Polyurethane anionomers synthesised with aromatic, aliphatic or cycloaliphatic diisocyanates, polyoxyethylene glycol and 2,2-bis-(hydroxymethyl)propionic acid. Part 3. Electrical properties of polyurethane coatings

The following electrical properties were found for polymer coatings obtained from polyurethane anionomers synthesised with the use of various diisocyanates: volume resistivity, permittivity and dielectric dissipation factor. The effects were discussed from the molecular structures and phase structures of those anionomers on the value of their ionic conductivity and polarizability. The anionomer prepared from the aliphatic diisocyanate was found to offer ionic conductivity; hence, that material can be considered to be a solid electrolyte, which exhibits a considerable susceptibility to structural modifications in the alternating electric field.     

Chain-extended polyurethane anionomers using ionic diols of varying methylene spacers

Ionic diols with varying methylene spacers were prepared from maleic anhydride and linear diols. Reaction across the unsaturated site by aqueous sodium bisulphite was used to prepare the ionic diols. Chain extended polyurethane ionomers were prepared by the reaction of prepolymer based on different polyols and diisocyanates with the ionic diols. The polyurethane anionomers were characterized by FT-IR and FT-NMR spectroscopy. The differential scanning calorimetric results show that T_g of the anionomers shifted towards low values as the ionic content in the polyurethane increases and as the length of the ionic diol increases. © 1996 John Wiley & Sons, Inc.     

磺酸型阴离子聚氨酯离聚物的研究(Ⅰ)——不同离子化程度对性能的影响

合成了不同离子化程度的磺酸型阴离子聚氨酯离聚物,并通过红外光谱、示差扫描量热、动态力学、应力-应变等方法研究了它们的性能,结果表明:离子化程度不同对聚氨酯离聚物的软硬段相容性有较大的影响,引入少量离子,使软硬段相容性提高,引入大量离子时,则又使软硬段相分离程度提高,随着离子化程度的提高,材料的抗张强度、水溶性逐步提高,为控制聚氨酯材料的亲水性及制备水溶性聚氨酯提供了一种新途径。     

Conformational aspects of segmented poly(ester-urethanes)

Segmented poly(ester-urethanes) containing hard and soft segments, were obtained from aromatic diisocyanates with thiodiglycol or diethylene glycol as chain extenders, and poly(ethylene glycol)adipate usig a multistep polyaddition process. Transition temperatures by differential scanning calorimetry and thermo-optical analysis were employed to characterize polyurethane materials. Changes in the conformation of these polyurethanes were analyzed also, by viscometer measurements in N,N-dimethyl-formamide. The obtained data revealed that the thermal curves are influenced by the soft and hard segment structures in the temperature range studied.     

Polyurethane anionomers. I. Structure properties of polyurethane anionomers

The influence of mono and divalent nontransition and transition metals on the glass transition and mechanical properties of polyurethane anionomers have been investigated. NCO-terminated prepolymer prepared from 4,4′-methylene-bis(phenyl isocyanate) (MDI) and poly(caprolactone) glycol (PCL) was chain extended with dimethylolpropionic acid (DMPA), and the anionomers obtained by neutralization of the prepolymer. The glass transition temperatures of polyurethane anionomers have been studied as a function of the counterion. From simple electrostatic considerations, it is shown that a linear relationship exists between the glass transition temperature and ionic potential (?) for these particular materials. The relation is; T_g = A? + B. The mechanical properties are greatly affected by the type of the counterion, and in some cases, such as monovalent and nontransition metals, the mechanical properties of the anionomers improved by increasing the ionic potential. On the other hand, transition metals containing anionomers exhibited good mechanical properties but no relationship was observed between the mechanical properties and the ionic potential. The extent of water absorption of PU anionomers follows the same relative trends as the tensile strengths of the transition metals with filled and partially filled d-orbitals.     

Synthesis and Properties of Reversible Disulfide Bond-based Self-healing Polyurethane with Triple Shape Memory Properties

A reversible disulfide bond-based self-healing polyurethane with triple shape memory properties was prepared by chain extending of random copolymer poly(lactide-co-caprolactone)(PCLA),hexamethylene diisocyanate (HDI),polytetrahydrofuran(PTMEG),and 4,4'-aminophenyl disulfide.The chemical structures were characterized using~1H nuclear magnetic resonance (~1H-NMR)spectroscopy,Fourier transform infrared spectroscopy (FTIR),and gel permeation chromatography (GPC).The thermal properties,selfhealing properties,triple-shape memory effect,and quantitative shape memory response were evaluated by differential scanning calorimetry (DSC),tensile tests,two-step programming process thermal mechanical experiments,and subsequent progressive thermal recovery.The self-healing mechanism and procedures were investigated using polarizing optical microscopy (POM) and an optical profiler.It was concluded that self-healing properties (up to 60%) and triple-shape memory properties around 35 and 500C (with shape fixation ratios of 94.3%and 98.3%,shape recovery ratios of 76.6%and 85.1%,respectively) were integrated to the shape memory polyurethane.As-prepared polyurethane is expected to have potential applications in multi-shape coatings,films,and step-by-step deploying structures.     

Chain-Extended Polyurethane Anionomers Using Fluorescin

Abstract

Polyurethanes were synthesized by chain extension of isocyanate end-capped prepolymer based on poly(tetramethylene oxide) glycol and toluene diisocyanate using fluorescin. The polyurethanes were characterized using FT-IR and FT-NMR. The polyurethanes were converted to their anionomers by treatment with the respective metal acetates. To study the changes accompanying ionomer formation, especially in the soft segment, differential scanning calorimetry experiments were performed in the low temperature region. Thermal stabilities of the polymers and ionomers were studied using a thermogravimetric analyzer.     

Polyurethane anionomers synthesised with aromatic, aliphatic or cycloaliphatic diisocyanates, polyoxyethylene glycol and 2,2-bis(hydroxymethyl)propionic acid

Taking advantage of the step-growth polyaddition method, which has been developed earlier, and applying it in the reaction of aromatic, cycloaliphatic and aliphatic diisocyanates with polyoxyethylene glycol, 2,2-bis(hydroxymethyl)propionic acid and 1,6-hexamethylene-diamine, a few polyurethane anionomers were synthesised, which were recovered from aqueous dispersions in the form of thin polymeric films. Analytical chemistry methods, like gel permeation chromatography with N,N-dimethylacetamide as the polar eluent and high-resolution nuclear magnetic resonance and IR spectroscopy, were employed to confirm their chemical structures, to find molecular weights and their distribution and to characterise the polarity of the chemical structure of the polyurethane chain formed.     

Pyrolysls of a fire-retardant coating consisting of polyurethane and chlorinated alkane

The pyrolysis of a clear fire-retardant coating was studied by using several analytical techniques, such as flash pyrolysis, thermogravimetry (TGA) and differential scanning calorimetry (DSC). The gaseous products were identified using gas chromatography-mass spectrometry (GC-MS). The coating consisted of a polyurethane film with or without chlorinated alkanes, which, when exposed to a flame, produced intumescence. The main ingredients of the coating were tenth-second butyrate and hexamethylene diisocyanate (Desmodur N) for polytrethane and Chlorowax 70 as the fire-retarding component. Pyrolysis was carried out in an inert medium. The pyrograms for polyurethane, Chlarowax and Chlorowax-polyurethane mixtures were obtained at 400, 600 and 800dgC. Some principal gaseous products resulting from the pyrolysis were identified by GC-MS. Other experiments were conducted using DSC under argon, and TGA with temperature programming. The pyrolysis began at 260°C for the Chlorowax-polyurethane system and at higher temperatures for polyurethane. Pyrolysis was also conducted using TGA under isothermal conditions and at selected temperatures.     

Physicochemical and antibacterial properties of polyurethane coatings modified by ZnO

The synthesis of polyurethane nanocomposite coatings containing 1% to 5% suitably dispersed ZnO by 1‐stage polyaddition process in the bulk using 4,4′‐methylenebis(cyclohexyl isocyanate), poly(ε‐caprolactone)diol, and 1,4‐butanediol was performed. Infrared and nuclear magnetic resonance spectra confirmed the structure of obtained polyurethanes. Scanning electron microscope and energy dispersive X‐ray analyzer methods showed randomly distributed ZnO in a polyurethane matrix. The differential scanning calorimetry and wide‐angle X‐ray diffraction patterns were used for the microstructural assessment of the obtained materials. Antimicrobial properties of ZnO and the effect of this modifier on the hydrophobicity of the coatings were demonstrated. The obtained coatings were characterized in terms of the mechanical properties and changes during incubation in a Baxter saline solution.     

Polyurethane cationomers modified by polysiloxane

The synthesis of waterborne polyurethane cationomers was successfully carried out. Different proportions of α,ω‐di(hydroxyl)polydimethylsiloxane (PDMS) modifier (0–7.3% by weight) were applied. Analysis of IR spectra confirmed the structure of obtained polyurethane cationomers and the incorporation of a modifier into the polyurethane structure. The differential scanning calorimetry (DSC) method was employed for the microstructural assessment of the obtained materials. A clear decrease of the degradation temperature with increasing amounts of incorporated PDMS indicates immiscibility part of the polysiloxane segments with soft segments derived from polyethylene glycol. Changes were discussed in the free surface energy and its components, as calculated independently according to the method suggested by Owens–Wendt, in relation to chemical and physical structures of cationomers as well as morphology of coating surfaces obtained from those cationomers. Test results of contact angle measurements indicated that with increasing content of the polysiloxane in the analyzed films, the contact angles increase. Copyright © 2017 John Wiley & Sons, Ltd.     

Preparation and properties of 3-aminopropyltriethoxysilane functionalized graphene/polyurethane nanocomposite coatings

Silicone-modified graphene was successfully synthesized by treating graphene oxide with 3-aminopropyltriethoxysilane (AMEO) and then reduced by hydrazine hydrate. Subsequently, the AMEO-functionalized graphene was incorporated into polyurethane (PU) matrix to prepare AMEO-functionalized graphene/PU nanocomposite coatings. The functionalized graphene could disperse homogenously by means of a covalent connection with PU. AMEO-functionalized graphene (AFG)-reinforced PU nanocomposite coatings showed more excellent mechanical and thermal properties than those of pure PU. A 227 % increase in tensile strength and a 71.7 % improvement of elongation at break were obtained by addition 0.2 wt% of AFG. Meanwhile, thermogravimetric analysis reveals that thermal degradation temperature was enhanced almost 50 °C higher than that of neat PU, and differential scanning calorimetry analysis demonstrates that glass transition temperature decreased by around 9 °C. The thermal conductivity of AFG/PU nanocomposite coatings also increased by 40 % at low AFG loadings of 0.2 wt%.     

Impingement mixing and its effect on the microstructure of RIM polyurethanes

The effect of impingement mixing on the microstructures developed during a reaction injection molding process in a thermoplastic urethane system was investigated. The polyurethane studied was a 4,4′-diphenylmethane diisocyanate/l,4-butane diol/poly(propyleneoxide) end-capped with poly(ethy1eneoxide) polyol system with a 5/4/1 molar ratio. Three different impingement mixing levels ranging from Re = 80 to Re = 210 were implemented by a laboratory RIM machine. The samples were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), optical microscopy, and transmission electron microscopy (TEM). Morphologies of hard-segment globules, hard-segment spherulites, and soft-segment rich matrix were observed. The multiple DSC endotherms were related to different crystalline structures. A higher level of mixing was found to increase the molecular weight and produce more paracrystalline structures. A lower mixing level produced better phase separation and spherulitic structures. High temperature annealing caused transurethanization, which may allow molecular rearrangement and change the crystalline structures.     

New polyurethane foams modified with cellulose derivatives

New polyurethane foams were elaborated with different cellulose derivatives as raw material, by the one-shot process. The foams were submitted to soxhlet extraction in order to quantify the amount of cellulose derivative incorporated in the foam by chemical bonding. The foams were characterized by means of FTIR, solid state ¹³C NMR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and dynamic mechanical analysis (DMA). The FTIR- and solid state ¹³C NMR showed characteristic peaks for cellulose derivatives and polyurethane. DMA measurements indicated that storage modulus increased with increasing content of cellulose derivatives. The highest value was obtained for foams prepared with cellulose sulphate.     

Synthesis,UV-curing Behavior and Surface Properties of New Fluorine-containing Aromatic Oxetane Monomers

In this paper,we combined high-end cationic UV-curable material with fluorinated chain obtaining a series of new fluorine-containing aromatic oxetane monomers via a mild nucleophilic substitution reaction.The structures and properties of monomers were characterized using 1H-NMR,19F-NMR,dynamic viscosity tests and differential scanning calorimetry (DSC).It was determined that all of the fluorinated monomers obtained had much lower viscosity and higher thermostability after the introduction of hexafluorobenzene.Then,UV-curable coatings were prepared using four fluorine-containing aromatic oxetane monomers (FOX1-4);the UV-curing kinetics,with three kinds of initiators,and properties of the cured films were evaluated using real-time Fourier transform infrared (FTIR) spectroscopy,water and diiodomethane contact angle tests,surface energy calculations and scanning electron microscopy (SEM).The FTIR spectroscopy results showed that the coatings possessed excellent conversion rate (＞ 99％ with liquid initiator PAG-201 in 150 s),and as the fluorine content increased,the monomers exhibited decreased mobility with the increasing viscosity and worse solubility with fluorinated monomers,resulting in a lower conversion rate.Moreover,the coatings possessed favorable hydrophobic and oleophobic properties and low surface energies owing to the fluoride chains floating to the membrane-air interface,which was also confirmed by discrete concave structures in SEM images.These new kinds of monomers can replace traditional fluorinated cationic monomers applied to the fingerprint resistant,fouling resistant,scratch resistant and anti-aging coatings,adhesives or printing ink materials.     

Effect of crystalline structure on the hardness and interfacial adherence of flame sprayed poly(ether-ether-ketone) coatings

Flame sprayed PEEK (poly-ether-ether-ketone) coatings, with an amorphous structure, were subjected to isothermal treatments with annealing temperatures from 180 to 300 °C and holding times from 1 to 30 min. The coating structures were studied by means of differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. All the annealed coatings exhibited semi-crystalline structures. Coexistence of thick and thin lamellae in the spherulites of annealed coatings can be deduced. The Knoop hardness and the interfacial adhesion of the coatings were examined. The annealed coatings exhibit higher hardness than the amorphous one. The formation of the thick lamellae is a determining factor for improving the coating hardness, which could restrict the motions and slippages of the polymer chains. However, the annealed coatings exhibit a weak adherence to the substrate. Some fissures or spherical porosities could be observed, in certain zones, on the coating/substrate interface. The formation of these fissures and porosities could be ascribed to the coating residual stress and the large volume contraction during the crystallization that occurred under the annealing conditions.     

Analytical Techniques Applied in Optimization of Electrophoretic Deposition of Thin Film YBCO Superconductors

 YBa₂Cu₃O _7−x (x = 0.1–0.2) compounds (YBCO) were produced by the oxalate coprecipitation and the solid state reaction methods. The powders obtained were used for the production of YBCO superconducting coatings on Pt/Si wafers, by the electrophoretic deposition technique. The optimum process conditions for the production of both powders and coatings were found by using a combination of modern analytical techniques. The thermal treatment of the samples was followed by thermogravimetry (TG) and differential scanning calorimetry (DSC). The optimization and characterization of the superconducting properties of the powders and coatings were achieved by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), optical microscopy, magnetic susceptibility and electrical resistivity measurements.     

Assessing the progress of degradation in polyurethanes by chemiluminescence and thermal analysis. II. Flexible polyether- and polyester-type polyurethane foams

The thermooxidative and thermal stability of polyether- and polyester-type polyurethane foams were investigated by non-isothermal chemiluminescence (CL), differential scanning calorimetry (DSC) and thermogravimetry (TG). In the presence of air and humidity, the effect of various routes and conditions of polyurethane ageing (induced thermally or by light) on the chemiluminescence, DSC and thermogravimetry patterns was assessed. The rate constants determined from non-isothermal thermogravimetry and chemiluminescence measurements at 250 °C and their not very pronounced dependence on the atmosphere of degradation indicated that depolymerisation of the polyurethane containing the aliphatic polyester and aromatic polyisocyanate moieties preceded or occurred in parallel with thermal oxidation. Under conditions of 50% relative humidity, samples of the polyester-type polyurethane, aged either by light or thermally, as well as specimens of the polyether-type polyurethane, aged by light, gave increased amounts of carbonaceous residue when heated in nitrogen to 550 °C.     

Diacetylene-containing polymers,II. Polyesters and polyurethanes containing m,m′-butadiynylenedibenzyl groups

Diacetylene-containing polyesters and polyurethanes were prepared by the reaction of m,m-butadiynylenedibenzyl alcohol with isophthaloyl chloride, sebacoyl chloride, hexamethylene diisocyanate and 2,4-tolylene diisocyanate. Their thermal behavior was studied by optical microscope and differential scanning calorimetry (DSC). The polyesters were crystalline. The polyurethane prepared from hexamethylene diisocyanate and polyphthalates crystallized on cooling from their melts. All turned a reddish brown color on heating at temperatures above 200°C, and prolonged heating led to a black resin, but thermal decomposition could not be avoided. Irradiation by γ-ray and UV light at room temperature deepened the color of the films, but the polymerization of the diacetylene groups was not appreciable. Simultaneous heating and irradiation was necessary to obtain transparent, amorphous, wine red colored films.     

Polyurethane–nanosilica hybrid nanocomposites synthesized by frontal polymerization

Polyurethane–nanosilica hybrids were synthesized with frontal polymerization. Structurally well‐dispersed and stable hybrids were obtained via a two‐step functionalization process: First, the silica was encapsulated with 3‐aminopropyltriethoxysilane (APTS). Second, poly(propylene oxide) glycol, toluene 2,4‐diisocyanate, 1,4‐butanediol, and a catalyst (stannous caprylate) were dissolved in dimethylbenzene and mixed together at room temperature along with the modified nanosilica. A constant‐velocity propagating front was initiated via the heating of the end of the tubular reactor. For the complete encapsulation of the silica with APTS, different weight ratios of APTS to silica were investigated. The polyurethane hybrids were characterized with Fourier transform infrared, differential scanning calorimetry, and transmission electron microscopy. The polyurethane hybrids produced by frontal polymerization had the same properties as those produced by batch polymerization with stirring, but the frontal polymerization method required significantly less time and lower energy input than the batch polymerization method. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1670–1680, 2005