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BACKGROUND: The surface properties of high-density polyethylene and linear low-density polyethylene were modified by grafting urethane monoacrylate monomer under UV irradiation. This graft polymerization was carried out on native substrates and on substrates pre-treated by wet oxidation, for different oxidation times. RESULTS: As the urethane monacrylate layer is crosslinked, its grafting efficiency was checked by dissolving the polyethylene substrates in hot toluene. Grafting was evidenced by Fourier transform infrared spectroscopy of the obtained residues, which showed that both the characteristic urethane acrylate (3350 cm(-1)) and polyethylene (2920, 730 and 720 cm(-1)) bands were observable for any polyethylene oxidation time. For an oxidation time longer than 10 hours, acrylate grafting was homogeneous and the grafted surface was smooth with a roughness of less than 10 nm. In addition, X-ray photoelectron spectroscopy analysis of the residues revealed that O/C had an average value of 0.19, which is lower than the value corresponding to pure acrylate (0.42), whereas N/C had an average value of 0.068, also lower than that of pure acrylate (0.09), thus confirming the grafting. CONCLUSION: A urethane monoacrylate layer was grafted on native and oxidized polyethylene films. For highly oxidized films, the grafted surfaces are smooth and homogeneous. (C) 2008 Society of Chemical Industry.

Surface modification of high-density-polyethylene (HDPE) and linear-low-density polyethylene (LLDPE) films is promoted by sodium hypochlorite solutions using two different processes (I and IT). Such an oxidation system introduces limited amounts of carbonyl-carboxyl and hydroxyl groups onto the surface of hydrocarbon polymers. FTIR, XPS, and SEM were used to assess the efficiency of the oxidation. The hydrophilicity of the studied surfaces was investigated by the sessile drop technique and the Wilhelmy plate and a plausible oxidation mechanism is proposed. (c) 2006 Wiley Periodicals, Inc.

The sulfonation kinetics of the fluoroarylketone chain-end repeat unit of PEEK was studied. To achieve this objective, the sulfonation reactions of a trimer, a tetramer and a polymer, each fluoroarylketone ended, were followed by F-19 NMR. A general kinetic model was developed to determine the kinetic constants from F-19 NMR data. The reliability of the kinetic model and of its mathematical expression was ensured. The kinetic constants are then calculated and discussed. In particular, they were compared with the dimer rate constants previously determined. Lastly and as a conclusion of this work, a general kinetic model describing the sulfonation of main chain repeat units of PEEK is proposed. (C) 2001 Society of Chemical Industry.

The sulfonation kinetics of fluorine ended poly(ether ether ketone) (PEEK) in solution in 95.9% and 96.8% concentrated sulfuric acid was studied with the help of a model compound representative of the PEEK chain repeat unit. The reaction rate of the model compound sulfonation was found to be first order with respect to the aromatic ring to be sulfonated. Consequently, PEEK kinetic data were treated following a first order with respect to the unsulfonated repeat unit concentration. Two rate-slowing effects were detected. They were attributed to 'long range' electronic effects resulting from the inductive nature of the fluorine atom, and from the electron-withdrawing character of the grafted sulfonic acid group. (C) 2001 Society of Chemical Industry.

Chlorinated polypropylene (CPO) is commonly used as an adhesion promoter for paint on polypropylene/ ethylene - propylene copolymer blends (PP/EP). An adhesion mechanism frequently proposed in the literature is the CPO diffusion into the substrate, leading to molecular entanglement. It is shown here that CPO and PP/EP are immiscible. On the other hand, the use of radiolabelled CPO allowed quantification of CPO diffusion into PP/EP substrates as a function of several parameters and under conditions which simulate industrial practice. Diffusion requires substrate swelling by the solvent. This explains that it increases with the EP content of the material, with the solvent ability to swell the substrate, and with the thickness of the paint. For baked samples, diffusion passes through a maximum when the delay between CPO application and baking is varied. This is due to a balance between two processes working in opposite directions, i.e. substrate swelling and solvent evaporation.

The mechanism and kinetics of sulfonation of two PEEK model compounds in concentrated sulfuric acid were studied. The first model compound (monomer) is representative of a PEEK repeat unit. The second one is a PEEK dimer. Because both model compounds are fluoroarylketone-ended, the sulfonation reactions were followed by F-19 NMR. The sulfonation reactions were treated following a first-order kinetics with respect to the unsulfonated PEEK repeat unit. The comparison between the monomer and dimer results showed two different types of sulfonation behaviour. If only one apparent kinetic constant is considered for monomer sulfonation, two kinetic constants were taken into account to describe the dimer sulfonation process. This is due to a rate slowing effect of a sulfonic acid group on the sulfonation of the adjacent PEEK repeat unit. Furthermore, the results also confirm the rate slowing effect of the fluorine atom on the sulfonation of the neighbouring PEEK repeat unit. (C) 2001 Society of Chemical Industry.

The purpose of this study is to propose a correlation between IR spectra and molecular structure of ethylene-propylene (EP) copolymers possibly blended with isotactic polypropylene (iPP). The method is based on the deconvolution of the spectrum in the CH2-rocking range, i.e., 800-680 cm(-1), where the bands of interest overlap. The six bands present in this region were signal averaged in position and width. The spectra were then deconvoluted (curve fitted) assuming a Lorentzian shape for the bands. The band at 1167 cm(-1) (with a shoulder at 1156 cm(-1)) corresponding to a CH3 vibration is considered as an internal standard. The method was checked by varying some fitting parameters. In order to realize some quantitative measurements, calibration curves were established with some EP samples, characterized by C-13 NMR, which were used as standards. The amounts of total -(CH2-CH2)- units (ethylene units), isolated ethylene and structural defaults in PP were determined for different iPP/EP blends. Ethylene crystallinity has also been determined. A good correlation was evidenced between infrared and C-13 NMR measurements. (C) 2000 John Wiley & Sons, Inc.

High-resolution solid-state C-13-NMR, differential scanning calorimetry, and Fourier transform infrared spectroscopy were used to compare the very low crystalline degree and crystallite dimensions of ethylene runs in a series of isotactic polypropylene/ethylene-propylene copolymer blends exhibiting a range of properties. Results obtained from the three techniques on samples with the same thermal history are in a satisfying qualitative agreement. They show that the morphology of the polyethylene domains is only very slightly dependent on the viscosity ratio of the two blend components. On the opposite, it is largely governed by the ethylene content of the ethylene-propylene copolymer. (C) 1999 John Wiley & Sons, Inc.

The fractionation of a statistical copolyester made of poly(ethylene terephthalate- isophthalate) has been performed using Temperature Rising Elution Fractionation (TREF). TREF fractions were analyzed by size exclusion chromatography, thermal analysis, H-1-nuclear magnetic resonance and small angle X-Ray diffractometry. Results show that the fractions exhibit both interchain and intrachain defect distribution. As the intrachain defect distribution can not be determined by experimental techniques, a computer simulation based on the determination of terephthalic sequences length in a virtual polymeric distribution was performed. The simulated chains were constructed using a stochastic process. The analysis of the results obtained on the distribution of the simulated sequences in the polymer correlates quantitatively well between the new fractionation mechanism proposed for copolyesters and the experimental results.

Characterization of high-temperature poly(ether sulfone) (HTPES) molar mass was performed using light scattering, viscometry and size-exclusion chromatography (SEC). In pure N-methyl-2-pyrrolidone (NMP), a large increase of the reduced viscosity at low concentration was observed. By addition of a salt such LiBr, this effect was suppressed. Using the viscosity laws of HTPES and poly(methyl methacrylate) (PMMA) in NMP + LiBr the SEC method was standardized via the universal calibration established with PMMA standards. The Mark-Houwink-Sakurada (MHK) relationship for HTPES in NMP containing 0,1 mol/L LiBr at 25 degrees C with the intrinsic viscosity [eta] and molecular weight M afforded the MHK constants K = 33,8 . 10(-5) dL . mol(a) . g(1+a) and a = 0,70. The weight-average molar masses obtained from SEC were very close to those obtained from light scattering. A comparison of number-average molar masses obtained from H-1 NMR, potentiometric titration of chain-ends, and from SEC has shown more discrepancy for high molar masses. The study of dilute solution properties of HTPES macromolecules has shown the marked decrease of anisotropy with the number of repeating units, the low values of the characteristic ratio and of the Kuhn segment. All these conformational properties are similar to those of freely rotating chains.

HTX, a poly(aryletherketone-co-sulfone), is characterized in solution in concentrated sulfuric acid. Upon dissolution in concentrated H2SO4, HTX is chemically modified by sulfonation of phenyl rings. The modification of the chemical structure is studied with a model compound by means of IR spectroscopy. The increase of the molar mass corresponding to a complete sulfonation is determined by means of mass spectrometry. Light scattering and F-19 NMR measurements are performed in order to obtain the weight- (M(w)BAR)s and number-average (M(n)BAR)s molar masses of sulfonated HTX samples. (M(w)BAR)s values allow the determination of the Mark-Houwink-Sakurada relationship for HTX in 99,5% H2SO4 at 25-degrees-C.

A new method for poly(ether ether ketone) (PEEK) molecular-mass characterization by room-temperature (r.t.) size (steric) exclusion chromatography (s.e.c.) based on a derivatization procedure that improves the polymer solubility is described. Upon dissolution in 99.5% sulfuric acid at room temperature, PEEK is chemically modified by sulfonation of phenyl rings without polymer degradation. As complete sulfonation is achieved, the reproducibility of the chemical modification is ensured as well as the increase of molecular mass. Sulfonated PEEK is soluble at room temperature in different solvents suitable for s.e.c. N-Methyl-2-pyrrolidine (NMP) is selected as PEEK s.e.c. solvent. Owing to the polyelectrolyte nature of sulfonated PEEK, a salt (0.1 M LiBr) is added to NMP. Various broad-dispersity PEEK standards are used to establish specific and universal calibrations. The viscosity laws of sulfonated PEEK in NMP + LiBr (0.1 M), in methanesulfonic acid (MSA) and in 99.5% H2SO4 are determined. As sulfonated PEEK is a hygroscopic polymer, some spectroscopic methods are developed to determine the absolute concentration of the standards in order to perform accurate viscometric experiments giving the Mark-Houwink-Sakurada parameters in NMP-salt and in MSA. The s.e.c. universal calibration curve is constructed with poly(methyl methacrylate) narrow-dispersity standards.

HTX, a poly(aryletherketone-co-sulfone), is characterized by size exclusion chromatography (SEC) at room temperature. As HTX is not soluble in any solvent compatible with the SEC instrumentation, a derivatization procedure is applied in order to prepare a modified copolymer with improved solubility properties. This derivatization consists in a sulfonation by concentrated sulfuric acid. The derivative polymer is soluble in N-methyl-2-pyrrolidone (NMP), a classical SEC solvent. Sulfonated HTX (HTXS) is a polyelectrolyte. Consequently, a salt is added to NMP to perform reliable viscometric and SEC analyses. The SEC method is standardized with the establishment of the universal calibration with poly(methyl methacrylate) standards and the determination of the Mark-Houwink-Sakurada relationship of HTXS in NMP-salt at 25-degrees-C. Finally, the reliability of the derivatization procedure and of the SEC method is confirmed by comparison with molecular masses from NMR.

The solution properties of poly(methylphenyl)silane are studied in tetrahydrofuran at room temperature. Combined measurements by gel permeation chromatography (g.p.c.) and light scattering indicate that the absolute molecular-weight values of poly(methylphenyl)silane do not differ from the g.p.c. values obtained using a classical g.p.c. calibration with polystyrene standards. Some calculations are performed on the molecular-weight values using the theory of Yamakawa and Fujii. These results allow one to conclude that the behaviour in solution of poly(methylphenyl)silane can be described using a model based on rigid-rod-like elements involving about 40 Si atoms.

Fast-crystallizing poly(ether ether ketone) (PEEK) and poly(ether ketone) (PEK) samples have been prepared by substitution of the F chain ends, leading to alkaline sulphonate groups. Ionic chain-end associations act as seeds for nucleation. The concept of chemical nucleation already demonstrated with poly(ethylene terephthalate) is shown to apply to PEEK and PEK.

19F n.m.r. spectroscopy of poly(ether ether ketone) (PEEK) and related model compounds has been performed in various solvents including sulphuric acid. Different chemical shifts have been observed on sulphonated samples and long range shielding effects are discussed. An alternative method for the M n evaluation of PEEK is proposed.

Attempts have been made to determine the weight average molecular weight ( M W ), the radius of gyration ( R G ) and the second virial coefficient (A2) of five samples of poly(ether-ether-ketone) (PEEK) by light scattering (LS) in concentrated sulphuric acid. Account has been taken of the sulphonation of the polymer. Correlations between LS-molecular weights, melt viscosities and intrinsic viscosities in sulphuric acid or in a 50 50 phenol-trichlorobenzene mixture have been established. Gel permeation chromatography (g.p.c.) analyses at 115°C have been performed in this latter solvent and two calibration methods were compared.

Two polypropylenes, PP1 and PP2, produced with different heterogeneous Ziegler-Natta catalytic systems were studied in this work. Preliminary characterization of the non-fractionated materials showed that a low difference in their average tacticity (PP2 > PP1) leads to an important modification of their rigidity properties. In order to establish correlation between the molecular structure parameters and the rigidity properties of these polymers, fractionation of the materials according to crystallizability was performed by means of temperature rising elution fractionation (TREF). Analysis of the fractions of both PP1 and PP2 was carried out by means of C-13 NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The results first showed that TREF does not strictly fractionate PP according to tacticity, but according to the longest crystallizable sequence in a chain. C-13 NMR, SEC and DSC analysis of the fractions demonstrated that the inter-chain tacticity distributions of the polypropylenes is affected by the change of the polymerization conditions, which, in turn, modifies the rigidity properties of the materials. Some results also seem to indicate that the intrachain tacticity distributions are different for the two PP. An AFM study of the elastic modulus was carried out for the first time on the TREE fractions. It showed that the rigidity or the fractions strongly increases as the TREF elution temperature increases in accordance with a concomitant increase of isotacticity and the crytallinity of the fractions. PP2 TREE fractions were, moreover, found to exhibit a higher elastic modulus than PP1 TREF fractions at all elution temperatures. This study allowed us to further identify the TREF fractions that were responsible for differences in rigidity. To summarize, it is shown how the experimentally observed increase of the average rigidity of one of these two polypropylenes can be rationalized via information collected from a TREF fractionation. (C) 2000 Published by Elsevier Science Ltd.