Deformation of polyurea: Where does the energy go?

Mott, P. H.; Giller, C.B.; Fragiadakis, D.; Rosenberg, David A.; Roland, C. M.

doi:10.1016/j.polymer.2016.10.029

Cited by 46 publications

(33 citation statements)

References 33 publications

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“…The calorimetric response has shown that the material's elasticity is mainly entropic, but it uses mechanical energy brought to it to change its microstructure. This is in good agreement with measurements recently performed in a compact polyurea in Mott et al() For samples of the highest density, viscous effects are found to increase with the loading rate, the density, and the maximum stretch applied. This is not observed for sample of the lowest density, for which the intrinsic dissipation remains low.…”

Section: Resultssupporting

confidence: 92%

“…The main physical origin involved in the hysteresis loop is therefore not viscosity in the range of the loading rates applied. This is in the same line as results recently obtained by Mott et al() who have shown that during extension, the polyurea they tested uses a significant part of the mechanical energy to change its microstructure, whatever the stretch level considered. This is analogue with what was observed in NR by Le Cam.…”

Section: Resultssupporting

confidence: 89%

“…In most of the tests performed, the loading rate is sufficiently high and the thermal dissipation does not really contribute to the mechanical hysteresis; (c)the part of the mechanical energy used by the material to change its microstructure W s t r u c t u r e . In this case, all the work done to the system is not measured as a temperature change (see, for instance, the recent study by Mott et al() on polyurea). The material stores part of the mechanical energy brought and releases it (or a part of it) with a different kinetics.…”

Section: Introductionmentioning

confidence: 99%

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Energy stored during deformation of crystallizing TPU foams

Lachhab

Robin

Cam

et al. 2018

Strain

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The hysteresis loop observed in the mechanical response of elastomers is classically assumed to be due to viscosity. In this study, a complete energy balance is carried out during cyclic deformation of compact and foamed crystallizing thermoplastic polyurethanes. Results show that viscosity is not the only phenomenon involved in the hysteresis loop formation: A significant part of the mechanical energy brought is not dissipated into heat and is stored by the material when the material changes its microstructure, typically when it is crystallizing. Some of this energy is released during unloading, when melting occurs, but with a different rate, which contributes to the hysteresis loop. The part of the mechanical energy stored by the material has been quantified through the γse ratio (Loukil et al. (2018) European Polymer Journal, 98, 448–455) to investigate the effects of the loading rate and the void volume fraction on the energetic response of thermoplastic polyurethane.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Energy stored during deformation of crystallizing TPU foams

Lachhab

Robin

Cam

et al. 2018

Strain

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“…The tack‐free times and demold times are consistent with those observed for the AT‐V223‐060LM and P‐1000 elastomers presented in Table . The data demonstrate the importance of thermal history on development of microphase‐separated phase structure and concomitant elastomer performance …”

Section: Resultsmentioning

confidence: 73%

Synthesis of aniline‐terminated polyethers and resulting polyurethane/polyurea elastomers

Sonnenschein

Virgili

Larive

et al. 2018

J. Polym. Sci. Part A: Polym. Chem.

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Functionalization of polyols with aromatic amines offers a potential route to modify properties of polyurethanes, polyamides, and epoxies. Additionally, aniline termination of polyether backbones provides the opportunity to speed up reactions with isocyanates relative to hydroxyl functionalization and slow down epoxy reactions compared to reactions with primary and secondary amines. In this article, the synthesis, characterization, and physical properties of aniline‐terminated polyols with varying molecular weight, monomer type, and functionality is described. Numerous analytical techniques are employed to track the chemical modification kinetics and the resulting aniline functionalized polyol properties. In addition, synthesis and properties of poly(urethane‐urea) elastomers from several of the modified polyols are presented. The effect of hard segment composition and process temperature on tensile properties, dynamic mechanical properties, phase morphology, and chemical resistance is explored. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1730–1742

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“…The improved rigidity of PUr is established by hard domains formed from a bidentate hydrogen bond network compared to the mono dentate hydrogen bonds formed between urethane groups in PU . Furthermore, increased hydrogen bonding strength in PUr contributes to an excellent solvent resistance, toughness, and mechanical performance important for a variety of applications such as coatings for storage tanks, military armor, and ships . The objective of this work is to combine the benefits of PUr chemistry with a soft acrylic matrix to form a hybrid system.…”

Section: Introductionmentioning

confidence: 99%

Self‐assembled polyurea macromer nanodispersion and resulting hybrid polyurea‐acrylic emulsions and films

Drake

Cardoen

Hughes

et al. 2019

J. Polym. Sci. Part A: Polym. Chem.

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A polyurea macromer (PUM) was synthesized and dispersed in basic conditions to form self‐assembled nanoparticles (<20 nm dispersions, up to 30 wt % aq. soln.). These nanoparticles enabled surfactant‐free emulsion polymerization to form hybrid polyurea‐acrylic particles despite the absence of a measureable water‐soluble fraction. The Tg of the starting PUM material was a strong function of the PUM's extent of neutralization and hydration (varying between 100 °C and >175 °C) due to changes in hydrogen and ionic bonding. Two separate hybrid polyurea‐acrylic emulsion systems were prepared: one by direct polymerization of (meth)acrylic monomers in the presence of the nanodispersion and a second by a physical blend of PUM nanodispersion with an acrylic latex control. The direct polymerization method resulted in a hybrid emulsion particle size that developed by a mechanism resembling conventional emulsion polymerization and was unlike that described for seeded polyurethane dispersion systems. Film hardness was shown to increase with increasing coating thickness for the hybrid film prepared by direct polymerization. The resulting mechanical properties could be explained by applying mechanical models for a composite foam structure. These results were unprecedented for normal elastomer films. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1373–1388

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Deformation of polyurea: Where does the energy go?

Cited by 46 publications

References 33 publications

Energy stored during deformation of crystallizing TPU foams

Energy stored during deformation of crystallizing TPU foams

Synthesis of aniline‐terminated polyethers and resulting polyurethane/polyurea elastomers

Self‐assembled polyurea macromer nanodispersion and resulting hybrid polyurea‐acrylic emulsions and films

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