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Artigo Científico | Fluência | Português | 31/12/1999
Autores: A. Bello, E. Laredo, M. Grimau
Palavras-chave: fluencia estimulada termicamente, polietileno, relajaciones estimuladas termicamente, relajaciones mecanicas, thermally stimulated relaxation, mechanical relaxa
Resumo: La fluencia termoestimulada (FTS) es una técnica aplicable al estudio de las relajaciones mecánicas en polímeros y provee información valiosa para el estudio y la determinación de los diferentes movimientos de las cadenas moleculares en estos materiales. Se presenta un nuevo sistema de medición de FTS enteramente automatizado, diseñado y construido en el laboratorio así como la metodología de análisis de los datos experimentales. Una aplicación al polietileno de baja densidad entrecruzado se presenta.
Abstract: Thermally Stimulated Creep in Polymers Thermally Stimulated Creep (TSCr) is a very simple experimental method for the study of the anelastic relaxations in polymers. The mechanical detection of the relaxation processes is particularly interesting since the chemical nature of the relaxing species is not involved, as in the case of the dielectric spectroscopy, where the presence of the dipolar moieties in the samples is a condition for the detection of the relaxation. In the TSCr method the recovery of a shear strain is thermally stimulated by heating the sample. Previously to this recovery, the strained sample has been quenched from the deformation temperature, which is higher than the final temperature of the recovery. An increase in the shear strain rate as the temperature rises, would be associated to the presence of a relaxation process in the sample, and this increase will appear as a peak when the shear strain rate is plotted as a function of the temperature. Furthermore, because TSCR is a quasi-static method (i.e. a very low equivalent frequency) these experiments are characterized by a better resolution than those corresponding to the classical dynamical mechanical techniques (DMA experiments). In this work we present a new experimental system for TSCr measurements, which has been completely build up in our laboratory. All the procedures in this system are fully controlled by a PC, including the deformation set-up and the strain recovery data acquisition. We also present some results of the mechanical relaxations in a crosslinked low density polyethylene (XLPE) studied by the TSCr method .
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