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Youblob · CC0
Hydroxyl-Ended Silicone Oil: D4 Opened with Potash, Then Water (Ceyzeriat 1964)
A trace of hot potash opens the ring of D4 and strings it into a long, thick chain. Water added a little at a time then cuts the chains back and leaves hydroxyl groups on their ends, which is what later lets the oil cure into rubber. This is Louis Ceyzeriat's oil A, the base of every sealant in his patent: 21,000 centistokes, 0.15 % hydroxyl.
Source: L. Ceyzeriat (Rhône-Poulenc), US 3,133,891 (1964), column 4. His neutraliser was the precipitated silica Hi-Sil X303; we use our precipitated silica in its place. The potash mix and the equipment are ours. Picture drawn by Youblob.
Advanced
2 days
Instructions
1
1
Make the 10 % potash
Make the 10 % potash
Dissolve 0.5 part of potassium hydroxide in 4.5 parts of water (our arithmetic for 5 parts of a 10 % solution). All parts are by weight.
Materials for this step:
Potassium Hydroxide0.5 parts
Water4.5 partsTools needed:
Glass Vessel
Balance Scale2
2
Heat D4 with the potash under nitrogen
Heat D4 with the potash under nitrogen
Heat 5000 parts of octamethylcyclotetrasiloxane (it melts at 17.5 °C) with the 5 parts of 10 % potash at 150 °C for 3½ hours under nitrogen. The oil thickens to 31,000 centistokes while hot.
Materials for this step:
Octamethylcyclotetrasiloxane (D4)5000 partsTools needed:
Glass Distillation Flask
Hot Plate
Thermometer
Stirrer
Nitrogen Gas Cylinder3
3
Add water a little at a time
Add water a little at a time
Still hot, add 16.5 parts of water in small portions over 3 hours 40 minutes. The hot oil thins to 1730 centistokes.
Materials for this step:
Water16.5 partsTools needed:
Glass Distillation FlaskHot PlateThermometerStirrer4
4
Cool, then neutralise with silica
Cool, then neutralise with silica
Let it cool for 15 hours. Then stir in 50 parts of precipitated silica to neutralise the potash. The liquid now measures 13,400 centistokes at 25 °C.
Materials for this step:
Precipitated Silica50 partsTools needed:
Glass Distillation FlaskStirrer5
5
Strip the volatiles at 195–200 °C
Strip the volatiles at 195–200 °C
Heat it to about 195–200 °C in a current of nitrogen, with a water condenser on the outlet. 655 parts of liquid distil over; 4345 parts of oil A stay in the boiler, 21,000 centistokes at 25 °C with 0.15 % hydroxyl groups.
Tools needed:
Glass Distillation Flask
Condenser CoilHot PlateThermometerNitrogen Gas Cylinder
Glass Jars with LidsMaterials
4- 0.5 partsPlaceholder
- 21 partsPlaceholder
- 5000 partsPlaceholder
- 50 partsPlaceholder
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