Evaluation of effects of molecular chain structure and crystallinity on mechanical properties of polyamide by finite element method using transient network model

Abstract

Polyamide (PA) is a semi-crystalline polymer in which main chain is configured by repeating units of amide bonds (-NHCO-). The strength of PA is achieved by intermolecular hydrogen bond between hydrogen and oxygen atoms of amide bonds. In this study, the effects of the crystallinity and crystallite size were investigated by uniaxial tensile tests of commercial PA6 and PA-MXD10. Furthermore, the time-dependent nonlinear mechanical model based on the transient network model was proposed to predict the mechanical behavior of PAs with different crystallinities. From experimental results, the stress-strain curves of the PAs with small crystallinity showed the sharp drop after the maximum stress and the necking occurred due to local deformation. In contrast, near the maximum stress of PA with large crystallinity, a gradual change in stress was observed, and the local deformation was suppressed. Simulation results indicated that the modified transient network model can predict the mechanical behavior of PAs with different crystallinities.