Real time mechano-optical study on deformation behavior of PTMO/CHDI-based polyetherurethanes under uniaxial extension

Ünsal, Emre; Yalcin, Baris; Jonáš, Alexandr; Çakmak, Mükerrem

doi:10.1016/j.polymer.2009.07.041

Cited by 27 publications

(39 citation statements)

References 51 publications

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“…To ensure good mechanical and thermal properties, it is important that hard segments in the hard domain have to be compactly packed. Based on Fourier transform infrared (FTIR) analysis, Yilgor and Wilkes16–21 reported that when compared with the ones in MDI‐based PUs, the hard segments in the PPDI‐based PU forms stronger hydrogen bonding that leads to the well defined microphase separated morphology. Similar observation has been made with the TODI based PUs 22…”

Section: Introductionmentioning

confidence: 99%

Effect of molecular shape of diisocyanate units on the microscopic/macroscopic phase separation structure of polyurethanes

Park

Lim

et al. 2011

J Polym Sci B Polym Phys

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Three diisocyanate units having different linearity and planarity on the basis of the arrangement of constituent aromatic rings are used to synthesize three polyurethanes (PUs) and the effects of the molecular structure of the diisocyanate units on phase separated morphologies of PUs have been studied. The linear and planar diisocyanate unit allows good packing of the hard segments in the hard domain by extensive intersegmental hydrogen bonding, and it forms a well ordered, long hard domain. However, the nonlinear and noncoplanar diisocyanate unit shows a lesser degree of hydrogen bonding in the short hard domain. Strong preferential orientation of the rigid/long hard domains inside a macroscopic grain boundary has been observed with the polarizing optical microscope especially for the PU based on the rigid diisocyanate. It was concluded that the molecular structure of the diisocyanate unit in PU plays an important role in determining the interchain interaction, the detailed phase‐separated domain structure, and local domain orientation in each grain boundary. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

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Section: Introductionmentioning

confidence: 99%

Effect of molecular shape of diisocyanate units on the microscopic/macroscopic phase separation structure of polyurethanes

Park

Lim

et al. 2011

J Polym Sci B Polym Phys

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“…[14][15][16] Segments in the soft phase (soft segments and dissolved hard segments) will first become oriented in the deformation direction due to the lower modulus of the soft phase and stress will be ultimately be exerted on the hard domains. If anisotropic in shape, the hard domains are expected to align with their long axis in the deformation direction.…”

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confidence: 99%

Dynamics of Uniaxially Oriented Elastomers Using Broadband Dielectric Spectroscopy

et al. 2010

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The molecular mobility of chemically cross-linked and thermoplastic elastomers is of utmost importance in establishing physical properties for uses ranging from automotive tires and shoe soles to more sophisticated aerospace and biomedical applications. In many of these applications, network chain dynamics under external stresses/strains are critical for determining ultimate performance. It is well established that T g (or T R , the dynamic T g ) and the breadth of the segmental (R) relaxation time distribution increase with increasing cross-link density for chemically cross-linked polymers. For elastomers, there are considered to be two contributions important in determining the change in T R upon uniaxial extension: a reduction in conformational entropy, encouraging an increase in T R , and a volume increase on uniaxial deformation, leading to a reduction in T R (nonideal networks are compressible to some degree). 1,2Considering the importance of mechanical deformation in elastomer applications, there have been relatively few previous investigations of mechanical strain on chain dynamics, e.g., 3,4 even fewer using broadband dielectric spectroscopy, and none on thermoplastic elastomers. [5][6][7][8] This is despite the fact that modern broadband dielectric spectroscopy is a powerful tool for the investigation of material dynamics over very wide frequency and temperature ranges.In this Communication, we report the findings of our initial dielectric spectroscopy investigation of the role of uniaxial extension on the relaxation behavior of cross-linked polyisoprene and segmented polyurethane elastomers. A Novocontrol GmbH Concept 40 broadband dielectric spectrometer was used to measure dielectric permittivity and loss over a broad range of temperatures and frequencies.Synthetic polyisoprene [PI, NIPOL-IR2200 (Zeon Chemicals), 98.5% cis-1,4 content] was cross-linked with dicumyl peroxide (Sigma-Aldrich) at 180°C for 4 min in an aerated oven. Crosslink density was determined by measuring the swelling ratio in toluene and the Flory-Rehner equation.9 A poly(tetramethylene oxide) (PTMO, MW ∼ 1000) soft segment polyurethane (PU) with 32.5 wt % of hard segments [4,4 0 -diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO)] was supplied by AorTech Biomaterials (Scoresby, QLD, Australia) in film form.For the uniaxial deformation experiments, the stretching rig shown in Figure 1 was developed in order to allow convenient loading of deformed specimens directly into the dielectric spectrometer. This rig has three essential parts: sample clamper, electrode, and stretching knob. A sample strip (10 mm Â 80 mm) was placed along the groove on the rig and drawn to a specific extension ratio (λ). An electrode was positioned in the middle of the strained sample and clamped. The strained sample-electrode assembly was then separated from the rig and dried in vacuum for 24 h before measurement.The influence of uniaxial extension on the dynamics of the cross-linked PI (cross-link density = 6.1 Â 10 -5 mol/cm 3 ) is displayed in Fi...

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“…These effects have been widely investigated in the literature. () Concerning more particularly the present TPU, an exhaustive analysis is provided in Lachhab et al() and is therefore not precisely detailed here. The main results can be summed up as follows: •decreasing the density leads to a decrease in the global stiffness and in the hysteresis area, slightly increases the residual stretch, and does not affect significantly the stress softening; •the loading rate has no significant influence on the stress softening, although it influences more the residual stretch and the hysteresis area.…”

Section: Resultsmentioning

confidence: 99%

“…From a mechanical point of view, they are subjected to many anelastic phenomena such as mechanical hysteresis, residual stretch, and softening. () These phenomena strongly depend on the material formulation.…”

Section: Introductionmentioning

confidence: 99%

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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Real time mechano-optical study on deformation behavior of PTMO/CHDI-based polyetherurethanes under uniaxial extension

Cited by 27 publications

References 51 publications

Effect of molecular shape of diisocyanate units on the microscopic/macroscopic phase separation structure of polyurethanes

Effect of molecular shape of diisocyanate units on the microscopic/macroscopic phase separation structure of polyurethanes

Dynamics of Uniaxially Oriented Elastomers Using Broadband Dielectric Spectroscopy

Energy stored during deformation of crystallizing TPU foams

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