Eric Nield

On the Molecular-weight Determination of a Poly(aryl-ether-ether-ketone) (peek)

Abstract 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.

Crystallization of Poly(ethylene-terephthalate) Induced By Organic Salts - Model-compound Study of the Mechanism of Action of the Nucleating-agent

Abstract Dimethyl terephthalate (DMTP), a model compound of poly(ethylene terephthalate) (PETP), is used to simulate the behaviour of PETP in the presence of an organic acid salt, sodium o-chlorobenzoate (SOCB). On heating SOCB/DMTP systems, it is shown that the salt first dissolves in liquid DMTP. At higher temperatures, a reaction takes place between SOCB and DMTP, methyl sodium terephthalate (MSTP) being formed. MSTP is insoluble in the reaction medium and precipitates. A second reaction occurs when solid MSTP thermally decomposes to form disodium terephthalate (DSTP) and dimethyl terephthalate. The kinetic constants governing these reactions are determined and the influence of temperature and concentration are described.

Reactions induced by triphenyl phosphite addition during melt mixing of PET/PBT blends: chromatographic evidence of a molecular weight increase due to the creation of bonds of two different natures

A detailed chromatographic investigation has been carried out on the influence of triphenyl phosphite addition in molten poly(ethylene terephthalate) or poly(ethylene terephthalate)/poly(butylene terephthalate) blends. The observed molecular weight evolution corresponds to torque and viscosity observations and fully confirms the occurrence of high temperature reactions between polyester and phosphite. The reaction mechanisms deduced from model compound studies are successfully applied to polymers. The formation of bonds of different types is verified: phosphite reactions with hydroxyl chain ends lead to the incorporation of significant quantities of phosphorus into the polyester backbone. A high sensitivity of these phosphorus containing links towards water, phenol or m-cresol has been observed. Subsequent carboxyl chain end attack on the phosphorus linkages leads to stable ester bonds

NMR study of ester-interchange reactions during melt mixing of poly(ethylene terephthalate) poly(butylene terephthalate) blends

The occurrence of ester-interchange reactions during PET/PBT blend processing has been confirmed by C-13-NMR measurements. The limitations of the method for precise quantification of the extent of reaction between high molecular weight polyester blends have also been pointed out. Titanium alkoxide has been confirmed as an efficient catalyst, and, within experimental precision, the stabilizing effect of triphenyl phosphite addition has been demonstrated

Reactions induced by triphenyl phosphite addition during melt mixing of poly(ethylene terephthalate) poly(butylene terephthalate) blends: Influence on polyester molecular structure and thermal behaviour

The influence of triphenyl phosphite addition in molten poly(ethylene terephthalate) or poly(ethylene terephthalate)/poly(butylene terephthalate) blends has been investigated. Torque measurements during polyester processing and corresponding intrinsic viscosity values confirm an expected chain extension. Chromatographic results similarly indicate a molecular-weight increase. The precise nature of this chain extension mechanism is questioned. Chromatographic and calorimetric observations strongly suggest the formation of ester bonds and of bonds including phosphorus atoms. The enhanced reactivity of these new links towards phosphorous by-products or phenolic solvents at high temperature could explain the degradation observed in specific conditions.

F-19 Nmr End-group Analysis of a Poly(aryl Ether Ether Ketone) (peek)

Abstract 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.

Reactions induced by triphenyl phosphite addition during melt mixing of poly(ethylene terephthalate)/poly(butylene terephthalate) blends: Influence of phosphite structure and polyester chain-end concentration

The addition of phosphite during melt processing of polyester leads to the creation of two different types of linkages: ester bonds and bonds including phosphorus atoms. The influence of different parameters on these reactions has been investigated. Experiments carried out with different grades of poly(ethylene terephthalate) show that variables such as total concentration of reactive end-groups and hydroxyl/carboxyl chain-end ratio control not only the number but also the nature of the reactions that occur. The addition of different phosphites also reveals the influence of the nature and structure of the organic groups attached to the phosphorus atom on the reaction with polyester chain ends. Finally, the mechanisms described for polyester/phosphite systems are successfully applied to acrylic polymers, broadening the scope for application of these reactions. Copyright (C) 1996 Elsevier Science Ltd.

Extension of the concept of chemical nucleation to poly(ether ketones)

Abstract 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.

Study of an appropriate procedure for the chromatographic analysis of poly(ethylene terephthalate), after melt processing with triphenyl phosphite

The performance of a chromatographic technique for polyester analysis at a moderate temperature was investigated. Sample dissolution at room temperature in phenol-1,1,2,2-tetrachloroethane (TCE) and analysis at 70°C in m-cresol, despite the efficiency for pure polyesters, proved to be inadequate for molecular mass determination of polyester/phosphite systems since it causes a rapid degradation of bonds created by the phosphite in the molten state. Furthermore, the presence of three different solvents makes the technique highly complex. Large modifications of the chromatographic conditions result, partly irreversibly, from the injection of samples dissolved in phenol-TCE. A new procedure, working close to room temperature with phenol-TCE eluent, was therefore developed, thus avoiding any polymer degradation and allowing for the study of polyester/phosphite samples by size exclusion chromatography.