| Popis: |
Temperature programmed desorption (TPD) was performed on M9787 silicone, Cab-O-Sil-M-7D (fumed) and Hi-Sil-233 (precipitated) silica particles that had been annealed to 460 K for 24 hours then exposed to different moisture levels. Our results suggest that moisture desorption and adsorption in M9787 can be approximated by the interaction of its silica contents (Cab-O-Sil-M-7D and Hi-Sil-233) with moisture. Our experimental data also reveal that, in general, as heat treated silica particles are exposed to moisture, chemisorbed states, then physisorbed states are gradually filled up in that order. However, there seems to have some rearrangement of bonds as moisture desorbs or absorbs on the surfaces of the silica particles. Nanoindentation was also performed on M9787 silicones that were simultaneously pumped down to a few hundred Pa of residual pressure at room temperature. Our data shows that the removal of physisorbed water in M9787 has none or reversible little effect on the mechanical properties of M9787. |
