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Extruded Polystyrene Foam
Otis Ray McIntire · Public domain (expired patent)
Emma

Imeundwa na

Emma

22. Septemba 2026SE
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Extruded Polystyrene Foam

Carl Munters had shown that polystyrene heated with methyl chloride under pressure puffs into a closed-cell foam when let out of the vessel (US 2,023,204) - but only in small pieces; with larger outlets the mass collapsed into brittle, irregular lumps. Otis Ray McIntire at Dow found the fix: keep the mass BELOW the critical temperature of methyl chloride, about 143 °C, so the gas stays dissolved, and let its own evaporation cool the foam fast enough to freeze the cells. **US 2,450,436**, "Manufacture of cellular thermoplastic products", McIntire, assigned to Dow Chemical, filed 26. July 1947, granted 5. October 1948. Its drawing is the pressure vessel with the bottom valve the foam flows out of. Dow sold the result as blue insulation board; the white bead foam of packaging is a later process. **Methyl chloride is toxic; you start from foam board.** You build a hot-wire cutter, cut an insulated box, and measure how long it keeps ice.
Mwanzo
3 hours plus an ice test

Maagizo

1

The cutter

Base on two feet, a post and an arm; the wire runs from the arm tip down through the base to a spring underneath.
Faili ya UsanifuBLENDCC0 - Free
Pakua modeli
2

Build the frame

From 18 mm plywood cut a 300 x 300 mm base, two 300 x 40 mm feet, a 280 x 50 mm post and a 200 x 50 mm arm. Glue and screw the post to the back edge and the arm square on top.

Vifaa kwa hatua hii:

Bati la mbao za kubandikaBati la mbao za kubandika1 kipande
Parafujo za mbaoParafujo za mbao10 vipande
Gundi ya MbaoGundi ya Mbao20 ml

Zana zinazohitajika:

Msumeno wa mkonoMsumeno wa mkono
Kekee cha BetriKekee cha Betri
Seti ya bisibisiSeti ya bisibisi
Rula ya chumaRula ya chuma
3

String the wire

Drill 2 mm through the arm tip and the base directly below. Fix the wire to an eye bolt on top of the arm, run it down through the base, and tie it to a spring under the base so it stays taut when it expands hot. Check it is square to the table.

Vifaa kwa hatua hii:

Waya wa nikromu 80/20 wa mm 0,64Waya wa nikromu 80/20 wa mm 0,641 mita
Bolti yenye jichoBolti yenye jicho1 kipande
Mkusanyo wa spring za mgandamizoMkusanyo wa spring za mgandamizo1 seti

Zana zinazohitajika:

Kekee cha BetriKekee cha Betri
Seti ya vichimbaji kwenye sandukuSeti ya vichimbaji kwenye sanduku
4

Power it

Clip leads to the wire at the arm and below the base. Set the bench supply to 1.5 V with a 4 A limit and raise it slowly (notebook) until the wire slides through a scrap cleanly. Ventilate.

Zana zinazohitajika:

Chanzo cha Umeme cha Meza KinachorekebishwaChanzo cha Umeme cha Meza Kinachorekebishwa
Alligator to Alligator CablesAlligator to Alligator Cables
Barakoa ya kupumua N95Barakoa ya kupumua N95
Miwani ya usalama iliyo waziMiwani ya usalama iliyo wazi
5

Cut the box

From 25 mm foam board cut a base and lid 200 x 200 mm, two sides 200 x 150 mm and two 150 x 150 mm. Feed slowly - let the wire do the work. Tape the box together.

Vifaa kwa hatua hii:

Ubao wa povu la polistarini iliyosukumwaUbao wa povu la polistarini iliyosukumwa1 karatasi
Utepe wa kufunikaUtepe wa kufunika1 rolii

Zana zinazohitajika:

Rula ya chumaRula ya chuma
6

Weigh a cube

Cut a 50 mm cube from an offcut and weigh it for the notebook.

Zana zinazohitajika:

Mizani ya dijitali ya jikoniMizani ya dijitali ya jikoni
7

The ice test

Put 500 g of ice in a bag in the foam box and another 500 g in a cardboard box of the same size, side by side in the same room. Note the room temperature and check both every hour until the ice is gone.

Vifaa kwa hatua hii:

Vipande vya barafuVipande vya barafu1000 g
Kasha la katoni yenye mikunjoKasha la katoni yenye mikunjo1 kipande

Zana zinazohitajika:

Mizani ya dijitali ya jikoniMizani ya dijitali ya jikoni
Kipimajoto cha ChumbaniKipimajoto cha Chumbani
8

Wire, density, heat leak

Inapakia daftari la Jupyter…
9

History & Context

**What the patent specifies:** polystyrene with methyl chloride dissolved under pressure below the gas's critical temperature, released through an outlet so evaporation expands and cools it into uniform closed cells, in blocks 2 inches thick or more. **Modern build (derived):** commercial extruded foam board, today made with other blowing agents. The patent names its target plainly: blocks big enough to cut into insulating panels for refrigerators. Its limits: it melts at low heat, burns unless treated, dissolves in many solvents (and in some glues and paints), and breaks down in sunlight.
Hatua 9 - Image 1

Vifaa

10

Zana Zinazohitajika

11

Faili za muundo

1

Blueprint zinazohusiana

Blueprint hizi zinashiriki maarifa — mbinu, vifaa au kanuni

High-Pressure Polyethylene

High-Pressure Polyethylene

na KarenSE

Utengenezaji wa Plastiki

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PTFE (Polytetrafluoroethylene)

PTFE (Polytetrafluoroethylene)

na MartinNO

Mitambo

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