Simulation of aggregate structure and SANS-spectra in filled elastomers

We report preliminary simulations of anisotropic scattering from aggregates of small hard spherical particles embedded in an elastic polymer matrix, u sing simple geometrical methods. First we build several types of aggregates in three dimensions: crystalline, amorphous compact, fractals, of differen t numbers of particles and varying polydispersity. We then turn to the spec tra of deformed samples simulated in two dimensions. We impose an affine di splacement inside the matrix to the fillers, which can be isolated particle s or small aggregates, and account for the collisions which arise due to la teral shrinking of the material. The two-dimensional scattering spectra are shown and discussed. They reproduce experimentally observed isointensity c urves: ellipses, banana-shaped maxima and splitting of these maxima in four spots. Finally, we explore the consequences of the reduction to two dimens ions via statistics of the number of collisions. It is found that even if c ollisions are more important in 3 dimensions, the behavior is qualitatively similar in two and three dimensions. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.