Structure-property relationships and constitutive viscoelastic behaviors of polyether-block-amide elastomers in melt and solid states

Abstract

In this study, effects of copolymer composition on the structural, thermal, and viscoelastic properties of segmented multi-block polyamide elastomers (PEBAX (R) 3533, 5533, and 6333) and polyamide-12 (PA12) were quantified by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, and dynamic mechanical analysis (DMA) methods and rheological measurements. Soft segment, poly(tetramethylene oxide) (PTMO), contents of copolymers were proved by FTIR analysis. It was found that the increase in PTMO content dramatically reduced the crystallization and melting temperatures and degree of crystallinity values of copolymers. Different rheological test protocols performed in melt state revealed that zero shear rate viscosity values of polyamide elastomers increased with the increasing amount of hard segment. On the other hand, increase in hard segment content yielded lower flow activation energy value. In this study, we mainly focused on understanding quantitative relationships between block copolymer structure and their rheological behaviors and found that the soft segment content of similar to 40 (mole %) is the critical point for changing the rheological behaviors of block copolymer PAEs, dramatically. DMA measurements implied that the solid-state viscoelastic behaviors of samples were governed by the hard content of copolymers. Higher hard content decreased long-term creep strain and creep rate.