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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Physical aging in PMMA/silica nanocomposites: Enthalpy and dielectric relaxation
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Physical aging in PMMA/silica nanocomposites: Enthalpy and dielectric relaxation

机译：PMMA /二氧化硅纳米复合材料的物理老化：焓和介电弛豫

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摘要

We have investigated the physical aging below the glass transition temperature, namely the slow evolution occurring in non-equilibrium glasses, of poly(methyl methacrylate)/silica (PMMA/silica) nanocomposites. To do so we have followed the time evolution of the enthalpy and that of the dielectric strength of PMMA β process during isothermal annealing. The results indicate that physical aging is generally accelerated in all nanocomposites in comparison to pure PMMA, despite the lack of effect of the nanoparticles on PMMA molecular dynamics. Furthermore, the shorter is the interparticle distance, and hence the higher is the area/volume of silica in PMMA, the more pronounced is such acceleration. The acceleration of the physical aging together with the invariance of PMMA dynamics in the nanocomposites in comparison to pure PMMA poses serious questions on the idea that the molecular mobility is the only responsible parameter for the rapidity of physical aging. Thus, an interpretation based on the free volume holes diffusion towards the external surface, in this case represented by the polymer/silica interface, is provided.
机译：我们已经研究了玻璃化转变温度以下的物理老化，也就是聚甲基丙烯酸甲酯/二氧化硅（PMMA /二氧化硅）纳米复合材料在非平衡玻璃中发生的缓慢演化。为此，我们遵循了等温退火过程中焓的时间演化和PMMAβ过程的介电强度的演化。结果表明，尽管没有纳米颗粒对PMMA分子动力学的影响，但与纯PMMA相比，所有纳米复合材料的物理老化通常都得到了加速。此外，粒子间距离越短，因此PMMA中二氧化硅的面积/体积越高，这种加速度越明显。与纯PMMA相比，纳米复合物中物理老化的加速以及PMMA动力学的不变性提出了一个严重的问题，即分子迁移率是物理老化速度的唯一负责任参数。因此，提供了基于自由体积的空穴向外表面扩散的解释，在这种情况下是由聚合物/二氧化硅界面表示的。

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