Radiation-chemical synthesis of tetrafluoroethylene telomers and their use for preparation of thin protective fluoropolymer coatings

The specific features and possibilities of preparation of protective coatings and composite materials based on fluoromonomers using high-energy rays (⁶⁰Co γ-rays, fast electrons) were analyzed. The emphasis was placed on synthesis and application of tetrafluoroethylene telomers in acetone. The structure and properties of telomers were examined by IR and NMR spectroscopy, as well as by X-ray diffraction analysis and diathermy. The radiation initiation allows preparation of new products with a broad spectrum of functional properties and opens wider prospects for technological application of fluoromonomers.     

Copolymerization of fluorinated monomers with nonfluorinated monomers. Reactivity and mechanisms

The copolymerization of two monomers usually leads to random copolymers except when one of both bears an electron-acceptor group and the other one has an electron-donor group. Many copolymers are commercially available, mainly in the series of hydrogenated monomers (S.M.A., GANTREZ, MALIALIM resins). The field of fluorinated copolymers is very interesting because of the strong electron-acceptor behaviour of the fluorine atoms and more generally of halogenated atoms. Thus, after HALAR (CTFE^a)-ethylene), TEFZEL (TFE-ethylene) and AFLAS (TFE^b)-propylene) resins, a new series of resins have been produced (copolymers of CTFE and vinyl ethers commercialized by ASAHI Corp.). So it can be considered that ACCEPTOR-DONOR copolymerization with fluorinated monomers is one of the most important applications of that kind of research. After reminding the main mechanisms of that reaction (homopolymerization of charge transfer complex and copolymerization of free monomers), it will be discussed about the mechanism in some examples (CTFE-vinyl ethers and other pairs of monomers). Then it will be explained how cotelomerization has provided new data to prefer a copolymerization mechanism by free monomers.     

EB/UV treatment of protective coatings for porous materials

A method for improving surface properties of porous inorganic materials is presented. The method is particularly tailored to cement-based materials in order to obtain properties suitable for mechanical applications such as dies manufacturing, where hardness, abrasion resistance and low friction are requested. The coating system is based upon using two coatings of different characteristics. The underlying base coating layer is infiltrated in air on three different formulations of hardened cement composite. Two different bi-component resins, one relatively soft and the other relatively hard, were tested as underlying surface coating. The outer surface coating, based upon a bi-component resin characterized by high hardness, is added after hardening and curing of the first layer. Both coatings were chemically hardened and then cured with EB. UV curing is also suitable for the outer surface coating. An experimental campaign was carried out in order to evaluate the influence of radiation processing as curing treatment with reference to particular investigated materials. Hardness and resistance to peeling of coating systems have been measured and are presented.     

Copolymerization of fluorinated acrylic monomers with p-vinylphenol and hydroxyethyl methacrylate

Copolymers of p-vinylphenol were prepared in bulk with heptafluorobutyl and pentadecafluorooctyl acrylates and trifluoroethyl, hexafluoroisopropyl, heptafluorobutyl, octafluoropentyl and pentadecafluorooctyl methacrylates using azobisisobutyronitrile as the initiator in sealed tubes. Intrinsic viscosities of the copolymers ranged from 0.44 to 1.85. Monomer reactivity ratios for copolymers of trifluoroethyl methacrylate (M₁) were: with hydroxyethyl methacrylate (M₂), r₁ = 0.47, r₂ = 1.0; with methyl methacrylate (M₂), r₁ = 0.82, r₂ = 0.50; with styrene (M₂), r₁ = 0.29, r₂, = 0.20; and with p-vinylphenol (M₂), r₁ = 0.096, r₂ = 1.5. Q and e values of trifluoroethyl methacrylate were 1.30 and 0.92, respectively. Monomer reactivity ratios of octafluoropentyl methacrylate (M₁) were: with styrene (M₂), r₁ = 0.26, r₂ = 0.20; and with p-vinylphenol, r₁ = 0.21, r₂ = 1.5. Q and e values for octafluoropentyl methacrylate were 1.27 and 0.92, respectively. Critical surface tensions of the homopolymers ranged from 17.9 to 14.8 dyn/cm. A copolymer of hexafluoro-i-propyl methacrylate and p-vinylphenol exhibited a critical surface tension of 16.5 dyn/cm.     

On the polymerization reactivity of fluorinated vinyl monomers

The polymerization reactivities of α,β,β‐trifluorovinyl compounds (CF₂=CF—R) and α‐trifluoromethylvinyl compounds (CH₂=C(CF₃)—R) are discussed since these monomers have scarcely been investigated and hardly yielded corresponding homopolymers, although tetrafluoroethylene and chlorotrifluoroethylene have been studied under radical polymerization conditions. In the case of α,β,β‐trifluorostyrene, a homopolymer is obtained in low yields by anionic polymerization and it is concluded that the reaction takes place without any side reactions once the reaction has started, since simple addition polymerization is observed and the molecular weight distribution is very narrow. Anionic polymerization of hexafluorobuta‐1,3‐diene is successfully achieved by the addition reaction of living end to the 2‐carbon of hexafluorobuta‐1,3‐diene followed by isomerization to produce excellently high thermostable polymers. ω‐Trifluorovinyloxyfluoroalkyl alcohol produces a polyether via a polyaddition reaction under anionic conditions. The homopolymers of α‐trifluoromethylacrylates are quantitatively obtained under anionic polymerization conditions. α‐Trifluoromethylstyrene derivatives are likely to polymerize under radical conditions, but are not well‐studied. The radical polyaddition reaction of perfluoroisopropenyl esters in 1,4‐dioxane, diethyl ether or 1,2‐dimethoxyethane yields the polymers possessing the solvent moiety in the polymer main chain, respectively. It is clearly demonstrated that each fluorinated vinyl monomer discussed in this article demands its own reaction conditions. Therefore, more experimental data on the polymerization of these individual monomers is needed, including research on developing the reactions discovered in the organofluorine chemistry field to the preparation of polymers.     

Microreactors for the synthesis of fluorinated materials

The utility of microreactor for the synthesis of α-fluoro-α,β-unsaturated esters, trifluoromethylation and Michael addition reaction, is described.     

High-temperature composite materials and coatings on the basis of glass and ceramics for aerospace technics

High-temperature composite materials and coatings developed in the RIAM, specifically construction composite materials with glass, glass-ceramic, and ceramic matrices, for use at 700–1500°C, ceramic composites on the basis of poly-carbosilanes, erosion resistant coatings with the effect of thermal control for heat shield systems of perspective aerospace technics, are reviewed. These coatings combine a complex of properties: high radiating capacity, phase stability, thermal shrinkage resistance, resistance against acoustic, vibration, atmospheric factors, etc. Technological coatings to protect steels and Ti and Ni alloys during heat treatment and isothermal and hot die forging are developed. New type enamels, pasts, thick-film electric heaters, etc., are described.     

Physicochemical properties of composite sorption-active materials based on zeolite and fluorinated ethylene derivatives

A procedure was suggested for preparing composite sorption-active materials based on zeolite and fluorinated ethylene polymers. The morphology of these materials, their resistance to mechanical action, and their ability to sorb water vapor under static and dynamic conditions were examined.     

Synthesis of fluorinated monomers through sulfinatodehalogenation and related reactions

Using sulfinatodehalogenation and related reagent systems several groups of perfluoroalkylated compounds including olefins, dienes, phenolic compounds and aromatic dicarboxylic acids were synthesized which may be useful as potential monomers.     

Synthesis of optically active fluorinated materials by use of immobilized enzymes for asymmetric hydrolysis

A synthetic approach to optically active fluorinated compounds was based on the enantiotopic specificity of asymmetric hydrolysis by an immobilized enzyme.     

Rational use of aluminosilicates from primorskii krai in protective coatings for ship building

Formulations of protective polymeric coatings for sea craft, which contain natural aluminosilicates (zeolite and vermiculite from Primor’e deposits) as fillers and polyheterosiloxanes, oxides, and fluorides of some metals and mixtures of these as modifiers of binding resins, were developed.     

A new strategy for fabrication Fe2O3/SiO2 composite coatings on the Ti substrate

We report here on the synthesis of homogenous, well-adherent composite film of Fe₂O₃/SiO₂, up to 7 μm thick, on the titanium substrate by anodic treatment optimized for an aqueous suspension of K₂O·SiO₂ and Fe₂O₃ powder under galvanostatic conditions. The end products were characterized by scanning electron microscopy, energy-dispersive X-ray, X-ray powder diffractometry, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy, concluding that the formation of composite coating at the SiO₂ to Fe₂O₃ ratio of approximately 1:1 proceeds just after formation of a thin TiO₂ layer with Fe₂O₃ particle inclusions without transformations via an electrophoresis deposition of negatively charged Fe₂O₃ species enveloped by silica ions.     

The effect of power on the plasma-assisted deposition of fluorinated monomers

The effect of power variation on the polymerization kinetics and on the polymer structure is reported for RF glow discharges fed with C₂F₆–H₂ mixtures. Both deposition rate and polymer structure trends can be correlated to the variations of gas-phase species density (atoms, radicals, and charged species) and can be explained by considering the competition of the deposition and etching process.     

Adhesion of protective coatings with modified filler

The effect of physical (ultrasonic) and chemical (exposure in 3% solution of acetic acid) activation of filler on the adhesion strength of the protective coatings based on styrene–acrylic dispersions to different substrates is studied. It is shown that modification of kaolins allows one to increase the adhesion strength by 40–50% in the case of the physical activation and by 1.1–1.2 times in the case of chemical activation. The best results are achieved with the use of E-21 dispersion as the polymer matrix.     

New fluorinated acrylic monomers for the surface modification of UV‐curable systems

New fluorinated acrylates were synthesized and used as modifying additives for acrylic UV‐curable systems. Their chemical structure is: C_nF_2n+1 R—OCO—CHCH₂, where the linear perfluorinated chain contains from 4 to 10 carbon atoms, while R is a linear alkyl group containing or not a thioether group. Notwithstanding their very low concentration, the fluorinated monomers caused a dramatic change of the surface properties of the films, without changing their curing conditions and their bulk properties. X‐ray photoelectron spectroscopy measurements showed that the monomers were able to concentrate selectively on the surfaces of the films, depending on their chemical structure and on the kind of substrate employed. The synthesis of the fluorinated monomers and the relationship between their chemical structure and the final surface properties of the UV‐cured films will be discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 77–87, 1999     

Copolymerization of novel reactive fluorinated acrylic monomers with styrene: reactivity ratio determination

The radical copolymerization of three polymerizable surfactants with styrene was investigated by NMR spectroscopy to assess their compositions. The reactivity ratios of these monomers were calculated according to the methods of Fineman–Ross and Kelen–Tüdos. Consequently, Q and e values were deduced by the Alfrey and Price method. The results indicated the positive effect of the fluorine chain on the reactivity of monomers bearing a long spacer between the ammonium head and the acrylic function. These monomers exhibit high e values which are in favor of an intramolecular conformation of the surfactant where the ester carbonyl function of the polymerizable group interacts with the onium nitrogen atom via a compact six-sided structure.     

季铵盐类阳离子单体的合成工艺研究进展

对季铵盐类阳离子单体的合成工艺及结构改性研究进展进行了综述。基于季铵盐类阳离子单体的基本结构与性质,从合成反应基本历程及代表性制备工艺方法出发,介绍了二烯丙基季铵盐类、丙烯酰胺烷基季铵盐类和丙烯酰胺烷基季铵盐类三类最为重要的季铵盐阳离子单体的合成、聚合及结构改性最新研究进展,指出了已有研究工作的特色与不足,并认为开发高质量丙烯酰胺烷基季铵盐类单体及聚合物产品以及高纯度质量稳定的阳离子单体制备新工艺是今后应努力的方向。     

Simple method of fabrication of hydrophobic coatings for polyurethanes

The aim of this study was to develop a method of manufacturing versatile hydrophobic coatings for polymers. Authors present a simple technique of polyurethane (PU) surface modification with covalently attached silicones (PDMS) or fluorocarbons (PFC). Diisocyanates were applied as linker molecules. The obtained coatings were characterized using spectroscopic analysis (FTIR), scanning acoustic microscopy (SAM) and water contact angle measurements. FTIR analysis revealed high efficiency of grafting reaction. The results of contact angle measurement indicated significant increase of hydrophobicity — from 66° (unmodified PU) to 113° (PU grafted with PDMS) and 118° (PU grafted with PFC). Acoustic microscopy analysis confirmed satisfactory homogeneity and smoothness of the fabricated layers. In vitro cell tests revealed non-adherent properties of the surfaces. Both, MTT assay and fluorescence staining confirmed non-cytotoxicity of the coatings, which makes them potential candidates for use in biomedical applications.      

Syntheses and properties of fluorinated carbon materials

In this review, the more recent topics in the field of fluorinated carbon materials are given with the emphasis on the research work presented by our group. The direct fluorination and/or oxyfluorination of various carbon materials, especially of new carbon materials, i.e. nanotubes, carbon fibers, and activated carbon fibers have been described. It has been shown that fluorination can be one of the most effective methods to modify and control physico-chemical properties of carbon materials.