Choosing The Right Base Material: Acrylic vs Polycarbonate

In the following, we will briefly introduce the two base materials. Then, we will cover the different factors to compare when choosing between them.

Acrylic, also called PMMA (polymethylmethacrylate), is a synthetic thermoplastic polymer that can be used in a variety of applications. PMMA is a plastic that can be cast and extruded in various shapes and sizes.

At PSC, we exclusively work with flat PMMA sheets and will mainly focus on cast and extruded PMMA.

Want to know more about the differences between cast acrylic and extruded acrylic? Click here to learn more.

Polycarbonate is another thermosoftening plastic like acrylic but is made of different chemical structures. While acrylic is made of methyl methacrylate, polycarbonate is made up of carbonate groups, making it easy to work, mold, and thermoform like PMMA.

While acrylic can be both cast and extruded, polycarbonate is only produced by extrusion.

While there are many similarities in the overall look and fabrication options of acrylic and polycarbonate sheets, there are significant differences in their material properties that can have a big impact on which option you should choose for your next display or sensor.

In the following, we will look at these similarities and differences so you can choose the right option for your project.

Both of these plastics have significantly more impact resistance than glass. Many different sources state different impact resistance numbers based on how they’re tested and in which context, but it is safe to say that acrylic is at least 10-20 times as impact resistant as glass in most scenarios.

Polycarbonate, however, is said to be about 250 times more impact-resistant than glass. Therefore, without fixating too much on the exact number, it is safe to say that polycarbonate is the most impact-resistant material of these options, but acrylic can still be a great substitute for glass in some cases.

The amount of impact resistance that polycarbonate provides is rarely needed for most but can still be a requirement for some applications in industries such as the public transportation industry.

Read our case with INIT to learn more.

If impact resistance is a core feature of polycarbonate, scratch resistance is a core feature of acrylic. Acrylic is much more resilient to scratching and scuff marks, which can be especially beneficial for displays and other devices that display information to the end user. This can also be a critical consideration for cameras or sensors designed to read information quickly and accurately but still need a filter in front to protect the device from the outside environment.

Especially if the device is touched or cleaned regularly, it has to withstand contact and be wiped regularly with chemicals such as cleaning agents and disinfectants. Acrylic is a much more suitable base material for these applications since it can withstand this kind of environment much better than polycarbonate.

Both acrylic and polycarbonate are similar in weight. They are both about half the weight of glass. and neither therefore has a significant advantage over the other. This means, however, that both are significantly lighter than glass, which makes them easier to handle and a better choice in applications where the weight of the cover glass is considered.

Cold

It is important to note that some applications placed in an external environment can be exposed to cold environments. This is worth noting because PMMA becomes more brittle in very cold environments – which is something that polycarbonate doesn’t suffer from.

Therefore, if the application is installed in an environment where the winters are super cold, polycarbonate might be worth considering, depending on which kind of application we’re talking about.

Heat

Another consideration to remember in some applications is the heat resistance of these materials.

There are many ways to measure how high temperatures acrylic and polycarbonate can withstand, which is why there are many different opinions on this. Furthermore, temperature tolerances also largely depend on a variety of factors, such as the material’s shape and thickness, the tolerances and installation of the material in the overall device, etc.

There are even differences between how much heat extruded PMMA can tolerate compared to cast PMMA, not to mention an even larger difference between the PMMA types and polycarbonate. For these reasons, we usually start at around 70-75 degrees C as the maximum service temperature for acrylic and 100-105 degrees C for polycarbonate. This is the lower limit, which can, depending on the application, be higher depending on various factors.

Cast acrylic, for example, could easily have a maximum service temperature of up to 95C if certain criteria are met. Some of these criteria include possible stress from the mechanical construction of the device at higher temperatures, the thickness of the acrylic, etc. If there is stress in the device and the filter is exposed to temperatures above our recommended temperatures for extended periods of time, you could risk bending or deformation of the filter.

Lastly, it should also be noted that surface treatments can have lower maximum temperatures than the base material itself, meaning that the coating will be the limiting factor in terms of the maximum temperature that the filter can withstand instead of the acrylic or polycarbonate. In conclusion, while heat resistance is not important to consider in most cases, in the applications where it is a factor, it is an extremely important consideration.

Some applications require fire retardation features. This is usually the case in some public transportation devices, and especially in the aviation industry.

There are very strict requirements for the fire- and smoke-toxicity ratings of the base material used in displays industries such as the aviation industry, meaning that polycarbonate is often the only option. This is because acrylic burns relatively easily compared to polycarbonate. Not only is this generally the case, but there are also specific polycarbonate solutions that have the flammability and smoke toxicity ratings required to even be considered in these kinds of applications. Therefore, polycarbonate might be the only option in these cases.

While both materials have excellent light transmission, acrylic also takes the cake on this occasion. While clear polycarbonate has a light transmission of 88%, clear acrylic has a light transmission of about 92%. Four percentage points difference might not sound like much since polycarbonate is still used in some cases, such as passenger information displays in the public transportation industry, but it can make a huge difference in devices such as industrial sensors where maximum transmission of the relevant wavelengths is crucial to the device’s performance.

Depending on which wavelengths the sensor is designed to operate in, the filter can be optimized with AR coatings to maximize the transmission in those specific wavelengths while minimizing transmission of all other wavelengths. This optimizes the filter’s signal-to-noise ratio, maximizing performance.

Want to learn more about signal-to-noise ratio? Then click right here to read our article about it.

Don’t forget that these numbers, and a lot of other specifications of polycarbonate and acrylic, are of the base material itself. The material’s properties can be significantly improved with various coatings to improve scratch resistance, light transmission, etc. An anti-reflective surface treatment on a PMMA filter, for example, can improve the light transmission of the material to up to 99%.

Because polycarbonate can only be produced through extrusion, it is an unsuitable base material for devices utilizing circularly polarized light (CPL). In fact, this also makes extruded PMMA unsuitable for these kinds of applications, meaning that cast acrylic is the only base material possible for these devices.

Polycarbonate is limited in the different colors available (except at high volumes). We supply polycarbonate in either clear or tinted variations. Acrylic, on the other hand, is much more customizable when it comes to color.

PMMA can be manufactured in basically any color desired, and we have many different kinds of solutions available. The Solaris™ S series are the variants that we cast ourselves in-house, but we also have preconfigured solutions with excellent properties.

Apart from the performance-related specifications above, it’s important to mention that both acrylic and polycarbonate can be customized and machined in a variety of ways to fit your application.

There is no clear-cut answer as to which base materials are more cost-effective since it largely depends on the availability of that specific type or color of the base material and order volume.

 

 

 

 

 

 

 

 

 

It is also worth mentioning that the initial cost of the optical filter is not the only cost consideration you should make. The initial cost of this display window we deliver to Medido might be slightly higher than their previous polycarbonate solution, but it has vastly reduced the number of devices that need to be refurbished from 100% (220 devices per week) to only 15% of this, making it a much more cost-effective solution even though the initial cost was higher with the acrylic solution.

In conclusion, the choice between acrylic and polycarbonate depends on a variety of factors. Apart from the base material alone, it is also important to remember that the performance of both PMMA and polycarbonate can be further improved with surface treatments.

We pride ourselves on being able to find the perfect solution for pretty much any kind of application out there, and we do so by combining our in-house manufacturing capabilities with our extensive supply chain network.

With the right base material and surface treatment, the lifetime of your device’s display window or optical filter can be maximized – and we are ready to help you do so.

With all this about acrylic and polycarbonate in mind, it’s important to remember that surface treatments can significantly improve the performance of both of these base materials.

Depending on whether you need scratch resistance, anti-glare, antireflective, or something completely different, coatings can significantly improve the performance of the base material to fit your device’s requirements.