All About the Different Types of Plastic Extrusion Processes

All About the Different Types of Plastic Extrusion Processes

Plastic extrusion is one of those manufacturing processes that look too good to be true. A cheaper, more efficient, and less wasteful one. What could we be asking for more?

Plastic extrusion is a continuous process that creates less waste and more consistent products. However, not all plastic extrusion processes might pair well with what you intend to extrude.

It’s essential for you to understand the details of all the options available to make a well-informed decision. If you want to know more about plastic extrusion, check out our quick guide on what is plastic extrusion, its advantages, and more.

What is Plastic Extrusion?

Plastic extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion is used to produce items such as pipe/tubing, fencing, deck railings, window frames, flooring, sheeting, wire insolation, thermoplastic coatings, and plastic films. Just to name a few.

What are the Plastic Processing Technologies Available?

In the extrusion process, the raw material is pushed forward in the barrel by means of screws and pressed through the die at the end of barrel. This process requires high temperatures (from 190°C to 220°C) over a short time to achieve expansion of the feed as it leaves the die.

There are mainly two ways to reach these high temperatures: either with or without an external heat source. It is from this detail that we can differentiate between “dry extrusion” and “wet extrusion”.

l  Dry extrusion = in this unique form of extrusion processing, no external heat source is used during the creation of the extruded product. Dry extrusion relies only on the heat generated from the friction of the material as it passes through the barrel by a screw;

l  Wet extrusion = a wet extrusion process may apply an external heat source - like, for example, steam - directly into the barrel during the extrusion process;

Both dry and wet extruders follow the same procedure for plastic extrusion. Click here to learn more about how a plastic extruder works 

A common misconception is that dry extrusion occurs in the absence of moisture. In fact, all extrusion procedures involve moisture, and are really not really dry. The differences between dry and wet extruders are related to heating sources, and moisture levels. Following extrusion, normal moistures for dry extruded product run 16-20%, while moisture in products following wet extrusion ranges from 22-28%. Of course, these values will vary depending on the polymer formulation, type of extruder, extrusion parameters, and perhaps, atmospheric conditions at the time of production.

What are the Plastic Extrusion Methods Available?

There’s not such a thing as a “plastic extrusion”, but rather a series of processes that differ in some parts while still taking advantage of the main logic behind this form of extrusion.

There are two major types of extrusion:

l  Direct extrusion = In the case of direct extrusion, the material is compressed on one side by the piston and exits on the opposite side, where the die is positioned.

l  In other words, the direction of outflow of the material is concordant with the motion of the piston. In this case the force required for extrusion decreases constantly with the decrease in the quantity of material to be extruded inside the container.

l  In the final part of the process there will be an increase in the force necessary for extrusion since the material, which has become very thin, will be able to protrude radially from the matrix;

l  Indirect extrusion = In the case of reverse extrusion, on the other hand, the die is integral with the piston, which has a central cavity so as to allow the extruded product to exit in the opposite direction to the motion of the piston.

l  In reverse extrusion there is the advantage of having lower frictional forces. In fact, there is no relative motion between the material and the container wall. The pressures that, on the other hand, can be exerted by the action of the piston are lower than in the case of direct extrusion and remain almost constant during the entire duration of the process.

What are the Types of Plastic Extrusion Processes Available?

There are different types of plastic extrusion depending on the type of application or desired final product.

The two main plastic extrusion processes are:

l  Profile extrusion

l  Blown film extrusion

Profile extrusion

l  Products: uniquely shaped products, from drinking straws to decorative molding and more;

l  Process: profile extrusion is a process where various plastic materials are used to develop plastic products with a continuous cross-section;

Blown Film Extrusion

l  Products: plastic film used for shopping bags and other similar products;

l  Process: blown film extrusion is a process used to produce commodity and specialized polymer films that are usually used in packaging, like shrink, stretch, barrier films (used to protect deli meat), frozen food packaging, and shopping bags;

Here is the full list of plastic extrusion methods:

l  Profile extrusion

l  Blown film extrusion

l  Sheet/film extrusion

l  Tubing extrusion

l  Over jacketing extrusion

l  Coextrusion

l  Extrusion coating

Each process is used to create different products and includes different parts of a plastic extruder. Let’s dig into more details to help you choose which one best suits your manufacturing needs.

Sheet/film extrusion

l  Products: plastic sheets or films that are too thick to be blown;

l  Process: a sheet extrusion process uses two types of dies: T-shaped and a coat hanger. The purpose of these dies is to reorient and guide the flow of polymer melt from a single round output from the extruder to a thin, flat planar flow;

Tubing extrusion

l  Products: pipes, tubes or hollow cylinders;

l  Process: this manufacturing process uses very similar dies as in blown film extrusion;

Over jacketing extrusion

l  Products: insulating wires;

l  Process: this extrusion process allows for the application of an outer layer of plastic onto an existing wire or cable;

Coextrusion

l  Products: (the same as other extrusion processes, with the main difference that several layers of material are extruded at the same time);

l  Process: the co-extrusion process consists in the extrusion of multiple layers of material simultaneously. In this process there is more than one polymer in the final extruded product. It is perhaps the most economical method of combining polymers into functional multilayer products such as films, sheets, profiles, bottles, pipes, and wire coatings;

Extrusion coating

l  Products: liquid packaging, aseptic drink containers, flexible packaging, toothpaste tubes, medical packaging, industrial wraps, insulation backed materials, and plastic coated tablecloths, as well as sacks for products as diverse as cement, cereal grain, and dry chemicals;

l  Process: this process uses a blown or cast film process to coat an additional layer onto an existing roll stock of paper, foil, or film. In this process, a polymer is required for coating other products;

The Types of Plastic Extruders You Can Order from Boyu

We have over 23 years of experience in plastic extrusion, especially flooring plastic extrusion. We have gathered over 60 patents for our production lines and ERP software. As a renowed plastic extruder manufacturer, we lead the trends in the SPC flooring industry, both in China and worldwide.

For us, R&D is not a buzzword, we believe in our mission to provide our customers with only the best extruders available on the market. Innovation is at the core of what we do; it’s also for this reason that we usually launch a new extruder series every year, just like we did for our proprietary SPC flooring line.

These are the major Boyu plastic extrusion lines:

l  Flooring production lines:

n  SPC Flooring

u  SPC Parallel Twin Screw Production Line

u  SPC Conical Twin Screw Production Line

u  SPC Building Block Twin Screw Production Line

u  PP Flooring Production Line

n  WPC Flooring (PVC Foam Board Line)

u  WPC Floor/PVC Foam Board Production Line

n  PVC Flooring

u  PVC Floor Line

l  PVC Floor Production Line

u  PVC Imitation Marble Sheet

l  PVC Imitation Marble Sheet Line Production Line

l  Meltblown non-woven fabric production lines:

n  Single Blow

u  Single Blow Meltblown Non-Woven Fabric Line

l  1600mm Single Blow Meltblown Non-Woven Fabric Production Line

n  Double Blow

u  Double Blow Meltblown Non-Woven Fabric Line

l  2400mm Double Blow Meltblown Non-Woven Fabric Production Line

l  3200mm Double Blow Meltblown Non-Woven Fabric Production Line

l  1600mm Double Blow Meltblown Non-Woven Fabric Production Line

l  Water electret production line;

Conclusion

For how cost-efficient plastic extrusion technology can be, setting up your extruder is still quite an investment that you shouldn’t make in the blink of an eye. We hope this article was useful in shedding some light on the different types, methods, and technologies used to extrude plastic.

Contact us today to receive a customized plan and even more detailed suggestions on what type of extruder best fits your manufacturing needs.