Jp. Mercier

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.

Nucleation of Poly(ethylene-terephthalate) By Sodium Compounds - a Unique Mechanism

Abstract The high nucleation efficiency of sodium salts in PET is not due to additives but to reaction products. Ester linkages of PET are broken and sodium carboxylate chain ends are created. The ionic chain ends are the effective nucleating species.

On the Molecular-weight Determination of Bisphenol-a Polycarbonate

Abstract In order to assess the reliability of absolute molecular weights of bisphenol-A polycarbonate samples measured by size exclusion chromatography, the results obtained from two experimental systems and two calibration methods are compared with each other as well as with data provided by light scattering determinations. The interest of coupling a light scattering detector to the chromatographic system is discussed.

Separation of polycarbonate oligomers by high-performance size exclusion and reverse-phase liquid chromatography

Abstract The separation of polycarbonate (PC) oligomers is achieved by high-performance size-exclusion chromatography (h.p.s.e.c.) with styrene-divinylbenzene microparticulate gel as stationary phase and methylene chloride as mobile phase. Oligomers were separated up to ten repeating units. H.p.s.e.c. is also shown to be useful for analysing the low-molecular-weight content of commercial PC samples. Retention times are significantly influenced by the nature of the end-groups (O or OHO), indicating that adsorption occurs with hydroxy-terminated oligomers. H.p.s.e.c. separations are compared with results obtained by reverse-phase h.p.l.c. A simple method for determining the u.v. molecular absorption coefficient of the oligomers is proposed.