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Morphological Changes under Strain for Different Thermoplastic Polyurethanes Monitored by SAXS Related to Strain at Break
Author(s) -
Stribeck Almut,
Li Xuke,
Zeinolebadi Ahmad,
Pöselt Elmar,
Eling Berend,
Funari Sérgio
Publication year - 2015
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201500255
Subject(s) - small angle x ray scattering , materials science , thermoplastic , composite material , ultimate tensile strength , strain (injury) , volume fraction , extrapolation , thermoplastic polyurethane , thermoplastic elastomer , scattering , polymer , elastomer , mathematics , optics , physics , medicine , mathematical analysis , copolymer
In tensile tests of six different hand‐cast thermoplastic polyurethanes (TPU) with a hard‐segment content = 0.51, the volume fraction of hard domains ( v h ) has been tracked. The materials exhibit a linear increase up to a strain of ≈0.5 (strain‐induced phase separation). Thereafter a linear decrease of v h is indicated. When stretched by 100% about 25% of the initially present hard domains are destroyed. The extrapolation to v h = 0 is close to the elongation at break. Characteristic materials parameters are suggested by the found relation. The tests (maximum strain: 3) are monitored by small‐angle X‐ray scattering. The morphology is closer to particle scattering than that of machine‐processed material. Therefore the longitudinal scattering appears fittable by a 1D statistical model that separates the weak discrete scattering from the height distribution of hard domains, whose weight returns the variation of v h with the strain. All TPUs are based on 4,4 ′ ‐methylene diphenyl diisocyanate (MDI). The other raw components are systematically varied. Two MDI units determine the height of the average hard domain. The variation of v h with strain is described by a tensile augmentation (in analogy to the tensile strength) which is realized at an end‐of‐growth strain. The following hard domain destruction is governed by a consumption factor. Deviations between extrapolated and measured strain at break may be related to the TPU composition.