Get to Know: Single-Screw Extrusion Systems
Our reputation for manufacturing extruded polyethylene foam products at Alcot Plastics didn’t come without having learnt a few things along the way.
While our proprietary extrusion process allows for a more versatile, cost-efficient, quicker, and high quality output of screening spline, this wouldn’t have been possible without iterating off the back of the existing technologies in place.
This technology was the single-screw extrusion system.
Today’s piece is dedicated to the fundamentals of how this technology operates:
What Is a Single-Screw Extruder?
Its initial introduction began in the 1870s and is predicted to have been used within the plastics and rubber sectors for compounding.
True to its name, a single-screw extruder houses just a single screw inside its cylindrical barrel; the purpose of which is to extrude granules and compounds prepared in advance.
A polymer, such as the polyethylene of the screening spline we manufacture at Alcot Plastics, is fed in powder or pellet form into the extruder barrel upon which the extruder can be seen to melt and form the material in question through the use of a die. Following this, the resultant product cools and solidifies into the required shape where it is then drawn at a constant velocity to conform to a specific cross-section required for the screening spline.
What Are Extruders Used For?
Think of almost any product that is long and continuous in nature, such as screening spline, and it is most likely fabricated through the use of an extruder. From tubing to backer rods, a number of different profiles can be made that can later be used to cut to a required length.
In some cases, the property of a polymer may need to fit a specific set of criteria (e.g. colour, thermal resistance, structural reinforcement, oxidative stability, etc.), in which case additives, such as stabilisers, are blended with the polymer before extrusion takes place.
What Materials Can Be Used for Extrusion?
The use of single-screw extruders are exclusively tied to the manufacture of compounding polymers (a melted mix of polymers and additives). Polymers that are a frequent sighting for use in single-screw extrusion processes are:
· Polyethylene
· Polyamide
· Polycarbonate
· Polystyrene
· Polyester
· Polypropylene
While this list is not exhaustive, the extrusion process allows these polymers to go on to serve an invaluable function within a multitude of areas, such as for the production of medical catheters (Padsalgikar, 2017).
REFERENCES
Padsalgikar, A. D. (2017) ‘Applications of Plastics in Cardiovascular Devices’, in Padsalgikar, A. D. B. T.-P. in M. D. for C. A. (ed.) Plastics Design Library. William Andrew Publishing, pp. 133–176. doi: https://doi.org/10.1016/B978-0-323-35885-9.00006-0.
