Departure from the Vogel behaviour in the glass transition -: thermally stimulated recovery, creep and dynamic mechanical analysis studies

被引:50
作者
Alves, NM
Mano, JF
Ribelles, JLG
Gómez-Tejedor, JA
机构
[1] Univ Minho, Dept Engn Polimeros, P-4710057 Braga, Portugal
[2] Univ Politecn Valencia, Ctr Biomat, E-46071 Valencia, Spain
[3] Univ Politecn Valencia, Dept Appl Thermodynam, E-46071 Valencia, Spain
[4] Univ Politecn Valencia, Escuela Informat, Ctr Biomat, E-46022 Valencia, Spain
[5] Univ Politecn Valencia, Escuela Informat, Dept Appl Phys, E-46022 Valencia, Spain
关键词
poly(methyl methacrylate); mechanical behaviour; fragility;
D O I
10.1016/j.polymer.2003.04.002
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
In this work the study of the dynamics of the segmental motions close to T, of a poly(methyl methacrylate), PMMA, network was analysed by distinct mechanical spectroscopy techniques. Three techniques were employed: dynamic mechanical analysis (DMA), creep and thermally stimulated recovery (TSR). The time-temperature superposition principle was applied to the DMA and creep results, and master curves were successfully constructed. A change from a Vogel to an Arrhenius behaviour was observed in these results. Above T, it was found a distinct temperature dependence for the retardation times calculated from creep and the relaxation times calculated from DMA. This unexpected behaviour was attributed to the merging of the a and the 0 relaxations that occurs in PMMA systems. The apparent activation energies (E-a) were also calculated from DMA, creep and TSR experiments. Above T-g the E-a values obtained agreed very well for all the techniques. In addition, the fragility exhibited by this material was investigated by the mechanical spectroscopy techniques referred above and by differential scanning calorimetry (DSC). The obtained values of the fragility index m indicated that the PMMA network is a kinetically fragile system. The thermodynamic manifestation of the fragility was also analysed. (C) 2003 Published by Elsevier Ltd.
引用
收藏
页码:1007 / 1017
页数:11
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