Aerosil

Example 5

Three sets of samples were prepared with polyamide 12 from RTP. 10,000 cSt PDMS, 23 wt % polyamide 12 relative to the weight of PDMS and polyamide combined, 1 wt % AEROSIL® R812S silica nanoparticles relative to the weight of the polyamide, and optionally surfactant (wt % relative to the weight of the polyamide) were placed in a glass kettle reactor. The headspace was purged with argon and the reactor was maintained under positive argon pressure. The components were heated to over 220° C. over about 60 minutes with 300 rpm stirring. At temperature, the rpm was increased to 1250 rpm. The process was stopped after 90 minutes and allowed to cool to room temperature while stirring. The resultant mixture was filtered and washed with heptane. A portion of the resultant particles was screened (scr) through a 150-μm sieve. Table 3 includes the additional components of the mixture and properties of the resultant particles.

FIGS. 16 and 17 are the volume density particle size distribution for the particles screened and not screened, respectively.

This example illustrates that the inclusion of surfactant and the composition of said surfactant can be another tool used to tailor the particle characteristics.

Example 2

A 2 L glass reactor from Buchi AG was used to prepare polyamide 12 particles by melt emulsification. The reactor was loaded with 1 wt % AEROSIL® R812S silica nanoparticles (by weight of the polyamide 12 in the final mixture) in 10,000 cSt PDMS oil. The mixture was heated to 200° C. before adding 23 wt % polyamide 12 pellets relative to the combined weight of the PDMS oil and polyamide 12. The reactor was mixed at 500 rpm for 30 minutes. The resultant mixture was discharged and cooled to ambient temperate at a rate of about 1° C. to about 3° C. per minute. The mixture was then washed with heptane and filtered through a 90 mm WHATMAN® #1 paper filter to recover the polymer particles. The resultant polymer particles were air dried overnight in a fume hood. The dried particles have a D50 of about 227 μm, and the dried particles passed through a 150-μm sieve have a D50 of about 124 μm.

Example 5

Both end dimethylvinylsiloxy-capped dimethylpolysiloxane having an average DOP of 1,800, 65 parts, was mixed with 40 parts of fumed silica having a BET specific surface area of 300 m²/g (Aerosil 300 by Nippon Aerosil Co.), 8 parts of hexamethyldisilazane, 0.1 part of 1,3-divinyl-1,1,3,3-tetramethyldisilazane (vinyl content 0.0116 mol/g), and 2.0 parts of water at 25° C. for 30 minutes. The mixture was heated at 150° C., continuously stirred for 3 hours, and cooled, obtaining a silicone rubber base. This silicone rubber base had a very high viscosity and was difficult to handle, with any further study interrupted.