Plastics Extrusion And It’s Manufacturing
Very wide variety of plastic products made from extruded sections, eg curtain rails, household guttering, window frames, plastic bags, and films.
Extrusion involves forcing molten thermoplastic polymer through a die. Polymer incorporated into the screw mechanism which takes the polymer through a heated zone and forced out through the die.
If the thin film or sheet is required, die can be used that provide material extrusion cylinders. The cylindrical extruded material is inflated by compressed air while still hot to give a tubular sleeve of a thin film.
The expansion of the material is accompanied by a reduction in thickness. The film can be easily converted into bags. At its most basic, the pipe extrusion process involves feeding the material into one end of a hopper where it is melted and then forced through a die which forms it into a pipe.
Polyethylene is easily processed to give a tubular sleeve with this method but polypropylene presents a problem in that the cooling rate is not sufficient to prevent crystallization and opaque films and somewhat fragile.
Plastic Blow molding
Blow molding is a process that is widely used for the production of hollow articles such as plastic bottles of thermoplastics. Containers of various sizes can be produced.
Vacuum forming plastics
A vacuum is a common method of thermoforming. It uses a vacuum on one side of the heat-softened thermoplastic sheet to force against the mold is cooled and hence produce the required shape.