Properties Of Tire Cords Research Articles

Study of thermomechanical properties of hybrid tire cord

Thermomechanical properties of tire cords, which have a considerable influence on tire functions, were investigated in the current research. The nylon and polyester cords are the most commonly used polymers in the tire. Many efforts have been made to produce a new tire cord having the capability of integrating the desired properties of these two polymers into one cord. In this study, a new cord structure was developed using nylon 6,6 and polyester tire yarns. The effect of thermal treatment was studied at the temperatures of 180°C, 200°C, and 220°C under two different loads of 600 and 1800gf on thermomechanical properties of the nylon 6,6/polyester hybrid tire cord. Shrinkage and shrinkage force as thermal properties, as well as static and dynamic mechanical properties, were investigated. The relationship between the aforementioned properties and variation in the crystal structure and fiber orientation obtained from Differential scanning calorimetry (DSC) and Wide‐Angle X‐Ray Scattering (WAXS) analysis were examined too. The results showed that the higher tension leads to the higher initial modulus and storage modulus due to the crystallization of polymers during heat treatment. The shrinkage and shrinkage force also increased, as the tension increased. In addition, a decrease in residual shrinkage and shrinkage force were acquired because of an enhancement in the temperature.

Study on dynamic mechanical properties of a nylon-like polyester tire cord

Tires might be the first technically significant composite out of rubber and play a vital role in the overall performance of a car. The essential functions of a tire rely to a great extent on the properties of tire cords. Polyester and nylon cords make up the majority of synthetic fibers used in tires. A new kind of polyester cord has been developed combining the performance characteristics of both polyester and nylon cords. This article examines the dynamic mechanical properties of this nylon-like polyester tire cord by adopting dynamic mechanical analysis, Instron, and DISC fatigue experiments, as well as its dynamic adhesion property using flex fatigue experiment. It demonstrated that the dynamic complex modulus of the nylon-like polyester cord was higher than that of nylon 6 cord but lower than that of standard polyester cord, which was a favorable characteristic when it came to replacing nylon 6 cord with nylon-like polyester cord in tires. Under cyclic loading, hysteresis loss of nylon 6 cord > nylon 66 cord > nylon-like polyester cord > standard polyester cord was observed. In the DISC experiment, nylon-like polyester had a similar compression resistance property to that of nylon 6 cord. At a temperature below 85°C, nylon-like polyester cord maintained roughly the same level of residual ratio of dynamic adhesion, but beyond this temperature point, nylon 6 exhibited a better performance.

Assessment of the compressive and tensile mechanical properties of materials used in the Jaipur Foot prosthesis.

Designed by Dr. Sethi, the Jaipur Foot prosthesis is ideally suited for amputees in developing countries as it utilizes locally sourced, biodegradable, inexpensive materials and is focused on affordability and functionality. To date, however, no data have been reported on the material properties of the foot components. The goal of this work was to evaluate mechanical properties of the Jaipur Foot components to guide foot design and manufacturing and reduce weight. Experimental. Mechanical testing was conducted on two types of woods (ardu and cheed), microcellular rubber, tire cord, cushion compound, tread compound, and skin-colored rubber. Each material was subjected to testing in either tension or compression based on its location and function in the foot. Samples were tested before and after vulcanization. Two-sample t-tests were used to assess statistical differences. Cheed compressed perpendicular to the grain had a significantly higher modulus of elasticity than ardu ( p < 0.05); however, cheed had a higher density. Vulcanization significantly increased the modulus of skin-colored rubber, cushion compound, and tread compound ( p < 0.05) and decreased the moduli of both microcellular rubber and tire cord ( p < 0.05). The material property results from this study provide information for computer modeling to assess material construction on overall foot mechanics for design optimization. Ardu wood was ideal based on the desire to reduce weight, and the tire cord properties serve well to hold the foot together. Clinical relevance With new knowledge on the material properties of the components of the Jaipur Foot, future design modifications and standardized fabrication can be realized, making the Jaipur Foot more available on a global scale.

Material Characterization of Tire Cords and the Effects of Cord Thermal-Mechanical Properties on Tires

Abstract Thermal-mechanical properties of tire cords have a great influence on tire dimension, shape, handling, and other performance related issues. This study focuses on characterizing the material properties for polymeric cords and quantifying their effects on pneumatic tires using finite element analysis (FEA). Various tire cord materials, including nylon and polyester, were characterized by obtaining a series of thermal-mechanical properties in the laboratory using tensile testing, thermal shrinkage measurement and creep testing. Prior to obtaining these laboratory measurements, cords in this study were subjected to thermal-mechanical pre-treatments to simulate the effects of curing and tire operating conditions. The properties derived from these measurements were used as input properties for a finite element analysis of a physical tire. Predictions of tire dimensions and shape, loaded footprint and pressure and cord loads were obtained from the FEA model and compared to measured values of the experimental tire. Good agreement was observed between the measured values and those predicted from the finite element analysis; therefore, future FEA studies of pneumatic tires should utilize the techniques developed in this study to characterize tire cord materials.

Thermal Properties of Tire Cords and their Effects on Post-Curing Inflation of Tires

Abstract We simulated tensile properties of several heat-treated tire cords in a laboratory in order to know the carcass cords' properties in post-curing and non-post-curing inflated tires. We also compared the tensile properties of the simulated cords with those of carcass cords in tires and examined an optimum post-curing inflation condition. After curing tires, EASL (Elongation At Specified Load) of carcass cords in tires was higher than that of raw cords. Following the curing, the EASL decreased orderly depending on post-curing inflation time. Tensile properties of carcass cords in non-post-curing inflated tires were almost the same as compared to those of fully relaxed cords by heating at a curing temperature. Post-curing inflation had an effect on increasing modulus of carcass cords in tires. The effect can also be significant when tires are cooled down to glass transition temperature of the carcass cords.

Heat Generation in Pneumatic Tires

Abstract A review of the entire literature on heat generation in tires shows that, while a considerable number of articles have reported the effect of running conditions, only the few cited here have provided clarification of the causes of heat generation. The overview presented here also has limitations in some respects, especially in that all the reported regression equations (except those for radial passenger car tires) have a large residual term. This is due to the scattering of the test results and the fact that only the viscoelastic properties of the tread and carcass stocks were varied, but not the tire cord and the other vulcanizates used. Tire cord properties have fixed properties, as far as the tire specialist is concerned and cannot be changed. A further regret is that almost all the investigations were carried out on laboratory test wheels, so that no experimental findings obtained from tires run on the road are included. This is so because road experiment conditions are difficult to make reproducible. On the whole, one can expect that the reported results would be qualitatively valid for tires run on the road, but the differences among different tire designs would probably not be as great, while surface friction effects would be more significant. Moreover, though the tire test parameters were different in the different laboratories, they remained constant in each test. No attempt was made to establish dependence on the load (except by Wesche), the internal pressure, the speed, the radius of the test wheel, etc., because each individual tire specialist is confronted, within his own development team, by certain standardized test conditions. The tires have to reach a sufficiently long running time under these conditions. Hence, they may not exceed certain limiting temperatures. Modifications of such requirements were not included in the scope of the present series of experiments. Almost all the authors took test samples for the measurement of viscoelastic properties from the tires, since correlations with laboratory-prepared test pieces were usually poorer. Nevertheless, in the course of compound development the tire chemist is forced to rely on laboratory test specimens and must establish relations to their properties. Consequently, the causes for the differences have to be elucidated for each individual case. In spite of these limitations, the state of the art, as presented here, permits reliable estimates to be made of the changes in tire running temperature that are caused by given changes in the recipes of the tire component stocks.

Viscoelastic properties of tire cords

AbstractThe viscoelastic properties of commercial rayon, nylon 66, and poly(ethylene terephthalate) tire cords have been investigated by dynamic mechanical techniques using the Vibron viscoelastomer DDV‐II. The effect of temperature, humidity, and geometric structure on the viscoelastic response has been determined for the tire cord assemblies. Subsequently, the underlying mechanisms and the polymer and fiber structural factors which influence them are discussed. Also, the consequences of the cord properties on tire hysteretic characteristics are discussed. This enables tires to be designed to meet specific service requirements. Characterization of materials in this way is becoming more important, particularly as the performance demands on tires become more stringent.

Tire Cord Application of High-Modulus Fibers Derived from Polyamide-Hydrazides

Abstract Recent developments in tire design have focused interest on new combinations of properties for fibers to be used in tire cords. Different fiber properties are of importance depending on whether the end use is in bias design, breaker belts, or radial design. X-500 class fibers of polyamide-hydrazides can be produced with a range of property combinations. The textile-like fiber with good tenacity, extensibility, and modulus similar to presently used organic fibers has advantages of greater dimensional stability and heat resistance. The high modulus variant shows better flex life, abrasion resistance, and water resistance than glass. X-500 class fibers can be made stronger and stiffer than glass or steel—when compared in textile units. Data, presented show typical prototype X-500 tire cord properties in the greige and the heat-treated form. Experimental tires were made using a polyamide-hydrazide X-500 fiber in the belts of radial and bias constructions. Nylon 66 and polyester were used in the carca...

Correlation of Nylon Tirecord Properties with Tire Flatspotting

The theory of flatspotting in tires is reviewed and found to be in essential agreement with that given in earlier publications. The importance of cord moisture content (humidity), temperature, and dynamic response rate in affecting the flatspotting per formance of tirecords is emphasized. Two methods are discussed for favorably altering the viscosity-temperature relationship of nylon tirecords: (a) incorporation of moleculea of bulky groups along the polymer chains (achieved through blending with other poly mers), and (b) plasticization. A new, dynamic flatspot cord testing machine is described which permits close simulation of tirecord stress cycles that duplicate the flatspotting phenomena under various cord moisture contents (humidity test atmospheres) corre sponding to both summer and winter driving conditions. Good correlation is obtained between the laboratory test results and tire results. Applications of the test machine in screening prospective low flatspotting tirecord materials is discussed.

A flywheel impact test for measuring physical properties of tire cords

AbstractThe development and operation of a dynamic tire cord testing apparatus is described. The apparatus consists of a rotating wheel which applies a transverse load to a tire cord and carries it to break. It can be operated at speeds which impact tire cord at velocities of from 10 to 80 ft./sec. The techniques used for detecting, recording, and calculating energy load‐elongation characteristics and time to break are described. Some data showing the effect of impact velocity on the physical properties of nylon, rayon, and polyester tire cords are presented.

STUDY ON DYNAMIC VISCOELASTIC PROPERTIES OF TIRE CORDS

Dynamic viscoelastic properties in relatively low amplitude (0.30% elongation) and low frequency (1.21 c. p. s.) have been measured for several tire cord samples prepared under various spinning conditions and also various twisting conditions. The results are discussed in connection with the internal structures of the individual filaments and also with the cord structures. The following. observations are made:1) The frictional properties of the filaments are varied by changing the oiling treatment. However it was found that the frictional properties has very minor effects on the overall viscoelastic properties measured under these conditions.2) The cord structure was controlled by changing the number of twists and also the procedure of twisting. Apparently the properties of tire cords are governed exclusively by the cord structures.3) The internal structure of filaments, determined by the combinations of factors such as crystallinity, size of crystallite, degree of orientation, contribute strongly to the cord structure. Thus, even the same number of twists and the identical proceedure of twisting were applied, the cord structures were markedly different depending upon the properties of individual filaments used. As the results, it was found difficult to isolate the direct effects of internal structures of individual filaments on the final viscoelastic properties of cords, because of the strong interposition of the effects of cord structures on the properties in the low amplitude.

Tire Testing

The use of tire tests for fiber characterization in research programs aimed at the development of improved tire yarns is discussed. Examples are included to demonstrate some of the factors which influence tire impact, fatigue, and heat resistance. The test results can be generally related to specific tire cord properties, thus defining the areas in which research should be concentrated.

Effect of a Dynamic Fatigue Test on the Mechanical Properties of Tire Cords

Changes in the mechanical properties of cords subjected to dynamic fatigue were measured for cotton, mercerized cotton, and rayon tire cords. These data were obtained by the use of an instrument which subjected the cords under tension to localized dynamic forces under con trolled atmospheric conditions. The forces, when observed on an oscilloscope screen, were found to vary during the flex cycle. Flex life and ultimate elongation were found to be cumulative, regardless of whether the cords were fatigued continuously or were allowed to relax with or without static tension between periods of flexing. Calculated activation energies for fatigue failure were less than those for heat degradation. From the differences in properties a quali tative evaluation of tire cord behavior could be made.

Hysteresis and Related Elastic Properties of Tire Cords

A method of evaluating mechanical hysteresis, elastic modulus, elongation, and growth rate of a yarn or cord subjected to cyclic loads in a fatigue test is described. The test is applied to seven typical tire cords-one Nylon, two rayon, and four cotton cords including both high stretch and low stretch cords. Results are presented showing the effect of cycle number, moisture content, temperature, and load range on the elastic properties of each of the cords tested. The influence of cyclic loading on the stress-strain curve is also discussed. It is concluded that moisture content is the dominant factor influencing the elastic properties of tire cords and that the heat produced by mechanical hysteresis of the tire cord contributes appreciably to the heat build-up observed in tires during heavy duty service.

The Effects of Temperature and Humidity on the Physical Properties of Tire Cords

Abstract It may be concluded from the foregoing experiments that measurements of tenacity and stretch at a single relative humidity have little meaning, since the important variable, moisture content, decreases rapidly with increasing temperature. The most revealing representation of tenacity or elongation appears to be as a function of temperature at constant moisture regain. Curves of this .type show that the tenacity of a modern viscose rayon cord decreases with increasing temperature in the range of regains 0–5 per cent. The same general behavior is exhibited by low-stretch cotton cord, but the tenacity vs. temperature curves for medium-stretch cotton cord flatten off at temperatures above 100° C. The tenacity of Fortisan cord decreases rapidly with temperature up to 100° C, and then increases slightly between 100° and 165° C. Nylon cord shows a rapid decrease of tenacity with increasing temperature, but maintains its advantage in tenacity over that of rayon for all temperatures and humidities included in these experiments. For any given temperature, increase of moisture content increases the tenacity of the cotton cords to an extent dependent on the “stretch” of the cord; decreases the tenacity of rayon cord. Fortisan increases in tanacity with increasing moisture content in the lower range of moisture contents (like cotton) and then decreases in tenacity for higher moisture contents (like rayon). The tenacity of Nylon decreases very slightly with increasing moisture content. All of the cord materials investigated, cotton, rayon, Fortisan, and Nylon, increase in stretch (10-pound or ultimate) as the moisture content increases. The effect of temperature at constant regain on stretch, however, is rather complicated. Until a method of measuring stretch with the whole cord continuously within the testing chamber is devised, further conclusions would be unjustified. Analyses of the creep characteristics of the various cord materials on the basis of two arbitrarily defined indices “initial compliance” and “weighted creep” yield several basic facts: The low-stretch cotton cord exhibits lower values of both indices compared to medium-stretch cotton, as might be anticipated from tensile measurements. The rayon cord, however, has a much lower “initial compliance” but a definitely higher “weighted creep,” compared to the low-stretch cotton. The Fortisan cord is comparable in “weighted creep” to low-stretch cotton, but has a much lower “initial compliance”. The Nylon cord has an “initial compliance” approaching that of low stretch cotton, but a much higher “weighted creep”, which is equal to or greater than that of rayon. The elongation increment vs. logarithmic time curves for cotton, rayon, and Fortisan are very nearly linear over the period 0.002–20 hour, but those for Nylon show a tendency to increase in slope at times beyond 1 hour. In conclusion, it may be said that the results of these experiments agree very well with current concepts of the structures of cotton, rayon, and Nylon, and have rather interesting implications in regard to the structure of Fortisan. It is well to remember that a complete evaluation of a tire cord should include dynamic fatigue measurements as well as tensile and creep data. The complicated nature of the fatigue problem, however, necessitates an extended separate discussion which is beyond the scope of this paper.

A Comparison of Some Elastic Properties of Tire Cords

Additional information concerning the elastic properties of tire cords is needed since the present criteria involving breaking strength and elongation are considered insufficient to enable prediction of tire cord performance. The elastic behavior of Nylon, of rayon, and of unstretched and stretched cotton tire cords are compared with respect to their rates of elongation during measurement of the stress-strain curves and their elongation under static loads at various temperatures between 25° and 200°C. Elongations under the influence of cyclic loads are shown for cotton and rayon cords, and an apparatus for determining mechanical hysteresis of tire cords during cyclic loading is described. The temperature and moisture content of the cord are shown to have considerable effect upon its elastic properties.

The Effects of Temperature and Humidity on the Physical Properties of Tire Cords

Apparatus by means of which tire cords may be conditioned and tested at elevated humidities (1.6–65 percent R. H.) and temperatures (20–165°C) is described. The apparatus consists of a portable conditioning unit which is used with a standard tensile testing machine. Equipment for measuring creep of tire cords under dead load at elevated temperatures is also described. Five representative types of tire cord were employed in the experiments, medium stretch cotton, low stretch cotton, viscose rayon, Fortisan, and Nylon. Tenacity, ``10 pound-stretch,'' and ultimate stretch are studied as functions of relative humidity, temperature, and moisture regain. It is shown that the tensile properties are best represented as functions of temperature at constant regain. The tenacity of viscose rayon cords decreases with increasing temperature at constant regain in the range of regains 0–5 percent. The tenacity of the medium stretch cotton cords at constant regain falls off with increasing temperature in the range of 20–100°C and then changes very little up to 165°C. That of the low stretch cotton cords, however, decreases in a manner similar to that found for rayon. The Fortisan cords show a decrease of tenacity in the range 20–100°C and then a slight increase for higher temperatures. The cotton, rayon, and Fortisan cords give nearly linear creep curves (elongation vs. log time) in the range of creep times 0.002 to 20 hours. The creep curves for Nylon show a tendency to increase in slope at extended creep times. The creep data are analyzed in terms of two arbitrarily defined indices, ``initial compliance'' and ``weighted creep.'' Both the tensile and creep characteristics are discussed from the viewpoint of current theories of structure and also in the light of their relations to serviceability in tires.