The time dependence of the thermal and mechanical properties of segmented urethanes following thermal treatment

Wilkes, Garth L.; Bagrodia, Shriram; Humphries, William; Wildnauer, Richard H.

doi:10.1002/pol.1975.130130601

Cited by 75 publications

(20 citation statements)

References 12 publications

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“…26,27 cate the amount of hard segment dissolved in the soft domains. A higher temperature T g (s) (comEnsuing studies by Wilkes et al [28][29][30] and Hesketh et al 7 concentrated on the kinetics of pared with that for the pure soft segment) indicates an increased presence of hard segments disphase separation in melt quenching and annealing studies. These workers found that samples solved in the soft domains.…”

Section: Introductionmentioning

confidence: 94%

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

Martin

Meijs

Gunatillake

et al. 1997

J. Appl. Polym. Sci.

167

119

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A series of eight thermoplastic polyurethane elastomers were synthesized from 4,4-methylene diphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) chain extender, with poly(hexamethylene oxide) (PHMO) macrodiol soft segments. The PHMO molecular weights employed ranged from 433 g/mol to 1180 g/mol. All materials contained 60% (w/w) of the macrodiol. The materials were characterized by differential scanning calorimetry (DSC) following up to nine different thermal treatments. In addition, three of the materials were selected for characterization by small-angle x-ray scattering (SAXS) following similar thermal treatments. The DSC experiments showed the existence of five hard segment melting regions (labelled T1-T5), which were postulated to result from the disordering or melting of sequences containing one to five MDIderived units, respectively. Evidence for urethane linkage dissociation and reassociation during annealing at temperatures above 150ЊC is presented. This process aids in the formation of higher melting structures. Annealing temperatures of 80-100ЊC provided the maximum SAXS scattering intensity values. Materials containing longer soft segments (and, therefore, longer hard segments) were observed to develop and sustain higher melting hard domain structures and also develop maximum average interdomain spacing values at higher annealing temperatures. Another additional series of three PHMO-based polyurethanes having narrower hard segment length distributions, was synthesized and characterized by DSC in the as-synthesized and annealed states. The resulting DSC endotherms provided further evidence to suggest that the T1-T5 endotherms were possibly due to melting of various hard segment length populations.

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Section: Introductionmentioning

confidence: 94%

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

Martin

Meijs

Gunatillake

et al. 1997

J. Appl. Polym. Sci.

167

119

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“…Thus thermal and mechanical data may be misleading unless the thermal history of the specimen has been given. 5 Finally, the method of fabrication, whether the sample is compression-molded or solution-cast, or whether a thin f i l m or a bulk specimen is used, can have a significant effect on the extent of phase separation and on the morphology of the separated phase. 3 Because of the wide variety of applications for these polymers, it is of practical interest to characterize their dynamic mechanical behavior with master curves of modulus and loss factor over a wide range of reduced frequencies using time-temperature superposition of the data.…”

Section: Introductionmentioning

confidence: 99%

Thermal and dynamic mechanical properties of polyurethaneureas

Hartmann

Duffy

Lee

et al. 1988

J of Applied Polymer Sci

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SynopsisMeasurements were made of the thermal and dynamic mechanical properties of 22 polyurethaneureas of varying diol molecular weight, type of aromatic chain extender, diol molecular weight distribution, and chain extender stoichiometry. The dynamic mechanical data, obtained as a function of temperature and frequency (in the kHz region), were used to construct master curves of shear modulus and loss factor over a wide range of reduced frequencies. Based on these master curves, interpreted in conjunction with the thermal analysis results, it was found that: Soft segment crystallization occurs at the higher diol molecular weights, dynamic mechanical properties are well correlated with the soft segment glass transition, diol molecular weight influences dynamic mechanical properties by affecting the degree of phase separation and hence glass transition temperature, and neither diol molecular weight distribution nor chain extender stoichiometry have a significant effect, in the ranges studied, on transition temperatures or dynamic mechanical properties.

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“…The 11 ° C endotherm is due to melting of PTMO crystals. 3. The 135 ° C transition is due to melting of nylon crystals.…”

Section: Resultsmentioning

confidence: 99%

“…HE STRUCTURE OF block copolymers has been under serious investigation for a number of years, and a great deal of insight into these materials has resulted [1][2][3][4]. On the other hand, there is an unlimited variety and compositions of materials that fall into the class of block polymers.…”

Section: Introductionmentioning

confidence: 99%

Strain-Induced Crystallization and Melting Behavior of Polyetheramide Block Copolymer

Warner

1990

Journal of Elastomers & Plastics

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The time dependence of the thermal and mechanical properties of segmented urethanes following thermal treatment

Cited by 75 publications

References 12 publications

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

The effect of average soft segment length on morphology and properties of a series of polyurethane elastomers. II. SAXS-DSC annealing study

Thermal and dynamic mechanical properties of polyurethaneureas

Strain-Induced Crystallization and Melting Behavior of Polyetheramide Block Copolymer

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