Infrared Dichroic Studies of Phase Separation and Orientation of Dibenzyl Hard Segments in Polyurethane

Prisăcariu, Cristina; Scortanu, Elena

doi:10.1177/0954008307080750

Cited by 8 publications

(11 citation statements)

References 5 publications

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“…5,[7][8][9] For the SPU series depicted in Table 1, the highest tensile strength (46.8 MPa) and the lowest residual elongation (20%) were observed for the material based on mixtures of diisocyanates included and reacted together in a random manner, SPU 1 , as shown in Table 4 ( Figures 10 and 11). …”

Section: Tensile Test Resultsmentioning

confidence: 91%

“…An important subgroup is the polyurethane elastomers, in which at least one ingredient has a glass transition below room temperature. [1][2][3][4][5][6][7][8] In the segmented polyurethane elastomers (SPUs) studied in the present work, molecules consist of alternating flexible (soft) and relatively rigid (hard) segments. Phase segregation occurs during and following polymerization, to produce an elastomeric matrix of the soft segments containing rigid inclusions (of size scale 10-100 nm) formed by association of the hard segments.…”

Section: Introductionmentioning

confidence: 99%

“…The latter is a novel diisocyanate, also now available commercially, first synthesized in our (Romanian) laboratory. [8][9][10][11][12] Rotation around the central -CH 2 -CH 2 -bond in DBDI allows alignment of successive aromatic rings thus favoring the tendency of crystallization which involves the DBDI hard phase. [9][10][11][12] The chain extender EG and the soft segment macrodiol polyethylene adipate (PEA) of molar mass 2000 g mol À1 were considered.…”

Section: Introductionmentioning

confidence: 99%

“…The present work is part of a wider study [8][9][10][11][12] of the effects on constitutive response of systematically varying the key structural variables: hard segment, soft segment and crosslinking. Such variations in composition lead to significant changes in the key mechanical properties of the elastomer, such as stiffness, strain recovery and strain energy recovery.…”

Section: Introductionmentioning

confidence: 99%

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Morphological features and thermal and mechanical response in segmented polyurethane elastomers based on mixtures of isocyanates

Prisăcariu

Scortanu

Stoica

et al. 2011

Polym J

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A family of segmented polyurethane elastomers (SPUs) was synthesized. Hard segments were chosen to be generated from two isocyanates: the rigid 4,4-diphenylmethane diisocyanate (MDI) and the flexible 4,4-dibenzyl diisocyanate (DBDI), alone or as mixtures. A polyester soft segment polyethylene adipate of molar mass 2000 g mol À1 and a small molecule chain-extender diol, ethylene glycol, were used. Hard segment fraction was maintained at B40%. The structure-property relationship of SPUs was investigated using several characterization techniques. Morphological features such as interdomains of the soft and hard segments were identified by means of atomic force microscopy. The thermal and mechanical behavior was evaluated by using dynamic mechanical analysis, differential scanning calorimetry and uniaxial tensile tests. Structural changes induced by varying the type and the number of isocyanates and the order of their introduction were also followed by using wide-angle X-ray. Materials with hard segments based on the single diisocyanate DBDI were observed to crystallize. Crystallinity was strongly reduced when DBDI was mixed with MDI. Improvement in elastomeric properties was obtained when both diisocyanates were included and reacted together in a random manner.

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Section: Tensile Test Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Morphological features and thermal and mechanical response in segmented polyurethane elastomers based on mixtures of isocyanates

Prisăcariu

Scortanu

Stoica

et al. 2011

Polym J

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“…Segmental orientation was studied by differential infrared dichroism experiments as detailed elsewhere [16]. A stretching device was made by us, which extended the TPU samples uniformly from both ends while it was centered in the IR beam.…”

Section: Ir Dichroic Measurementsmentioning

confidence: 99%

Effect of the hydrogen bonding on the inelasticity of thermoplastic polyurethane elastomers

Prisăcariu¹,

Scortanu²,

Agapie³

2013

Journal of Industrial and Engineering Chemistry

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Structural Studies and the Correlation with the Stress–Strain Response in Polyurethanes

Prisăcariu¹,

Scortanu²

2010

Encyclopedia of Analytical Chemistry

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The purpose of this article is to review and bring new contributions in understanding the relationship between molecular/supramolecular architecture at the nanometer scale and macroscopic mechanical properties in polyurethanes. In this article, this problem is addressed by studying numerous conventional segmented polyurethanes, based on several diisocyanates, macrodiols, and chain extenders. In order to widen the range of structures achievable beyond those normally available, in this review, we have also included recent developments that have been made in polyurethane materials by producing polymers based on isocyanates of variable geometry, giving hard segments that allow the variation of hard‐domain crystallinity as a key structural variable. They were used to probe the sensitivity of inelastic effects to structural details of the materials. Mechanical responses studied were large strain, constant strain rate, and cyclic strain responses, including interrupted tests. Results were related to microstructural changes, on the basis of evidence from small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray scattering (WAXS) and infrared (IR) dichroic measurements. Inelastic effects were most pronounced when the hard segment crystallized, and when the phase segregation was more pronounced. Thermal techniques such as differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to study the thermal behavior of the materials. There were tendencies to phase separation, with a characteristic length of ca. 20 nm, and, when isocyanates of variable geometry were employed with certain chain extenders, to crystallization of the hard phase. Such materials display higher flow stress in the hard phase caused by stronger phase segregation. This has clearly revealed that inelastic features in the constitutive response of polyurethane elastomers are sensitive to microstructural detail on length scales of the order of nanometers. Hard‐domain crystallinity exerts a strong effect on inelasticity of the elastomers. There is a clear indication that the physical origin of the flow stress is the relative displacement of the hydrogen‐bonded hard segments. Inelasticity, as measured by hysteresis and unrecovered strain, was increased by increased phase separation.

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Infrared Dichroic Studies of Phase Separation and Orientation of Dibenzyl Hard Segments in Polyurethane

Cited by 8 publications

References 5 publications

Morphological features and thermal and mechanical response in segmented polyurethane elastomers based on mixtures of isocyanates

Morphological features and thermal and mechanical response in segmented polyurethane elastomers based on mixtures of isocyanates

Effect of the hydrogen bonding on the inelasticity of thermoplastic polyurethane elastomers

Structural Studies and the Correlation with the Stress–Strain Response in Polyurethanes

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