Compounding Fumed Silicas into Polydimethylsiloxane: Bound Rubber and Final Aggregate Size
✍ Scribed by Mirta I. Aranguren; Elsi Mora; Christopher W. Macosko
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 586 KB
- Volume
- 195
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
silica, which are fused together. These aggregates are as-The properties of mechanically mixed suspensions of fumed sumed to be the primary structure of the filler in the suspensilicas in polydimethylsiloxane (PDMS) were studied. The work sions. Agglomerates are clusters of aggregates linked by focuses on two aspects: (i) Adsorption of PDMS onto silicas by physical forces. means of the mechanical mixing of the bulk polymer and untreated Dispersion and attrition of agglomerated fillers during rubor chemically modified fumed silicas. The silica-PDMS suspenber compounding has been treated previously. In most of sions were completely dispersed or only swollen by a solvent, dethe literature the mixing times reported are shorter than those pending on the filler concentration, the silica surface chemistry, used in this paper (20-40 min). Rwei et al. show that the and the polymer molecular weight. The bound rubber content of extent of erosion of the clusters is linear with time at short the different preparations was determined by a weight difference technique and by carbon analysis of the samples and was compared mixing times but changes to an exponential behavior for with previously reported values in similar systems. (ii) The effect long mixing times (3).
of the mechanical mixing on the final aggregate size of the silica
Most of the previous work focused on the adsorption from and on the polymer molecular weight distribution. One PDMS polymer solutions onto solids (4, 5). One of the reasons, and silicas of different surface area and surface chemistry were which will be further discussed, is that there are no simple used. The final size of the aggregates after a long mixing time with techniques to measure adsorption from the bulk. Indirect the bulk polymer was approximately the same in all cases. ᭧ 1997 measurements of bound rubber are the most common results
Academic Press
reported for systems similar to those used here (6-9). Vial-Key Words: silica-PDMS suspensions; compounding; bound lat et al. proposed that in mechanically induced sorption the rubber; aggregation. macromolecules are only partially adsorbed as a consequence of the strong entanglements formed with other chains in the bulk (7). Thus, mechanically mixed suspensions must 1 Current address: INTEMA-Facultad de Ingenierı ´a, Juan B. Justo (ii) To discuss the effects of the long mechanical mixing 4302,