Tensile deformation and morphology changes in segmented elastomer films and fibers including mechanical property modeling

• Published in: Journal of applied polymer science 2020-11, Vol.137 (43), p.n/a
• Main Authors: Sauer, Bryan B., Kampert, William G.
• Format: Article
• Language: English
• Subjects: Birefringence; crystallization; Elastomers; Fibers; Materials science; Mechanical hysteresis; Melting; Modelling; Morphology; Polyamide resins; Polymers; Properties (attributes); Strain hardening; Strain rate; structure‐property relationships; Temperature dependence; Tensile deformation; Tensile tests; theory and modeling; thermal properties
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.49315

Segmented polyether soft segment (SS) elastomers with different hard segments (HS) in film and fiber form were studied by birefringence, DSC, and tensile tests. To understand the morphological contributions to property differences, high resolution tapping AFM resolved ribbon‐like highly anisotropic hard domain (HD) lamellae in low modulus Pebax (polyamide 12 HS) and polyetherester (PEE), films, while lower HS content high melting poly(urethane urea) (PUU) had much smaller less anisotropic but higher melting HDs, explaining its enhanced thermal and mechanical hysteresis properties. Stress–strain tensile data demonstrate the excellent strength and toughness of PUUs and some spun PEE fibers, and film and fiber birefringence data applied during strain cycling up to very high stresses provided the molecular basis for the varying properties. The parameters from non‐Gaussian fits of tensile data provide insight into network properties for these systems exhibiting very high strengths and a large degree of strain hardening. Modeling of PEE and Pebax films also shows the effects of substantial plastic yielding of the HD networks. Tensile data were obtained as a function of strain rate and temperature to help understand the contributions of network restructuring and other factors. For fibers, strain rate data spanning seven decades show and unusual drop in strengths at very high strain rates. Temperature‐dependent tensile data also show large differences between PUU materials versus lower melting PEEs. Tapping‐mode AFM data for film surfaces of three solvent cast segmented elastomers with polyether soft segments, and one hard biaxially melt‐oriented PET film. The pebax and polyetherester (PEE‐B) samples have hard segments consisting of PA12 and PBT, respectively. PUU‐A is a low hard segment polyureaurethane with aromatic MDI based hard segments. Scan boxes are 500 × 500 nm for each plot, and the phase angle range is 0–20°.