Direct Observations on Structure Evolutions in Polyamide 6 During Deformation at High Temperatures with WAXS and SAXS

The deformation induced structure evolutions of polyamide 6 (PA6) during uniaxial tension at high tensile temperatures (60 °C and 90°C) were investigated with in situ wide‐ and small‐angle X‐ray scattering (WAXS and SAXS) technologies. The obtained data on structure evolutions revealed that they were different from the results measured at low temperature (30 °C). The α‐phase got oriented once upon the beginning of deformation. After yielding the γ‐phase started to be oriented following the α‐phase. While, the breakdown of PA6 crystals along a and c axis overcame partial crystalline orientation at the high tensile temperatures (60 and 90 °C). The competition between stretch of amorphous phase and slippage of lamellae after yielding affected the deformation behavior of PA6. The collapse of lamellae was also confirmed from SAXS analysis and such disrupted lamellar structure resulted in the decrease of long spacing of PA6. The results showed that PA6 materials may show higher ductility at high temperatures. Therefore the crystals could be broken more easily and the formed lamellar fragments of PA6 could be preserved at larger strain at 90 °C. In addition, the yielding of PA6 and γ‐phase orientation depended on the lamellar slippage during the deformation. POLYM. ENG. SCI., 60:581–586, 2020. © 2019 Society of Plastics Engineers