Poly Ether Urethane Research Articles

Influence of the free isocyanate content in the adhesive properties of reactive trifunctional polyether urethane quasi-prepolymers

The effect of the free isocyanate (NCO) content on the adhesive properties of urethane quasi-prepolymers was studied. Polyether-based isocyanate ended quasi-prepolymers containing between 13 and 21 wt% NCO were prepared by reacting a trifunctional polypropyleneglycol with polymeric MDI. The quasi-prepolymers were characterized by infrared spectroscopy (IR), proton nuclear magnetic resonance ( 1H-NMR) spectroscopy, Brookfield viscosity, and differential scanning calorimetry (DSC). Immediate adhesion of quasi-prepolymers was studied by means of a probe test performed with a texture analyzer. Adhesion properties of the moisture-cured quasi-prepolymers have been obtained from single lap shear tests of vulcanized styrene–butadiene (R1) rubber/cured quasi-prepolymer joints. The increase in the free isocyanate content produced quasi-prepolymers with lower average chain length and less intermolecular interactions between polymer chains. Due to the presence of free isocyanate molecules, lower Brookfield viscosity values and lower glass transition temperatures were obtained by increasing the free isocyanate content in the quasi-prepolymers. The lower the free NCO content, the higher the cohesion and the immediate adhesion of the quasi-prepolymers because of the increase in the average molecular weight. During debonding, fibrillation was observed in the quasi-prepolymers with free NCO content lower than 20 wt%. Single lap shear strength values of R1 rubber/moisture cured quasi-prepolymers joints showed a particular trend as a function of the increase in the NCO content, which can be ascribed to the opposite trends in the cohesion and adhesion properties of the cured quasi-prepolymers.

Influence of chemical crosslinks on the elastic behavior of segmented block copolymers

Polyether(ester–amide)s (PEEA) segmented block copolymers with di- and tri-functional poly(propylene oxide)s and amide segments were synthesized and the elastic properties studied. The difunctional polyether used had a molecular weight of 2300 g/mol end capped with 20 wt% ethylene oxide. The trifunctional polyether had a molecular weight of 6000 g/mol of which each arm had a molecular weight of 2000 g/mol. The concentration of the trifunctional polyether of the total ether content was varied from 0 to 40 mol%. The amide segments were of a non-crystallizing type with a content in the copolymers of 27 wt%. Phase separation occurred, therefore, only by liquid–liquid demixing. The thermal mechanical properties of the polymers were analyzed by dynamic mechanical thermal analysis and the elastic properties by compression set and tensile set. The materials are model blockcopolymers for the more complex chemically crosslinked polyether(urethane–urea)s (PEUU). With increasing amounts of chemical crosslinks the glass transition temperature and the modulus did not change noticeably. However, the elastic behavior as measured by compression set and tensile set, improved dramatically. Giving time all materials recovered completely and with increasing amount of chemical crosslinks this recovery happened faster. An explanation is given for the (viscoelastic) deformation in these copolymers.

SAW sensor array for wine discrimination

A surface acoustic wave (SAW) sensor array has been developed in order to discriminate Spanish wine coming from different grape varieties and elaboration processes. Sensors were coated with diverse thicknesses of polyepichlorohydrin (PECH), polyetherurethane (PEUT) and polydimethylsiloxane (PDMS). Linear techniques as principal component analysis (PCA) and linear discriminant analysis (LDA) and non-linear ones as probabilistic neural networks (PNN) have been used for pattern recognition. A classification success rate of 86% has been achieved.

Detection of volatile organic compounds using surface acoustic wave sensors with different polymer coatings

This paper compares the obtained experimental results with surface acoustic wave devices coated with three different polymers, polydimethylsiloxane (PDMS), polybutadiene (PBD) and polyetherurethane (PEUT), by detecting low concentrations of three volatile organic compounds (VOCs): octane, toluene and propanal. The polymer type and thickness and so as the test gas nature have a great influence on the sensitivity and selectivity of this sensor type. The different coatings have been prepared with the same thicknesses and they have been tested with the same gas concentrations. It has been possible to measure low concentrations of volatile organic compounds obtaining very good results of sensitivity and very short response and recovery times. There is difference of response among the different tested concentrations and the responses have been linear.

Enhanced biocompatibility in biostable poly(carbonate)urethane.

In this work, we synthesized two MDI-based polyurethanes, including a poly(ether)urethane (PEU) and a poly(carbonate)urethane (PCU), by using different soft segments, poly(tetramethylene oxide) and poly(hexyl, ethyl)carbonate diol (M approximately 2,000). We demonstrated that, in addition to the enhanced biostability of PCU over PEU, the biological performances of PCU in vitro were also improved in general. These included, better cellular attachment and proliferation, less platelet activation, as well as reduced monocyte activation. The unusual wide-ranging enhancement in biocompatibility for PCU was believed to be related to the larger micro-phase separation in PCU (approximately 25 nm) that caused distinct protein adsorption on the surface. The total number of adherent monocytes (nonactivated and activated) on the bare sample surfaces, albumin pre-adsorbed sample surfaces, and fibrinogen pre-adsorbed sample surfaces.

Elastic behavior of flexible polyether(urethane–urea) foam materials

Polyether(urethane–urea) foams (PEUU) with varying urea contents and different polyether segments (PPO and PPO- co-PEO (93/7 w/w)) were compacted to transparent solid plaques via compression molding. The thermal, mechanical and elastic properties of the compacted PEUU materials were studied. With increasing urea content, the shear modulus was increased, while the glass transition temperature ( T g) remained low and unaffected. The T g's of PEEU's with PPO segments were, however, lower than with PPO- co-PEO segments, indicating more mixing of urea segments with PPO- co-PEO. The flow temperatures of both PEUU's were high (∼300 °C) for all compositions. The compression sets, tensile sets and hysteresis energy of the PEUU's were low and increased with urea content. The use of PPO- co-PEO segments resulted in PEEU's with higher compression sets and tensile sets and also more hysteresis. The recovery of the PEUU's showed two relaxation regimes: a fast (elastic) recovery and a slower (viscoelastic) recovery. The recovery of these PEUU's is almost complete giving time.

Mechanical properties of polyurethane film exposed to solutions of nonoxynol‐9 surfactant and poly(ethylene glycol)

AbstractMechanical properties of two polyether urethane films (Estane and Tecoflex) were studied after exposure to solutions of nonoxynol 9 (N9) surfactant and poly(ethylene glycol) 400 (PEG) for various times. Large amounts of N9 were absorbed from N9/PEG solutions, resulting in soft‐segment plasticization and lower mechanical properties. As the N9 concentration increased, Estane absorbed more liquid and its mechanical properties decreased more compared to Tecoflex, although the mechanical properties of Estane were higher than Tecoflex at low concentrations of N9. Hard‐segment domain disruption is probably not occurring because the relationship between the elastic modulus and polymer volume fraction followed Flory's theory for swollen elastic rubber networks and the liquids do not fully dissolve the polymers. The diffusion behavior of N9 and PEG was observed to follow Fickian behavior. Most of the absorption and decrease in mechanical properties occurred within the first 20 h after soaking, implying that additional loss in strength over longer times would be minimal. Mechanical property anisotropy suggests that condoms should be cut from Estane film in an orientation that optimizes the property–orientation relationship for specific end uses. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1086–1096, 2004

Polymers with nano-dimensional surface features enhance bladder smooth muscle cell adhesion.

Previous studies investigating the design of synthetic bladder wall substitutes have involved polymers with micro dimensional structures. Since the body is made up of nano-structured components (e.g., extracellular matrix proteins), the focus of the present in vitro study was to design nano-structured polymers for use as synthetic bladder constructs that mimic the topography of natural bladder tissue. In order to complete this task, novel nano-structured biodegradable polymeric films of poly-lactic-co-glycolic-acid (PLGA), poly-ether-urethane (PU), and poly-caprolactone (PCL) were fabricated and separately treated with various concentrations of NaOH (for PLGA and PCL) and HNO(3) (for PU) for select time periods. These treatments reduced the polymer surface feature dimensions from conventional micron dimensions to biologically inspired nanometer dimensions. Select cytocompatibility properties of these biomaterials were tested in vitro. Results provide the first evidence that adhesion of bladder smooth muscle cells is enhanced as polymer surface feature dimensions are reduced into the nanometer range. In addition, surface analysis results reveal that the polymer nanometer surface roughness is the primary design parameter that increases bladder smooth muscle cell adhesion. For this reason, the "next generation" of tissue-engineered bladder constructs with increased efficacy should contain surfaces with nanometer (as opposed to micron) surface features.

Surface modification of a segmented polyetherurethane using a low-powered gas plasma and its influence on the activation of the coagulation system

A medical grade segmented polyetherurethane (PEU) was treated with a low-powered gas plasma using O 2, Ar, N 2 and NH 3 as the treatment gases. Changes in the surface functional group chemistry were studied using X-ray photoelectron spectroscopy. The wettability of the surfaces was examined using dynamic contact angle measurements and the surface morphology was evaluated using atomic force microscopy. The influence of the surface modification to the polyurethane on the blood response to the polyetherurethane was investigated by measuring changes in the activation of the contact phase activation of the intrinsic coagulation cascade. The data demonstrate that the plasma treatment process caused surface modifications to the PEU that in all cases increased the polar nature of the surfaces. O 2 and Ar plasmas resulted in the incorporation of oxygen-containing groups that remained present following storage in an aqueous environment. N 2 and NH 3 plasmas resulted in the incorporation of nitrogen-containing groups but these were replaced with oxygen-containing groups following storage in the aqueous environment. In all plasma treatments there was a lowering of contact phase activation compared to the untreated surface, the N 2 and NH 3 treatments dramatically so.

Degradation and stabilization of cosmetic polyetherurethane in alcoholic solution

A polyetherurethane (PEU) was synthesized for potential cosmetic applications by coupling poly(tetramethylene oxide) (PTMO, Mn = 2000 g mol−1) and poly(ethylene oxide) (PEO, Mn = 2000 g mol−1) with 4,4′-diphenylmethane diisocyanate (MDI), without using a chain extender. The PEU polymer, synthesized with PEO and PTMO in the ratio of 1:3 by weight, was soluble in ethanol–water mixed solvents. The solution formed a thin film in situ on the skin by coating, which was flexible and elastomeric with appropriate skin adhesiveness. However, PEU was susceptible to degradation when it was exposed to an ethanol–water (80/20 v/v %) mixed solvent and stored in an air-filled and sealed bottle at 60°C for 4 weeks. These conditions resulted in deterioration of PEU molecular weight (Mn), viscosity, and mechanical properties. Peak analysis of the Fourier transform infrared spectrum of the aged PEU revealed that >97% of the urethane carbonyl bonds remained, whereas ether bonds were significantly reduced (∼82% of initial value). The degraded PEU contained ester bonds, which were confirmed by proton and carbon-13 nuclear magnetic resonance spectroscopy. This observation suggests that oxidative chain cleavage rather than hydrolysis was the dominant reaction in the degradation process. Two approaches were adopted to minimize oxidative degradation of PEU dissolved in an ethanol–water (80/20 v/v %) mixed solvent; they were, applying a nitrogen environment and adding an antioxidant (1.8 wt % dry PEU). The results indicate that reduction of oxidative degradation produced a synergistic effect. Vitamin E was a more effective antioxidant than butylated hydroxytoluene (BHT), which is a typical antioxidant for commercial polyurethanes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2270–2276, 2003

Isolation of methylene dianiline and aqueous-soluble biodegradation products from polycarbonate-polyurethanes

Polycarbonate-polyurethanes (PCNUs) have provided the medical device industry with practical alternatives to oxidation-sensitive polyether-urethanes (PEUs). To date, many studies have focused on PCNUs synthesized with 4,4′-methylene diphenyl-diisocyanate (MDI). The relative hydrolytic stability of this class of polyurethanes is actually quite surprising given the inherent hydrolytic potential of the aliphatic carbonate group. Yet, there has been little information reporting on the rationale for the material's demonstrated hydrolytic stability. Recent work has shown that PCNU materials have a strong sensitivity towards hydrolysis when changes are made to their hard segment content and/or chemistry. However, knowledge is specifically lacking in regards of the identification of cleavage sites and the specific nature of the biodegradation products. Using high-performance liquid chromatography, radiolabel tracers and mass spectrometry, the current study provides insight into the distribution of biodegradation products from the enzyme-catalyzed hydrolysis of five different PCNUs. The hydrolytic sensitivity of the materials is shown to be related to the distribution of products, which itself is a direct consequence of unique micro-structures formed within the different materials. While an MDI-based polymer was shown to be the most hydrolytically stable material, it was the only PCNU that produced its diamine analog, in this case 4,4′-methylene dianiline (MDA), as a degradation product. Given the concern over aromatic diamine toxicity, this finding is important and highlights the fact that relative biostability is a distinct issue from that of degradation product toxicity, and that both must be considered separately when assessing the impact of biodegradation on biomaterial in vivo compatibility.

Ion transport in polymer electrolytes containing nanoparticulate TiO2: The influence of polymer morphology

Recent studies have shown that composite polymer electrolytes, formed by dispersing nanosized ceramic particles in polyether-based electrolytes, have improved ion transport properties as compared to their unfilled analogues. In the present study polymer electrolytes with different loadings of nano-sized ceramic particles (TiO2) and different polymer chemistry and morphology have been investigated. Of special interest are filler induced effects on polymer, solvent and cationic mobility. Partly crystalline polymer electrolytes based on poly(ethylene oxide) have been compared to fully amorphous polymer electrolytes based on a polyether urethane, as well as gel electrolytes based on PMMA. 7Li pfg-NMR, linewidth and spin–spin relaxation times as well as 1H pfg-NMR and spin–spin relaxation times, were measured as a function of temperature and composition. The 1H spin–spin relaxation measurements reveal increased average polymer mobility with the addition of filler up to a maximum at 4 and 8 wt.% TiO2 for the fully amorphous and the partly crystalline electrolytes, respectively. The 7Li linewidth measurements for the fully amorphous system show a broadening of the linewidth with addition of filler. Based on variable temperature measurements this broadening is interpreted as a result of the inhomogeneity introduced by the filler particles. Pulsed field gradient (pfg) diffusion measurements were employed to determine ion and solvent self-diffusion coefficients. In the case of the PMMA-based gel electrolyte and the fully amorphous electrolytes enhanced cation self-diffusion was observed upon addition of TiO2.

The influence of protein adsorption and surface modifying macromolecules on the hydrolytic degradation of a poly(ether–urethane) by cholesterol esterase

Previous investigations have demonstrated that the inflammatory cell derived enzyme, cholesterol esterase (CE) could degrade polyurethanes (PUs) by hydrolyzing ester and urethane bonds. Studies that have investigated the development of protective coatings for PUs have reported that the polymer degradation of polyester–urethanes (PESUs) can be reduced with the use of fluorine containing surface modifying macromolecules (SMMs). Since these latter studies were carried out in the presence of relatively pure enzyme, it has not been shown if SMMs would still provide an enhanced inhibitory effect if surfaces were pre-exposed to plasma proteins. This would be more representative of the in vivo scenario since protein adsorption would occur before the appearance of monocyte-derived macrophages which would be a primary source of esterase activities. The current investigation has focused on studying the influence of fibrinogen (Fg) as a simple model of protein adsorption in order to assess the effect of CE in combination with protein on polyether–urethane (PEU) surfaces. The materials were prepared with and without SMMs, and were pre-coated with Fg prior to carrying out biodegradation studies. The pre-adsorption of Fg onto the modified and non-modified surfaces provided a significant delay in the hydrolytic action of CE onto the PEU substrates. However, the effect was gone by 70 days and by the 126th day of incubation, both Fg coated and non-Fg coated groups had the same level of degradation. The difference between Fg coated and non-coated substrates was much smaller for materials containing SMMs. In addition, the pre-adsorption of Fg did not alter the SMMs’ ability to provide a more biostable surface over the 4 month incubation period.

Characterization of the interactions in polymer–filler systems by inverse gas chromatography

Inverse gas chromatography (IGC) has been applied to observe the interactions in filled polymer–organic solvent as well as modified filler–polymer systems under conditions approaching infinite dilution of the volatile component. We investigated polyether–urethane–modified silica systems containing different kinds of modified silicas (filler) at 10% w/w loading. The fillers were modified with N-2-aminoethyl-3-aminopropyltrimethoxysilane (B2), 3-aminopropyltriethoxysilane (B3), 3-mercaptopropyl-trimethoxysilane (B4), n-octyltriethoxysilane (B5). The values of Flory–Huggins parameter χ ∞ 12 calculated from the retention volumes indicate that interactions between filled polymer and solvent probe varied with type of the modifier and temperature. Authors propose to express the magnitude of modified filler–polymer interactions by Flory–Huggins χ′ 23 parameter. The influence of conditions of IGC experiment (temperature, the type of filler, the nature of test solute) on the evaluated parameters is presented and discussed.

Studies on the tumor promoting mechanism of hard and soft segment models of polyetherurethane: Tyr265 phosphorylation of connexin43 is a key step in the GJIC inhibitory reaction induced by polyetherurethane.

Gap junctional intercellular communication (GJIC) is inhibited by 4,4'-di(ethoxycarboamide) diphenylmethane (MDU) and polytetramethylene oxide 1000 (PTMO1000), which are model chemicals of hard and soft segments of polyetherurethane (PEU), respectively. In our previous study, we suggested that the inhibition of GJIC induced by MDU and PTMO1000 may lead to accelerate promotion step by both segments after the initiation step by hard segment, MDU. To examine this hypothesis, we established connexin 43 overexpressed clones from Balb/c 3T3 A31-1-1 clones (A31-1-1 cells) by transfection. Here we show that these clones acquired much higher GJIC ability than parental A31-1-1 cells and kept them even if MDU or PTMO1000 was added to the culture. We also found that Mutation of Cx43 at Tyr-265 resulted in reduced inhibition of GJIC induced by MDU and PTMO1000. These findings suggest that inhibition of GJIC by PEU may be caused by Tyr-265 phosphorylation of Cx43 molecule.

Segmentowe polieterouretany kondensacyjne jako skladniki tworzyw skoropodobnych

Segmentowe polieterouretany kondensacyjne jako skladniki tworzyw skoropodobnych

Structural modification in electron-irradiated polyetherurethane

Doppler broadening spectroscopy (DBS) using a slow positron beam has been applied to investigate degradation induced by 200 keV electrons irradiation in polyetherurethane (PU). The low momentum fraction S (and respectively the high momentum fraction W) characteristic of the irradiated films is shown to decrease (and respectively to increase) when the electron deposited energy increases. The DBS results are compared to the mass loss measured by ‘solvent swelling’ of the films which shows that the cross-linking increases as the electron deposited energy increases.

Fluorinated surface-modifying macromolecules: modulating adhesive protein and platelet interactions on a polyether-urethane.

Polyether-urethanes (PEUs) have been the materials of choice for the manufacture of conventional blood-contacting devices. Nevertheless, biostability and blood compatibility are still among the principal limitations in their long-term application. Studies investigating the development of protective coatings for PEUs have shown that degradation can be reduced with the use of fluorinated surface-modifying macromolecules (SMMs). It has also been hypothesized that SMM-modified PEU surfaces may exhibit improved blood compatibility because other studies have shown a modulation in fibrinogen adsorption onto these surfaces. To determine the blood compatibility of a PEU-containing fluorinated SMMs, a series of in vitro experiments were designed to study the pattern of protein adsorption from plasma and then to assess the nature of platelet adhesion and activation on each substrate. Western blot analysis as well as single protein studies revealed that the dominant "adhesive proteins" [fibrinogen (Fg), fibronectin (Fnc), and vitronectin (Vnc)] were adsorbed on two of the SMM-containing PEUs in lower amounts relative to unmodified base. Platelet adhesion and activation data further highlighted the differences among the various substrates. It was shown that the unmodified base had a higher number of adhered platelets relative to the SMM-modified surfaces, and that of the SMM-containing substrates, which showed the lowest levels of adhesive proteins also, exhibited significantly lower platelet densities. Close morphological examination further revealed that platelets residing on these latter substrates were not appreciably activated. Based on the current evidence, it is believed that the fluorinated SMMs demonstrate good potential for the development of surfaces with minimal thrombogenic character in in vivo applications.

Evaluation of the cytotoxicity of polyetherurethane (PU) film containing zinc diethyldithiocarbamate (ZDEC) on various cell lines.

A polyetherurethane (PU) film containing 0.1% zinc diethyldithiocarbamate (ZDEC) is the international standard reference material for testing the in vitro cytotoxicity of polymer based biomaterials. Nowadays, culturing L929 or BALB/3T3 cells in direct contact or in an extract dilution condition is the most frequently using method for evaluating the cytotoxicity from biomaterials and medical devices. However, the results often vary, because it is directly related to the cellular functions and the mechanism of the toxicity of the contacting cells. In this study, 13 cell lines originating from various tissues were used to detect the cytotoxic activities of a PU film containing 0.1% ZDEC (PU-ZDEC). The correlation between the reactivity zone size and the relative cytotoxicity by quantifying the released total protein from each cell in the direct contact testing method was investigated. Hepa-1c1c7 cells demonstrated the highest sensitivity in the reactivity zone size, while CHO/dhFr(-) cells were the most sensitive in terms of the relative cytotoxicity. A correlation between the two processes in each cell line was not found (r=-0.478). In the extract dilution method, which involved cultivating the cells in the medium with various ZDEC concentrations prepared by diluting the PU incubation, the cytotoxicity increased with increasing ZDEC concentration in all cell lines. The BALB/ 3T3 cells demonstrated the highest sensitivity in the extract dilution method. No correlation in a comparison of the relative cytotoxicity from the direct contact method with the extract dilution method in each cell line, was found (r=-0.445). In this experiment, Hepa-1c1c7, BALB/3T3, CHO/dhFr(-) and L-929 cells among the 13 types of cell lines were the sensitive cell lines according to the two methods. The preliminary results suggest that a comparison of at least one or more cytotoxicity testing methods and many cell lines is necessary for an in vitro cytotoxicity test of biomaterials.

New conducting thermoplastic elastomers. I. Synthesis and chemical characterization

AbstractIn the last 20 years, much interest has been focused on conducting polymers to find new materials to transfer from research to industry. However, in many cases, as for elastomers for which intrinsically conducting materials are unavailable, it is necessary to use conducting particles that are physically mixed with the polymeric matrix to give loaded rubbers. In this work we report the synthesis and the chemical characterization of an intrinsically conducting material with good mechanical and electrical conduction properties. To achieve such a global goal, we covalently linked, by an amidation reaction, the terminal NH2 of Emeraldine (EB) and sulfonated Emeraldine (SPAN) to a free carboxylic group belonging to the repetitive unit of a functionalized segmented polyurethane. The reaction was carried out by activating such a carboxylic group with N,N′‐dicyclohexylcarbodiimide and N‐hydroxysuccinimide. The reaction yields and the chemical properties of the polymers were studied by proton and carbon‐13 nuclear magnetic resonance, ultraviolet, and Fourier transform infrared spectroscopy. The average numbers of EB or SPAN aromatic rings per polyether urethane acid (PEUA) repetitive unit, which cannot be assumed to be amidation degree because at this moment the molecular weights of the inserted EB and SPAN chains are unavailable, were 6 in case of the polymer obtained from the pristine Emeraldine and 1 for that obtained from the sulfonated Emeraldine. This result could be because SPAN was used in the acidic form, which depresses the nucleophilicity of the NH2 group because of the presence of the sulfonic protons. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 857–867, 2002