Strain hardening in glassy polymers: Influence of network density on elastic and viscous contributions

ABSTRACT In this study, the rate‐ and temperature‐dependent strain hardening and the Bauschinger effect is studied for three glassy polymers. It appeared that for all materials, an equal distribution of elastic and viscous hardening was necessary to accurately predict the Bauschinger effect, as well as the rate‐ and temperature‐dependent strain hardening response. As for the elastic contribution, the viscous contribution appears to increase with an increase in entanglement network density. Investigating the effect of temperature on the Bauschinger effect revealed that at elevated temperatures the model predictions are not accurately enough. It is shown that this is caused by the magnitude of the elastic hardening contribution; to improve the predictions, a temperature‐dependent elastic contribution is necessary. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1001–1013 Strain hardening was initially modeled using rubber elastic models. However, there are many arguments against a purely elastic description; therefore, recent improvements of the strain hardening models were sought in a, more appropriate, combination of elastic and viscous process. In this article, the effect of entanglement density on the elastic and viscous contributions was studied; like the elastic contribution, the viscous contribution increases with an increase in entanglement density.