• PCL has a low enough melting point that it can be molded by hand
• 3D printing hobbyists have generated quite a bit of information about what plastics are suitable for their machines. However, these tend to be a little higher melting point than what I work with, and they focus on a small number of plastics with specific criteria I don't care about (namely shrinkage).
• Otherwise, there are some commodity plastics that might make due. Their melting points are:
  • PVC, 100 - 260°C Be sure to NEVER BURN this, as it releases dioxins which bioaccumulate.
  • LDPE, 104 - 113 °C
  • UHMW-PE, 130 - 136 °C
  • polyethylene, 115 - 135 °C
  • PEX, ≥ 160 °C

If PVC burns, it will release dioxins, which are a serious health hazard. If you're heating PVC, you must take precautions to make sure it does not overheat.

However, many hobbyists do heat PVC safely. Polymer clay is mainly PVC, and hobbyists have to bake it to cure it.

• The instructions on Sculpey say "DO NOT EXCEED THE ABOVE TEMPERATURE OR RECOMMENDED BAKING TIME".
• The MSDS for Sculpey says:
  • "Do not heat above 175°C (350°F), allow to come in contact with an open flame or use with a hot knife or wire. Use an oven thermometer when hardening material in oven. Do not use a microwave oven for baking. Do not overbake. Do not exceed the recommended baking temperature or time."
  • "Do not inhale fumes during baking. Overheating oven hardening polymer clays will result in blackening and release of irritating gases including hydrogen chloride vapor."