Poly Urethane-urea Research Articles

New Polyurethane Urea Thermoplastic Elastomers with Controlled Mechanical and Thermal Properties for Medical Applications

The method of synthesis of new polyurethane urea thermoplastic elastomers with controlled physical network density by varying the crystallization rate of the soft block and the structure of the interphase has been developed. Fine-tuning of morphology and mechanical properties allows to desighn adaptive materials with shape memory. By combination of calorimetric and X-ray diffraction methods, the influence of chemical nature of diaisocyanates and the ratio of two types of crystallizable blocks, polybutylene glycol adipate diol (PBA) and poly-ε-caprolactone diol (PCL), on the structure and termal behavior of the thermoplastic elastomers has been studied.

Blending Polymer Labile Elements at Differing Scales to Affect Degradation Profiles in Heart Valve Scaffolds.

After more than 22 years of research challenges and innovation, the heart valve tissue engineering paradigm still attracts attention as an approach to overcome limitations which exist with clinically utilized mechanical or bioprosthetic heart valves. Despite encouraging results, delayed translation can be attributed to limited knowledge on the concurrent mechanisms of biomaterial degradation in vivo, host inflammatory response, cell recruitment, and de novo tissue elaboration. This study aimed to reduce this gap by evaluating three alternative levels at which lability could be incorporated into candidate polyurethane materials electroprocessed into a valve scaffold. Specifically, polyester and polycarbonate labile soft segment diols were reacted into thermoplastic elastomeric polyurethane ureas that formed scaffolds where (1) a single polyurethane containing both of the two diols in the polymer backbone was synthesized and processed, (2) two polyurethanes were physically blended, one with exclusively polycarbonate and one with exclusively polyester diols, followed by processing of the blend, and (3) the two polyurethane types were concurrently processed to form individual fiber populations in a valve scaffold. The resulting valve scaffolds were characterized in terms of their mechanics before and after exposure to varying periods of pulsatile flow in an enzymatic (lipase) buffer solution. The results showed that valve scaffolds made from the first type of polymer and processing combination experienced more extensive degradation. This approach, although demonstrated with polyurethane scaffolds, can generally be translated to investigate biomaterial approaches where labile elements are introduced at different structural levels to alter degradation properties while largely preserving the overall chemical composition and initial mechanical behavior.

The effect of plasticization on the functional properties of thermoplastic polyurethane ureas

Several series of plasticized segmented polyether urethane of linear structure which can be used as the polymer base of thermoplastic materials were synthesized. The possibility of obtaining thermoplastic segmented polyurethane ureas with a softening temperature of 100 ÷120°C when using isophorone diisocyanate as the main element for building polymer chains, and DEHS as a plasticizer was proven. The original method for the purification of aromatic amine 4,4′-methylene-bis(2-chloroaniline) used in the process of synthesizing polyurethane ureas as a chain extender was developed. The polymers obtained have a uniquely low glass transition temperature close to -100°C with a plasticizer concentration of not more than 40%. The strength of these materials is more than 10 MPa at room temperature, and it is more 40 MPa at -70°C.

Calcification resistance of polyisobutylene and polyisobutylene‐based materials

Calcification of implanted biomaterials is highly undesirable and limits clinical applicability. Experiments were carried out to assess the calcification resistance of polyisobutylene (PIB), PIB‐based polyurethane (PIB‐PU), PIB‐PU reinforced with (CH3)3N+CH2CH2CH2NH2 I−‐modified montmorillonite (PIB‐PU/nc), PIB‐based polyurethane urea (PIB‐PUU), PIB‐PU containing S atoms (PIBS‐PU), PIBS‐PU reinforced with (CH3)3N+CH2CH2CH2NH2 I−‐modified montmorillonite (PIBS‐PU/nc), and poly(isobutylene‐b‐styrene‐b‐isobutylene) (SIBS), relative to that of a clinically widely implanted polydimethylsiloxane (PDMS)–based PU, Elast‐Eon (the “control”). Samples were incubated in simulated body fluid for 28 days at 37°C, and the extent of surface calcification was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray photoelectron spectroscopy (XPS), and Fourier‐transform‐infrared (FT‐IR) spectroscopy. Whereas the PDMS‐based PU showed extensive calcification, PIB and PIB‐PU containing 72.5% PIB, ie, a polyurethane whose surface is covered with PIB, were free of calcification. PIBS‐PU and PIB‐PUU, ie, polyurethanes that contain S or urea groups, respectively, were slightly calcified. The amine‐modified montmorillonite‐reinforcing agent reduced the extent of calcification. SIBS was found slightly calcified. Evidently, PIB and materials fully coated with PIB are calcification resistant.

Synthesis and characterization of eco‐friendly siloxane‐semifluorinated polyurethane coatings for underwater application

ABSTRACTSiloxane‐semifluorinated polyurethane coatings were prepared for robust underwater application. Initially, acrylic polyol (FS‐GPTACP)‐containing fluoroalkoxysilane (1H,1H,2H,2H‐Perfluorooctyltrimethoxysilane) pendant group was synthesized by the free‐radical polymerization method. Different weight percentages of polydimethylsiloxane (0, 10, and 20 wt %) were added to the polyol to tune the mechanical and the surface energy of the coating. Subsequently, this polyol mixture was cured with 4, 4′‐methylenebis(cyclohexyl isocyanate) (H12MDI) to prepare a series of siloxane‐semifluorinated polyurethane–urea hybrid coatings (APUS 0%, APUS 10%, and APUS 20%). The synthesized coating showed low surface energy, hydrophobicity with exceptional water, and alkali resistance. Moreover, the coating displayed excellent mechanical properties with low pseudobarnacle adhesion strength. The coatings also showed nontoxicity against gram‐positive and gram‐negative bacterial strains. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47720.

Thermo-oxidative degradation kinetics of renewable hybrid polyurethane–urea obtained from air-oxidized soybean oil

This study explores the synthesis and kinetics of non-isothermal thermo-oxidative degradation of renewable hybrid polyurethane (PU)–urea obtained from air-oxidized soybean oil. Fourier transformed infrared spectroscopy (FTIR) and thermogravimetry (TG) analyses were performed, aiming to verify chemical changes and the kinetics parameters using different approaches for the samples obtained. FTIR confirmed that a polymerization process occurred as well and modification in the relative hydrogen bonds is due to the formed urea groups that formed in the hybrid materials. TG analysis showed a dependence of the activation energy (using the FWO and KAS model-free methods) on the degree of conversion for all samples studied in three different degradation steps. The most probable degradation mechanism was tested by using a multivariate nonlinear regression by using the F statistical test. For all samples, the autocatalytic model successfully described the thermo-oxidative degradation, which is in accordance with the chemical degradation process for polyurethanes. Finally, thermal degradation in the time function was estimated and more satisfactory results were obtained by comparing the literature data for similar systems. So, it was possible to obtain reliable and consistent results of the kinetic parameters, which are essential for academic and industrial purposes.

Stretchy and strong polyurethane-urea supramolecular (PUUS) hydrogels with various stimulus-responsive behaviours: the effect of chain-extenders.

The development of an easy synthetic strategy combined with straightforward tailoring of physical properties and functionalities, such that optimal performance can be targeted for various applications, still remains challenging. Previously, we reported the construction of thermo- and water-responsive strong and tough supramolecular hydrogels based on the cooperatively enhancing effect between H-bonding and hydrophobic forces. Recently, the strategy was greatly simplified to a one-pot two-step approach. In this work, by simply changing the chain extenders used in the second step, different kinds of functional units are easily introduced into the hard segments in the main chain of the copolymers to endow the resultant strong and tough supramolecular hydrogels with various stimulus-responsive properties. A dynamic covalent bond (disulphide or imine bond, e.g.-S-S- or -C[double bond, length as m-dash]N-) in the main chain provides the resulting hydrogels with reduction or pH responsive degradation (gel-to-sol transition) on demand behaviors, respectively; the azobenzene unit endows the yielding hydrogels with UV-Vis controlled stiffness; the pyridine group containing supramolecular hydrogel shows metal ion responsive mechanical and fluorescent behavior. These results provide progress toward addressing the challenges of achieving structural and synthetic simplicity married with sophisticated functionalities.

Blending In Situ Polyurethane-Urea with Different Kinds of Rubber: Performance and Compatibility Aspects.

Specific physical and reactive compatibilization strategies are applied to enhance the interfacial adhesion and mechanical properties of heterogeneous polymer blends. Another pertinent challenge is the need of energy-intensive blending methods to blend high-tech polymers such as the blending of a pre-made hard polyurethane (-urea) with rubbers. We developed and investigated a reactive blending method to prepare the outstanding blends based on polyurethane-urea and rubbers at a low blending temperature and without any interfacial compatibilizing agent. In this study, the polyurethane-urea (PUU) was synthesized via the methylene diphenyl diisocyanate end-capped prepolymer and m-phenylene diamine based precursor route during blending at 100 °C with polar (carboxylated nitrile rubber (XNBR) and chloroprene rubber (CR)) and non-polar (natural rubber (NR), styrene butadiene rubber (sSBR), and ethylene propylene butadiene rubber (EPDM)) rubbers. We found that the in situ PUU reinforces the tensile response at low strain region and the dynamic-mechanical response up to 150 °C in the case of all used rubbers. Scanning electron microscopy reveals a stronger rubber/PUU interface, which promotes an effective stress transfer between the blend phases. Furthermore, energy filtered transmission electron microscopy (EFTEM) based elemental carbon map identifies an interphase region along the interface between the nitrile rubber and in situ PUU phases of this exemplary blend type.

Improvement in mechanical properties of polyurethane‐urea nanocomposites by using modified SiO2 nanoparticles

ABSTRACTPoly(propylene glycol) (PPG)‐based nanocomposites have been prepared one shot using various contents of functionalized SiO2 nanoparticle as filler‐crosslinker agent. Triethoxy silyl propane‐1‐amine has been used as coupling agent for functionalization of SiO2 nanoparticle to improve its reactivity. The results revealed that the mechanical properties of the samples have been improved due to the functionalized SiO2‐nanoparticle effect on chemical and three‐dimensional physical crosslinking of the polyurethane–urea nanocomposites. Addition of the functionalized nanoparticle increased strength from 0.75 to 1.58 MPa in comparison to polyurethane sample. Moreover, storage moduli of PPG‐based polyurethane sample reduced in higher than room temperatures. While, using functionalized nanoparticle improves elasticity from 0.88 MPa in polyurethane sample to 2.84 MPa in polyurethane–urea nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46707.

Coining attributes of ultra-low concentration graphene oxide and spermine: An approach for high strength, anti-microbial and osteoconductive nanohybrid scaffold for bone tissue regeneration

Lack of auto osteogenesis and clinical complexities of repairing of bone after severe injuries, urge to develop a significant approach to promote regeneration of bone. The present work represents ornamentation of 2D rod-like nanohydroxyapatite (nHA) on ultra-low concentration graphene oxide (GO) sheet. The nanohybrids (GO-nHA) were incorporated into the spermine based high strength thermoplastic polyurethane-urea (PUU) matrices by in situ technique and the porous scaffolds were fabricated. 1 wt% GO-nHA filled scaffold displayed dramatically improved physico-mechanical properties. Cytotoxicity study using osteoblast cell like MG-63 cell line revealed positive cell viability (above 95%) and increased proliferation over a period of 14 days of culture. Semi-quantitative Real Time polymerase Chain Reaction (qRT-PCR) showed positive expression of collagen type I and osteocalcin indicating excellent maturation and biomineralization of osteoblasts. To avoid burden of carbonaceous particulate in body, very low percentage of GO (0.15%) was incorporated into the scaffold to improve mechanical properties, surface wettability, cell viability and cell proliferation drastically. Furthermore, in vivo study confirmed the promoted osteogenesis of PUU/GO-nHA scaffold in vivo without any cytotoxicity. Based on mechanical, in vitro and in vivo study the high strength nanohybrid scaffold exhibited tremendous potential for orthopedic applications.

Moisture-mediated self-healing kinetics and molecular dynamics in modified polyurethane urea polymers

Self-healing materials offer the ability to repair cracks within a polymeric material of molecular, micro- and macroscopic scale. The previously reported polyurethane urea (PUU) polymer with a high number of associative hydrogen bonding moieties was prepared containing 1-(2-aminoethyl) imidazolidone (UDETA). This chain terminating molecule defines the network density of the polymer and the affinity to water. Self-healing was observed if samples were exposed to moisture at room temperature. The reversible changes of the glass transition temperature Tg caused by variations in moisture, as well as the healing kinetics based upon visual crack disappearance and image grey scale analysis at different relative humidities, were examined in detail. Water is able to change the polymers microstructure and morphology leading to an increase of a mobile fraction (MF) within the polymer network structure. Self-healing kinetic studies proved that exposure to high relative humidity (23 °C, 73% RH) combined with a UDETA amount of 34 mol% facilitated higher molecular dynamics for a complete healing process. Combining the self-healing kinetic studies and dedicated time-domain NMR measurements, a MF threshold for efficient self-healing was defined. In addition, NMR results reported on the softening associated with Tg. MDSC experiments confirmed substantial dynamic inhomgeneities within the samples.

Anterior tibial tendon repair with polycaprolactone-based polyurethane urea based graft (Artelon)

Category: Sports Introduction/Purpose: Ruptures of the anterior tibial tendon are rare injuries usually occurring in patients over the age of 40. Delayed diagnosis is common and reconstruction often involves the use of autograft or allografts. This paper reports on the use of a polycaprolactone-based polyurethane urea (PUUR) hyperelastic polymer (Artelon) in the repair or reconstruction of anterior tibial tendon ruptures. Methods: Artelon® is a knitted textile matrix that is manufactured from fibers of polycaprolactone-based polyurethane urea (PUUR), a hyperelastic and creep-resistant polymer. Previous studies have demonstrated that Artelon integrates without immune reaction, has mechanical properties that resemble healing tendons and ligaments, and degrades benignly through hydrolysis over a 5-6 year span. This is a retrospective examination of the first 6 cases of anterior tibial tendon reconstruction using the Artelon PUUR graft. Patient outcomes are measured with AOFAS scores. In addition, range of motion and strength of the injured side is compared to the native, uninjured side. Results: There were no complications using the Artelon graft to augment anterior tibial tendon reconstruction and repair. Patient outcomes at 6 months were significantly improved compared to preoperative. Range of motion and strength were similar to the contralateral, uninjured side. Conclusion: Artelon is a safe, effective soft tissue augmentation device that can be used in the setting of anterior tibial tendon repaair or reconstruction.

Structure and adhesion properties before and after hydrolytic ageing of polyurethane urea adhesives made with mixtures of waterborne polyurethane dispersions

Several waterborne polyurethane urea dispersions (WPUUs) were prepared by mixing different amounts of two waterborne polyurethane urea dispersions made with polyester (WPUU-Polyester) and polycarbonate diol (WPUU-PCD). Their crystallinity, thermal, rheological, viscoelastic and adhesion properties depended on the segmented structure and degree of phase separation which were determined by the different content of the parent dispersions. The PUU films made with WPUU-Polyester+WPUU-PCD mixtures containing more than 50 wt% of WPUU-PCD showed higher hard segments content and lower degree of phase separation, and the addition of 25 wt% of WPUU-Polyester imparted crystallinity to the polyurethane urea due to the interactions between the carbonate groups in the soft segments. The differences in the degree of phase separation and crystallinity of the PUU films made with WPUU-Polyester+WPUU-PCD mixtures were evidenced by the increase in the glass transition temperature associated to the alpha relaxation of the soft segments, and the higher modulus at the cross-over between the storage and loss moduli. Excellent adhesion was obtained in plasticized PVC/WPUU/plasticized PVC joints, and a cohesive failure of PVC was always obtained, irrespective of the composition of WPUU-Polyester+WPUU-PCD mixtures. Furthermore, the adhesion of surface-chlorinated vulcanized styrene-butadiene (SBR) rubber/WPUU+5 wt% hardener/roughened leather joints were high and similar in all joints and a dominant cohesive failure in the rubber substrate was produced. The accelerated ageing by immersion in water at 70 °C during different times showed that the polyurethane urea film and the surface-chlorinated vulcanized SBR rubber/WPUU+5 wt% hardener/roughened leather joint made with WPUU-PCD dispersion were not affected, but noticeable hydrolytic degradation of the ester units in the soft segments was produced in PUU-Polyester and, to a less extent, in PUU-50Polyester/50PCD films and adhesive joints.

Curcumin incorporated polyurethane urea elastomers with tunable thermo-mechanical properties

Polyurethane urea (PUU) elastomers were synthesized using 1,4-diaminobutane (DAB) as a chain extender, hexamethylene diisocynate (HMDI) as a hard segment and polycaprolactone (PCL) as a soft segment with different concentrations of curcumin (CUR). A series of curcumin polyurethane ureas (CURPUU) containing different mole ratio of: CUR: PCL (0:100, 15:85, 25:75 and 35:65) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength, scanning electron microscope (SEM) and contact angle to study the effect of curcumin on the polymer properties. Thermal analysis revealed that CURPUU with the mole ratio 15:85 of CUR: PCL exhibited better thermal stability. The observed tensile strength, breaking strain and initial modulus were found to be in the range of 7.34 to 19.08 MPa, 213.20 to 925.38% and 2.18 to 23.33 MPa respectively. The hydrophobicity of CURPUU film increased by increasing the ratio of curcumin. The morphological characterizations of PUU were revealed by SEM. UV-Spectrophotometer was employed to investigate the physically entrapped curcumin into CURPUU elastomers. Finally, antimicrobial activity of all the PUU samples was investigated against two bacterial strains (E. coli and S. aureus) which exhibited that these elastomers can be used as potential biomedical materials.

A new amino-alcohol originated from carbon dioxide and its application as chain extender in the preparation of polyurethane

In this work, CO2 was chemically fixed by reacting with 1, 4-butanediol diglycidyl ether in the presence of a basic polystyrene resin catalyst. Under the 100% conversion of 1, 4-butanediol diglycidyl ether, five-membered cyclocarbonate with a selectivity of 98.5% was obtained. The cyclocarbonate was then reacted with an excess of 1, 2-ethylenediamine and the product was characterized by Fourier transform infrared spectrometer and nuclear magnetic resonance spectrometer. The results confirmed the successful synthesis of NH2 terminated product with a selectivity of 98.9%, accompanied by the formation of hydroxyls on β-C to the carbonyl groups, which can be regarded as a new amino-alcohol. Further, the obtained amino-alcohol was applied for the preparation of polyurethane urea as chain extender in a prepolymer way. Since the reactivity of isocyanate with NH2 is much faster than that with OH, the OH groups can be maintained in the system and hence strengthen the hydrogen bonding in polyurethane urea, which endows the materials with some unique properties. Comparing with the polyurethanes yielded from 1, 6-hexanediamine and 1, 6-hexanediol, polyurethane urea synthesized from the new amino-alcohol possessed better water/solvents resistance, considerable mechanical and thermal properties.

Shape Memory Properties and Enzymatic Degradability of Poly(ε-caprolactone)-Based Polyurethane Urea Containing Phenylalanine-Derived Chain Extender.

Biodegradable shape memory polymers are promising biomaterials for minimally invasive surgical procedures. Herein, a series of linear biodegradable shape memory poly(ε-caprolactone) (PCL)-based polyurethane ureas (PUUs) containing a novel phenylalanine-derived chain extender is synthesized. The phenylalanine-derived chain extender, phenylalanine-hexamethylenediamine-phenylalanine (PHP), contains two chymotrypsin cleaving sites to enhance the enzymatic degradation of PUUs. The degradation rate, the crystallinity, and mechanical properties of PUUs are tailored by the content of PHP. Meanwhile, semicrystalline PCL is not only hydrolytically degradable but also vital for shape memory. Good shape memory ability under body temperature is achieved for PUUs due to the strong interactions in hard segments for permanent crosslinking and the crystallization-melt transition of PCL to switch temporary shape. The PUUs would have a great potential in application as implanting stent.

Preparation of radiopaque polyurethane–urea/graphene oxide nanocomposite using 4-(4-iodophenyl)-1,2,4-triazolidine-3,5-dione

New radiopaque nanocomposites were prepared based on iodinated polyurethane–urea (PUU) and graphene oxide (GO). The iodinated PUU was synthesized using 4,4′-methylenediphenyl diisocyanate (MDI), polyethylene glycol (PEG, Mn = 1000), and 4-(4-iodophenyl)-1,2,4-triazolidine-3,5-dione (IUr) as a novel chain extender and radiopacifying agent. The synthesized urazole, PUU, and the related nanocomposites are characterized by fourier transform infrared spectrum, nuclear magnetic resonance, X-ray diffraction, field-emission scanning electron microscopy, elemental analysis (CHNO), thermogravimetric analysis, and dynamic mechanical thermal analysis (DMTA). The X-ray visibility of the radiopaque PUU and nanocomposites was investigated using X-radiography. To evaluate the biocompatibility of the samples, the indirect MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay was carried out on the non-cancerous mouse fibroblast cell line NIH3T3 D4 according to the ISO10993-5 standard. The DMTA results proved introduction of the GO layers into the iodinated PUU matrix, and has improved mechanical properties of the nanocomposites compared to the pure polymer. The X-ray images showed significant radiopacity of the pure polymer and the nanocomposites.

Surface morphology of chlorine and castor oil-based polyurethane–urea coatings

The present work deals with surface properties of chlorine containing polyurethane–urea (PU–urea)-coating films. First, isocyanate-terminated pre-polymers were synthesized using castor oil as renewable resource, isophorone diisocyanate, and different weight percentages of 2-chloroethanol and 2,2,2-trichloroethanol. The resultant isocyanate-terminated pre-polymers were cured under atmospheric moisture to obtain chlorine containing PU–urea coatings. The surface properties of the coating films were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. All characterization techniques suggest that the presence of chlorine species on the surface results in different surface properties when compared to control PU–urea (without the chlorine group)-coating film surface. The viscoelastic, swelling, and contact angle (CA) properties were studied for the prepared coating films. The glass-transition temperatures (Tg) were obtained in the region 29.2–35 °C for the coating films. Tg increased by increasing the chlorine content in polyurethane-coating formulations. The CA for the coating films was found to be in the range of 76°–64° and these properties were found to be decreased with increase in the weight percent content of the chlorine moiety in the final coating formulation. Similarly, the higher chlorine content-coating films have shown more water uptake properties. The overall comparative results indicate that the chlorine containing PU–urea-coating films have different surface-coating properties and these depend upon the chlorine content in the final coating formulation as compared with PU–urea surfaces.

T-Butyl-Oxycarbonylated Diamines as Building Blocks for Isocyanate-Free Polyurethane/Urea Dispersions and Coatings.

t-Butyl-oxycarbonylated diamines ("di-Boc-carbamates") are investigated as dicarbamate monomers for diamine/dicarbamate polymerizations. Polyureas (PUs) and polyurethanes (PURs) with high molecular weights are prepared from stoichiometric polymerizations of diamines or diols with N-N'-di-t-butyl-oxycarbonyl isophorone diamine (DiBoc-IPDC) using KOt-Bu as a catalyst, while gelation is observed when an excess of DiBoc-IPDC is used with respect to the diamines or diols. Stable dispersions are obtained from PUs and PURs with 3,3'-diamino-N-methyldipropylamine (DMDPA) as internal dispersing agent. The corresponding PU-based coatings exhibit superior mechanical properties and solvent resistances compared to the polyurethane urea coatings synthesized from diols, DiBoc-IPDC, and DMDPA.

Tetrablock Copolymers Based on Oligoether Diols, 2,4-toluene diisocyanate, Isophorone Diisocyanate, and Methylene-bis-о-chloroaniline

Tetrablock polyurethane ureas with mixed soft segments and dissimilar hard urethane urea blocks, based on oligo(propylene oxide)diol, oligo(tetramethylene oxide)diol, 2,4-toluene diisocyanate, isophorone diisocyanate, and methylene-bis-o-chloroaniline as a low-molecular-mass chain extender were synthesized and studied. The fragmentary ordering of the polymer chains of the new polyurethane urea was proved by rheokinetic data. The structure–property relationship for the polymer was found. The new polyurethane ureas surpass in the true strength the available diblock polyurethane ureas with poly(propylene oxide) soft segments by a factor of 1.5. The strength properties of the new tetrablock polyurethane ureas only weakly depend on the strain rate varied in the range 0.56–0.006 s–1.