A combined SAXS-shear analysis of polymer nanocomposites for the first time between parallel plates is presented. This set-up allows investigating microstructural changes accompanying macroscopic rheological phenomena, such as the Payne effect. The latter is known to induce filler network destruction and subsequent flocculation when the shear strain amplitude is increased or decreased, respectively. First, a detailed SAXS analysis of the microstructure of carbon black in styrene-butadiene nanocomposites is applied to a series of increasing filler loading. The average size and mass of primary particles and small aggregates are estimated using a model of inter-aggregate polydisperse hard-sphere interactions. In a second time, the impact of a new geometry of the shear experiments with a horizontal X-ray beam passing through a disc-shaped nanocomposite on the SAXS pattern is analyzed in terms of sample heterogeneity (different positions), anisotropy (orientations), and sample thickness (transmission and heterogeneity). Application of our quantitative analysis shows that hot molding induces a slight anisotropy of the aggregate shapes into prolate ellipsoids oriented parallel to the rubber sheet. The Payne effect is then followed by scattering, surprisingly showing no modification of the intensity under oscillatory shear. Thus, the aggregate structure observed on the scale of standard SAXS is not broken up during Payne experiments, hinting at either an averaging effect over oscillation periods, or to the reorganization of large-scale agglomerate or network structures.

中文翻译：

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橡胶-炭黑纳米复合材料的剪切流变学与 SAXS 耦合


首次提出了平行板之间聚合物纳米复合材料的 SAXS 剪切组合分析。这种设置允许研究伴随宏观流变现象的微观结构变化，例如佩恩效应。众所周知，当剪切应变幅值增加或减少时，后者会分别引起填料网络破坏和随后的絮凝。首先，对苯乙烯-丁二烯纳米复合材料中炭黑的微观结构进行了详细的 SAXS 分析，应用于一系列增加的填料负载。使用团聚体间多分散硬球相互作用模型估计初级颗粒和小聚集体的平均尺寸和质量。第二次，从样品异质性（不同位置）、各向异性（方向）和样品厚度（透射和异质性）方面分析了水平 X 射线束穿过圆盘形纳米复合材料的剪切实验的新几何形状对 SAXS 图案的影响。我们的定量分析应用表明，热成型会使骨料形状产生轻微的各向异性，形成平行于橡胶板的长椭球体。然后，佩恩效应之后是散射，令人惊讶的是，在振荡剪切下强度没有改变。因此，在标准 SAXS 尺度上观察到的聚集体结构在 Payne 实验期间没有被打破，这暗示了振荡周期的平均效应，或者是大规模团聚或网络结构的重组。