The rheo‐optical and mechanical behavior of a systematic series of hard‐soft segmented urethanes

Samuels, Sam L.; Wilkes, Garth L.

doi:10.1002/polc.5070430115

Cited by 70 publications

(22 citation statements)

References 34 publications

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“…The validity of the infinite slit assumption can be checked by comparing the two desmeared curves. 2 (1) In the ease of segmented urethanes it might be expected that there will always be some degree of mixing between the phases and that the boundaries between the phases are not sharp. Therefore pi and p2 as well as Ε and S/V are not known, and the measurement of the invariant Ç cannot give us numerical values for φ1 and φ2· However, it is still a useful parameter for comparing materials, particularly a given material undergoing phase, separation.…”

Section: Methodsmentioning

confidence: 99%

Time Dependence of Mechanical Properties and Domain Formation of Linear and Crosslinked Segmented Polyurethanes

Ophir

Wilkes

1979

Advances in Chemistry

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A systematic series of segmented polyester-MDI polyurethanes were investigated by SAXS, DSC and stress strain measurements. The linear polymer as well as three peroxide cured samples of different crosslinking levels were utilized. Correlations were made between time-dependent changes in structure and mechanical properties following specific thermal treatments. Higher crosslinking leads to lower final domain formation and to lower modulus. Also, the crosslinked samples had their domain texture more easily disrupted at lower temperature than did the linear system. Finally, the rate of phase separation upon cooling was increased as the degree of crosslinking was decreased. Segmented polyurethanes are thermoplastic materials that generally ^ display elastomeric behavior-the degree of which depends on the relative amounts of "soft" and "hard" segments. The properties also depend on the extent of microphase separation and the morphological characteristics of the phases. Because of the basic thermodynamic incompatibility of these two segment types, localized microphase formation occurs leading to the well-recognized "domain" morphology. It is widely accepted that the mechanical properties of the final bulk material are 0-8412-0457-8/79/33-176-053$05.00/0

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Section: Methodsmentioning

confidence: 99%

Time Dependence of Mechanical Properties and Domain Formation of Linear and Crosslinked Segmented Polyurethanes

Ophir

Wilkes

1979

Advances in Chemistry

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“…Early literature [17,18] attributed these endotherms to different types of hydrogen bonds, where the urethane NH bond is the donor, and either the urethane carbonyl or the macrodiol is acting as acceptor. This hypothesis was later rejected by Samuels & Wilkes [19], who investigated a TPU without hydrogen bonding and proved that the explanation of hydrogen bonding is insufficient. Therefore, alternative explanation were coined, based on various levels of packing order [11,20,21].…”

Section: Introductionmentioning

confidence: 97%

Linking the morphology of a high hard segment content polyurethane to its thermal behaviour and mechanical properties

Swolfs

Bertels

Verpoest

et al. 2015

Polymer

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Understanding and controlling the morphology of thermoplastic polyurethane (TPU) is crucial, as it is closely linked with its thermal and mechanical properties. The morphology of a TPU with a high hard segment content was investigated. When hard segment crystallisation was avoided by fast cooling, a crystallisation-induced phase separation occurred upon reheating. At higher temperatures, a second polymorph was additionally created. Cooling slowly from the melt directly induced the formation of both polymorphic forms. The complex thermal behaviour could hence be explained by the (cold) crystallisation and melting of two polymorphs. The disordered two-phase nanomorphology, revealed by AFM at room temperature after cooling slowly, was validated for both fast and slowly cooled samples at higher temperatures by fitting model SAXS patterns to time resolved synchrotron SAXS data. Annealing fast cooled samples at high temperature induced some ordered, lamellar stacks in addition. Finally, the morphology was linked to the evolution of storage modulus with increasing temperature.

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“…[1][2][3][4][5][6][7][8] The occurrence of phase separation can be predicted, on a thermodynamic basis, 9 when the solubility parameters ␦ and the molecular weights of the building blocks are known. The larger the difference in ␦ and the higher the molecular weight, the higher the probability of demixing of blocks.…”

Section: Introductionmentioning

confidence: 99%

Phase behavior and some calorimetric and physical properties of diurethanes from perfluoropolyether macromonomers

Tonelli¹,

Bassi²,

Ajroldi³

1999

J. Polym. Sci. B Polym. Phys.

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The rheo‐optical and mechanical behavior of a systematic series of hard‐soft segmented urethanes

Cited by 70 publications

References 34 publications

Time Dependence of Mechanical Properties and Domain Formation of Linear and Crosslinked Segmented Polyurethanes

Time Dependence of Mechanical Properties and Domain Formation of Linear and Crosslinked Segmented Polyurethanes

Linking the morphology of a high hard segment content polyurethane to its thermal behaviour and mechanical properties

Phase behavior and some calorimetric and physical properties of diurethanes from perfluoropolyether macromonomers

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