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Carbon Resistance Element: Lampblack in Alkyd and Chinese Wood Oil on Laminated Phenolic
A carbon resistance film for radio sets. Chicago Telephone Supply's Cooper (US 2,120,930, 1938) found that lampblack bound in phenolic resin kept drifting, so he bound it in alkyd resin modified with Chinese wood oil (tung oil). Sprayed on laminated phenolic and baked up to 165 °C, the film becomes insoluble and holds its value in heat and damp. His mix gave about 50,000 ohms in an element of ordinary size, with a film about 0.003 inch thick.
The picture: our diagram.
Intermediate
1 day
Instructions
1
1
Make the binder: 72 alkyd, 28 wood oil
Make the binder: 72 alkyd, 28 wood oil
Mix 72 parts of alkyd resin with 28 parts of Chinese wood oil (tung oil).
Materials for this step:
Glyptal Alkyd Resin72 parts
Tung Oil28 partsTools needed:
Balance Scale
Glass Beaker
Stirrer
Rubber Gloves2
2
Mix 25 binder, 14 lampblack, 61 solvent
Mix 25 binder, 14 lampblack, 61 solvent
Thoroughly mix 25 parts of the binder with 14 parts of lampblack and 61 parts of a solvent for the binder. The patent does not name the solvent. Ours: xylene.
Materials for this step:
Lampblack14 partsTools needed:
XyleneBalance ScaleGlass BeakerStirrer
Full-Face RespiratorRubber Gloves3
3
Spray onto laminated phenolic
Spray onto laminated phenolic
Spray the mixture as a thin film onto a base of laminated phenolic. The patent's film is about 0.003 inch thick.
Materials for this step:
Phenolic Resin Composite Sheet1 pieceTools needed:
Spray Gun
Air CompressorFull-Face RespiratorRubber Gloves4
4
Bake: 40 °C up to 165 °C, hold 1 hour
Bake: 40 °C up to 165 °C, hold 1 hour
Put it in an oven at about 40 °C, raise the heat gradually over one hour to 165 °C and hold there one more hour. Take it out and let it cool; it is ready for use.
Tools needed:
Drying Oven
Oven Thermometer
Heat-Resistant GlovesMaterials
4- 72 partsPlaceholder
- 28 partsPlaceholder
- 14 partsPlaceholder
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Tools Required
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- 1 vendor sell this, none ship to you yetPlaceholder
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