Tesis doctoral de Nathalie Gonzalez Vidal
This thesis deals with aromatic polyesters and aliphatic-aromatic copolyesters synthesized by ring-opening polymerization of cyclic oligoesters, as well as with their nanocomposites made from nanoclays and carbon nanotubes. In this thesis were prepare new copolyesters and polyester nanocomposites with improved thermal and mechanical properties, and in some specific cases, improved biodegradability or flame resistance. The ring-opening polymerization in the melt of cyclic oligoesters is invariably the method used to prepare the polymers involved in this study. poly(ethylene terephthalate) (pet) is the most used polyester in the thermoplastic industry. Poly(hexamethylene terephthalate) (pht) is a homologue aromatic polyester that has not reached yet commercial development but that is continuously explored for its potential interest. These two polyesters were the parent systems selected to carry out the research of this thesis. Copolyesters of pet containing 1,4-cyclohexamethylenedimethylene and copolyesters of pht with ¿-caprolactone (cl) are prepared by ring-opening polymerization. To accomplish this purpose it was necessary to synthesize the corresponding cyclic oligomers in those cases where they are not commercially available. Thus considerable efforts are devoted to study the cyclo-depolymerization of pet, pht and poly(1,4-cyclohexamethylenedimethylene terephthalate) (pct) and to characterize properly their corresponding cyclic oligomers by different techniques like nmr, maldi-tof, hplc and dsc. ring-opening polymerization or copolymerization of the cyclic oligomers is then studied and applied to obtain polyesters and copolyesters with different composition, microstructure and properties. The chemical structure and microstructure of poly(ethylene-co-1,4-cyclohexylenedimethylene terephthalate) copolyesters are characterized by nmr and their thermal properties are evaluated by dsc and tga. For poly(hexamethylene terephthalate-co-caprolactone) copolyesters, we study in detail the ring-opening polymerization reaction, paying special attention to the influence of the reaction time on the molecular size, the composition, the microstructure, and the thermal properties. The study also includes the evaluation of the hydrolytic degradability of these copolyesters compared with that of the parent homopolymers pht and pcl. In addition, was evaluated the influence of the size of the hexamethylene terephthalate cyclic oligoesters on the ring-opening polymerization reaction and on the structure and properties of the resulting pht polyester and poly(hexamethylene terephthalate-co-caprolactone) copolyesters. the second part of this thesis is devoted to the preparation and characterization of nanocomposites obtained from pht and two different types of nanofillers, layered silicates and carbon nanotubes, by using different synthesis approaches. The preparation of pht-filled nanocomposites offers an interesting approach to obtain new materials with improved mechanical and fire resistance properties. two well-known preparation methods, the in situ ring-opening polymerization of low-viscosity hexamethylene terephthalate cyclic oligomers and direct blending of the organo-clay with pht in the melt have been comparatively applied. The main novelty afforded in this work is exploring a third method that combines ring- opening polymerization with melt blending. A highly filled masterbatch is previously prepared and then diluted with additional amount of pht finally offering the pht nanocomposites containing remarkable properties. The nanocomposites were characterized by electron microscopy, thermal analysis, and mechanical testing. In all cases, the nanocomposites showed an efficient distribution within the pht matrix. For carbon nanotubes, the objective was evaluate the effect of multiwalled carbon nanotubes on the basic properties of pht taking into account the amount loaded and side-wall functionalization.
Datos académicos de la tesis doctoral «Terephthalate copolyesters and nanocomposites produced by ring opening polymerization«
- Título de la tesis: Terephthalate copolyesters and nanocomposites produced by ring opening polymerization
- Autor: Nathalie Gonzalez Vidal
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 04/06/2010
Dirección y tribunal
- Director de la tesis
- Sebastián Muñoz Guerra
- Tribunal
- Presidente del tribunal: Mª teresa Martinez fernandez de landa
- cornelis e. Koning (vocal)
- john m. Hutchinson (vocal)
- philippe Dubois (vocal)