Vincent Carlier

Quantification of the maleic anhydride grafted onto polypropylene by chemical and viscosimetric titrations, and FTIR spectroscopy

An acid-base titration method for an accurate and reproducible quantification of maleic anhydride grafted onto polyolefins is proposed. The use of an organic base (tetra-butylammonium hydroxide) enhances the base solubility in organic solvents and prevents phenomena like coarcervation. The titration goes on until the visual endpoint of a coloured indicator, corresponding to the neutralisation of the grafted functions. Bromothymol blue is chosen as the coloured indicator to determine this equivalence point. It is critically correlated with a Fourier transform-infrared spectroscopy quantification developed previously by De Roovers et al. [J Polym Sci, Part A: Polym Chem 1995;33:829] and with a viscosimetric titration method here-proposed Finally, the titration mechanism is confirmed by the titration of some well-defined amount of anhydride model compounds and by FTIR analyses of their products after titration

Quantitative Analysis of Epoxy Resin Cure Reaction: A Study by Near-Infrared Spectroscopy

Near-infrared spectroscopy was used to quantify the cure reaction of 4,4′-methylene-bis-(2,6-diethylaniline) (MDEA)–epoxy resins (E/A = 1.4) carried out at 72 and 160 °C. The absorption bands of the functional groups of interest in MDEA–epoxy resins are assigned according to the literature. A new assignment at 6580 cm−1 is also proposed for the secondary amine: it was supported by a synthesized model compound. Two different spectrum treatments were proposed. The first one is based only on a normalization at 4610–4620 cm−1, while the second one needs the subtraction of the normalized spectrum of a post-cure sample. To follow the curing process, amines and epoxy were studied at the same time in the combination and the overtone regions. The results are compared. In the combination region, quantitative results are obtained from absorbance measurements, while in the overtone region spectrum decompositions and area measurements are necessary. Complementary and reliable information are so obtained and allow us to calculate conversions of epoxide and amine I and concentrations in amine II, amine III, hydoxyl groups, and ether links. Kinetics are also established. The curing process mechanism is at last discussed for both curing temperatures.

Phase separation in epoxy-copolyethersulphone blends: morphologies and local characterisation by micro-Raman spectroscopy

This study was aimed at using micro-Raman spectroscopy for the local characterisation of phase separated blends based on epoxy polymer and copolyethersulphone thermoplastic. The morphologies developed in the blends containing 25% by weight of thermoplastic were studied. The calibrations of the Raman data for the determination of the copolyethersulphone content and the epoxide conversion are presented in this paper and their applicability for spatially resolved Raman characterisation discussed. From spectra collected in both phases after increasing cure times, the evolution of the copolyethersulphone content in each phase was quantitatively determined, whilst a qualitative evolution of the epoxide conversion was obtained. To our knowledge, this study provided for the first time direct measurements of phase characteristics in thermoset-thermoplastic blends

Supported dynamic mechanical thermal analysis: an easy, powerful and very sensitive technique to assess thermal properties of polymer, coating and even nanocoating

A dynamic mechanical. thermal analysis (DMTA) performed on stacked coated supports or on samples sandwiched between rigid supports (carbon or glass fibers, metal or glass plates, ...)is described. The choice of a dual cantilever deformation favors the shear strain of the less stiff material between the more rigid supports. A theoretical model demonstrates that the less stiff material response is mainly recorded and moreover amplified. An exceptional sensitivity to the soft material is therefore observed. This method does not require any special sample (only stacking of coated supports or sample sandwiching) whilst it enables to characterize in situ polymer coating, even nanocoating. This characterization is of prime interest in technological coating developments such as paints, fiber sizings, glues, ... This possible measurement of thermal transitions peculiar to nanocoatings also opens more fundamental studies as the probing of interface influence on thermal transitions

About the synthesis of a high-temperature, crystalline poly[aryl ether(ketone-co-sulfone)] .1. synthetic reactions study

The synthesis of a new poly[aryl ether(ketone-co-sulfone)] proceeds through a chemical mechanism similar to that in the poly(ether ether ketone) and poly(ether sulfone) polymerizations. It is basically a nucleophilic substitution of a dihalogenated species by two alkaline bisphenates. This paper considers the possibility of the occurrence of some side reactions previously observed during the synthesis of poly(ether ether ketone), poly(ether ketone) or poly(ether sulfone). Unwanted nucleophilic substitutions either by phenates (transetherifications) or by fluoride or hydroxyl anions are considered. Their effectiveness during the copolymer synthesis is demonstrated by different techniques and their influence on the final sequence distribution in the chain is discussed.

The use of Raman spectroscopy to study the reaction between an amine-terminated thermoplastic and epoxy resins

Reactive thermoplastics are increasingly used as toughening modifiers for epoxy resins. A way to understand the influence of the reactive end-groups on the toughening and curing mechanisms is to observe in situ the reaction between the thermoplastic and the growing epoxy network. For this purpose, Raman spectroscopy has been used to follow the reaction of aromatic amines with epoxide monomers through the evolution of an amine-substituted aromatic vibration. A double shift of this peak was correlated with the formation of secondary and tertiary amines. Band assignment was confirmed by the study of model compounds. Through this method, qualitative observation of the reaction between an amine-ended copolyethersulphone thermoplastic and epoxide was performed. Unfortunately, in the studied blend containing the curing agent, a band appearing upon curing overlapped with the band characterising the end-group reaction

Raman spectroscopy determination of the thermoplastic content within epoxy resin-copolyethersulfone blends

The possibility of using Raman spectroscopy to determine the local thermoplastic content within blends of epoxy resins and copolyethersulfone was studied. The required calibration of the Raman data is presented here. It was obtained by multivariate methods and was based on homogeneous samples of known content in amine-ended thermoplastic (expressed in weight %). Blends cured with two types of diamine curing agents were separately studied, the curing agents being the methylene bis(2,6-diethylaniline) (MDEA) and the 4,4′-diaminodiphenylsulfone (DDS). Partial least-squares (PLS) regressions with external validation were performed. With MDEA, root mean square error of prediction (RMSEP) values at validation were 3.2, 3.7, and 3.0% (depending on the spectral pre-treatment and on the wavenumber selection). RMSEP values were 2.4 or 3.0% with DDS (depending on the wavenumber selection). The applicability of the calibrations to blends containing chlorine-ended copolyethersulfone is discussed. Results obtained with small or large Raman confocal holes are also compared.

About the Synthesis of a High-temperature, Crystalline Poly[aryl Ether(ketone-co-sulfone)] .2. Model Compounds Study

From a detailed study of the syntheses and physical properties of semicrystalline poly[aryl ether(ketone-co-sulfone)] model compounds, this paper leads to a better understanding of the chemistry of the polymer synthesis and of its thermal behaviour. Long, crystallizable sequences are shown to arise from the heterogeneous nature of the synthesis. These sequences are responsible for the high melting points observed. Conclusions are drawn on the necessity for a revision of the synthesis procedure in order to avoid the appearance of such sequences.

Nucleophilic cleavage of activated aryl ethers by a fluoride anion

The nucleophilic cleavage of differently activated aryl ethers by a fluoride anion is studied. Two sulphone groups in para positions to the ether link appear to activate this sufficiently to allow its nucleophilic substitution by F- to occur from 280-degrees-C upwards. No reaction is observed up to 300-degrees-C when two ketone links are para to the ether, whilst the reaction occurs from 300-degrees-C upwards in the case of a mixed sulphone-ketone activation.

Solvolysis of the methoxymethyl protecting group in penicillin derivatives.

The methoxymethyl (MOM) moiety, used as protecting group for the carboxyl function of penicillin derivatives, their sulfoxides and sulfones, could be easily cleaved in aqueous methanol at room temperature. The rate of deprotection by solvolysis is not sensitive to the nature of the substituent in position 6, but depends on the state of oxidation of the thiazolidine sulfur. Copyright (C) 1996 Published by Elsevier Science Ltd.