Polyurethane elastomers with hydrolytic and thermooxidative stability. I. Polyurethanes with N-alkylated polyamide soft blocks

Segmented polyurethanes with N-alkylated amides as soft blocks as prepared. Comparisons are made with both a poly(ester urethane) and a poly(ether urethane) with the same hard block; the poly(amide urethane) is more hydrolytically stable than the polyester containing material and demonstrates greater thermooxidative stability than that with the polyether moiety. The aliphatic poly(amide urethane)s remain transparent upon exposure to uv light.     

A high-strength technological compound on the basis of oligobutane diendiol,isophorone diisocyanate,and aromatic diamine

2,4-Toluene diisocyanate is substituted with isophorone diisocyanate during the synthesis of polybutadiene urethane urea. The obtained polydiene urethane urea is shown to be superior to the physicomechanical and rheological properties of the traditional material synthesized with the use of 2,4-toluene diisocyanate. It is established that polybutadiene urethane urea is more than twice as good as steel adhesion to polydiene urethane epoxy compounds.     

Formation of a linear-polyurethane-linear-polystyrene blend in situ

Blends of linear poly(urethane) and linear polystyrene formed simultaneously in situ by different mechanisms (radical polymerization and polyaddition) at various initial mixture compositions and initiator and catalyst concentrations have been studied by DSC and light scattering. It has been shown that formation of the poly(urethane)-polystyrene blend is characterized by the same kinetic and thermodynamic features as the previously studied poly(urethane)-poly(methyl methacrylate) system. However, the poly(urethane)-polystyrene blend forms much slower than the poly(urethane)-poly(methyl methacrylate) blend owing to different reactivities of the starting components, which are determined by their chemical nature. Phase separation in the poly(urethane)-polystyrene system, which at initial stages proceeds via the spinodal mechanism, occurs much faster than that in the poly(urethane)-poly(methyl methacrylate) system because of a poor mutual solubility of the poly(urethane) and polystyrene being formed and probably because of a higher mobility of their macromolecules at the onset of phase separation.     

Development of urethane acrylate composite ion-exchange membranes and their electrochemical characterization

With the objective of introducing antifouling characteristics into interpolymer types of cation and anion exchange membranes, the surface of these membranes was coated with a 12-microm-thick urethane acrylate layer and was cured by UV radiation of wavelengths 308 and 172 nm under a complete inert atmosphere. Different urethane acrylate composite ion exchange membranes developed were characterized in NaCl solution by measuring their ion-exchange capacity, volume fraction of water, contact angle with water, membrane conductance, and membrane potential. It was found that the electrochemical transport properties of urethane acrylate composite cation-exchange membranes were increased due to resonance stabilization of the urethane group, which acts as a weak acid and dissociates as a negatively charged urethane ion and a positively charged proton. This contributes toward the net charge density of the membrane matrix responsible for enhanced selectivity and conductivity, while for urethane acrylate composite anion-exchange membranes reduction in net charge density was responsible for reduction in electrochemical transport properties. Counterion transport number, permselectivity, and counterion diffusion coefficient values for these membranes were also estimated. Experiments were also carried out in higher homologs of sodium carboxylate solutions in order to observe the fouling tendencies of these membranes. It was concluded that it is possible to obtain antifouling characteristics of ion-exchange membranes by coating and curing thin hydrophilic layers of urethane acrylate on their surfaces without sacrificing their electrochemical transport properties.     

Urethanase of Bacillus licheniformis sp. isolated from mouse gastrointestine.

Trace levels of urethane, a cancer causing chemical, were detected in many kinds of wine, sherry, whisky, brandy and sake. Urethane formation from urea and ethanol in sake can be prevented by the treatment of acid urease, which is produced by Lactobacillus fermentum, but urethane, once formed, is very difficult to decompose. In order to keep the safety of alcoholic beverages, enzymatic removal of urethane has become an urgent problem. We found that Bacillus licheniformis sp., isolated from mouse gastrointestine, decomposed urethane to ethanol and ammonia. The enzyme showed higher urethanase activity at an acidic condition than at a neutral condition, and was resistant against ethyl alcohol of high concentrations. However, the enzyme had a low affinity to urethane for the industrial removal of the compound from alcoholic beverages.     

Preparation of PEG-modified urethane acrylate emulsion and its emulsion polymerization

In order to improve stability and reduce droplet size, the PEG-modified urethane acrylates were synthesized by the reaction of polyethylene glycol (PEG) with residual isocyanate groups of urethane acrylate to incorporate hydrophilic groups into the molecular ends. The droplet sizes of the PEG-modified urethane acrylate emulsions were much smaller than those of unmodified urethane acrylate emulsions at the same surfactant composition, and the droplet sizes of these emulsions were significantly effected not by surfactant compositions and types, but by the reaction molar ratio of PEG, because the urethane acrylate containing polyoxyethylene groups as terminal groups aided the interfacial activity of surfactant molecules and acted as a polymeric surfactant. The actions of PEG-modified urethane acrylate were confirmed by the investigation of adsorption of urethane acrylate in a water/benzene interface.For polymerization of emulsions, the stability of emulsion in the process of emulsion polymerization was changed by the type of surfactant or initiator. In the case of emulsion polymerization with a water soluble initiator (K₂S₂O₈), the emulsions prepared using TWEEN 60 were broken in the process of polymerization. However, polymerization of these emulsions could be carried out using an oil soluble initiator (AIBN). The conversion of emulsion polymerization changed with the type of urethane acrylates, that is, the reaction molar ratio of PEG to 2-HEMA.     

Morphology of micron-sized polystyrene particles crosslinked with urethane acrylate

The morphology of micron-sized polystyrene particles crosslinked with a urethane acrylate crosslinker was studied with different concentrations of urethane acrylate and medium solvency by means of simple dispersion polymerization. The urethane acrylate employed as a crosslinker showed an excellent effect on maintaining the monodispersity of the polystyrene particles at a moderate crosslinker concentration (to about 5 wt%) in terms of the monomer-swellable surface of primary particles. By enhancing the medium solvency, the amount of urethane acrylate incorporated was increased, while the monodispersity of the final particles was maintained. It was believed that the increase in solvency on adding xylene to ethanol solution helped the diffusion of the styrene monomers into the primary particles. At high concentration of urethane acrylate, however, nonspherical particles, ellipsoidal or egg-like singlets and asymmetric doublets, were observed. The increased crosslinking density seemed to repel the styrene monomers during particle growth. Received: 30 June 1998 Accepted in revised form: 9 September 1998     

The influence of thixotropic additives on the properties of sealants based on oligoester urethane thiol

The influence of thixotropic additives on the viscosity and thixotropy of sealants based on oligoester urethane thiol was examined. It was found that the fumed A-175 silica aerosil is the most efficient as a thixotropic additive for the sealants based on oligoester urethane thiol. The introduction of glycols along with the aerosil or hydrated silicon dioxide makes it possible to vary widely the viscosity and thixotropy of the sealant compositions based on oligoester urethane thiol.     

Mesoporous hybrid organosilica containing urethane moieties

Mesoporous hybrid material containing urethane moieties in functionalized long chain organic group have been synthesized by using bis[3-(triethoxysilyl) propyl urethane]ethane (BTESPUE) and tetraethoxysilane as structural ingredients. The incorporation of BTESPUE within the framework of mesoporous material was confirmed by Fourier transform-infrared, X-ray photoelectron spectroscopy, solid-state NMR spectroscopy and thermogravimetric analysis. This material had a thick wall and uniform pore, which may be attributed to the hydrogen bonding inside framework due to urethane moieties.     

Ir- spectroscopy of hydrogen bond as a method of analytical determination of physical network in poly(ether urethane)s

The equilibrium association of urethane groups in a series of 4, 4′ - diphenylmethane diisocyanate (MDI)/polypropylene oxide) (PPO) based poly(ether urethane) elastomers (PUE) was studied on the basis of IR-spectroscopy data. The concentration of associates containing 2,3 and 4 urethane groups is calculated, which permits immediate monitoring of changes in PUE mechanical properties using the model of a physically cross-linked polymer.     

Gas chromatographic-mass spectrometric determination of ethyl carbamate as the xanthylamide derivative in Italian aqua vitae (grappa) samples.

A selective reaction of ethyl carbamate (urethane) and methyl urethane (urethylane), as internal standard, with xanthydrol was effected to detect urethane after extraction from Italian aqua vitae (grappa) samples. The xanthylamides formed were determined by gas chromatography-mass spectrometry in the selected ion monitoring mode on an apolar DB 5 silica column. The linearity of the method was tested from 10 to 1000 micrograms/l, with a detection limit of 1 micrograms/l.     

Direct pyrolysis mass spectrometry of diphenyl methyl allophanate

The thermal decomposition mechanism of α,γ-diphenyl methyl allophanate as a model compound for the crosslinking site in polyurethane networks was investigated by direct pyrolysis in the mass spectrometer. The primary degradation reactions were dissociation of allophanate into isocyanate and urethane followed by dissociation of the urethane produced into isocyanate and alcohol. However, decarboxylation of the urethane fragment also took place slowly.     

Novel silver/polyurethane nanocomposite by in situ reduction: Effects of the silver nanoparticles on phase and viscoelastic behavior

A novel silver/poly(carbonate urethane) nanocomposite was prepared through in situ reduction of a silver salt (AgNO₃) added to a solution consisting of a commercial poly(carbonate urethane) dissolved in N,N‐dimethylformamide (DMF). In this system, the presence of the poly(carbonate urethane) was proved to protect the silver nanoparticles, whose formation was confirmed by means of UV–vis spectroscopy, from aggregation phenomena. The silver morphology developed in the solid state after DMF casting was imaged by FESEM. Homogeneous dispersion of silver nanoprisms in the poly(carbonate urethane) matrix was clearly observed. The effects of dispersion of silver nanoparticles within the poly(carbonate urethane) matrix were investigated by means of ATR‐FTIR and multifrequency dynamic mechanical thermal analyses. The obtained results revealed that the presence of silver nanoparticles modifies both the phase and the viscoelastic behaviors of poly(carbonate urethane). As a matter of fact, the hydrogen bond formation in the hard and soft segments was found to be hindered and the molecular motions of the soft segments were restricted, because a comparatively higher activation energy was required for the related α‐relaxation process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 344–350, 2008     

Highly monodisperse crosslinked polystyrene microparticles by dispersion polymerization

 Highly monodisperse polystyrene microparticles cross-linked with urethane acrylates were produced by dispersion polymerization in ethanol solution in the presence of 2,2′-azobis (isobutyronitrile) initiator, polyvinylpyrrolidone stabilizer, and Aerosol–OT costabilizer. Different from conventional crosslinkers, the urethane acrylates employed as a crosslinker showed an excellent effect on maintaining the monodispersity of polystyrene microparticles even in the moderate crosslinker concentration. This was believed that the urethane acrylate helped forming the monomer-swellable surface of primary particles, because of its structurally long tetramethylene oxide groups in its molecule. However, at high concentration of the urethane acrylate, the rough surface and the coagulum of particles were observed, which was attributed to the seriously decreased solubility of the monomer mixtures in ethanol solution. The solubility of the mixtures of styrene monomer and urethane acrylate in the media had a serious effect on the average particle size and morphology of the final particles. This could be confirmed by the measurement of cloud points and fractional conversions. Received: 21 February 1997 Accepted: 25 May 1998     

Influence of isocyanate type of acrylated urethane oligomer and of additives on weathering of UV-cured films

The weathering of UV-cured films containing the isocyanate type of acrylated urethane oligomer, and the influence of different additives (HALS, UVA and TiO₂), was investigated by various methods. The UV-cured film containing the acrylated aromatic urethane oligomer showed worse photodegradation than that containing the acrylated aliphatic urethane oligomer. In the case of the UV-cured films containing the acrylated aromatic urethane oligomer, those stabilized using both HALS and UVA showed the highest photostability.     

Evaluation of PFO formation from the biodegradation of a fluorotelomer-based urethane polymer product in aerobic soils

This study is the first to evaluate the rate of formation of perfluorooctanoate (PFO) from the aerobic biodegradation of a fluorotelomer-based urethane polymer and to use this information to assess the global environmental significance of this source. A fluorotelomer-based urethane polymer product test substance was studied in four aerobic soils over two years to determine the rate at which the fluorotelomer side-chains covalently bonded to the polymer backbone were cleaved and subsequently transformed to form the anions of perfluorocarboxylic acids including PFO. Over the two year duration of the experimental study, a polymer biodegradation half-life of 102 years (range: 28-241) was calculated for the urethane polymer based on regression analysis of the rate of PFO formation in four test soils. When this half-life was applied to the estimated total historic production, use and disposal of fluorotelomer-based urethane polymer, the annual potential global generation of PFO was estimated to be less than one tonne per year.     

Flame-retardant modification of UV-curable resins with monomers containing bromine and phosphorus

UV-curable urethane acrylate resin and oligoester acrylate resin have been effectively flame retarded with vinyl-type flame-retardant monomers containing both bromine and phosphorus atoms. Thermogravimetric analysis indicates that the decomposition temperature of flame-retardant monomer is more closely matched to the decomposition temperature of cured oligoester acrylate resin than to that of cured urethane acrylate resin. The efficiency of each flame-retardant monomer in oligoester acrylate resin is higher than in urethane acrylate resin by a factor of ～ 2.2. The individual and the combined effects of tribromophenyl acrylate and triphenyl phosphate on the oxygen index of UV curable urethane acrylate resin have been studied. The bromine phosphorus synergistic action of the two flame-retardant components is evaluated quantitatively, and a maximum intermolecular bromine phosphorus synergism was observed in a flame-retarded formulation containing a Br/P atom ratio of 2. In the three acrylic monomers containing both bromine and phosphorus atoms, the optimum intramolecular bromine phosphorus synergism was observed at a monomer also containing a Br/P atom ratio of 2.     

Ring-opening polymerization of cyclic urethanes and ring-closing depolymerization of the respective polyurethanes

The cationic ring-opening polymerization of trimethylene urethane (tetrahydro-2 H-1,3-oxazin-2-one) in the melt with methyl trifluoromethanesulfonate as initiator results in poly(trimethylene urethane) in yields of ≈70%. Under the same reaction conditions 2,2-dimethyltrimethylene urethane (5,5-dimethyltetrahydro-2H-1,3-oxazin-2-one) cannot be polymerized. Poly(2,2-dimethyltrimethylene urethane), however, was obtained via polycondensation polymerization. Both polymers exhibit a uniform microstructure as deduced from NMR spectroscopic analysis. Ring-closing depolymerization in the melt with dibutyltin dimethoxide or titanium tetraisopropoxide at 140°C results the respective monomers in yields of ≈90%.     

New routes to [n]‐polyurethanes. [3]‐polyurethane: synthesis,characterization, and polymerization‐depolymerization equilibrium

The ring‐opening polymerization of dimethylene urethane ( 3 ) (systematic name: 2‐oxo‐1,3‐oxazolidine) with methyl trifluoromethane sulfonate as the initiator is inefficient. It was shown that equimolar amounts of dimethylene urethane and trifluoromethane sulfonate result in the expected active species ‐ 2‐methoxy‐4,5‐dihydro‐1,3‐oxazolium trifluoromethane sulfonate ( 5a ) ‐ : propagation, however, does not occur. Poly(dimethylene urethane) ( 4 ), was obtained by means of polycondensation of a linear monomer, i.e., 2‐(2‐phenoxycarbonylimino‐1‐ethoxycarbonylimino)‐ethanol ( 9 ). This [3]‐polyurethane is a semicrystalline material with a melting point of 200.7°C. Heating above its melting point leads to dimethylene urethane by ring‐closing depolymerization. The thermodynamical data support the experimental results with respect to the polymerization/depolymerization equilibrium.     

Image recording material based on the polymeric photobase generator containing oxime‐urethane groups

A polymeric photobase generator containing oxime‐urethane groups was prepared from copolymerization of MMA with N‐[4‐(benzophenoneoximino‐carbonylamino)phenyl]maleimide, a maleimide monomer containing oxime‐urethane group, and its properties as an image recording material were studied. The irradiation of this copolymer with UV light dissociates the urethane linkage to result in the formation of aromatic amino groups, which can be developed by the diazo‐coupling reaction. Various colors could be developed depending on the phenolic coupling reagents as the developer.