A Comparison of Phase Organization of Model Segmented Polyurethanes with Different Intersegment Compatibilities

Hernández, Rebeca; Weksler, Jadwiga; Padsalgikar, Ajay D.; Choi, Taeyi; Angelo, Elena; Lin, Jianzhen; Xu, Lichong; Siedlecki, Christopher A.; Runt, James

doi:10.1021/ma8014454

Cited by 161 publications

(155 citation statements)

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“…11,12 Two relaxations are observed in the temperature range of the current experiments. The low-temperature β process follows an Arrhenius form (see Figure 3b) with an activation energy of ∼35 kJ/mol and is associated with local motion of the soft segments.…”

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confidence: 62%

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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Dynamics of Uniaxially Oriented Elastomers Using Broadband Dielectric Spectroscopy

et al. 2010

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“…From the comparison of the spectra received for PTUR and EPTURs it follows that bands at 1,637-1,633 and 1,660-1,659 cm -1 are related to the H-bonded and nonbonded C=O stretching of the thiourethane group, and those at 1,687-1,680 and 1,720-1,715 cm -1 can be ascribed to H-bonded and nonbonded C=O stretching of the urethane group. In the spectra of PHCD-based EPTURs the band at about 1,715 cm -1 can also be ascribed to H-bonded C=O stretching of the carbonate group, whilst the band at 1,740-1,738 cm -1 originates from nonbonded C=O stretching of the carbonate group [19]. Moreover, in all spectra one band at 3,313-3,275 cm -1 connected with N-H stretching vibrations of thioure thane and urethane groups can also be observed, as well as two weakly separated bands at 1,513-1,511 and 1,525-1,523 cm -1 which can be associated with N-H bending vibrations of thiourethane and urethane group, respectively.…”

Section: Polymer Synthesis and Characterizationmentioning

confidence: 99%

New thermoplastic poly(thiourethane-urethane) elastomers based on hexane-1,6-diyl diisocyanate (HDI)

Rogulska

Kultys

Olszewska

2013

J Therm Anal Calorim

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Two series of new thermoplastic poly(thiourethane-urethane) elastomers (EPTURs), with different hardsegment content (40-60 wt%), were synthesized by a onestep melt polymerization from poly(oxytetramethylene) diol (PTMO) of M n = 1,000 g mol -1 or poly(hexamethylene carbonate) diol (PHCD) of M n = 860 g mol -1 as a soft segment, hexane-1,6-diyl diisocyanate and (methylenedi-1,4-phenylene)dimethanethiol as a chain extender at the NCO/(OH ? SH) molar ratio of 1. The structures of all the EPTURs were examined by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy and X-ray diffraction analysis. Their thermal behavior was investigated by means of differential scanning calorimetry and thermogravimetric analysis (TG). For the chosen polymers the gaseous products evolved during the decomposition process were analyzed by TG-FTIR. Moreover, physicochemical, adhesive and tensile properties as well as Shore A/D hardness were determined. The resulting highmolecular-mass EPTURs were stable up to 254-262°C, as measured by the temperature of 1 % mass loss. They decomposed in three or four stages. The main decomposition products were carbonyl sulfide, isocyanate, carbon dioxide, aromatic hydrocarbons as well as aliphatic ethers and aldehydes (in PTMO series) and alcohols (in PHCD series). All the polymers showed partially crystalline structures, associated with crystallization of thiourethane hard segments. Their melting temperatures were in the range of 184-186°C. The PTMO series EPTURs exhibited better low-temperature properties (glass-transition temperature in the range of -64 to -44 vs. -26 to -22°C), but poorer tensile strengths (20-28 vs. 37-43 MPa). These EPTURs showed improved adhesive properties in comparison with their polyurethane analogs.

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“…It is obvious to assume that interactions will be different in polyurethanes prepared from the two kinds of polyols, and experience supports this assumption by showing that the properties of products prepared from them differ considerably [26]. Although the effect of the structure and characteristics of the polyol on PU properties have been investigated extensively [27][28][29][30], many questions related to structure-property correlations in these materials remain open. The goal of this communication is to discuss the possible effect of specific interactions on the structure and properties of segmented linear polyurethane elastomers.…”

Section: Introductionmentioning

confidence: 99%

Specific interactions, structure and properties in segmented polyurethane elastomers

Bagdi

Molnár

Sajó

et al. 2011

Express Polym. Lett.

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Abstract. Two sets of segmented polyurethane (PU) elastomers were prepared from 4,4!-methylenebis(phenyl isocyanate) (MDI), 1,4-butanediol (BD) and a polyester or a polyether polyol, respectively. The molecular mass of both polyols was 1000 g/mol. The stoichiometric ratio of isocyanate and hydroxyl groups was 1 and the polyol/total diol ratio changed from 0 to 1 in 0.1 steps. One step bulk polymerization was carried out in an internal mixer and the samples were compression molded for testing. The results proved that specific interactions determine the phase structure and properties of these materials. Crystallinity was approximately the same in the two types of polyurethanes and the amount of relaxing soft segments was also similar. The determination of interaction parameters from solvent absorption and differences in glass transition temperatures indicated stronger interaction between hard and soft segments in the polyester than in the polyether polyurethane. Larger transparency of the polyester PU indicated the formation of smaller dispersed particles of the hard phase. The larger number of smaller hard phase units led to the formation of more physical cross-links distributed more evenly in the polymer. These differences in the phase structure of the polymers resulted in stronger strain hardening tendency, larger strength and smaller deformations for the polyester than for the polyether polyurethane.

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A Comparison of Phase Organization of Model Segmented Polyurethanes with Different Intersegment Compatibilities

Cited by 161 publications

References 47 publications

Dynamics of Uniaxially Oriented Elastomers Using Broadband Dielectric Spectroscopy

Dynamics of Uniaxially Oriented Elastomers Using Broadband Dielectric Spectroscopy

New thermoplastic poly(thiourethane-urethane) elastomers based on hexane-1,6-diyl diisocyanate (HDI)

Specific interactions, structure and properties in segmented polyurethane elastomers

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