PHYSICAL CHEMISTRY OF POLYMERS

Author: ARRANZ ANDRÉS JAVIER.
Year: 2004.
University: AUTÓNOMA DE MADRID [www.uam.es].
Place of defense: UAM.
Place of preparation: INSTITUTO DE CIENCIA Y TECNOLOGÍA DE POLÍMEROS CSIC..

Summary: Most of the efforts in investigating materials polymers are moving toward understanding the relationship between structure and properties of these materials, as well as the development of production processes to improve quality, competitiveness and compatibility with environmental conservation. Polymers are among the most versatile materials, can compare favorably with other materials because they offer the classic combination of their excellent properties, together with significant advantages in weight, processing and price. This work has deepened our knowledge of polypropylene carrying out a systematic study of the relationship between structure and properties of polymer attached thereto. They have dealt with different methodologies in changing the microstructure of the material has been analyzed and the influence on the properties of this end. Different methods empleadosen this research have allowed obtaining polipropilenos heterofásicos, blends of polypropylene isotáctico and plastomers and homopolimeros and polypropylene copolymers with different -olefinas using catalysts metalocenos iso and sindioespecificos, as well as supported and unsupported. As is clear from what commented earlier, the solid-state structure and the study of phase transitions in the various systems is vitally important. Therefore, the investigation of the structural changes that may take place as well as the kinetic and thermodynamic factors that determine these changes are crucial in order to obtain materials with the desired properties. The techniques most immediate empieadas for this study were the diffraction of X-rays and the differential scanning calorimetry, supplemented by others, such as optical microscopy, scanning electron microscopy and Raman spectroscopy. The methods difraccióh, phase transitions have been studied in real time using synchrotron radiation. The variation of the properties over time during the evolution of the structure to the balance has been studied in a polypropylene sindiofáctico. This type of research has a stake implemented immediately, as the polymers that are used as advanced materials must have stringent specifications for dimensional stability which may clash with the structural relaxation of the material if the temperature of your final application is below the transition vitreous during his lifetime. One of the most useful techniques for the characterization of polymers is the action mecanodinámicas. Changes in the mechanical damping depending on the frequency and temperature provided very valuable information about different modes of relaxation of the macromolecule. The analysis of the behavior viscoelástico not only allows the detection of relajaciones secondary, but also on the Tg, whose location in polymers semicristalinos often difficult by calorimetric techniques usual. The evaluation of the diagrams esfuerzo of polymers obtained and the process variables of deformation (temperature and speed drawing) has helped study the mechanical response (module, tensile strength, effort at the point of flow resistance impact), which determines the practical applications of any material, and are of great significance in studying the materials originally used 8 ados at 358 this report. These macroscopic mechanical properties of polymers can also correlated with microdureza measures, which are carried out on small surfaces of polymer and are representative of the whole sample if it is homogenous. For all these reasons, this thesis provides a comprehensive overview of the relationship between structure and properties in the field of polypropylene, as it was a matter of great industrial interest.