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In this paper, the properties of some polymeric materials used as consolidating and protective products in the restoration field of stone manufactured objects of artistic interest are discussed. The penetration of polymeric consolidating products is very small because of their macromolecular nature, and in situ polymerization of the monomers is suggested as an alternative technique to the use of macromolecular solutions. The effects of plasticizer agents in the reaction system have been investigated, in order to decrease T g and make the products more elastic.

In this paper the consolidating and protective products used in the restoration of stone manufactured objects of artistic interest are discussed; advantages of the different products and the relevant properties of the polymeric materials are underlined. The penetration of polymeric consolidating materials is very small and the in situ polymerisation of the monomers is suggested as an alternative technique to using macromolecular solutions. Some experimental results are presented showing that the in situ polymerisation improves the consolidating and the protective properties of polymers.

Poly(vinylidene fluoride) (PVDF) samples, obtained by casting from tetrahydrofuran solutions and submitted to various thermal treatments, have been examined by Fourier transform-infrared microspectroscopy (FTIR-M) and differential scanning calorimetry (DSC). This kind of analysis allowed us to examine microdomains of samples with different morphological characteristics and to obtain an indication of the polymorphism of PVDF. In some cases the simultaneous presence of two or three forms has been evidenced thanks to the comparison of FTIR-M spectra and DSC traces. Vibrational spectra of single crystalline forms can be recorded by FTIR-M on phase homogeneous microdomains.

The kinetic features of vinylidene fluoride (VDF) radical polymerization in solution, initiated by bis(4-butylcyclohexyl)peroxydicarbonate, have been investigated in three different solvents (acetone, ethyl acetate and methyl acetate) under homogeneous conditions. Many significant deviations of the dependence of the polymerization rate on the ‘ideal’ 1.0 and 0.5 exponent values of monomer and initiator concentrations, respectively, are indicative of anomalous kinetic behaviours linked to concurrent reactions, which are operative during such polymerization. The complexity of the kinetic behaviour prevents, inter alia , the correct evaluation of chain transfer constants to the solvents from kinetic data. 19 F nuclear magnetic resonance spectroscopy has been used in order to get full microstructural characterization of the low-molar-mass poly(vinylidene fluoride) (PVDF) synthesized under the above conditions. Both chain transfer constants to the solvent and extent of chain inversions in PVDF have been evaluated by this technique.

An ethylene—propylene (EPR) copolymer functionalized with (1,2-dicarboethoxy)ethyl groups has been blended with a vinylidene fluoride—hexafluropropene elastomer (NML). The existence of intermolecular interactions involving mainly the carbonyl groups of the side chains of the functionalized copolymer and the methylene hydrogens of the fluoroelastomer through hydrogen bonding was shown by means of FT—IR spectroscopy. The structure and composition of some microdomains in the mixture was examined by means of FT—IR microspectroscopy.

Peroxide initiated vinylidene fluoride (VDF) telomerization was investigated in the presence of bromine terminated perfluoropolyethers CF 3 (OCF 2 CF 2 ) m (OCF 2 ) p Br, (R f -Br). R f -Br act as telogen agents producing the above reaction compounds of general formula R f -(VDF) n Br. Data on telomer microstructure by fluorine NMR, glass transition temperature and crystallinity of (VDF) n moiety are also reported and discussed. The products show properties of di-block copolymers.

Copolymers of 1,1-difluoroethene with tetrafluoroethene, chlorotrifluoroethene, and bromotrifluoroethene have been prepared by emulsion polymerization, and their crystallinity has been investigated by means of x-ray diffraction. The results are discussed in relation to copolymer composition and structure.

Fluorine containing alcohols, esters and ethers have been obtained by peroxide induced radical addition of alcohols, esters and ethers to 1,2-dichlorodifluoroethene. The influence of the kind and amount of the peroxide has been studied and the reactivity of alcohols, esters and ethers compared.

The dynamic-mechanical properties of some fluoroelastomers were determined as a function of composition at low frequency (≈ 1 Hz), by means of a free oscillation torsion pendulum, between −180°C and the softening point. Vinylidenefluoride (VDF)-hexafluoropropene (HFP) copolymers of molar composition 0–39% HFP and terpolymers of VDF and HFP with up to 30mol% tetrafluoroethylene (TFE) and a constant VDF to HFP molar ratio of 3.4 were considered. Two relaxation processes typical of the amorphous phase were found. The first, located at about −87°C, is related to local motions and the transition temperature was found to be independent of composition for copolymers, while it depends on TFE molar content for terpolymers. The second is related to the glass transition and the transition temperature depends on the composition. However, for semicrystalline copolymers the double glass transition phenomenon was observed. When crystallinity goes to zero at about 20 mol% HFP, only one transition is observed. It was also found that ordered structures can take place for terpolymers when TFE molar concentration exceeds 20%. The crystal disorder transition of pure PVDF (75°C) is observed also for low HFP concentrations but the transition temperature is strongly reduced. Analogies between the VDF-HFP and E-P systems are also discussed.

Several fluoroalcohols have been prepared by the free-radical addition of methanol, ethanol and isopropanol to such fluoro-olefins as C3 F6, CFH[dbnd]CF-CF3, (CF3)zCFCF[dbnd]CFCF3 and H(CF2)4CF[dbnd]CF2. Proper experimental conditions for their synthesis are described. Owing to their strong tendency to form hydrogen bonds, fluoroalcohols are excellent solvents for polymeric materials which possess receptive sites for hydrogen bonding formation. The solvent power of the fluoroalcohols on some polar polymers, mostly aliphatic polyamides, has been tested. 2,2,3,4,4,4-Hexafluorobutanol (HFB) shows the best solvent ability among compounds of this class. Its properties and solvent power have been evaluated and compared to those of trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP).

Liquid phase fluorination of diethyleneglycol dimethyl ether tetraethyleneglycol dimethyl ether, 2[1,2-dichloro-1,2-difluoroethyl] tetrahydrofuran and 2[1,2-dichloro-1,2-difluoroethyl] dioxane 1,4 produce the corresponding perfluoroethers in 56, 43, 67 and 74 % yields respectively. The by-products are partially fluorinated compounds and no fragmentation is observed. The simplicity of the reactions and method of preparation make this approach to fluorinated fluids and oils industrially attractive.

19F nuclear matnetic resonance spectra of vinylidene fluoride-hexafluoropropene copolymers and vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymers are reported and discussed. Their interpretation allows average composition and sequence distribution to be determined. Sequence distribution is shown to be relevant in determining the trend of glass transition temperatures and in the study of the mechanism of vulcanization.

The Fox, Gordon-Taylor-Wood, Johnston and Barton equations have been applied to predict the glass transition temperatures, Tg of vinylidene fluoride-hexafluoropropene (VDF-HFP) copolymers and VDF-HFP-tetrafluoroethene (TFE) terpolymers. The Fox equation fails to describe the co- and terpolymer systems. The experimental data for VDF-HFP copolymers are well interpreted by the Gordon-Taylor-Wood equation. The Johnston and Barton equations, based on sequence distribution, yield good results for VDF-HFP and VDF-HFP-TFE. The assumptions made about kinetic constants of propagation and the Tg contributions of alternating monomer dyads and polyTFE are also 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.

Copolymers of vinylidene fluoride (VDF) with fluoroolefins of the series CF2CFX (X = F, Cl, Br, CF3 and C5F11) have been synthesized in the 0–16 mole % CF2CFX range. Results of physico-chemical characterisation by means of DSC techniques (Tg, TM, ΔHf) and X-ray diffraction are examined and related to the nature of the substituent of the fluoroolefin. The Tg/TM ratio varies from 0.5 for the VDF homopolymer to higher values at increased CF2CFX content, although to a different extent for the various series of copolymers. The results show that the Beaman-Boyer empirical rule (Tg/TM=2/3), developed for homopolymers, also applies to some copolymeric systems.

Tetrafluoroethene (TFE)–chlorotrifluoroethene (CTFE) and TFE–bromotrifluoroethene (BTFE) copolymers have been synthesized by solution copolymerization over the entire range of comonomer composition. Crystallinity data are reported and first- and second-order transitions have been investigated by DSC. Glass transition temperatures of TFE-CTFE copolymers vary in a nonlinear fashion in the range defined by the homopolymers conforming best to the Johnston equation; the behavior in the TFE-BTFE system is more linear. Whereas TFE-BTFE copolymers show a steep decrease of melting temperature at higher BTFE content, due to the amorphous character of the polymers, more regular behavior was found for TFE-CTFE copolymers. Enthalpies of fusion are also reported. The results are discussed in relation to copolymer composition and structure and are compared with data on tetrafluoroethene–hexafluoropropene (FEP) fluorocarbon resins.

Hexafluoropropene (HFP) — 1,1-difluoroethene (VDF) copolymers have been synthesized in the 0–16 mole % HFP range and the results of a physico-chemical characterization by means of XRD (cristallinity index) and DSC techniques are related to the microstructure of the polymers, as determined by 19F NMR. The addition of a small percentage of the HFP comonomer does not affect the polymorphism of poly(vinyl-idenefluoride).

The comonomer system based on vinylidene fluoride (VDF) and hexafluoropropene (HFP) has been polymerized in soapless emulsion, at various pressures of the gaseous feed and different concentrations of the free-radical initiator. The particle size and number, evaluated as a function of conversion, suggest a rather long nucleation period. In Smith-Ewart's Interval II the limiting particle number decreases with increasing monomer fugacity (which is proportional to the monomer concentration in water), and increases with increasing initiator concentration. The kinetic data cannot be fully accounted for by changes of particle number. On the contrary, there is evidence that the average number of free radicals per particle is affected by experimental conditions and follows a trend very similar to that predicted by Stockmayer's model.

Five samples of Poly (vinylidene fluoride) with a molecular weight from 45,000 to 260,000 were analyzed by means of FT-IR spectroscopy in order to study the influence of molecular weight $$\left( {\bar Mv} \right)$$ on the crystallization process. The spectra of films obtained from methylethylketone solutions revealed the prevalence of form II (α) in the case of lower $$\bar Mv$$ and of form III (γ) in the higher molecular weight samples. The amount of form III was found to increase as the Mv decreased and as annealing temperatures increased. The deconvolution technique of vibrational spectra allowed detection of small amounts of other forms accompanying the prevailing one.

Reactions occurring in the first steps of crosslinking of vinylidene fluoride (VDF)-hexafluoropropene (HFP) elastomer copolymers (molar ratio 4/1) are investigated operating in homogeneous solution, phase transfer catalysis conditions and bulk. Two kinds of principal unsaturation, monitored by FT-IR and 1H-NMR spectrometry, -CH=CF- and (CF3)C=CH-, have been detected. The former seems to be the curing site in the nucleophilic crosslinking of the fluoroelastomer. Polymer chain scission is also observed and has to be related to the HFP units as well as to the base content in the system.

Les spectres RMN de 13 C d'une serie de composes du type R 1 P(NR 2 2 ) n Ph 3−n X − sont mesures. On observe une nette tendance vers les plus grandes valeurs de 1 J(PC) avec l'augmentation du nombre de substituants dialkylamino

Reactions of hydrofluorocarbons with excess of antimony pentafluoride gives a series of very stable conjugated carbocations; a remarkable contiguous di-allyl, di-cation is described.

Some fluoroalcohols have been prepared by free-radical addition of methanol, ethanol and isopropanol to fluoroolefins as C3F6, CFHCFCF3, (CF3)2CFCFCFCF3, H(CF2)4CFCF2, The general reaction is (1) RfCFCF2 + RR′CHOH = RfCFHCF2CRR′OH where Rf is a fluoroalkyl group, R and R′ are H or CH3. NMR data of these alcohols are reported. 2,2,3,4,4,4-hexafluorobutanol (HFB) shows the best solvent ability among the compounds of this class. Its properties and solvent power have been evaluated and compared to the ones of trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP). Some toxicological data related to HFB, TFE and HFIP are also reported. Owing to their strong tendency to form hydrogen bonds, fluoroalcohols are excellent solvents for polymeric materials which possess receptive sites for hydrogen bonding formation. The bonding power of the OH has been investigated by IR and NMR Spectroscopy on amide-group containing substrates. The properties and the correlations observed have pointed out that HFB may be usefully used as solvent for some aliphatic polyamides as Nylon 6. The polymer-solvent system Nylon 6-HFB has been studied and the constants of Mark-Houwink equation determined.

The alkaline dehydrofluorination of Vinylidene Fluoride (VDF) -Hexafluoropropene (HFP) copolymers in dimethylacetamide has been reported by Schmiegel [1]. Basing on the reduction of 19F NMR signals related to HFP-VDF-HFP sequences and the apprearance of small low-field resonances attributed to allilic CF3, he suggested that the reaction takes place at HFP-VDF-HFP sequences, to give conjugated dienes and α, β unsaturated ketones deriving from OH− addition to dienes. This communication presents a study of the dehydrofluorination of VDF-HFP copolymers in THF, by alcoholic KOH. The reaction has been followed by analysis of the fluoride ion in solution. The intrisinc viscosity of the polymer did not change after elimination of up to 7.9 x 10−4 moles F− per g polymer. Higher reaction extents resulted in a decrease of intrinsic viscosity, suggesting polymer chain degradation. The reation products exhibit IR absorptions at 1720, 1684 and 1638 cm−1, that can be attributed to isolated double bonds and/or carbonil groups. No IR bands indicate conjugation that is also not evidenced by UV spectra. 19F NMR spectra are similar to those reported by Schmiegel, but show a larger variety of new CF3 signals, both in the low-field and the usual CF3 regions. The Tg of the unsaturated polymers and the reation of these products with phenate anions have also been studied.

Copolymers of Bromotrifluoroethene (BTFE) with Tetrafluoroethene (TFE) and with 1,1-Difluoroethene (VDF) have been synthesized in the whole composition range by solution polymerization in 1,2,2-Trichloro-1,1,2-Trifluoroethane (FC 113), free radical initiator bis(4-terg.butylcyclohexyl)percarbonate, reaction temperature 40°C, monomer conversion < 10%. Monomer composition was adjusted in order to yield the desired copolymer. Polymer composition was determined by elementary chemical analysis. The reactivity radios for BTFE-TFE copolymerization have been computed: rBTFETFE = 0.24, rTFEBTFE = 0.82 19F NMR spectra of BTFETFE and BTFEVDF copolymers are also reported and discussed. The latter show patterns similar to those of VDF-Chlorotrifluoroethene copolymers.

Phase transfer catalysis (PTC) in dehydrofluorination of polyvinylidene fluoride (PVDF) has been recently investigated. Operating at 70–90°C on powder or film PVDF with aqueous NaOH 4–5 N and a PTC catalyst an amount of 9–100% of unsaturation was obtained [1] . No information was given about degradation of the polymer that likely seems to occur in these conditions. Aim of this work is a preliminary study on the PTC dehydrofluorination of vinylidene fluoride-hexafluoropropene copolymers in a wide range of composition (HFP from 0 to 40 mol %) and operating in milder conditions than above (T = 25–50°C, NaOH < 0.5 N, with a ratio meq base/g polymer ranging from 1 to 3). The level of unsaturation was detected by F− analysis in the aqueous phase on the assumption that the elimination of one HF affords one unsaturation in the polymer chain. The resulting structure has been studied by I.R. and N.M.R. spectra. Polymer degradation, indicated by the decrease of the intrinsic viscosity, seems to occur only by strong alkaline treatment. In our reaction conditions no change of the intrinsic viscosity is observed with unsaturation content up to 4%. The ability to give unsaturation has been related to the HFP content in the copolymer. The results show an increase of the rate of dehydrofluorination with increasing HF content.

Radical reactions of 1,1-difluoroethene (VDF) in the presence of halogenated telogens RX have been widely investigated in the literature; they give products of general formula R(CH2CF2)nX where n ranges mainly from 2 to 8 [1]. The present work is concerned with the study of peroxide induced telomerization of vinylidene difluoride in the presence of bromofluoroethanes as CF3CF2 Br, CF3CFBr2 and CF2BrCF2Br. Reactions were carried out at 150°C in the presence of di-tert-butylperoxide (0.5–40 mol % based on VDF) with telogen/VDF molar ratios ranging from 1/20 to 5/1. Liquid, waxy and solid telomers are obtained with n < 30. The different behaviour of the telogens is also reported and discussed. For instance in the same reaction conditions CF3CF2Br gives n values higher than CF2BrCF2Br. The structure of the telomers has been determined by 19F and 1H NMR spectroscopy. Glass transition temperatures of the telomers are reported and discussed.