Polycarbonate Extrusion: A Complete Guide
Polycarbonate extrusion has unlimited applications in modern industries.
A know-how in the extrusion process will obviously guarantee success in your business
Because you can make virtually anything in the advertising, leisure, building, lighting, and medical industries, just to mention a few.
Today’s guide will take you through every stage of polycarbonate extrusion process.
It will walk you through a hands-on process on manipulating polycarbonate to the right shape and size.
What is Polycarbonate Extrusion?
Well, probably, you’ve seen this process before especially in an industrial setting but didn’t realize what it is.
Whatever the case, polycarbonate extrusion refers to a high volume manufacturing technique where raw plastic materials are melted and formed into a continuous profile.
It is a process which involves forcing of melted polycarbonate, also known as resin through a die into shape with a fixed cross-section.
In layman’s language, it refers to the process of converting plastic materials from solid to liquid then reconstituting it into the finished product.
In simpler words, polycarbonate material melts down and then it’s reshaped into a useful item. Isn’t that now clear?
I hope it is.
Ideally, it is a process which tends to create two-dimensional shapes on length hence providing a number of products in short sections or continuous measures.
Polycarbonate extrusion is incidentally the preferable way for producing several shapes both in domestic and industrial product applications.
It is quite an involving process which requires some of the best machinery and knowledge to come up with desirable results.
The good thing, however, is that you can either use the extruded products as they are or better still transform them into more complex assemblies.
Now that you understand the basics revolving around polycarbonate extrusion in terms of what it involves let’s look at some of its advantages.
Advantages of Polycarbonate Extrusion
The truth is that polycarbonate is a solid polymer which possesses some of the great properties like high impact and temperature resistance.
Therefore, it gives you the best options for using this particular technique to enable you to come up with products ideal for several applications.
In this section, I want us to look at some of the advantages of this technique and how helpful it is in the overall undertaking.
The truth nonetheless is that polycarbonate extrusion offers an efficient, economical and feasible method for producing plastic products.
Some of the advantages include the following;
a) It is fast and efficient in producing continuous product shapes
Polycarbonate extrusion as a technique is vital in making it possible for you to attain efficient and faster processing of continuous product shapes.
You see, this is important since it enables you to get the products which are homogenous in terms of shapes.
Better still, it becomes vital when producing such products in large quantities because it means you will be able to attain and maintain uniformity.
Therefore, if you’re looking for an efficient polycarbonate processing technique for producing continuous shapes for products, then extrusion is the ultimate one.
b) Relatively cheaper than other polycarbonate tooling methods
You see, what happens is that polycarbonate material can utilize several methods in producing a wide range of products.
However, it is imperative to know that most of these techniques are somewhat costly owing to the several machinery and processes they involve.
Extrusion, on the other hand, is comparatively cheap given that it does not inherently require high-end machinery and processes.
It is a basic technique which you only need to master appropriately for you to be able to attain the best results.
So in comparison to other techniques, you’ll notice that extrusion is somewhat cheaper but at the same time efficient.
c) Allows you to obtain products with complex shapes, varying thickness, and textures
Now, this is another significant advantage that is worth talking about as far as the advantages of this process are concerned.
What happens is that polycarbonate extrusion makes it possible for you to create products with different complex shapes.
At the same time, you can also use it to produce products that have varying textures and thickness.
This is fundamental because you realize that in many plastic processing techniques, you hardly get one that enables you to obtain products with all these properties.
In general, this gives you the liberty to come up with some of the best plastic products that suit a wide range of applications.
d) Easy to integrate with numerous additives in improving the properties of the product
Then the other fundamental advantage of this process is that you can use it alongside other additives to enhance the quality of the product.
In other words, extrusion enables you to easily mix other elements that help in improving the properties of the final product.
For instance, you can choose to add additives which enhance anti-fogging or anti-scratching properties when undertaking the extrusion process.
Other properties include fire resistance, durability as well as reducing static or friction of the material.
This, by the way, is essential since it makes it possible for you to attain the best results as far as the product quality is concerned.
And product quality, in this case, refers to some of the essential properties that make it stand out and ideal for the particular application.
e) Allows for easy post extrusion alterations
This is arguably the only plastic manufacturing technique which enables you to manipulate properties of the product after completing the process.
In that case, it happens that the plastic resin remains hot the moment it leaves the extruder.
This, therefore, makes it possible for you to undertake a post-extrusion manipulation accordingly depending on your specific needs.
In most instances, you’ll find that many manufacturers tend to use various elements including rollers, shoes and die to alter the properties of the extruded polycarbonate.
The bottom line nonetheless is that this process enables you to make all the possible modifications on the product as long as they fit your needs.
Well as you can see, the advantages of this process are quite sensible.
But at the same time, we also need to understand that it has its few shares of shortcomings, which would be ideal to mention.
So let’s look at a few of these disadvantages before we proceed to the next section.
Disadvantages of Polycarbonate Extrusion
Just like I have mentioned in the earlier statement, polycarbonate extrusion also has a few shortcomings which would be ideal to have an idea about.
Some of these disadvantages include the following;
a) Product limitations
What happens in most instances is that the nature of polycarbonate extrusion molding process tends to limit products it can manufacture.
You’ll notice that in many instances there are alternatives which tend to require an investment in the different type of extrusion machinery.
Injection molded lenses
This, therefore, makes it somewhat difficult for you to use it as a reliable process for all the types of products you would wish to manufacture.
b) The possibility of the size variance
This is also another common shortcoming of this particular polycarbonate manufacturing process.
It happens that at the moment when plastic exits the extruder, it tends to expand frequently.
It is the expansion of the polycarbonate at this stage of the process that is known as die swell.
Now, it becomes challenging to predict the precise extent of expansion given that it arises from different factors of the process.
And it is this unpredictability of the expansion of the material that would make you accept significant extents of deviation from product tolerance or dimensions.
Of course, you also need to understand that we have several methods for limiting this kind of issue.
However, the problem to do with the tolerance problem significantly disqualifies extrusion molding as a means for the precision of manufacturing parts.
So these are the few disadvantages of the polycarbonate extrusion process.
The good thing with these shortcomings is that you can effectively manage them from time to time.
Now, in the next section, I want us to look at the types of polycarbonate extrusion techniques fundamental in this plastic manufacturing process.
And without taking much time, let’s shift directly into these types and find out more of what they revolve around;
Polycarbonate Extrusion Techniques
Modern technology integrates a number of extrusion methods as a way of finding or yielding the best method for processing the products.
Ideally, you also need to know that the underlying factor which determines the specific extrusion technique to undertake is the type of die.
As we’ll come to learn, later on, die types and complexity play a fundamental role in identifying the polycarbonate extrusion technique to use.
At the same time, you also need to know nevertheless that all types of die allow for continuous extrusion of the polymer melt.
So in this section, I want us to focus on some of the critical techniques revolving around polycarbonate extrusion, which include the following;
1. Sheet/film extrusion of polycarbonate
This is a type of extrusion technique generally used for extruding polycarbonate sheets that are relatively too thick to be blown.
In this method, the coat hanger and the T-shaped dies are commonly used given that they are purposed to reorient and direct the flow of polymer melt.
Cooling in this particular type of extrusion is often by pulling through a set of cooling rolls.
It happens that these cooling rolls other than offering the necessary cooling, they also help in determining the sheet thickness as well as the surface texture.
The good thing with sheet extrusion is that it makes it supports some posts –extrusion processes.
For example, a thermoforming process where the polycarbonate sheet is formed until it becomes soft and the desired shape formed via a mold.
2. Blown film extrusion of polycarbonate
Blown film extrusion method is more common with the manufacturing products that require continuous sheeting.
It is somewhat similar to regular extrusion process but only until they die.
When undertaking blown film extrusion, annular, spider and spiral are the key dies that you will use.
Blown film extrusion – Photo courtesy: TERMOPLASTI
In general, though, the melt during this form of extrusion is often cooled before leaving the die to produce a weak semi-solid tube.
And by the end of it all, you’ll notice that as the film of the polymer it tends to crystallize at what is referred to as frost line.
And as the films keep on cooling, it is drawn through various nip rollers which allow it to flatten into lay flat tubing.
3. Tubing extrusion of polycarbonate
This is a form of polycarbonate extrusion which is common with the manufacturing of products such as PVC pipes.
In this process, you tend to apply positive pressure to the internal cavities through a pin.
Alternatively, you can choose to apply negative pressure to the outside diameter by utilizing vacuum sizer.
This is to ensure that you obtain the final accurate dimensions.
While at it, you may as well choose to add holes or lumens possibly by adding the appropriate inner mandrels to the die.
4. Over-jacketing extrusion of polycarbonate
This is the type of plastic extrusion that is ideally used for insulating wires.
As the name suggests, this type of extrusion enables for the application of an outer layer of polycarbonate into an existing cable.
In this form of extrusion, you can use jacket tooling in which the polycarbonate resin does not touch the interior sections of the cable until before the die lips.
Plastic extrusion process
You can as well use pressure tooling where the soft resin contacts the inner parts of the cable quite earlier before it reaches the die lips.
Remember this occurs at a relative pressure to make it possible for proper adhesion of the melt.
5. Co-extrusion of polycarbonate
This refers to a form of an extrusion of multiple layers of material concurrently.
It is a type of extrusion that uses two or more extruders to melt as well as produce a steady volumetric throughput of various viscous plastics.
This happens to a single extrusion head which in turn extrude the material in the appropriate shape.
It is also a critical method especially when it comes to joining two materials and colors into a single part.
It is also a type of extrusion which retains and even separate materials as various layers in the extruded product.
This makes it possible for the appropriate placement of materials with different properties.
So these are the key types of polycarbonate extrusion methods that you ought to know.
The most important thing nevertheless is knowing the particular one that suits your needs also guarantees you better results.
Main Parameters of Polycarbonate Extrusion
Listen, it is always fundamental to ensure that you understand all the control parameters of a polycarbonate extrusion process.
What happens is that in most instances, you will need to determine the best control measures if at all you want to attain best results.
And for that reason, we want to discuss a few but vital control parameters of this process in this section.
So that by the end of it all, you shall be able to determine how to best control each of it as well as understanding their impact in the process.
Plastic extrusion parameters
· Melting temperature
Well, this ordinarily refers to the temperature at which the polycarbonate material changes its state from solid to liquid during heating.
In some instances, it is referred to as the melting point or even the liquefaction point.
This is an important parameter in the extrusion process which indicates that the solid and liquid phases now exist in equilibrium.
Usually, the melting temperature in the extrusion process is dependent on pressure.
It helps in determining the ideal state for processing the material in this extrusion process.
In determining this particular parameter, you need to note that it should never be extremely high since this could lead to degradation of the material.
At the same time, it should never be too low since it might become difficult for the extrusion process actually to take place effectively.
· Screw speed
This is yet another fundamental control parameter that you have to take note of in polycarbonate extrusion process.
You see, the speed of the screw ordinarily tends to exert a significant influence on the overall quality of the extrudate.
Therefore, whenever you set your machine into somewhat low speeds, it means that the melt will spend quite long in the extruder.
And the possibility of the melt getting damaged by heat becomes high.
At the same time, excessive screw speed also results in thermal decomposition due to friction.
You, therefore, need to determine a moderate screw speed of course depending on the nature of polycarbonate material you’re extruding.
This is what shall make it possible for you to ensure that you get the best results from this particular parameter.
· Extrusion pressure
The truth is that pressure is a significant element in the overall process of polycarbonate extrusion.
You see, the pressure inside the extruder barrel at the time of undertaking the extrusion process is normally high.
But in most instances, the barrels for many extruders tend to withstand high operating pressures.
While at it, it is necessary to understand that too much extrusion pressure can also rupture the barrel.
So at the end of it all, it is imperative to understand the actual level of extrusion that would be ideal for processing the polycarbonate.
Of course, several factors determine this parameter especially the type of polycarbonate material you’re using as well as the maximum capacity of the machine.
· Types of die
As we had seen earlier, the type of die plays a significant role in the overall making of polycarbonate extrusion.
The good thing with extrusion dies is that you can make them form a completely limitless array of shapes as well as sizes.
In many instances, extrusion dies are grouped as solid which tend to produce solid shapes.
Another classification of dies is hollow dies which you can use to produce hollow or semi-hollow shapes.
You also need to take note that you can as well incorporate solid, hollow and semi-hollow shapes into a single die.
Typically, an extrusion operation tends to use the entire die assembly, which also includes the die itself.
What you need to know with this control parameter is the effect that the particular type of die you are using has on the overall process and final product.
The most important thing is to figure out the precise type of die which you are confident will enable you to attain the best results.
This is yet another critical control parameter of the polycarbonate extrusion.
The truth is that you’ll always need to cool every extruded shape to a particular temperature where it maintains its desired dimensions.
While at it, you can use a wide range of cooling medium such as liquid, gas as well as contacting metal surface.
But what you must know is that irrespective of the cooling medium or extruded shape, removal of heat to hold the dimension is critical.
In cooling, you need to know the product shape or thickness as a better way of determining the ideal cooling requirements.
In general though, it the heat transfer through the polycarbonate material itself that determines the cooling limit.
And for that reason, it could be somewhat difficult to predict the cooling rate of a particular polycarbonate material.
So these are the primary control parameters of a polycarbonate extrusion process.
The most important thing that you ought to understand is that many at times, there is no standard level of measuring any specific parameter.
This is primarily to say that these parameters are dependent on several instances and circumstances.
For that reason, you need to ensure that you figure out precisely how you need to adjust the measures to yield desired results.
And that is what leads us to the next section of the polycarbonate extrusion process.
Step by Step Process of Polycarbonate Extrusion Process
Listen, it happens that for polycarbonate extrusion to take place, you need to ensure that you figure out all the stages of the process.
And this is often critical because any mishap might lead to degradation of the material which eventually hinders from you attaining the desired results.
Polycarbonate extruded pipes
Well in this section, we want to focus on understanding the nitty-gritty surrounding the step by step process of this particular process.
The first thing you need to do is figuring out which specific type of polycarbonate material you want to extrude.
Remember we have different types of polycarbonate materials and not all of them can yield desired results as far as extrusion is concerned.
Nonetheless, your final product is also a great factor in determining the type of polycarbonate material to use as well as the particular application.
You also need to remember that polycarbonate extrusion involves the use of machinery.
So you need to ensure that you set the machinery appropriately to facilitate the efficiency of carrying out the process.
The good thing nowadays is that you will come across extruders that integrate modern technology.
Therefore, it becomes easy for you to set it given that the entire process becomes straightforward.
Feeding the materials into the machine is the next step to take.
Now at this point, what you need to do is primarily feeding in the plastic material or resin into a barrel of an extruder from a top mounted hopper.
It is also at this point that you may consider adding additives such as UV inhibitors and colorants be it in the form of liquid or pellet.
You will realize that this process is somewhat similar to injection molding only that in extrusion, it seems to be more of continuous.
The resin material then gets into contact with the screw as it enters the feed throat close to the rear of the barrel.
Since the screw is rotating at a set speed, it forces the polycarbonate resin to forward into the barrel so that it’s heated to the appropriate required melt temperatures.
In many instances, you will need to set a heating profile particularly for a barrel that utilizes three or more independent PID controlled heat zones.
PID, which in this cases refers to the proportional integral derivative controller is set to gradually increase the barrel’s temperature from the rear to the front section.
So this is what enables the polycarbonate resin to melt steadily while it is pushed through the barrel.
Again, it helps in reducing the risk of overheating which in many instances may cause polymer degradation.
Well, at the front of the barrel, the resin tends to leave the screw while it travels through screen which is reinforced to eliminate any contaminants.
The screens are reinforced by breaker plates given that the pressure at this particular point may be of an excess of 5000 psi.
So once it passes through the breaker plate, the polycarbonate resin now enters the die.
This is apparently what gives the final product its shape or profile.
And for that matter, its design has to be in a manner that allows molten plastic to flow evenly from a cylindrical profile to the profile shape of the product.
What happens is that uneven flow of the plastic resin at this stage may result in unnecessary stresses at specific points in the profile.
And the worse thing about these stresses is that they can cause warping upon cooling.
Nonetheless, it’s necessary to understand that you can as well create any imaginable shape as long as it is a continuous profile.
After all these, you then need to figure out how to cool the product and by using the ideal medium.
You can easily attain this by pulling the extrudate through a water bath.
What you also need to understand is that polycarbonate material is naturally an excellent thermal insulator.
For that reason, it becomes somewhat difficult for it to cool down as fast as you may think.
So the best approach is using a set of cooling rollers in this particular process cool the sheet the moment is starting exiting the extruder.
You will notice that in some instances, a secondary process may seem to occur before the product finishes its run.
So this is, in general, the basic process of polycarbonate extrusion.
As you can see, it is quite simple but at the same time involving given that you have to understand all the aspects revolving around different parameters.
In fact, the most important element in the entire process is understanding how to regulate the control parameters.
Now that we have seen the basic principle of the polycarbonate extrusion process let’s now shift gears and turn to factors surrounding an extruder.
Considerations when Buying a Polycarbonate Extruder
You know how critical a polycarbonate extruding machine is to the overall efficiency of the entire process.
First, you also have to acknowledge that nowadays, you’ll find many different brands of extruders in the market.
That notwithstanding, it is necessary to ensure that you know some of the vital factors to consider as far as buying polycarbonate extruder is concerned.
To start with, this type of machine incorporates quite a lot of elements which ideally, we can’t discuss all here.
However, we can still look at some of the crucial ones which apparently have been mentioned throughout this particular guide.
So let’s have a relatively more detailed perspective regarding the same.
a) Tubular barrel
It refers to a hollow cylindrical steel body which contains a screw auger that functions as a propeller of the material to the feed hopper.
This element is vital in an extruder because it enables compression of the material and turning it into homogenous mass before getting into the die.
It is always vital to look into this component because it helps in facilitating the homogenous mixing of compressed mass through the application of uniform pressure.
b) Revolving screw
It refers to sturdy component often made of cast steel, and it is chrome plated.
The revolving screw plays quite a lot of functions in the extrusion process including mixing, homogenizing, dispersing and gassing among others.
Revolving screws rotate in the same direction whereas the material exchanges from one screw to another.
As you can see, it is vital for you to consider this component given that it plays critical roles in the overall process of polycarbonate extruder.
c) Plunger within barrel
The plunger, in this case, refers to a kind of positive displacement pumping device that has a stationary high-pressure seal.
It is a critical component to also look into when buying a polycarbonate extruder given that it helps in enhancing efficiency as far as pressure is concerned.
You need to understand that the essence of pressure in polycarbonate extrusion is fundamental; hence the vitality of this particular component.
This refers to a restricted opening which is at the end of the barrel that gives the preferred cross-sectional shape to the extruded product.
So this component as we have earlier on discussed plays a crucial role in the overall determination of the final product.
What happens is that upon exiting the metering section of the barrel, the homogenized plastic resin mass goes through a pressure a drop while getting into the die.
So this is vital since it helps in preventing clogging of the extruded products.
Therefore it is always essential to ensure that you look into the particular type of die to fit in an extruder.
And while at it, you also need to ensure that the die doesn’t have any defects or scratches if at all you would need to attain high quality extruded product.
Common Problems in Polycarbonate Extrusion Process
Well, polycarbonate extrusion just like any other plastic manufacturing process also has its fair share of challenges.
What I mean here is that in some cases during the process, you might end up experiencing a few problems especially at the end of the final product.
So it is always wise to have a basic idea of what such problems are and a possible way of dealing with the same in case they arise.
Extrusion process – Photo courtesy: Alibaba
Some of the common problems in polycarbonate extrusion process include the following;
1. Aesthetic flaws
These refer to a wide range of defects that compromise the quality of the finished products in regards to appearance.
In polycarbonate extrusion, they can be quite a number depending on various factors.
Some of them include, sink marks, pinholes, die lines, drag marks and black specs.
The causes of these aesthetic flaws are different, and so is the remedies for the same.
The most critical element in this case, however, is to fully understand the cause for each as a way of preventing its recurrence.
This refers to a cyclical product variation in terms of thickness in the direction of extrusion.
The causes for this defect may be internal as well as external.
And in most cases, it is always easier to prevent and correct external causes.
The other cause might be as a result of variation in the screw design extruder drive as well as improper temperature gradient.
The better approach for dealing with this defect is by evaluating the foreign material and increasing the RPM back pressure for ideal mixing.
You may also consider making precise addition of resin material.
3. Dimensional variation
It is also another serious problem you’re likely to face in the polycarbonate extrusion process.
The cause for this problem often arises from the machine, material or the process.
An ideal way of dealing with this problem is by adding scanning gauge control systems.
Nevertheless, you also need to determine the exact cause of this particular problem whether it arises from the material, equipment or the process.
Applications of Polycarbonate Extrusion
So far, just from reading this guide, you can relate this particular process with quite a number of applications.
Therefore, let’s quickly look at some of its typical applications;
· Building and construction
Many building and construction engineers use a wide range of polycarbonate extruded products in constructing different parts of a building.
It is ideal since the variety of products extracted from this process makes it possible for you to have several options to pick from.
Some of such products include window profiles, cable ducts, safety barriers, plumbing profiles, roofing profiles as well as electrical equipment housing among others.
· Office furniture and partitions
In almost every office nowadays, you can hardly fail to find a polycarbonate extruded product.
In fact, many furnitures, partitions, and doors in the office are made of plastic extruded parts.
Office partition with polycarbonate
Such products in the office include wall fittings, screen posts, door tracks, jointing profiles, office partition trims, and cable trays among others.
Scientific research and exploration are some of the specialist industries that utilize a number of polycarbonate plastic products.
This is vital given that the material guarantees quality and durability among other fundamental properties.
Therefore, you’ll realize that many gadgets for such specialist industries incorporate plastic extruded products in one way or the other.
· Retail and display
Several plastic profiles ideal for retail applications are made of polycarbonate extruded products.
The good thing with this is that it gives you a wide range of options to choose from a wide range of available polycarbonate materials.
Poster hangers, menu holders, display poles, decorative shelf trims and frame sections among others are some of the applications in the retail industry.
· Medical appliances
Use of polycarbonate extruded products is nowadays mostly common in the medical field.
Several medical appliances and equipment are made of these materials due to the fact that they are of high quality and durable.
Polycarbonate capillary tubes
Right now if you get to any medical facility, you’ll find various products made of this particular material.
The lighting industry has for the longest time now been using a number of plastic profiles made from a polycarbonate extrusion process.
Polycarbonate light guide panel
Some equipment such as reflectors, refractors, lenses, luminaries, lighting profiles and lighting diffusers are some of the extruded plastic products.
Such products are preferable for lighting because they are resistant to weather and other physical elements.
As you can see from this guide, polycarbonate extrusion is indeed an in-depth process that requires better understanding.
In many instances, this process often takes place in industrial settings.
Nonetheless, it is important to note that the quality of the products made from polycarbonate extrusion process is always top notch.
I thus believe that you have learned quite a lot of information from this guide that might give you an idea or two on what to do and expect about the same.
But if you still have any questions or suggestions regarding polycarbonate extrusion, feel free to put it across in the comment section.