Determination of the Equivalent Radii and Fractal Dimension of Polystyrene Latex Aggregates from Sedimentation Coefficients
✍ Scribed by Miriam Michiyo Takayasu; Fernando Galembeck
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 103 KB
- Volume
- 202
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
However, Eq. [1] is only useful to describe completely Sedimentation coefficients of small polystyrene latex aggregates fused aggregates and does not apply properly to loose sys-(n Å 2, 3, 4) were determined by centrifugation of a coagulated tems because it assumes a large packing factor, disregarding latex sample within a density gradient and fitted to the R* Å n c r voids within aggregates. equation, where R* is the equivalent radius of the aggregate, r is Another equation for the calculation of the equivalent rathe radius of each individual sphere, and c Å 0.58. This equation dius R (g) of a spherical aggregate was empirically proposed was also satisfactorily used to fit latex aggregate diffusion data, by Reynolds and Goodwin (2): previously published by other authors. The constant c agrees with the value calculated from the fractal dimension D f reported for larger aggregates in the literature, using c Å 1/D f . As a conclusion,
aggregate sedimentation and diffusion coefficients can be obtained from light-scattering and microscopical data, and vice versa, using a scaling factor which is related to the aggregate fractal dimension.