This report details the work carried out on the synthesis and characterisation of branched polyesters. The experimental effort concentrated on the branching of PET-type polymers with a variety of potential branching agents, such as trimesic acid, and the control of branching with end-capping agents, such as benzyl alcohol. The polymers synthesised were then characterised by solution viscosity, end-group analysis, DSC analysis, theological analysis and light scattering. Extensive branching of polymers has been observed and controlled via end-capping agents. One group of polyesters synthesised with increasing levels of brancher, were characterised by absolute Mw values which increased from -10K to -350K. Despite this, all of the macromolecules displayed roughly the same solution viscosity. Though the corresponding melt viscosity increased with Mw, the values achieved were far below those expected for analogous linear polymers of comparable Mw. A second group of polyesters synthesised with a fixed level of brancher and increasing levels of end-capper were characterised by a much narrower range of Mw values. These polymers however had melt viscosities lower than those of linear polymers yet had Mw's of between -3 and - 15 times greater than those of linear polymers.

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Thesis (M. Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 37-38.

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Dissertation (Ph.D.)--University of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy Degree in Engineering." Bibliography: leaves 200-205.

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The effect of various inorganic and organic additives as possible nucleating agents on the crystallisation behaviour of P. E. T. and the suosequent influence on the morphological and mechanical properties has been examined. Various methods of mixing(: the polymer and additive were investigated and a method involving the screw-Extrusion of the polymer and the additive was ultimately adopted. Crystallisation studies were carried out using differential scanning calorimetry under dynamic and isothermal modes. The results produced under conditions of isothermal crystallisation were analysed by means of a computer. Despite differences between batches of polymer all the additives with the exception of indigo produced a nucleating effect in the polymer as indicated by an increase in the rate of crystallisation compared with that of the base polymer. Two organo-metallic substances (sodium benzoate and sodium stearate) proved to be the most effective in this respect by decreasing the degree of supercooling of the polymer by 20 [degrees]. Morphological studies were carried out on isothermally crystallised samples, after etching and replication using a transmission electron microscope. A nodular structure whose dimensions were sensitive to both the nucleating agent and the temperature of crystallisation was observed. Mechanical testing of samples direct from the D. S. C. was carried out using a compression method. The breaking loads were found to vary with both the type of nucleating agent used and the crystallisation temperature chosen. A separate study involving the exanination of the resulting fracture surfaces by scanning electron microscopy revealed that a, high breaking load was associated with a fine discontinuous structure whereas lower breaking loads were characterised by a more continuous linear appearance. This implies a higher energy of fracture due to the increased surface area of the fracture surface of the former.

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed July 9, 2009; title from PDF t.p. Includes bibliographical references (p. 69-76).