Formation of Organophilic Montmorillonite-Oil Gels bv Use of a Magnetostrictive Oscillator J
V. R. DAMERELL W e s t e r n Reserve University, Cleveland 6 , Ohio
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HE clay mineral montmorillonite undergoes ion exchange reactions with quaternary ammonium salts t o yield organophilic derivatives which will thicken various organic liquids (1-3). T h e ability t o thicken and gel such liquids has made these ion exchange products of importance in 1ubricating greases, protective coatings, and other systems. Organophilic montmorillonite gels in hydrocarbon oils can be formed in a few cases by simple stirring, in other cases by use of a Waring Blendor, colloid mills, or paint mills, and in the most difficult systems t o gel, by these same methods in the presence of a polar additive. T h e writer was interested in learning whether a IO-kc. magnetostrictive-type oscillator, which is useful for making some types of colloidal dispersions, could be used t o form organophilic montmorillonite gels. A series of exp e r i m e n t s s h o w e d t h a t a marked thickening and gellation could be produced by use of this oscillator. THE OSCILLATOR
Figure 1.
Electron micrograph of dimethyl dioctadecyl ammonium montmorillonite
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The dispersing apparatus used in these experiments was a Raytheon aOO-watt, 10-kc. magnetostrictive oscillator, Model DF-101, which consists of a driver unit and a sonic oscillator or treatment unit. The driver unit is a cabinet containing a power supply and an electronic oscillator which can be tuned to match the resonance of the cup and rod assembly, including the sample. The bottom of the cup is a vibrating diaphragm which is activated by an acoustic transformer linked to a laminated nickel rod. The rod is made t o vibrate by having around it a field coil which provides a changing magnetic field: the vibrations of the rod result
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from the magnetostrictive nature of the laminated nickel. The vibration frequency is about 10 kc. per second. This is in the sonic range; hence, a piercing, high-pitched sound is emitted from the uncovered cup, and care must be taken to cover it, or to have the ears otherwise protected. The unit is referred t o in this laboratory as a sonic oscillator or generator, t o distinguish it from other, ultrasonic types.
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d. The oscillator was run for 2 millutes l o r eachportiou. Thickening was measured by use of a Brookfield viscometer. I
