Shopping Bags to Frisbees


Someone once told me that about the only way to join polyethylene plastic was with heat and pressure.

Plastic shopping bags are a recycling problem.  I think they are polyethylene plastic.  Heat and pressure might turn them into Frisbees, or other essential things. 

I visualize a vertical, heat-resistant cylinder with a removable  Teflon-coated bottom cap in the shape of a Frisbee -- black to absorb solar heat.  A piston inside with the other half of the Teflon-coated mold could have a weight on it to provide pressure. 

Fill the cylinder with shopping bags, with the piston inside, and suspend it over a solar reflector to heat the end cap of the cylinder.   There you have heat and pressure -- and free energy to turn the shopping bags inside into Frisbees, or other objects.

Personally, I don't have need for more Frisbees, and don't collect enough bags to keep the equipment busy.  On a community recycling scale, though, it might be a way to get rid of a lot of bags that nobody wants. 

Would anybody like to run the experiment? 

NachoMahma6 years ago
> I think they are polyethylene plastic.
.  Yep. I just checked two plastic shopping bags in my kitchen and both were marked as HDPE.

> Teflon-coated bottom cap
> Teflon-coated mold
.  No need for Teflon. Polished chrome works well. There should be some cheaper metals that will work as well.

> A piston inside with the other half of the Teflon-coated mold could have a weight on it to provide pressure.
.  The pressure required is measured in hundreds to thousands of pounds per square inch. Over the face of a Frisbee, that adds up.
 
.  Considering how much power is needed to get the plastic and mold up to operating temperature, I doubt if you will be able to make them very quickly (unless you have a very large reflector). Maybe not the best technique for making Frisbees, but it has potential for other items.
Thinkenstein (author)  NachoMahma6 years ago
Thanks for the reply. My idea doesn't sound very likely to succeed. Packing a smaller cylinder with bags would be difficult.

Do you think they could be melted down in some way fire-safe and then injection molded? Maybe the heating chamber could have a vacuum pulled on it first, to eliminate oxygen inside it.
. Injection molding or extrusion are about your only options with HDPE. Fire is not the problem, it's that the HDPE stays very thick and it doesn't flow well unless you put it under a lot of pressure.
Thinkenstein (author)  NachoMahma6 years ago
Sounds like it's beyond my home workshop capability. Thanks for the info.