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OMCV (Wikimedia Commons) · Public domain

أنشأه

Martin

22. سبتمبر 2026

PTFE (Polytetrafluoroethylene)

On 6. April 1938 Roy Plunkett at DuPont opened the valve on a cylinder of tetrafluoroethylene gas, a candidate refrigerant, and nothing came out - though the cylinder still weighed full. Sawn open, it held a white waxy powder: the gas had polymerised by itself. The powder resisted every solvent and acid tried on it, did not melt like other plastics, and almost nothing would stick to it. **US 2,230,654**, "Tetrafluoroethylene polymers", Plunkett, assigned to Kinetic Chemicals, granted 4. February 1941. Its first claim is two words: "Polymerized tetrafluoroethylene." **Tetrafluoroethylene is explosive and is never handled outside a plant.** You build what the material is for: a hinged tilting ramp that measures the coefficient of friction of PTFE against steel, beside nylon, acrylic and steel itself.

مبتدئ

3 hours

التعليمات

The rig

The whole rig: a 400 mm base, a hinged ramp with a steel strip on top, a prop under the raised end, and a faced sled.

ملف التصميمBLENDCC0 - Free

تنزيل النموذج

Cut base and ramp

From 18 mm plywood saw two boards 400 x 120 mm. Sand the edges.

المواد لهذه الخطوة:

لوح خشب رقائقي1 قطعة

الأدوات المطلوبة:

منشار يدوي

مسطرة فولاذية

ملزمة على شكل حرف C

Hinge them

Lay the boards end to end and fit the butt hinge across one short joint with 4 wood screws, pilot-drilled 2 mm. The ramp must lift from flat to 45° without rocking.

المواد لهذه الخطوة:

مفصلة باب1 قطعة

براغي خشب4 قطع

الأدوات المطلوبة:

مثقاب لاسلكي

طقم لُقم ثقب في علبة

طقم مفكات

Fit the steel counterface

Stick a 360 x 100 mm strip of mild steel sheet to the ramp's top face with double-sided tape. Wipe it with isopropyl alcohol - grease halves any reading.

المواد لهذه الخطوة:

لوح فولاذ طري1 قطعة

شريط لاصق من الوجهين1 لفة

كحول إيزوبروبيلي 99 %10 مل

الأدوات المطلوبة:

نظارة أمان شفافة

Make four sleds

Saw four 60 x 60 mm plywood blocks. Face one each with PTFE, nylon, acrylic and steel cut to 60 x 60 mm, fixed with double-sided tape. Clean every face with alcohol.

المواد لهذه الخطوة:

لوح PTFE1 قطعة

لوح نايلون (6/6)1 قطعة

لوح أكريليك1 قطعة

لوح فولاذ طري1 قطعة

شريط لاصق من الوجهين1 لفة

الأدوات المطلوبة:

منشار يدوي

سكين قصّ

Tilt until it goes

Set a sled 100 mm from the top. Raise the ramp slowly, about 1° per second. Stop the instant it slides and read the angle finder on the ramp. Five tries per sled.

الأدوات المطلوبة:

منقلة / مقياس زوايا

مسطرة فولاذية

Load it

Repeat the PTFE sled with a weight taped on top. The angle should not change.

الأدوات المطلوبة:

ثقل

منقلة / مقياس زوايا

Angles into friction

جارٍ تحميل دفتر Jupyter…

History & Context

**What the patent specifies:** the polymer of tetrafluoroethylene itself, a solid insoluble in ordinary solvents. **Modern build (derived):** machined PTFE sheet against clean mild steel on a tilting plane. Its first large use was seals and gaskets for the Manhattan Project's uranium hexafluoride plant, a gas that attacked everything else. DuPont registered Teflon in 1945; non-stick pans followed in the 1950s, and stretched PTFE became Gore-Tex. Its limits: it creeps under steady load, wears quickly without fillers, cannot be glued without etching, and above about 260 °C in use it begins to give off harmful fumes.