David Richard Fagerburg

Characterisation and identification of fluorescent hydroxylated terephthalate species in the thermal and UV degradation of poly(ethylene-co-1,4-cyclohexanedimethylene terephthalate) (PECT)

Poly(ethylene-co-1,4-cyclohexanedimethylene terephthalate) (PECT) doped with mono and dihydroxyterephthalate esters has been characterised by fluorescence analysis in solution and the solid state (reflectance method). The fluorescence excitation and emission spectra of mono and dihydroxyterephthalate chromophores show that they are initially present in low levels in processed polymer material. The monohydroxy species exhibits emission bands at 380 and 460 nm with a corresponding excitation at 330 nm while the dihydroxy species exhibits emission bands at 450 and 550 nm and a corresponding excitation at 260 and 390 nm. In the solid polymer there is an indication that these units may form associated aggregates with either themselves or the polymer. On thermal and UV degradation/oxidation of the PECT three reactions are evident from this type of analysis. In thermal degradation smaller chain fragments are primarily formed giving rise to aggregates coupled with the formation of low concentrations of mono and dihydroxylated species. On the other hand on UV degradation small chain fragments and restructuring to form aggregates also occurs but, in this case, the reaction is dominated by monohydroxylation. Some dihydroxylation is also evident but its contribution is minor.

Effects of branching on melt-prepared poly(phenylene sulfide)

Abstract Poly(phenylene sulfide), made via the melt polymerization of p-diiodobenzene and sulfur, has been prepared with added branching species at levels up to 1.0 mol%. Effects of increasing branching on the thermal characteristics were seen to be quite large for even 0.25 mol% brancher. Both the Tm and the apparent rate of crystallization, as judged by the undercooling for melt crystallization, Tm minus the crystallization upon cooling from the melt, decreased rapidly with increasing brancher level. Melt rheology also confirmed the large increase in melt elasticity in this system with increasing branching level, even at the moderate melt viscosities of the polymers of this work. Melt elasticity for polymers with 0.5 mol% brancher or above was sufficiently high to preclude rheological testing.