128 research outputs found
Photoactive Perfluorinated Ionomeric Transparent Coatings in the Oxidative Abatement of Hydrosoluble Pollutants in Turbid Suspensions
No full textPhotoactive perfluorinated ionomeric transparent coatings in the
oxidative abatement of hydrosoluble pollutants in turbid suspensions
Walter Navarrini*(1,2), Federico Persico(1,2), Maurizio Sansotera(1,2)
(1) Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”, Politecnico di
Milano, Via Mancinelli 7, 20131, Milano, Italy.
(2) Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali, Via G. Giusti
9, 50121 Firenze, Italy.
*Walter Navarrini: Tel: +39.02.2399.3035; email address: [email protected];
The abatement of organic pollutants in water phase promoted by photoactive titanium dioxide has
been widely studied in the last decade [1]. Despite the high photodegradative rates guaranteed by
slurry TiO2, its industrial use is strongly limited by the catalyst recovery cost. To overcome this
obstacle powder TiO2 was immobilized into a multilayer ionomeric-perfluorinated matrix and the
activity of this Photoactive Coating (PAC) was studied.
In order to obtain the correct interaction between the activated TiO2 and the polluted aqueous
solutions the polymeric matrix must be characterized by high chemical resistance, high
transparency towards UV light, good wettability and good permeability to oxygen and water vapor
[2,3].
The multilayer coating photocatalytic activity towards hydrosoluble organic pollutants was
evaluated in clear as well as in highly turbid conditions obtained by dispersing barium sulphate
microparticles in the polluted solution.
The perfluorinated multilayer photoactive coating was applied directly on the UV source and
employed as substrate for immobilization of the photocatalyst. A TFE/perfluorodioxole copolymer
double-layer acted as primer; a dispersion of TiO2 in the perfluorinated ionomeric solution of a
copolymer between TFE/perfluorosulphonylvinylether acted as photoactive layer. The strong
acidity of the ionomeric side chains conferred hydrophilicity to the coating , allowing a good
interaction with the polluted aqueous solutions. Rhodamine B-base (RhB) and Crystal Violet (CV)
were used as organic hydrosoluble pollutants and their
concentration in solution was monitored by UV-Vis
spectroscopy and HPLC-MS technique.
In both clear and turbid conditions, TiO2-embedded
transparent fluorinated coating revealed higher
photocatalytic activity than merely dispersed TiO2
(Image1). This behavior was particularly evident at low
pollutant concentrations. In addition, catalyst
immobilization prevented TiO2 separation and catalyst
losses, allowing the development of a simple and
efficient continuous apparatus.
I Image 1. Degradative efficiency of PAC compared
to the performances obtained with slurry TiO2
References
[1] M. Sansotera, et al., Appl. Catal., B, 148 (2014) 29.
[2], F. Persico, et al., Thin Solid Films, 545 (2013) 210.
[3] W. Navarrini, et al., Prog. Org. Coat., 74 (2012) 794
EPR AND ENDOR OF PERFLUOROALKYL RADICAL INTERMEDIATES IN THE REACTION BETWEEN PERFLUOROHYPOFLUORITES AND PERFLUOROALKENES
No full textEPR and ENDOR spectra of the reaction products of sterically hindered perfluoroalkenes with perfluoromethyl
hypofluorite and with the perfluoroether hypofluorite X(CF,O),(CF,CF,O),CF,OF, where X is either OCF, or a
second hypofluorite group OCF,-OF, have been recorded. Tertiary and secondary free radicals are produced by
the addition to the alkene double bond of a fluorine atom or of the partner radical formed by the homolysis of the
hypofluorite 0-F bond. Analysis of the spectra reveals that hyperfine splitting by "F nuclei in the y and 6
positions, and even further from the radical centre, contribute spectra. The a- and B-"F hyperfine splitting are
discussed in relation to the radical structure and conformation. The /?-''F splittings are accounted for by the well
known equation a! = B cos2(8); different values of the constant B have to be used according to the number of
/?-fluorine substituents bonded to the same a-carbon
Simplified kinetic study of the reaction between perfluoro-methyl-hypofluorite and perfluoro-olefins
No full textIn the reaction between perfluoroolefins and perfluoroalkylhypofluorites [1] the existence of two different free radical reaction mechanisms is demonstrated by the presence of characteristic by-products.
In particular in the reaction between trifluoromethyl hypofluorite and highly reactive perfluoroolefins like CF2=CFOCF3 and CF2=CF2, the free radical oligomerization and dimerization products can be suppressed by utilizing the opportune experimental conditions.
These experimental conditions are characterized by the presence of hypofluorite during the addition reaction and can be performed by adding the olefin to the hypofluorite, these conditions herein referred as “Reverse hypofluorite addition”. are different from the standard methodologies described in the literature where generally the hypofluorite is added to the olefin.
The main products of the addition of CF3OF to CF2=CFOCF3 are perfluoro-2,2-bis-(methoxy)-ethane and perfluoro-1,3-bis-(methoxy)-ethane [2] in the molar ratio of 20% and 80% respectively.
We found experimental evidence for the termination products peroxide CF3OOCF3 and perfluoroethers C8F18O4 respectively. The first termination product CF3OOCF3 was present at high amount in the reaction where the CF3OF concentration was maintained always above zero and substantially constant, on the contrary the termination products C8F18O4 were completely absent. In this conditions the oligomerization and polymerization of the perfluoroolefins were also suppressed, as well as in the case of the very reactive TFE.
[1] W. Navarrini, V. Tortelli, A. Russo, S. Corti, J. Fluorine Chem. 95(2),(1999)27-39
[2] W. Navarrini, G. Resnati, P. Metrangolo, M. Cantini, F. Venturini, IT Patent app. MI2007A001384 (2007)
UV- resistent fluorinated coating for anodizated titanium surfaces
No full textUV-resistant amorphous fluorinated coating for anodized titanium surfaces
Presenting: Wu Menghua*‡,Walter Navarrini‡, Maria Vittoria Diamanti‡, Maurizio Sansotera‡, Federico Persico‡, Luca Magagnin‡, Stefano Radice§
‡: Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico
di Milano, via Mancinelli 7, 20131,Milano,Italy.
E-mail:[email protected]
§: Solvay Solexis, Research & Technology, Viale Lombardia 20, 20021,
Bollate (MI), Italy.
Abstract
A high molecular weight copolymer of tetrafluoroethylene and perfluoro-4-trifluoromethoxy-1,3-dioxole (Hyflon® AD60), and two perfluoropolyether containing ammonium phosphate or triethoxysilane functionalities, Fluorolink® F10 and Fluorolink® S10 respectively, have been evaluated as protective coatings that can be easily applied on anodized titanium surfaces. Based on CIELab model, spectrophotometric analysis have been made to quantify chromatic variations of substrates after the application of fluorinated coatings. Water and n-dodecane contact angle measurements have been done by using the sessile drop method for both bare and coated surfaces in order to determine the hydrophobic and oleophobic properties of the coatings. The UV-stability of coatings have been studied by observing the variation of water contact angles and by FT-IR analyses on coated substrates before and after UV irradiation at regular time intervals. The thickness of the fluorinated films have been measured by ellipsometry and by weight evaluation. Preliminary adhesion test between films and substrate as well as their soiling resistance with castor oil have been investigated. Among the above three fluorinated polymers, we observed that the high Tg amorphous transparent Hyflon® AD60 revealed a good adhesion on the anodized titanium substrate, no evident modification of the sample original color, and in addition it conferred both hydrophobicity and oleophobicity to the substrate, more over resulted in a good UV resistance. 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 0,09 0,10 0,11 0,12 0,13 0,14 0,15Absorbance 1100 1200 1300 1400 1500 1600 Wavenumbers (cm-1)
Fig. 1 Water-droplets on Hyflon® AD60 coated and on uncoated anodized titanium surfaces.
Fig. 2 Constant IR absorbance of Hyflon® AD60 coating on anodized titaniu
Fluorovinyl ethers and polymers obtainable therefrom
No full textABSTRACT
FLUOROVINYL ETHERS HAVING THE FORMULA CFX=CXOCF2OR, WHEREIN X= F, H; R IS A C2-C6 LINEAR, BRANCHED OR C5-C6 CYCLIC (PER)FLUOROALKYL GROUP, OR A C2-C6 LINEAR, BRANCHED (PER)FLUORO OXYALKYL GROUP CONTAINING FROM ONE TO THREE OXYGEN ATOMS; WHEN R IS FLUOROALKYL OR FLUOROOXYALKYL GROUP AS ABOVE DEFINED, IT CAN CONTAIN FROM 1 TO 2 ATOMS, EQUAL OR DIFFERENT, SELECTED FROM THE FOLLOWING: H, CL, BR, I; AND HOMOPOLYMERS OR POLYMERS OBTAINABLE POLYMERIZING SAID FLUOROVINYL ETHERS WITH AT LEAST ANOTHER POLYMERIZABLE MONOMER
Method of making fluoro vinyl ethers and polymers obtainable therefrom
No full textFluorovinyl ethers having the formula CFX-CXOCF2OR, wherein R is a C2-C6 linear, branched or C5-C6 cyclic (per)fluoroalkyl group, or a C2-C6 linear, branched (per)fluoro oxyalkyl group containing from one to three oxygen atoms; when R is fluoroalkyl or fluorooxyalkyl group as above defined, it can contain from 1 to 2 atoms, equal or different, selected from the following: H, Cl, Br, I; X-F, H; and homopolymers or polymers obtainable polymerizing said Fluorovinyl ethers with at least another polymerizable monomer
Fluoroelastomer
No full textFIELD: polymer materials. ^ SUBSTANCE: invention provides fluoroelastomers including, in their polymer chain, units obtained from fluorovinyl ethers having general formula CFX=CX-O-CF2-OR wherein R represents C2-C6-linear or branched or C5-C6-cyclic (per)fluoroalkyl group, or C2-C6-linear or branched (per)fluorooxyalkyl group containing 1-3 oxygen atoms, provided that, when R is above-defined fluoroalkyl or fluorooxyalkyl group, it can contain 1-2 identical or different atoms selected from group including H, Cl, Br, and I; and X represents F or H. ^ EFFECT: increased choice of fluorinated elastomer materials. ^ 18 cl, 17 e
Perfluorodiacylperoxides as polymerization initiators Inventors: November 14, 2006
No full textAbstract
Perfluorodiacylperoxides having the following structures: ##STR00001## wherein: when R.sub.f is F, R.sub.f', R.sub.f'' are both --CF.sub.3; when R.sub.f is --CF.sub.3, R.sub.f', R.sub.f'' are C.sub.1 C.sub.3 linear or branched perfluoro-oxyalkyl groups; said perfluorodiacylperoxides being such as to meet the following proviso: the thermal decomposition constants K.sub.d (sec.sup.-1) in the presence of water do not undergo substantial variations with respect to the thermal decomposition constants in absence of water
PERFLUORODIACYL PEROXIDE AS POLYMERIZATION INITIATOR
No full textPROBLEM TO BE SOLVED: To provide a polymerization initiator stable against hydrolysis when used in an aqueous solvent. SOLUTION: The purpose is achieved by a perfluorodiacyl peroxide shown bellow: it has a structure expressed by the formula (wherein, when Rf is F, Rf ', and Rf" are each a 1-3C linear or branched perfluoroalkyl group); and its thermal decomposition constant Kd (sec ) in the presence of water does not differ substantially from that in the absence of water
New perfluorodioxol, its production and homo-polymer and copolymer obtained therefrom
No full textprovide a novel perfluorodioxole which is suitable for producing a homopolymer and a copolymer both having excellent mechanical properties and a good thermal stability.
CONSTITUTION: A perfluorodioxole of formula I (wherein RF is 1-5C perfluoroalkyl; and X1 and X2 are each F or CF3) (e.g. 2,2,4-trifluoro-5- trifluoromethoxy-1,3-dioxole of formula II) is provided, which is obtd. e.g. by reacting a dioxole of formula III with a fluorooxy compd. of the formula: RFOF and reacting the resultant dioxolane of formula IV with a metal in a dipolar aprotic solvent to dehalogenate the dioxolane of formula IV or by reacting a compd. of formula V with a bisflurooxy compd. of formula VI at -140 to -20°C and dehalogenating the resultant dioxolane of formula IV in the same way as above. The perfluorodioxole of formula I may be homopolymerized or copolymerized with an olefinically unsatd. comonomer
- …
