Structural investigations of sulphonated poly(butylene terephthalate) and its blend with polycarbonate using thermal ans scattering techniques
The work described in this thesis aims at a better understanding of several ionomers and their blends on a microscopic level especially poly (butylene terephthalate) (PBT) and sulphonated poly (butylene terephthalate) (SPBT). The commercial importance of ionomer blends stems from the fact that the inclusion of sulphonate groups can improve or enhance the optical clarity of a blend made with non-sulphonated material. In particular, the present work investigates the optimum blend composition and level of sulphonation for a partially miscible sulphonated poly (butylene terephthalate) and polycarbonate (SPBT/PC) blend system. It has been found that the most transparent blends were SPBT/PC 7.9 mole % sulphonation 25/75 and 11.1 mole % sulphonation 50/50. The principal part of this thesis deals with characterisation of polymer blends using primarily differential scanning calorimetery (DSC) and thermogravimetry analysis (TGA). The second part of the thesis contains an investigation of the structural and microstructural properties of the functionalized PBT both in the homopolymer and in a blend with PC, and polystyrene ionomers by wide angle X-ray diffraction, (WAXD) and light microscopy. For comparison, a series of polystyrene ionomers were studied. The similar behaviour of PS ionomers (which are model random ionomers) to that of PBT ionomers gives an additional support to this study. It follows from the above studies that upon increase of the level of sulphonation a change in the structural properties of the material results in a reduced crystallinity of PBT. This leads to increased miscibility of the PBT/PC blend.