Search

Fluorinated polyurethanes characterized by a segmented structure, containing hard segments based on 4,4′-methylenebis (phenylisocyanate) (MDI), chain-extender 1,4 n-butandiol (BDO), and soft blocks like perfluoropolyether (PFPE), and poly-e-caprolactone (PCL) were synthesized keeping constant the equivalent ratio among reagents, but varying the experimental conditions. Copolymers show a complex micro- and macrostrucrture with different morphology and calorimetry, similar tensile properties and undistinguishable, but strongly upgraded surface properties. The morphology should be governed by the different fluorine content of the polymeric chains along with the hard segment structure; tensile properties are little influenced by the morphology. All these characteristics are interpreted in terms of polymerization procedure which results to be a key parameter for ruling the composition of the different polymeric chains, due to a very limited mutual solubility of the reagents. Surprisingly, a beneficial effect of the catalyst dibutyltindilaurate for the increase of the reaction kinetics among segregated phases in the reaction mass was observed.

Urethane reactions of cycloaliphatic and aromatic diisocyanates with hydroxy-terminated fluoropolyethers (FPEs) of various molecular weights and structure, at NCO: OH = 2, have been studied by monitoring, by IR analysis, the rate of decrease in NCO absorbance at 2264-2268 cm -1 . Different diisocyanates have been tested, among them the following: 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI); 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate (IPDI); 2,4-toluene diisocyanate (TDI). Ethyl acetate (EA), methyl isobutyl ketone (MIBK), and hexafluoroxylene (HFX) have been used as solvents in presence of dibutyltin dilaurate (DBTDL) or 1,4-diazabicyclo[2,2,2]octan (DABCO) as catalysts. These reactions gave rise to NCO-end-capped FPE-oligourethanes. Preliminary solubility tests for HO-terminated FPEs in various solvents made it possible to select proper candidates for carrying out reaction in homogeneous conditions at high concentrations of reagents (30-50% w/w). The second-order kinetic mechanism was shown to be valid. Positive deviations from linearity for the second-order kinetics around 40-80% conversion, found for most of the FPE diols, were attributed to the autocatalysis of the isocyanate-hydroxyl reaction by the arising urethane groups. Uncatalyzed reactions with cycloaliphatic diisocyanates are very slow at 40°C. The tertiary amine DABCO is a much less effective catalyst than DBTDL. FPEs having terminal OH groups separated from the perfluorinated main molecular chain by -(OCH 2 CH 2 ) n - segments (n = 1-2) are generally more reactive than FPEs with end -CH 2 OH groups.

Perfluoropolyether polymers have been described as high performance fouling-release materials for marine coatings. Moreover, they have a good potential to be exploited in the biomedical field too. In this article several perfuoropolyether photopolymers were characterized in terms of surface and mechanical properties outlining the relationship between these properties and the polymer molecular structure. In particular the anti-fouling and fouling-release performances, evaluated using Bovine Serum Albumin as testing protein, was correlated to other material properties, like a parameter considering both surface tension components γ and elastic modulus E . A good correlation between the anti-fouling/fouling-release of perfluoropolyethers and ( E * γ polar ) 1/2 can actually be established. Our results show that perfluoropolyether photopolymers are good protein anti-fouling/fouling-release materials.

New fluoropolyether polyolic resins are presented suitable to be cured with conventional hardeners as polyisocyanates or melamines. These resins are prepared by addition of fluoropolyether macrodiols (Fomblin® ZDOLTX) of various molecular weights to isophorone diisocyanate (IPDI) to give oligomeric NCO-terminated prepolymers. The final hydroxy functionality is obtained by the reaction of those prepolymers with trimethylolpropane (TMP). The viscosity of the resins is measured at various concentrations (weight fraction 0.8 – 0.4) and temperatures (T = 25–65°C). The results are discussed in terms of the Erickson equation (η vs. concentration) and using the WLF and Arrhenius models (η vs. T). The thermal behavior is studied by DSC for both the resins and cured films indicating the presence of two Tgs, corresponding to the segregated fluorinated and hydrogenated phases, the former particularly evident with the highest molecular weights of the fluorinated macromer. Tensile curves of selfsupported films are then analyzed showing an evident tough-plastic behavior especially for the isocyanate-cured films. The application of such materials as high-durability clear coats is finally proposed. Neuartige Fluoropolyether-Polyol-Harze, die mit konventionellen Hartern wie Polyisocyanaten oder Melaminen aushartbar sind, wurden hergestellt. Zunachst wurden oligomere NCO-terminierte Prepolymere durch Addition von Fluorpolyether-Makrodiolen unterschiedlicher Molekulargewichte an Isophorondiisocyanate erhalten. Durch die Reaktion dieser Prepolymeren mit Trimethylolpropan wurden endstandige Hydroxygruppen eingefuhrt. Die Viskositat von Losungen dieser Harze wurde bei unterschiedlichen Konzentrationen (Massenbruch 0,4–0,8) und Temperaturen (25°C–65°C) gemessen. Die erhaltenen Werte wurden auf der Basis der Erickson-Gleichung (Konzentrationsabhangigkeit von η) und unter Berucksichtigung des WLF-und des Arrhenius-Modells (Temperaturabhangigkeit von η) diskutiert. Das thermische Verhalten der Harze und von ausgeharteten Filmen wurde mit DSC bestimmt. Dabei wurden zwei Glasubergange beobachtet, die den separierten fluorhaltigen und nicht-fluorhaltigen Phasen zugeordnet werden konnen. Die Analyse des Zugverhaltens der Filme zeigte besonders bei den mit Isocyanat geharteten Proben ein ausgepragtes hart-plastisches Verhalten. Diese Werkstoffe erscheinen fur die Anwendung als hoch-wertige, dauerfeste und klare Beschichtungen geeignet.

New fluorinated thermoplastic elastomers (FTE) with perfluoropolyether (PFPE) blocks have been synthesized by reacting a fluorinated macrodiol with aromatic diisocyanates in the presence of a solvent, followed by subsequent chain extension with low molecular weight aliphatic or aromatic diols. Tensile properties measurements and dynamical-mechanical analysis (DMA) have been carried out and the relationship between chemical structure and final properties has been determined. These new thermoplastic fluorinated polyurethanes show an elastomeric behavior over a wide temperature range (between −75 and 100°C), thanks to their multiphase morphology consisting of a continuous fluorinated phase with a very low Tg (−120°C) and a dispersed high melting hydrogenated hard phase, as verified by a calorimetric and dynamic-mechanical analysis. At the same time, some of the outstanding properties of fluorinated oligomers, such as chemical inertness and low surface tension, are retained in the final polymers. Thanks to these characteristics this new class of polymeric materials provides new opportunities for the application of thermoprocessable elastomers in advanced technological fields. © 1996 John Wiley & Sons, Inc.

The synthesis of new functionalised macromers containing perfluoropolyether structures (PFPE) is reported. They are obtained by reaction of bis-CH 2 OH terminated PFPE with isocyanato-ethyl methacrylate (EIM). giving rise to the formation of perfluoropolyether bisurethane methacrylate (PFEUMA) oligomers. The products are characterised by NMR and FTIR analyses. The thermal behaviour reveals two amorphous phases, corresponding to the fluorinated and the hydrogenated moieties, while a crystalline phase can be present depending on the macromer structure. The functionalised macromers are UV-cured in the presence of a photoinitiator and the complete disappearance of the double bonds is obtained. The cured films are characterised by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) confirming the presence of a multiphasic structure. Moreover the optical properties and the surface properties of the cured systems are investigated and discussed.

Copolymers of tetrafluoroethene (TFE) with hexafluoropropene (HFP) have been prepared in the 0-14mol% HFP composition range. Their melting temperatures (Tm), enthalpies (ΔHf) and entropies (ΔSf) of first and second fusion, and crystallinities (X) according to x-ray diffraction(x.r.d.) and differential scanning calorimetry (d.s.c.) have been determined. The results indicate that ΔHf/Xx.r.d of the polymer crystals decreases with higher HFP content.

New functionalised macromers containing perfluoropolyether (PFPE) structures and methacrylic end groups were synthesised and used as modifying additives for acrylic UV-curable systems. Their chemical structure is Rh-Rf-Rh, where Rh= -CH 2 O-CONH-CH 2 CH 2 OCOC(CH 3 )=CH 2 and Rf=-CF 2 O-(CF 2 CF 2 O) p (CF 2 O) q -CF 2 - with p ≃ q. Notwithstanding their very low concentration, below 0.5 wt.-%, the fluorinated macromers cause a dramatic change of the surface properties of the films, without changing their curing conditions and their bulk properties. X-ray photoelectron spectroscopy (XPS) measurements showed that the macromers are able to concentrate selectively at the surfaces of the films, depending on their chemical structure and on the kind of substrate employed.