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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.

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.

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.

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 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.

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).

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.

Films of blends of Paraloid(R) B72 (copolymer of ethyl methacrylate and methyl acrylate) and Tecnoflon NM(R) (copolymer of vinylidene fluoride and hexafluoropropene) with different compositions were investigated by means of FT-IR spectroscopy and FT-IR microspectroscopy before and after UV and thermal treatments. Preliminary results of DSC measurements are also reported. Paraloid B72 has been extensively applied as a protective agent for stone since the 1950s. More recently considerable research has also been carried out on the application of fluorinated polymers in the field of stone conservation, eg, the fluoroelastomer Tecnoflon(R). A high content of Tecnoflon with respect to Paraloid increases the stability of the blends when they are submitted to UV radiation and thermal treatments. A THF solution of a blend of this kind was successfully applied to a marble surface of the Saint Maria Cathedral in Lucca, Tuscany, Italy. The changes in the properties of such mixtures with different compositions can offer new possibilities in developing suitable protective materials. (C) 2000 Society of Chemical Industry.