Polyamide

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Revision as of 10:15, 12 June 2012 by Nathan7 (talk | contribs) (Important safety data)
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BIG FAT WARNING

Polyamides will decompose to highly toxic hydrogen cyanide (HCN) when heated. Use a certified fume hood unless you're feeling very suicidal and keep a cyanide emergency kit around anyway. Keep someone else around who is aware of the risks and knows how to administer the cyanide kit.

Unlike most of the other thermoplastics we use in repraps, polyamide (nylon) absorbs moisture from the air. When extruded, the nylon will react with the absorbed moisture and create bubbles. It will also clog your extruder. In order to make Nylon line fit for extruding, it must be dried. I used a set up with a plastic container and a blow dryer.

Preperation

  1. Get a plastic container big enough to hold your spool of trimmer line/ fishing line. It needs to have a top, and the container part needs to have no holes in it. Look for a container with vent holes in the lid (for microwaves). This will make it easier to set up later. I got mine at the 99 cents store. (pictures below)
  2. Get a cheap blow dryer that has a low setting. You can find them at thrift stores for a couple bucks.
  3. Cut a hole in the middle of the lid of your container, so that the blow dryer can slide into the container tightly. I tried to use an exacto, which cracked the plastic, and then I used a dremel, which worked much better. A perfect seal is not required (as you can see by my set up). The blow dryer should be able to stand up in the container without it tipping over.
  4. If you don't have microwave vent holes, then drill some in the lid. Maybe 2 or 3 holes that are about 3/8 diameter.
  5. Put a scoop of rice (or any another desiccants available) into the bottom of the container. This will act as a desiccant, absorbing any moisture given off by the nylon.
  6. Put the Nylon trimmer line into the container. Try to get as much air space in between the strands of nylon as you can. This will help it dry. You might need to dry only part of your trimmer line and seal the rest and store it.
  7. Stick the blow dryer into the hole and turn it on low. For recently opened trimmer line that has been sealed, this will probably take around 3 hours to dry. For trimmer line that is not sealed, it will take around 5-6 hours like mine.
  8. Test if the nylon is dry by bending it with your fingers. It should be much stiffer than it was originally. Then feed it into your extruder to test if it bubbles. If it comes out smoothly with no bubbles, you are ready to go!
  9. Hints:

Make sure that the line you buy is sealed from the air, this will make it much easier to dry out later! Do not open the nylon trimmer line until everything is set up! Breaking the seal will allow moisture to absorb into the nylon.

The extruding temperature varies with different types of nylon, with a minimum of 190 C and a max of 260 C. You will have to see what works for you. In order to keep the nylon dry while you extrude it, you can put a hole in the container you use to dry, with a rubber grommet the size of your trimmer line. Then seal the top of the container with plastic wrap and put the lid over it. You need to have a spool holder that can fit in the container. The line should feed through the hole in the box without too much effort. The extruder can then be fed through this hole.

Media

Images:

A costeffective with plasticwrap as gasket.

Video:

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Sources

Link to a amazon-productwhere you can get it for about 2.50 per lb. ebay (US) ebay (DE) ebay (UK)