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High-Pressure Polyethylene
Lluis tgn (Wikimedia Commons) · CC BY-SA 3.0
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22. Septemba 2026SE
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High-Pressure Polyethylene

In March 1933 Eric Fawcett and Reginald Gibson at ICI squeezed ethylene gas with benzaldehyde to about 1400 atmospheres and found a white waxy solid in the vessel. It could not be repeated reliably until 1935, when Michael Perrin's team traced the trick to a trace of oxygen that started the chains. The product was polyethylene - light, tough, a superb electrical insulator, and soon the cable insulation of wartime radar. **US 2,153,553**, "Polymerization of olefins", Fawcett, Gibson and Perrin, assigned to Imperial Chemical Industries, granted 11. April 1939, claims "subjecting ethylene to a pressure above about 500 atmospheres and a temperature above about 100 C"; its example runs at 2000 atmospheres and 170 °C. **Nobody reproduces 2000 atmospheres at home.** You work the polymer instead: fuse polyethylene bags into a tough sheet with an iron, then measure its density to tell high-pressure (branched, low-density) polyethylene from its later straight-chain sibling.
Mwanzo
90 minutes

Maagizo

1

Sort the bags

Collect clean, dry carrier or produce bags marked LDPE (recycling code 4). Cut off handles and seams; open each into a flat sheet.

Vifaa kwa hatua hii:

Mifuko ya plastikiMifuko ya plastiki8 vipande

Zana zinazohitajika:

MkasiMkasi
2

Stack between parchment

Stack 6 layers of bag film, printed side inward, between two sheets of baking parchment. The film must never touch the iron.

Vifaa kwa hatua hii:

Karatasi ya kuokeaKaratasi ya kuokea2 karatasi
3

Fuse with the iron

Iron on a low-medium setting, no steam, moving constantly for 15 seconds. Ventilate. Too hot and it shrivels and smokes - lower the setting.

Zana zinazohitajika:

Pasi ya MvukePasi ya Mvuke
Barakoa ya kupumua N95Barakoa ya kupumua N95
4

Flip, repeat, cool

Flip and iron the other side. Peel the parchment once cool. Re-iron any bubbled patches. The layers are now one welded sheet.

Zana zinazohitajika:

Pasi ya MvukePasi ya Mvuke
5

Pull-test both

Cut 20 mm strips from the fused sheet and from a single bag layer. Clamp each in the vise and pull with the spring scale. Record the peak force.

Zana zinazohitajika:

Kipima-nguvu (mizani ya springi)Kipima-nguvu (mizani ya springi)
Kibano cha meza ya kaziKibano cha meza ya kazi
MkasiMkasi
6

Float test

Pour 50 ml isopropyl alcohol into a beaker. Drop in a small chip of the sheet - it sinks. Add water 10 ml at a time, stirring, then 1 ml at a time once the chip starts to lift, until it hangs mid-liquid. Note the total water added.

Vifaa kwa hatua hii:

Alkoholi ya Isopropili 99%Alkoholi ya Isopropili 99%50 ml

Zana zinazohitajika:

Bikari ya kiooBikari ya kioo
Silinda yenye vipimoSilinda yenye vipimo
Seti ya Pipeti na KidondoshiSeti ya Pipeti na Kidondoshi
Fimbo ya KukorogaFimbo ya Kukoroga
7

Pressure, density, siblings

Inapakia daftari la Jupyter…
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History & Context

**What the patent specifies:** ethylene above about 500 atm and 100 °C (preferred 1000+ atm, 150–250 °C). **Modern build (derived):** post-consumer LDPE film, fused well below its decomposition temperature. Low-pressure routes in the 1950s gave straight-chain, denser HDPE; both are still made in huge volumes because the branches that make LDPE weaker also make it softer and clearer. Limits: it creeps under load, softens around 100 °C, and burns.

Vifaa

3

Zana Zinazohitajika

9

Blueprint zinazohusiana

Blueprint hizi zinashiriki maarifa — mbinu, vifaa au kanuni

Plasticised PVC (Plastisol)

Plasticised PVC (Plastisol)

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Utengenezaji wa Plastiki

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