of elastomers as a function of strain and ambient temperature. Measurements were also made to determine the temperature distribution in the elastomer samples during the tests. These measured properties were compared with analytical predictions based on a visco-elastic model designed to take into account the self-heating of the materials as a function of strain. The test method used was well-established Base Excitation Resonant Mass Technique. The specimens tested were two cylindrical button compression specimens and a shear specimen. One of the compression specimens was instrumented with thermocouples embedded in several of the elastomer samples to provide information relative to the temperature distribution in the samples. Tests were performed for strains from 0.0005 to 0.08. The ambient temperature ranged from 32°C to 80°C. Strain was shown to be an important parameter in determining the dynamic properties of the elastomers. In general, these properties were much more sensitive to strain than to frequency. The self-heating effect was found to account for a portion of the strain sensitivity of these properties.

The dynamic properties of elastomers above the limit of linear viscoelastic response

AbstractA method of measuring the dynamic viscoelastic properties of polymers at large strain magnitudes, well above the limit of linear viscoelastic response, has been developed. A straight line relationship has been found between the dynamic stress and the dynamic strain above the limit of linear viscoelastic response. This straight line relationship can be described by a dynamic in‐phase modulus that is a function of the maximum strain applied and the frequency of the applied dynamic strain. This rheological characterization method is demonstrated for a series of synthetic elastomers with various carbon black loadings.

Adaptation of the Rheovibron to the Measurement of Dynamic Properties of Vulcanizates at Elongations up to Sample Rupture

Abstract The Rheovibron dynamic tester can be adapted to the measurement of dynamic properties of elastomers at high deformations, up to sample rupture. The method used is superimposing small sinusoidal oscillations on statically extended specimen. In order to obtain significant dynamic data it is necessary to determine the value of Kc exactly, the correction factor for instrumental displacements, as well Kv, to correct for the deformation of the part of the specimen held within the clamps. It appears that Kv is dependent on amplitude, frequency, temperature, and sample characteristics and must be determined for each sample at each imposed condition separately. At higher extensions Kv corrections assume a major ro^le in the measurements, greatly complicating the procedures. The method for calculation of the correction factors advanced by Massa for glassy polymers does not hold for elastomers. A novel specimen arrangement has been developed, resulting in a zero Kv correction, independent of amplitude, frequency or temperature. With elastomers the Kc correction is generally also zero, leading to greatly simplified measurements as well as to more accurate results. The temperature control system of the Rheovibron was modified to permit specimen temperatures in the range of − 70° to +120° C, either at programmed increases or decreases or at any constant temperature in the range. The movement of the extension clamp was motorized, to ensure a regular, reproducible motion.

Temperature Dependence of Dynamic Properties of Elastomers. Relaxation Distributions

Abstract By the use of reduced variables, the temperature dependence and frequency dependence of dynamic mechanical properties of rubberlike materials can be interrelated without any arbitrary assumptions about the functional form of either The definitions of the reduced variables are based on some simple assumptions regarding the nature of relaxation processes. The real part of the reduced dynamic rigidity, plotted against the reduced frequency, gives a single composite curve for data over wide ranges of frequency and temperature; this is true also for the imaginary part of the rigidity or the dynamic viscosity. The real and imaginary parts of the rigidity, although independent measurements, are interrelated through the distribution function of relaxation times, and this relation provides a check on experimental results. First and second approximation methods of calculating the distribution function from dynamic data are given. The use of the distribution function to predict various types of time-dependent mechanical behavior is illustrated.

Dynamic Shear Properties of Rubberlike Polymers

Abstract A simple apparatus for determining the dynamic properties of elastomers in shear at audio frequencies is appraised. Typical values of shear modulus and viscosity for several elastomers are given, both at room conditions and at 150° F. The frequencies of test range from 100 to 5250 cycles per second, the shear moduli from 0.5×106 to 480×106 dynes per sq. cm. and the viscosities from 20 to 75,000 poises.