Acrylic, also known as PMMA or plexiglass, is a transparent thermoplastic. It is most commonly found in sheet stock format, though other shapes such as tubes and rods are also available. It is commonly used as a lightweight, shatter-proof alternative to glass. But because of its range of desirable properties, it can also be used in a diverse range of applications.
Acrylic is readily available from many retail locations, from Home Depot to Rona. Because it is cost-effective and quite easy to work with, many people purchase acrylic for their custom DIY projects. However, comparing to all the other types of materials out there, from glass to other kinds of plastic, one may wonder, what do I gain and lose by using acrylic? What are the pros and cons of this material?
One of the biggest advantages of using acrylic is that it is one of the most transparent plastics out there. Acrylic plastic in general has a light transmittance percentage of 92%. Unlike glass, which can have a slight greenish tint with increased thickness, transparent acrylic stays clear with no tinting. This property makes acrylic plastic very popular for display purposes, from display cases to window replacements. The crystal-like appearance of thicker acrylic pieces also makes it a popular choice for designer products. For example, the Magino Series by Karim Rashid.
Because a lot of the products made with acrylic sit indoors, it can be surprising to some to learn that acrylic is quite UV-resistant. It has been known that clear acrylic can last up to 30 years without yellowing when used outdoors. Comparing to other types of clear plastics (Styrene, PETG, Polycarbonate), acrylic offers a lot more weatherability.
Easy to Process
Another big reason for why acrylic is so popular with the consumer market is that it is very easy to work with. With everyday household tools, one is able to cut, form, and assemble acrylic into many finished products.
Unlike polycarbonate, which will burn and turn yellow when cut with a laser cutter, acrylic cuts like butter and the cut edges will look crystal clear, just like the rest of the material. And if you don’t have a laser cutter at home? Simply use a plastic cutting tool like this one offered by Home Depot to score the sheet acrylic, and then the piece can be snapped off.
Because acrylic has a relatively low melting temperature, it is also very easy to thermoform using simple tools. Thermoforming is just a fancy way of saying softening the plastic with heat and forming it into a specific form. Acrylic is kind of like chocolate, in that once it is heated, it becomes soft and pliable. There are videos on Youtube showing how one might go about thermoforming acrylic, like this one by the amazing fititsamo.
Though there are cheaper plastics out there, comparing to other common clear materials like polycarbonate and glass, acrylic is relatively cheaper. For example, polycarbonate on average is 2 to 3 times more expensive than acrylic. Combining that with how easy one can work with acrylic; it is easy to see why acrylic is so popular with DIY makers and big companies alike.
Low Scratch Resistance
A big weakness that acrylic has is that it is not very scratch-resistant. Therefore, it is crucial to handle finished acrylic pieces with care to avoid unwanted marks on the transparent plastic. Most times than not, the acrylic stock you purchase will have a protective film on it to prevent scratching.
There are scratch-resistant acrylics available on the market for when you do require that extra durability in your application, perhaps for things like public installations; however, they are a bit pricier than normal acrylic stock, as one might expect.
If your acrylic was scratched accidentally, there are plastic polish products which you can use to quickly get rid of the scratches.
Low Heat Resistance
As mentioned in the pros section, acrylic has a relatively low melting temperature, 160 degrees Celsius to be exact. Now, this is of course good enough for normal everyday applications, given that the summer heat won’t get any hotter than it already is, but for engineering applications, this melting temperature is perhaps too low.
Low(er) Impact Resistance
Though acrylic has a much better impact resistance than your average glass, comparing to other types of plastics, the impact resistance of acrylic is nothing to write home about.
Using the Izod Impact Test, where a metal arm is dropped onto a material sample, acrylic was able to withstand 0.4 feet pound-force, while ABS plastic (the plastic that Lego pieces are made from) can withstand 7.7 feet pound-force, and polycarbonate, known for its amazing impact-resistance property, was able to withstand 12.0 to 16.0 feet pound-force.
Depending on the thickness, acrylic plastic can handle normal everyday use quite well, but when it comes to extreme situations where durability is the utter most priority, materials such as polycarbonate or polysulfone would likely be more suitable.