FORMING THE FINAL PRODUCT

The polymerized polyethylene made in the fluidized bed must then be melted and formed into sheets. This is because the plastic coming out of the polymerization reaction is in pellet form, which must be melted. The melted plastic is then forced between two flat plates or a die, to be shaped as desired.

To put the difficulty of this is perspective, consider that a baker must practive for years to write with frosting, but engineers must take a fluid that is 10,000 times thicker than honey and form it into uniform, thin sheets.

To understand some of what is happening to the polyethylene between the flat plates, some difficult boundary value problems must be solved. To look at these equations, click here: