Order in the amorphous state of (polyethylene terephthalate) as revealed by microhardness: Creep behavior and physical aging
| Autor: | Rueda, Daniel R., García-Gutiérrez, Mari Cruz, Baltá Calleja, Francisco José, Piccarolo, S. |
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| Jazyk: | angličtina |
| Rok vydání: | 2002 |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| Popis: | The internal order in the amorphous state of poly(ethylene terephthalate) (PET), prepared either by rapid cooling from the melt or by thermal annealing of melt pressed films above Tg, has been studied using the microhardness technique. The hardness increase contribution due to physical aging, as well as the influence of the cooling rate on the hardness values of the glassy samples are independently discussed. The rate of creep under the indenter (creep constant) for these materials has been also investigated. It is found that the largest value for the creep constant corresponds to the highest cooling rate of the rapidly quenched samples (7500°C/s), and to the starting melt pressed films. In addition, results reveal that the samples, showing the lowest degree of chain ordering, contain the lowest density of >embryonic> or >ordered> nanoregions; the latter controlling the viscoelastic behavior, as well as the induction time for cold crystallization. The isothermal crystallization of amorphous samples with different degree of internal order, studied by calorimetry, and the hardness increase occurring during the induction period prior to crystallization, are also comparatively discussed. Copyright © 2002 Taylor and Francis. |
| Databáze: | OpenAIRE |
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