Water effects in polyurethane block copolymers

Pissis, P.; Apekis, L.; Christodoulides, C.; Niaounakis, Michael; Kyritsis, Apostolos; Nedbal, J.

doi:10.1002/(sici)1099-0488(19960715)34:9<1529::aid-polb1>3.0.co;2-g

Cited by 113 publications

(103 citation statements)

References 4 publications

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“…The broadening of the response at the low-frequency side of the spectrum is due to the presence of the slower β relaxation, assigned to the local motion of associations of carbonyl groups and water molecules, as indicated by DRS measurements on samples at various water contents (not presented here), in agreement with the results of TSDC measurements on similar hydrated PUs [37]. The strong loss peak at T > T g , which shifts significantly with temperature, is due to the α relaxation associated to the glass transition, in agreement with previous studies [11,13,37], the DSC result for T g and the results of the analysis to be reported in the following section. Fig.…”

Section: Experimental Partsupporting

confidence: 92%

“…In addition to the γ relaxation at about 120 K and the α relaxation at about 220 K, a peak is observed at T > T α , where T α is the peak temperature of the α relaxation. In previous works this peak has been associated with interfacial Maxwell-Wagner-Sillars (MWS) polarization, i.e., mesoscopic transport of charge carriers and trapping at interfaces arising from the microphase-separated structure of PUs [11,13,37]. Thus, analysis of the characteristics of this peak may provide information on the morphology.…”

Section: Experimental Partmentioning

confidence: 96%

“…Results to be reported elsewhere give for the glass transition temperature T g of this sample, determined by DSC, 217 K. At low temperatures a broad secondary relaxation is observed as a step in ε'(f) and a peak in ε''(f) (centred at about 10 4 Hz at 173 K). In agreement with previous reports on PUs [11,13], this signal is attributed to the γ relaxation, related to the local motion of (CH 2 ) n sequences with attached dipolar groups [37]. The broadening of the response at the low-frequency side of the spectrum is due to the presence of the slower β relaxation, assigned to the local motion of associations of carbonyl groups and water molecules, as indicated by DRS measurements on samples at various water contents (not presented here), in agreement with the results of TSDC measurements on similar hydrated PUs [37].…”

Section: Experimental Partmentioning

confidence: 99%

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Comparative dielectric studies of segmental mobility in novel polyurethanes

et al. 2004

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Molecular dynamics in selected novel linear/low-branched polyurethanes (PUs), based on oligo(oxytetramethylene glycol), 4,4'-diphenylmethanediisocyanate (MDI) or 2,6-toluenediisocyanate (TDI), and unsymmetrical dimethylhydrazine (I) and a derivative of that (II) as chain extenders (CE), were studied by dielectric techniques. Special attention was paid to the investigation of the α relaxation, associated to the glass transition, by dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarization currents (TSDC). The TSDC method was used to study the interfacial Maxwell-Wagner-Sillars (MWS) relaxation, related to the accumulation of charges at the interfaces between soft-segment and hardsegment microdomains. The results obtained by DRS and TSDC were in good agreement with each other and in reasonable agreement with results for the microphase separation (MS) obtained by small-angle X-ray scattering and differential scanning calorimetry. TSDC proved to be an attractive complementary technique to DRS for the study of MS in PUs. The results suggest that the position of the MWS band, as well as its separation from the α band, is a good measure of the degree of MS. As regards the PUs studied here, the degree of MS enhances by increasing the mole ratio of CE, and by replacing MDI by TDI or CE I by CE II.

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Section: Experimental Partsupporting

confidence: 92%

Section: Experimental Partmentioning

confidence: 96%

Section: Experimental Partmentioning

confidence: 99%

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Comparative dielectric studies of segmental mobility in novel polyurethanes

et al. 2004

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“…The nanocomposite with 30 wt.% clay also shows the highest tan δ value, which reveals its best energy absorption capacity among these samples [26]. It was reported that the damping effect of the polymer depends strongly on the content of hard segment, crystallization of the soft segment and cross-linking rate [27,28]. In this study, the best damping effect was achieved for the nanocomposites with 30 wt.% clay, because of the significant increase in the content of hard segments.…”

Section: Methodsmentioning

confidence: 89%

Thermal-Mechanical Properties of Polyurethane-Clay Shape Memory Polymer Nanocomposites

Huang

et al. 2010

Polymers

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Shape memory nanocomposites of polyurethane (PU)-clay were fabricated by melt mixing of PU and nano-clay. Based on nano-indentation and microhardness tests, the strength of the nanocomposites increased dramatically as a function of clay content, which is attributed to the enhanced nanoclay-polymer interactions. Thermal mechanical experiments demonstrated good mechanical and shape memory effects of the nanocomposites. Full shape memory recovery was displayed by both the pure PU and PU-clay nanocomposites.

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“…SIBS with 0.35% weight of absorbed moisture showed a 5°C reduction in glass transition compared to dry samples. This type of behavior is not uncommon in polymer materials, and is generally attributed to plasticizing of the material due to the interaction of water molecules with the polymer network [18,19]. Of note is the proximity of the glass transition temperature to 100°C, which is potentially important due to the use of steamsterilization techniques for some implantable devices.…”

Section: Figure 2 Moisture Uptake Of Different Sibs At 37 Cmentioning

confidence: 96%

The effect of water absorption on the viscoelastic properties of poly(styrene-block-isobutylene-block-styrene) for use in biomedical applications

Fittipaldi¹,

Rodríguez²,

Grace³

2015

AIP Conference Proceedings

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Abstract. The decrease in glass transition temperature and change in creep compliance due to water diffusion in a biocompatible thermoplastic elastomer was studied and quantified. Knowledge of the mechanical and viscoelastic performance of the styrene-isobutylene-styrene block (SIBS) copolymer is important to determine the feasibility of certain in-vivo applications. Furthermore, the deterioration in these types of properties due to the plasticizing effect of water must be well understood for long term usage. Samples were formed with an injection molding press and fully dried prior to immersion in distilled water at 37 C. Water diffusion kinetics were studied for four different SIBS copolymers of varying molecular weight and styrene content by measuring weight changes as a function of time. These gravimetric diffusion studies showed an inverse relationship between diffusivity and styrene content and molecular weight for the first thousand hours of immersion. Measurements of storage modulus, loss modulus, tangent delta, strain recovery and creep compliance were performed using a dynamic mechanical analyzer for the high molecular weight, high styrene content SIBS version at different absorbed water contents. A measurable and nearly linear decrease of the glass transition temperature and creep recovery with respect to water content was observed for the samples tested even at relatively low water content: an increase in water content of 0.27% correlated to a decrease of 4 C in glass transition temperature while a 0.16% weight increase corresponded to a 12.5% decrease in creep recovery. These quantified material properties restrict the use of SIBS in certain implantable operations that undergo cyclic strains, and in sterilization techniques that require high temperatures. As such, they are important to understand in order to determine the viability of in vivo usage of this biocompatible polymer.

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Water effects in polyurethane block copolymers

Cited by 113 publications

References 4 publications

Comparative dielectric studies of segmental mobility in novel polyurethanes

Comparative dielectric studies of segmental mobility in novel polyurethanes

Thermal-Mechanical Properties of Polyurethane-Clay Shape Memory Polymer Nanocomposites

The effect of water absorption on the viscoelastic properties of poly(styrene-block-isobutylene-block-styrene) for use in biomedical applications

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