A study on the viscoelastic behaviors of tire cords using dynamic mechanical analysis. (May 2020) - Tian, Liyong
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.