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PTFE Ring: Pressed Cold, Sintered Out of the Mould (Brubaker & Hanford 1946)
PTFE will not flow like other plastics, so it cannot be injection moulded. Du Pont's answer was to press the powder cold into shape, take it out of the mould, and only then heat it above 327 °C. The soft, weak pressing keeps its shape in the furnace and comes out tough. This is their Example IV: a ring 8 in across.
Source: M. M. Brubaker and W. E. Hanford (du Pont), US 2,400,099 (1946), Example IV. The press, die and furnace are ours. Picture drawn by Youblob.
Ophakathi
1 day
Imiyalelo
1
1
Fill the ring mould with powder
Fill the ring mould with powder
At room temperature, fill a ring mould with powdered PTFE. The finer the powder, the better the result (the patent).
Izinto zokwakha zalesi sinyathelo:
Impuphu ye-resin ye-PTFE1 as required to fill the mouldAmathuluzi adingekayo:
Isikhunta Sokucindezela Izindandatho2
2
Press at 1000 psi
Press at 1000 psi
Press it at 1000 lb/sq in into a ring ½ in thick, 8 in outside and 4 in inside diameter. The pressed ring is soft and weak: handle it gently.
Amathuluzi adingekayo:
Umshini wokucindezela we-hydraulicIsikhunta Sokucindezela Izindandatho
Irula3
3
Sinter at 355 °C for 6 hours
Sinter at 355 °C for 6 hours
Take the ring out of the mould and heat it, free-standing, in a furnace at 355 °C for 6 hours. Air is fine; no mould is needed to hold its shape.
Amathuluzi adingekayo:
Isithando se-muffle
I-thermocouple enesibonisi4
4
Quench in cold water
Quench in cold water
Lift the hot ring out and quench it in cold water. It comes out hard and tough. It shrinks a little but stays symmetrical.
Amathuluzi adingekayo:
Udlawu
Ibhakede lokupholisaIzinto
1- 1 as required to fill the mouldIsibambeli
Amathuluzi Adingekayo
7- Isibambeli
- Isibambeli
- Isibambeli
- Isibambeli
- Isibambeli
- Isibambeli
- Isibambeli
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