Interfacial rheology of coextruded elastomeric and amorphous glass thermoplastic polyurethanes

Silva, J.; Maia, João M.; Huang, Rongzhi; Meltzer, Donald; Cox, Michael; Andrade, Ricardo

doi:10.1007/s00397-012-0652-8

Cited by 12 publications

(11 citation statements)

References 30 publications

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“…The final structure, and consequently the rheological behavior, are affected by the chemical structure of HS and SS, hydrogen bonding, molecular weight, molecular weight distribution, thermal history, and ratio of hard and soft blocks . Most of the studies that investigate the phase transition behavior of TPUs were conducted by DSC, small angle X‐ray scattering (SAXS) wide angle X‐ray scattering (WAXS), infrared spectroscopy, and atomic force microcopy (AFM) . While the understanding of phase transition behaviors are important to understanding thermal postprocessing conditions, these techniques leave a gap in the relationship between exposure conditions and the physical performance of the system.…”

Section: Introductionmentioning

confidence: 99%

Effect of Soft‐to‐Hard Segment Ratio on Viscoelastic Behavior of Model Thermoplastic Polyurethanes during Phase Transitions

Gadley

Andrade

Maia

2016

Macro Materials & Eng

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Model thermoplastic polyurethanes (TPUs) are prepared with the aim of investigating the effect of soft‐to‐hard segment ratio on the phase transition and the resulting structure that forms upon isothermal exposure to temperatures near their phase transition temperature. The dynamic rheological properties of TPUs before exposure to these isothermal conditions show a phase transition at high temperatures that is directly related to the content of hard segments. The extensional viscosity data indicate a strain‐hardening behavior that becomes less pronounced with the increase of hard segments. After isothermal treatment, the DSC results show that the high‐temperature endotherm peak narrows and shifts to higher temperatures, suggesting a transition in structure. Small angle X‐ray scattering, wide angle X‐ray scattering, and atomic force microcopy results indicate a phase‐separated system in which the hard domain sizes and crystallinity change during this process. The rheological data collected after recrystallization show a significant increase in both moduli, transitioning from viscoelastic fluid‐like to glassy behavior. Concurrently, the uniaxial elongation viscosity presents a significant increase in absolute values, but with a shift from strain‐hardening to strain‐softening behavior for all strain rates. A transition from traditional phase separated viscoelastic melt behavior to more brittle rupture is also observed, marking a significant fundamental difference in properties before and after recrystallization.

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Section: Introductionmentioning

confidence: 99%

Effect of Soft‐to‐Hard Segment Ratio on Viscoelastic Behavior of Model Thermoplastic Polyurethanes during Phase Transitions

Gadley

Andrade

Maia

2016

Macro Materials & Eng

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“…Figure a demonstrates the time evolution of relaxation modulus G ( t ) assessed at a small deformation (5%) for bilayers and monolayers after annealing at 230 °C for 5 min. To clearly depict the contribution of the layer–layer interfacial reactions, the theoretical G ( t ) for bilayers is also calculated (see dashed lines in Figure a) by a serial model by assuming the absence of interlayer interaction among layers , where G net ( t ), G A ( t ), and G B ( t ) correspond to the relaxation modulus for bilayers and constituent A and B layers, and ϕ A and ϕ B are the volume fraction of A and B layers, respectively. It is clearly viewed that the nonreactive bilayers subjected to a step strain deformation almost relax as the theoretical predictions of bilayers without any interlayer reactions and even faster at a longer time compared with the latter values.…”

Section: Results and Discussionmentioning

confidence: 99%

“…It is ever reported that the interfacial roughness for systems modified by graft copolymers is much larger than that by diblock copolymers. , Meanwhile, the thickness for interfaces compatibilized with graft copolymers was reported to be bigger than that with the diblock and triblock copolymers . Furthermore, the addition of these copolymers alters the viscoelastic responses, characterized by the time evolutions of both the elastic modulus and viscosity. , It is therefore understandable that the molecular architecture of generated copolymers plays a critical role in determining the interfacial and end-use properties. When it comes to the practical processing of multiphase polymers, the intense flow fields might further induce the interfacial phenomena different from that at the equilibrium state.…”

Section: Introductionmentioning

confidence: 99%

“…18 Furthermore, the addition of these copolymers alters the viscoelastic responses, characterized by the time evolutions of both the elastic modulus and viscosity. 19,20 It is therefore understandable that the molecular architecture of generated copolymers plays a critical role in determining the interfacial and end-use properties. When it comes to the practical processing of multiphase polymers, the intense flow fields might further induce the interfacial phenomena different from that at the equilibrium state.…”

Section: Introductionmentioning

confidence: 99%

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Role of the Macromolecular Architecture of Copolymers at Layer–Layer Interfaces of Multilayered Polymer Films: A Combined Morphological and Rheological Investigation

Lü

Bondon

Touil

et al. 2020

Ind. Eng. Chem. Res.

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It is known that copolymers are critical in modifying interfaces of multilayered polymeric products. However, not much is known about the influence of the macromolecular architecture of copolymers on the interfacial morphology evolution, viscoelasticity, and processability of layered systems. Therefore, we demonstrate the role of macromolecular architecture of copolymers at layer−layer interfaces of multilayered polymers from the equilibrium to flow conditions, based on a combined morphological and rheological investigation. Intriguingly, in comparison to a pure grafting case, the formation of interfacial copolymers of a complex grafting architecture of a branching and cross-linking mixture substantially increases the overall viscosity. With a higher grafting density of copolymers of such an architecture, layer−layer interfaces become more corrugated upon reaction. Particularly, under real coextrusion processing flows, with these copolymers, interfacial roughness and irregularities are further amplified in the die exit as compared to that in the feedblock because of the accelerated reaction kinetics by the compressive flow field. Besides, the configuration of copolymers containing a mixture of branched and cross-linked chains at the interface significantly hinders the structural stress relaxation process and resists the interfacial slip. Under fast extensional flows, multilayered films display an unexpected strain-hardening behavior with a strong dependence on the number of layers, arising from the interfacial stitching and elastic network formed with copolymers of the complex architecture. These findings will enable the better understanding of copolymer architectures in the control of interfaces of multilayered films with improved flow stability and macroscopic properties.

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“…As shown in Figure , while TPU A shows long‐range order in which bright areas represent the hard domaines and the black parts are the soft domaines, TPU B shows an amorphous structure. Because of the chemical compatibility of TPUs, interdiffusion between TPU B and TPU A layer is expected and the cross‐section of the bi‐layer TPU film shown in Figure , in which an interphase with 2‐µm width is observed …”

Section: Resultsmentioning

confidence: 99%

Microconfinement effect on gas barrier and mechanical properties of multilayer rigid/soft thermoplastic polyurethane films

Huang

Chari

Tseng

et al. 2015

J of Applied Polymer Sci

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In this article, rigid/soft thermoplastic polyurethane (TPU) films were produced via layer-multiplying co-extrusion and the effect of confinement on morphology and gas barrier and mechanical properties is studied. The soft TPU, which is 52% hardsegment, shows phase separation, while the rigid, 100% hard-segment TPU exhibits amorphous structures. Even though the viscosity ratio of the two TPUs is over 10 and the elasticity ratio around 100, optical and atomic force microscopies show that a multilayer structure was successfully achieved. Then, the multilayer TPU films were uni-axially stretched to different amounts of deformations, from 0% to 300%. DSC and WAXS results show that microconfinement occurs during orientation, which causes a significant reduction in oxygen permeability of multilayer TPU films, when stretched at 75%, by comparison to the mono and bi-layer TPU. The dependence of gas barrier properties on temperature and deformation was also investigated, and a 100% improvement in elongation at break was found when compared to films of the rigid TPU.

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Interfacial rheology of coextruded elastomeric and amorphous glass thermoplastic polyurethanes

Cited by 12 publications

References 30 publications

Effect of Soft‐to‐Hard Segment Ratio on Viscoelastic Behavior of Model Thermoplastic Polyurethanes during Phase Transitions

Effect of Soft‐to‐Hard Segment Ratio on Viscoelastic Behavior of Model Thermoplastic Polyurethanes during Phase Transitions

Role of the Macromolecular Architecture of Copolymers at Layer–Layer Interfaces of Multilayered Polymer Films: A Combined Morphological and Rheological Investigation

Microconfinement effect on gas barrier and mechanical properties of multilayer rigid/soft thermoplastic polyurethane films

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