Technologies

The Extruder To Convert Plastics Into Objects

19 June 2020 | by Alexandre Dechelotte

Progress status: Installed on the vessel

Presentation

Extrusion is a shaping process widely used in the plastic industry. It is the key process for mechanical recycling. Extrusion consists of gradually heating shredded plastic particles to form a soft, viscous paste later shaped to create new objects.

Items Description

An extruder is composed of four main elements, which include a motor that rotates and a worm screw inside a sheath heated by resistors.

Process Description

Once shredded, washed, and dried, plastic particles are placed in the hopper. They flow progressively into the sheath, heated by the surrounding warm resistors. A worm rotates in the sheath propelling the plastic to its end.

The plastic is gradually heated by the sheath’s warmth and its friction with the screw. The initially shredded plastic then becomes a homogeneous soft paste. At the end of the sheath, a die allows the molten plastic to flow out.

Entrance

Shredded PE – PP

Exit

Malleable Molten Plastic Paste

Case Study

Extrusion is rarely known on smaller scales, as the machine requires an initial investment that can be substantial, as well as a certain level of expertise concerning its process. However, it is an essential part of the recycling chain as it allows the shaping of previously developed plastic waste into new objects. Thus, it adds significant value to plastic waste.

The alternative to extrusion is to melt the plastics in a heated container, like a pan on the gas. The melting temperature cannot be regulated, so plastic tends to burn and emit noxious and polluting fumes.