Segmented Poly Urethane-urea Research Articles

Abrasive resistance of polyetherurethane ureas

The relationship between the structure of the polymer chains and the abrasion resistance of segmented polyurethane ureas based on polyoxytetramethylene oligoether was studied. Experimental data were obtained for systems with the hard segments content above 39%. It was found that the function of the volumetric wear of polyurethane-urea samples on the content of hard segments had an extremum; at high contents of these segments (more than 35%), a further increase in this content lead to a deterioration in the abrasion resistance. The reasons for this effect can be associated with a sharp deterioration in the strength and strain properties of the studied elastomers when additional amounts of diisocyanate are introduced into the system, which can lead to the formation of excessive interchain bonds.

A judicious approach of exploiting polyurethane-urea based electrospun nanofibrous scaffold for stimulated bone tissue regeneration through functionally nobbled nanohydroxyapatite

Complete natural healing of skeletal tissues may take several months or even years, depending on the type and size of defects owing to slow auto-osteogenesis. Numerous techniques have been explored to gear-up the bone-healing process, as bone tissue has complex nanohybrid hierarchical meshwork containing nano apatite layers. Healing of such tissues associates with risks of pathogenic infection and ectopic bone formation. Therefore, most of the approaches fail to meet the requisite criteria to adopt in clinical practice. Carbonaceous bone substitutes may trigger healing, but an excess of it may render many adverse effects. In the current study, nanohydroxyapatite (nHA) was prepared, doped with a minute amount (0.15%) of carboxyl functionalized multiwall carbon nanotube (CCNT). The hybrid nanomaterial (CCNTH) was introduced within the synthesized biomolecule tethered segmented polyurethane-urea (SP) through in-situ technique and scaffolds were fabricated by electrospinning technique. CCNT doping improves the tensile strength and the hardness of the nano-scaffold by 94.5% and 173.6%, respectively. In vitro MTT assay, FESEM and protein adsorption study indicated the excellent cytocompatibility of the nanohybrid scaffolds. The qRT-PCR study indicates the significant expression of the osteogenic bone marker, osteocalcin (OCN) and the alkaline phosphatase (ALP) of the CCNTH incorporated nanohybrid scaffolds compared to the SP scaffold. Furthermore, the in vivo rat tibia and skull model exhibit excellent bone regeneration efficacy compared to the control without showing any sign of organ toxicity. Thus, a minute amount of CCNT doped nHA incorporated SP based micro-porous nanohybrid scaffold can be used as an alternate suitable biomaterial for osteoinduction application.

The Influence of Fillers on Abrasive Wear of Segmented Polyurethane Urea

The Influence of Fillers on Abrasive Wear of Segmented Polyurethane Urea

Roles of phase separation and crystallization in the structure formation of new segmented polyurethane ureas and their nanocomposites with single-walled carbon nanotubes

Crystal structure and supramolecular organization of new segmented thermoplastic polyurethane ureas and their nanocomposites with ultra-small additives (less than 0.1 wt.%) of single-walled carbon nanotubes (SWCNTs) have been been investigated using DSC and X-ray diffraction analysis. Taking into account the Avrami model, effects of physical aging and thermal history of the samples on the crystallization rate was described. It was demonstrated that the introduction of ultra small amounts of SWCNTs does not decrease the crystallinity, but decreases the crystallization rate.

Analytical description of stress-strain dependence for segmented polyurethane ureas swollen in physically aggressive media

The article is devoted to the problem of analytical description of the strain behavior of elastomers under various conditions. It summarizes experimental data on the stress versus strain dependences of polyurethane urea elastomers swollen in two plasticizers. These data can be adequately described using the approach taking into account relaxation properties of elastomers and non-relaxation ones. All factors affecting the strain behavior of investigated elastomers are considered.

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.

Effect of morphology on the hydrolytic degradation of segmented polyurethane-urea films

La estabilidad hidrolítica de una serie de polímeros de Poliuretanourea segmentado (PUUs) fue estudiada bajo degradación in vitro en buffer de fosfato salino (PBS) con pH de 7.4 y 37 °C durante 20 semanas. La degradación y las propiedades mecánicas de los productos finales fueron controladas por el contenido de segmentos rígidos y el tratamiento cercano a la temperatura de fusión del glicol utilizado. La asociación de los segmentos rígidos se incrementó usando diisocianato y dioles lineales. Las interacciones moleculares promovieron diversas respuestas viscoelásticas, que a su vez, fueron influenciadas por el envejecimiento térmico promovido en las cercanías del glicol. Los estudios de degradación se realizaron en películas delgadas obtenidas por evaporación lenta del solvente. Los PUUs fueron caracterizados mediante técnicas de espectroscopia de IR, calorimetría, análisis dinámico-mecánico y difracción de rayos X

The Effect of Chain Extender Type on the Physical, Mechanical, and Shape Memory Properties of Poly(ε-Caprolactone)-based Polyurethane-ureas

ABSTRACTA series of segmented polyurethane-ureas were synthesized, based on poly(ε-caprolactone), hexamethylenediisocyanate, and different chain extenders. The effect of chain extender on physical, mechanical, and shape memory properties of the polyurethane-ureas was examined at constant hard-to–soft–segment molar ratio. Polyurethane-urea from piperazine showed higher degree of phase separation, mechanical characteristics, shape fixity, and shape recovery temperature than polyurethane-ureas from aliphatic chain extenders. Furthermore, the degree of phase separation was decreased by increasing of chain length of aliphatic chain extenders. This was attributed to the dissimilar compatibility and flexibility of the hard segments, resulting from different chain extenders.

Preparation, characterization, and thermo-mechanical properties of poly (ε-caprolactone)-piperazine-based polyurethane-urea shape memory polymers

A series of segmented polyurethane-urea (PUU) shape memory polymers were synthesized from poly e-caprolactone (PCL)-diol, hexamethylene diisocyanate, and piperazine (PP) with different hard to soft segment ratios. Chemical structure of PUUs was characterized using hydrogen nuclear magnetic resonance and attenuated total reflective-Fourier transform infrared spectroscopy methods. The results confirmed the formation of urethane and urea groups as well as incorporation of PP ring into polymer chain. Differential scanning calorimetry and wide angle X-ray scattering analyses were conducted to study the thermal properties and crystalline morphology of PUUs. It was found that crystallization of PUUs originated from PCL crystals. The reduction in degree of crystallinity was also observed with increasing of hard segment content (HSC). Mechanical properties were examined by tensile test at two different temperatures; above and below the PCL melting temperature. It was revealed that the chemical composition and temperature greatly affect the mechanical behavior of PUUs. A correlation between mechanical properties and physical structure of PUUs was established. Shape memory properties of PUUs were studied at two different programming processes. All of the samples show shape recovery over 94 % with a broad recovery temperature ranging from 40 to 65 °C. However, the shape fixity showed a great dependence on both HSC and programming process. The reasons of this dependency were discussed.

Synthesis, Characterization, and Electrospinning of Calcium-Containing Polyurethane Urea

Calcium-containing segmented polyurethane urea was synthesized using a calcium salt of p-aminobenzoic acid, polytetramethylene glycol, and 4,4′-methylene bis(cyclohexyl isocyanate) and thereafter fabricated into three-dimensional scaffolds for the use in biomedical applications. Biocompatibility evaluation of the polymer showed that this newly developed metal-containing polyurethane urea demonstrated good cytocompatibility and hemocompatibility. The fabricating ability of the metal-containing polymer was studied by the electrospinning process. The effect of various parameters such as polymer concentration, applied voltage, and flow rate on the electrospinning process, morphology, and diameter of the resultant fibers was investigated. The findings indicate that increasing the concentration and flow rate of the solution increases the fiber diameter. It was also demonstrated that increasing the applied voltage decreases the fiber diameter. Mechanical property evaluation of the scaffolds showed that the strength of the scaffold depends on both the diameter and morphology of the fibers. As the fiber diameter increases from 1.6 to 3.02 μm, the tensile strength enhanced from 3 to 7 MPa.

New multi-block isophorone diisocyanate-based copolymers with urethane urea hard segments

Segmented polyurethane ureas (SPUUs) were synthesized on the base of oligopropylene oxide (PPO), oligotetramethylene oxide (PTMO), 2,4-toluene diisocyanate, isophorone diisocyanate (IDI), and methylene- o-chloroaniline. Structure of polymer chains with thermodynamically compatible PTMO and PPO soft segments (SS) was identified using data from rheokinetic studies of reactionary mixes with different diisocyanates. The significant swelling value in low-polar solvent toluene and non-elevated softening temperature indicates the formation of loose (defect) structure of the hard phase in compositions, synthesized using IDI. Thermal, thermomechanical, and physicomechanical properties of SPUU with variable compositions of hard segment and SS (blocks) were investigated. An interrelation between structure and properties of block copolymers of new type was estimated. Investigation results showed a significant increase in the strength of polyurethane urea at the equimolar ration between various hard blocks and SS on the base of PPO and PTMO. High strength values were obtained for SPUU in a wide diapason of stretching rates (0.56–0.003 s−1). Structural factors contributing to stability of strength properties of tetrablock-copolymers, namely: stronger inter-chain interaction in the soft phase and a “loose” structure of the hard phase. were revealed. The data relating to elevation of thermostability of these materials were given. New materials can be applied for various conditions of mechanical loading.

Stress–Strain Dependence of Segmented Polyurethanes and Polyurethane Ureas

The stress–strain dependences of segmented elastomers based on polyetherurethanes, polyesterurethane ureas, and polybutadieneurethane ureas were investigated. These dependences were adequately described using the generalized approach proposed earlier by the authors for amorphous elastomers. The experimental data obtained for four series of samples with chemical cross-linking confirmed an applicability of this approach for segmented elastomers. Unlike amorphous elastomers, the effective network density value was affected not only by the density of the chemical network, but the contribution of the network formed by the hard domains also needs be taken into account.

High-performance segmented polyurea by transesterification of diphenyl carbonates with aliphatic diamines

In an effort to develop a green process for the production of elastomeric polyurethane–urea (PUaE) through a nonisocyanate route, a highly practical method was found using diphenyl carbonate (DPC) instead of diisocyanate as the carbonylation agent. The transesterification of aliphatic diamines in a solvent such as tetramethylene sulfone (TMS) with DPC results in a new process obtaining new segmented PUaE with high molecular weights and excellent mechanical performance. The key to the present success lies in the timing and sequence of the diamine addition forming initial carbamate intermediates in situ and then in shifting the equilibrium toward polyurea product formation by phenol removal from the TMS solution so that high-molecular-weight polyurea could be formed favorably. The most optimized polyurea films made in this study has a ηinh of 0.64, with high-performance characteristics showing tensile strength of greater than 30 MPa and elongation exceeding 400% with decomposition temperature (5%) of >280 °C. Well-defined soft- and hard-segment domains were observed for the products as determined by atomic force microscope. This new improved process to produce segmented polyurea thereby complies fully with the principles of green chemistry using readily available chemicals. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2781–2790

Study on thermal stability of polyurethane-urea based on polysiloxane and polycaprolactone diols

Different grades of segmented polyurethane-urea were synthesized through two-step solution polymerization of polydimethylsiloxane (PDMS) and polycaprolactone (PCL) polyols with methylene diphenyl diisocyanate (MDI) and mixture of 1,4-buthanediol and 4,4-methylene bis (3-chloro 2,6-diethylaniline) in toluene/tetra-hydrofuran media. Structural characterization of the synthesized samples was conducted using Fourier transform infra-red spectroscopy. X-ray diffraction, dynamic mechanical thermal analysis, thermal gravimetric analysis, and differential scanning calorimetry techniques were utilized to assess material characteristics. The results showed a relationship between PDMS content and thermal stability, morphology and mechanical properties of the urethane-urea samples. Onset degradation temperature was increased by increasing the PDMS content in the polyurethane backbone where the crystallinity was varied versus PDMS content. Strong interaction established between hard and soft segments resulted in a positive shift in PCL glass transition temperature. Tracking E′, E″ and damping factor in DMTA measurements confirmed the two-phase morphology. Hydrophobicity of polymer surfaces was traced by contact angle measurement.

Advancement in Textile Technology for Defence Application

The early development of textiles involved use of natural materials like cotton, wool and flax. The advent of the new technology revolutionized textiles which enables to develop synthetic fibers like lycra®, a segmented polyurethane-urea, which has exceptional elastic properties, Kevlar®, which has ultra high strength properties and is used as bulletproof vest. For the improvement of personal mobility, health care and rehabilitation, it requires to integrate novel sensing and actuating functions to textiles. Fundamental challenge in the development of smart textile is that drapability and manufacturability of smart textiles should not be affected. Textile fabrics embedded with sensors, piezoelectric materials, flame retardant materials, super hydrophobic materials, controlled drug release systems and temperature adaptable materials can play major role in the development of advanced and high-tech military clothes. Advancement in the textile materials has the capacity of improving comfort, mobility and protection in diverse hostile environment. In this study, the advancement in energy harvesting textiles, controlled release textiles and engineering textiles are presented.Defence Science Journal, 2013, 63(3), pp.331-339, DOI:http://dx.doi.org/10.14429/dsj.63.2756

Interrelationship between ultimate mechanical properties of variously structured polyurethanes and poly(urethane urea)s and stretching rate thereof

The ultimate mechanical properties of polyurethane determine their possible applications under various conditions of mechanical action. The mechanical properties of nine polyurethane and polyurethane urea samples were investigated in a range of stretching rates 0.56÷0.002 s−1. A part of experiments was performed at several temperature values under conditions of stepwise variable stretching rates. The interrelationship between rate dependence of strength–strain properties of polyurethane compositions and the structure thereof was ascertained. The influence of molecular structure’s variations, of physical network density and of segmented polyurethane and polyurethane urea morphology on said interrelationship was examined on samples subjected to large strain values. The structure of some samples was radically distorted by plasticizers oppositely influencing micro-phase segregation of soft and hard segments. Multiple kinds of dependency (direct, inverse, moderate and strong) of elastomers’ strength versus stretching rate were demonstrated. Produced data and ascertained regularities are useful to perceive reasons for diversity of mechanical behavior of polyurethane materials and to control properties thereof.

X-ray Scattering Analyses on Deformation Behaviors of Thermoplastic Elastomers

Deformation behaviors of thermoplastic elastomers and structural changes upon uniaxial stretching and upon the subsequent release of the stretching load, as revealed by in-situ measurements of X-ray scattering, are reviewed. Exclusively, the following three subjects are focused; (1) changes in packing regularity of glassy spherical microdomains in styrenic block copolymer samples upon uniaxial stretching and upon the subsequent release of the stretching load, (2) changes in nano-structures in styrenic block copolymer samples bearing glassy lamellar nano-structures upon uniaxial stretching and upon the subsequent release of the stretching load (fracture of the glassy nano-structures), and (3) ultra-small-angle X-ray scattering analyses of structural changes in elastomeric segmented polyurethaneureas upon uniaxial stretching (formation of crazes in sub-micron scale).

Structure and properties of segmented polyurethane-ureas with dissimilar soft blocks

Structure and properties of segmented polyurethane-ureas with mixed nonpolar and polar soft segments were studied. Advantages of elastomers based on mixtures of oligobutadiene and oligoether diisocyanates in providing high strength properties combined with frost resistance are demonstrated.

Behavior in a humid medium of segmented polyurethane-ureas with dissimilar thermodynamically compatible and incompatible flexible blocks

Fundamental aspects of how moisture sorption affects physicomechanical properties of polyurethaneureas based on mixtures of oligoether and oligodiene diisocyanates were studied. Advantages of elastomers with dissimilar flexible blocks in providing an enhanced strength of the material in a humid atmosphere and in contact with water were revealed.

Simultaneous and sequential micro-porous semi-interpenetrating polymer network hydrogel films for drug delivery and wound dressing applications

Abstract Novel semi-interpenetrating polymer networks (so-called simultaneous SIPNs) of various compositions were synthesized using segmented polyurethane urea (SPUU), N-isopropylacrylamide (NIPAM), acrylic acid (AA), and butylmethacrylate (BMA), resulting in an SIPN film denoted as SPUU/poly(NIPAM-co-AA-co-BMA). The resulting simultaneous SIPN films were neutralized by exposure to pH 7.4 phosphate buffer solution (PBS). The neutralized films were dried and then characterized by differential scanning calorimetry (DSC). The DSC results showed that the Tg of the SIPNs depends mostly on SPUU content and on the composition of the acrylate monomers. PNIPAM was incorporated as a second network in one composition of simultaneously prepared SIPN film through a sequential polymerization method (so-called sequential SIPNs). Both simultaneous and sequential SIPN films were examined by scanning electron microscopy (SEM) after freeze drying at their equilibrium states. The SEM study revealed that simultaneous SIPNs had a porous morphology in the absence of BMA, but the porosity disappeared at higher BMA content. The morphology of the sequential SIPN film was almost similar to that of pure PNIPAM. Finally, simultaneous and sequential SIPNs were used for swelling and drug release studies at different pH values and at different temperatures to determine the environmental sensitivity of these gels. Simultaneous SIPNs absorbed more water than sequential SIPNs, but both had a poor rate of water absorption at pH 1.2. In the drug release study, a higher thermosensitivity was observed for sequential SIPNs than for simultaneous SIPNs.