Multiscale Filler Structure in Simplified Industrial Nanocomposite Silica/SBR Systems Studied by SAXS and TEM

Abstract

Simplified silica (Zeosil 1165 MP) -SBR (140k carrying silanol end-groups) nanocomposites have been formulated by mixing of a reduced number of ingredients with respect to industrial applications. The thermo-mechanical history of the samples during the mixing process was monitored and adjusted to identical final temperatures. The filler structure on large scales up to microns was studied by transmission electron microscopy (TEM) and very small angle Xray scattering (SAXS). A complete quantitative model extending from the primary silica nanoparticle (of radius 10 nm), to nanoparticle aggregates, up to micron-sized branches with typical lateral dimension of 150 nm is proposed. Image analysis of the TEM-pictures yields the fraction of zones of pure polymer, which extend between the branches of a large-scale filler network. This network is compatible with a fractal of average dimension 2.4 as measured by scattering. On smaller length scales, inside the branches, small silica aggregates are present. Their average radius has been deduced from a Kratky analysis, and it ranges between 35 and 40 nm for all silica fractions investigated here ( si = 8 -21%v).A central piece of our analysis is the description of the inter-aggregate interaction by a simulated structure factor for polydisperse spheres representing aggregates. A polydispersity

The Payne effect revisited

“…A recent SAXS (Small Angle X-ray Scattering) study of silica filled rubbers finds a significantly larger value, i.e. d f ≈ 2.4 [21]. Thus, even if the above scaling relation holds true, the problem then becomes the calculation of C and d f for different material composition.…”

“…This means that the (average) gap width is greater in the lesser filled systems, which is consistent with the model, even though filler dispersion depends on many parameters of course. The authors of the aforementioned mentioned SAXS and TEM study in reference [21] find typical aggregate dimensions of around 50 nm. If this is our D, then D⁄d = 10 corresponds to d ≈ 5 nm and D⁄d = 10 to d ≈ 0.5 nm.…”

Determination of Filler Structure in Silica-Filled SBR Compounds by Means of Saxs and Afm

“…Considering these particles as homogeneous spheres, the radius p R can be related with the radius of gyration Table 3 and Table 4. 15,19,20 . The main reason could be related to the fact that the pre-factors H [1][2][3][4] are not correlated among each other.…”

“…On the other hand, SAXS data is highly representative due to the macroscopic sample size that is probed but these data have to be fitted with a suitable model function in order to obtain structural information. Several structural studies in SBR and NR filled compounds have been undertaken by different groups [15][16][17][18][19][20] . However, due to the complex hierarchical morphologies associated to the fillers and their diversity of sizes, to date there is no analytical model consistently describing the structure at all length scales.…”

Effectiveness of X-ray computed microtomography to determine structure-property relationships of Gutta-percha

“…The degree of loading and the distribution of the particles within the Gutta-percha modulate the mechanical properties and allow the practitioner to tailor the material to the specific needs of the patient and the dental repair work that is being performed. It is well established that the mechanical properties of the material will vary with the volume fraction of the fillers, but it has recently been pointed out that the particle distribution can also be an important factor 6,7) . Yet, very little information is available regarding the internal structure of the material.…”