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Aging Phenomena in Silica-Filled Polydimethylsiloxane
Journal of Colloid and Interface Science
|August 12, 1999
Summary
Silica-filled polydimethylsiloxanes soften over time, unlike typical hardening. Surface treatments that prevent polymer adsorption enhance filler dispersion and material stability, crucial for rheological properties.
Area of Science:
- Polymer Science
- Materials Science
- Rheology
Background:
- Polydimethylsiloxanes (PDMS) filled with silica are widely used.
- Understanding their aging behavior is critical for material performance.
- Typical silica-filled systems exhibit crepe hardening upon aging.
Purpose of the Study:
- To investigate the aging behavior of silica-filled PDMS with varying molecular weights.
- To evaluate the impact of different filler surface treatments on aging.
- To understand the role of polymer adsorption in system stability.
Main Methods:
- Examined silica-filled PDMS (9,000-140,000 g/mol) with fumed silica.
- Utilized hexamethyldisiloxane and hexamethyldisilazane for silica surface treatment.
- Monitored rheological properties, bound rubber, and filler dispersion over time.
Main Results:
- Observed softening instead of expected crepe hardening.
- Polymer adsorption onto silica surfaces significantly influenced system stability.
- Filler dispersion changes depended on polymer molecular weight and surface treatment.
- Surface treatments inhibiting polymer adsorption increased dispersion stability and improved rheological properties.
Conclusions:
- Polymer adsorption is a key factor in the aging stability of silica-filled PDMS.
- Surface modification of silica can enhance material durability.
- Filler migration during aging is driven by an increase in bridging chains.