Many efforts have been made to study new reinforced materials to meet the increasing demands of various products. Hybrid cords have attracted a great deal of attention due to low cost and incomparable properties. Nylon and polyester are currently two of the most prevalent materials used as tire cords, while how to incorporate both of their desirable properties into one cord has been a meaningful scientific research. In this study, a new advanced polyester tire cord was developed by adopting the design of experiment. Its stress-strain curve demonstrated a high modulus typical for the standard polyester thus improving tire dimensional stability and handling performance and high breaking elongation up to 21.7% that was a favorable characteristic of nylon cord creating a hybrid effect. H-adhesion experiment showed that this advanced cord had comparable adhesion to rubber as the standard polyester tire cord and could be used for production of tires.
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.
Design of experiments was adopted to evaluate the effect of selected test parameters on the viscoelastic behaviors of polyester tire cords through dynamic mechanical analysis systematically. Design of experiments results showed that temperature, static load, and dynamic amplitude had significant effects on the responses of complex modulus (E*) and Tan δ. Furthermore, temperature had significant interactions with static load and dynamic amplitude factors on the responses. None of the test parameters had any significant effect on the response of glass transition temperature (Tg). Below Tg, thermoplastic tire cords exhibited a high and constant dynamic modulus, whereas, beyond this point, the modulus decreased dramatically. The thermosetting tire cords exhibited a constant performance due to an ordered and tight molecular chain arrangement. The magnitude of Tan δ reached its peak value at Tg due to the increase in internal friction as a result of increasing temperature. The dynamic modulus increased and Tan δ decreased with the increasing static load as a result of restricting the mobility of chain segments. The reverse was true when the dynamic amplitude increased, most probably because of higher chain segment mobility and early stage of polymer chain slippage. Activation energy (Ea), derived from Arrhenius equation, can be used to predict its long-term performance. Tg shifted to a higher temperature as the frequency increased. In addition, by increasing the twist level of the polyester tire cord, the dynamic modulus decreased and Tan δ increased. Tg was evaluated as the upper limit working temperature, Tan δ was related to energy dissipation, and E* determined the overall performance of the tire cord. By displacing Tg to a higher temperature, reducing the magnitude of Tan δ and increasing the dynamic modulus are of great importance to a tire cord’s performance.
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