Working with thermoplastic

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Tips for Working With Thermoplastic

  • It's important to note that, when extruding, it is a polymer's glass transition temperature that matters, not its melting point. The glass transition temperature is the point where the amorphous phase of the polymer begins to flow, and the melting temperature is the point where the crystalline phase in the polymer breaks apart and begins to flow. It is generally advisable to extrude at a temperature significantly higher than the glass transition temperature to bring down the polymer's viscosity and allow it to flow more readily.

Do

  • Keep things clean. Any muck, grit, dust or hair that contacts softened plastic doesn't come out.
  • Probably the best way to heat thermoplastic is in a large capacity toaster oven, also known as a fan oven or convection oven.
  • You can suspend a mesh seive containing CAPA in the outflow from a fan heater. Do not overheat the plastic as: It can cause burns if overheated, and it flows intractably into the seive mesh.
  • Use silicone or teflon as much as you can. Silicone or teflon brownie pans, silicone or teflon muffin pans for left-over plastic, etc. Thermoplastic doesn't stick to silicone! (It does stick to most everything else.) Correction - Thermoplastic does stick to silicone! It just sticks to everything else even better. If you're using silicone for a mold, you'll get it out. But even trying to remove thermoplastic from a silicone spatula can be surprisingly difficult.
  • Use cooking parchment. Cooking parchment is silicone-impregnated paper, available in many grocery stores and all specialty cookware shops.
  • If you're heating it on a stove top, use a double boiler, also known as a bain-marie. This can be as simple as a pot of water with an empty soup can in it. When you heat the plastic in a double boiler, it doesn't get any hotter than 100C, the boiling point of water. If you overheat your plastic, it can catch fire!
  • Know what to do in case of a fire. Cover the pot. Remove the source of heat - turn off the burner. If you have to, use your fire extinguisher and call the fire department. (If you don't have a fire extinguisher or a safe exit plan, get one!)
  • Use a candy thermometer to monitor the temperature of your plastic.
  • Be a bit careful. Molten plastic is sticky and hot. Don't get it on you. Artery forceps or wide tweezers are most useful, though not essential. Have some oven mitts or oven pads if you think you'll need them.

Don't:

  • Don't leave the room when heating plastic. Keep an eye on it, and make sure it doesn't get too hot. If you do have to leave the room, turn the heat off.
  • Don't use waxed paper to line a mold. The hot plastic will melt the wax, and then bond to the paper.
  • Don't reuse any cooking implements for food. Once you've used a pot or spoon for processing plastic, keep it out of the kitchen.
  • Don't expect to get all the thermoplastic out of a steel saucepan or off a wooden spoon after you've coated them with plastic. Can't be done.
  • Don't put the softened plastic on varnished surfaces. The plastic will integrate nicely with varnish to form a wondrous glue.

-- Main.SebastienBailard - 07 Sep 2006