Short‐Term Morphology Relaxation of Thermoplastic Polyurethane Elastomers after Fast Strain Steps

Stribeck, Norbert; Schneider, Konrad; Eling, Berend; Pöselt, Elmar

doi:10.1002/mame.202000386

Cited by 4 publications

(10 citation statements)

References 22 publications

(23 reference statements)

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“…The curves of all samples have two common features. A fast, exponential relaxation within about 250 ms (already found in earlier work [4] ) is followed by a slow, linear decay with different slopes.…”

Section: Orientation F Hm = −2f H Of the Chains From The Bundles At 𝝐...supporting

confidence: 68%

“…The Relaxometer: For sudden loading or unloading of the samples, a pneumatic relaxometer described in a previous paper was used. [4] With each expansion pulse, the jaws reached their end position in less than 13 ms.…”

Section: Methodsmentioning

confidence: 99%

“…The second door to be opened concerns the deformation device: with a conventional tensile tester, one cannot shoot the elastomer back and forth between two strain levels so quickly that the transformation time is small compared to the necessary short exposure of the scattering patterns. For this reason, we are engaged in the further development of our selfconstructed impact relaxometer, [4] its integration into the highspeed data acquisition system of a beamline, and the development of software to analyze the huge amounts of data.…”

Section: Introductionmentioning

confidence: 99%

“…In a previous study [4] we used our impact relaxometer for the first time. Within 13 ms, we shoot the samples back and forth between two strain levels.…”

Section: Introductionmentioning

confidence: 99%

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Wide‐Angle Scattering Halo Analysis and the Evolution of Oriented Amorphous Structure after Elongation Jumps in Some Elastomers

Stribeck

Schneider

Pöselt³

et al. 2022

Macro Chemistry & Physics

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Amorphous and low-crystallinity thermoplastic polyurethane elastomers are shot back and forth between two elongation levels (𝝐 = 0.2 and 𝝐 = 1.2) and observed between the excitations for 10 s using wide-angle X-ray scattering (WAXS) (50 Hz). For orientation analysis, the fiber patterns are projected, expanded in multipoles, and discussed as a function of relaxation time. Normalized WAXS suggests that the oriented halo observed during extension is predominantly due to selective extinction of unfavorably oriented probes (chain bundles). During retraction, neighborhoods and thus clusters are restored. Discussed are the relaxation curves depending on material and the number of load cycles. The separation of the halo into narrow rings introduces "bundle airiness" as a second coordinate. The now bivariate cluster density is the product of two univariate functions. Its factor "airiness distribution" seems to be a material property which is not changed by annealing. In contrast, the bivariate preferred orientation is not product-separable. Especially with harder materials it shows two bundle ensembles of different airiness. Interactions between the ensembles explain complex trajectories of the orientation-relaxation curves. The formation of the additional airier oriented component is inhibited by annealing in most of the materials studied. In contrast, multiple load changes promote its formation.

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Section: Orientation F Hm = −2f H Of the Chains From The Bundles At 𝝐...supporting

confidence: 68%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…In a previous study [4] we used our impact relaxometer for the first time. Within 13 ms, we shoot the samples back and forth between two strain levels.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Wide‐Angle Scattering Halo Analysis and the Evolution of Oriented Amorphous Structure after Elongation Jumps in Some Elastomers

Stribeck

Schneider

Pöselt³

et al. 2022

Macro Chemistry & Physics

Self Cite

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show abstract

“…The high brilliance of the X-ray source allows monitoring structural and morphological evolution with adequate time resolution. In particular, a combination of SAXS/WAXS with DSC [ 20 , 21 , 22 , 23 , 24 , 25 ], FTIR [ 26 ], and relaxometry [ 27 ] is capable of providing important information about structural evolution under external factors.…”

Section: Introductionmentioning

confidence: 99%

Multiblock Thermoplastic Polyurethanes: In Situ Studies of Structural and Morphological Evolution under Strain

et al. 2021

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The structural evolution of multiblock thermoplastic polyurethane ureas based on two polydiols, poly(1,4-butylene adipate (PBA) and poly-ε-caprolactone (PCL), as soft blocks and two diisocyanites, 2,4-toluylene diisocyanate (TDI) and 1,6-hexamethylene diisocyanate (HMDI), as hard blocks is monitored during in situ deformation by small- and wide-angle X-ray scattering. It was shown that the urethane environment determines the crystal structure of the soft block. Consequently, two populations of crystalline domains of polydiols are formed. Aromatic TDI forms rigid domains and imposes constrains on the crystallization of bounded polydiol. During stretching, the TDI–polydiol domains reveal limited elastic deformation without reorganization of the crystalline phase. The constrained lamellae of polydiol form an additional physical network that contributes to the elastic modulus and strength of the material. In contrast, polydiols connected to the linear semi-flexible HMDI have a higher crystallization rate and exhibit a more regular lamellar morphology. During deformation, the HMDI-PBA domains show a typical thermoplastic behavior with plastic flow and necking because of the high degree of crystallinity of PBA at room temperature. Materials with HMDI-PCL bonding exhibit elastic deformation due to the low degree of crystallinity of the PCL block in the isotropic state. At higher strain, hardening of the material is observed due to the stress-induced crystallization of PCL.

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Optimizing TPU performance: The role of mold temperature on injection molding of TPU

Grønborg,

Pedersen,

Spangenberg

et al. 2024

J of Applied Polymer Sci

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This study explores the influence of mold temperatures below 60°C on thermoplastic polyurethane (TPU) properties during injection molding, focusing on phase separation and its impact on mechanical, thermal, and viscoelastic properties. Using a combination of micro‐indentation, temperature scanning stress relaxation, and conventional characterization methods, the research highlights how increased mold temperatures promote more distinct phase separation, enhancing mechanical stability and physical properties. The novel use of micro‐indentation revealed a gradient in material stiffness from the surface to the core of injection‐molded samples, attributed to differential cooling rates and shear forces, which affect phase separation and crystallinity of the hard domains. These insights are critical for applications requiring specific surface properties and underscore the importance of understanding the interplay between chemical composition and processing conditions for optimizing TPU properties. Furthermore, the paper shows that tensile testing, differential scanning calorimetry, and Shore hardness cannot quantify the effects of mold temperatures below 60°C. The research highlights the influence and importance of chemical composition, rheological history, and thermal history on the properties of TPU.

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Short‐Term Morphology Relaxation of Thermoplastic Polyurethane Elastomers after Fast Strain Steps

Cited by 4 publications

References 22 publications

Wide‐Angle Scattering Halo Analysis and the Evolution of Oriented Amorphous Structure after Elongation Jumps in Some Elastomers

Wide‐Angle Scattering Halo Analysis and the Evolution of Oriented Amorphous Structure after Elongation Jumps in Some Elastomers

Multiblock Thermoplastic Polyurethanes: In Situ Studies of Structural and Morphological Evolution under Strain

Optimizing TPU performance: The role of mold temperature on injection molding of TPU

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