What is Acrylic?
On the most basic level, “Acrylic” is a form of plastic that is transparent and has thermoplastic qualities. It is more commonly known by the brand name “Plexiglass”. Acrylic is similar to polycarbonate as both are used as alternatives to glass. They are both transparent but much more damage resistant than glass. Acrylic was first produced nearly 100 years ago in 1928. It was introduced to the market five years later by the Rohm and Hass Company. The material is considered to be among the clearest plastics around. Acrylic was originally used back in World War 2 to make periscopes for submarines, as well as turrets, canopies, and airplane windows. Pilots who had their eyes damaged by shards of broken acrylic tended to fare much better than those who were injured by shattered glass.
These days, acrylic is generally used for applications that take advantage of the natural transparency and resistance of different varieties of acrylic. It is commonly used to make acrylic nails, lenses, paints, medical devices, security barriers, furniture, and LCD screens. The transparency of acrylic means it can also be used to create windows, tanks, and enclosures for museums and zoos.
While acrylics are commercially available in a range of different colors – some of which are translucent – the raw material of acrylic itself allows for light to pass through at close to the same rate as glass. This makes it a great alternative to glass, similar to polycarbonate. There are a few differences with acrylic, one of which is that it is free from the harmful substance bisphenol-A (BPA). Another difference is that polycarbonate has a higher impact strength than acrylic.
Acrylic is available widely at a relatively inexpensive price. It makes for a good alternative to polycarbonate in situations where material strength isn’t important. Sometimes acrylic is laminated onto polycarbonate (PC) in order to combine the strength of polycarbonate with the scratch resistance of acrylic. This is how some kinds of bulletproof glass are made. The polycarbonate stops the bullet while the acrylic prevents scratches during everyday use.
The Characteristics of Acrylic
Now we’ve looked at the uses for acrylic, let’s take a closer look at the characteristics of the material. Acrylic is considered to be a thermoplastic, which relates to how it interacts with heat. A thermoplastic material will become a liquid at a certain temperature, knowing as a melting point. The melting point of acrylic is 160 Celsius. One advantage of using thermoplastics is they are more malleable as they can be heated to their melting point, shaped, cooled, and reheated without any damage to their internal structure. Rather than being burned, these plastics liquefy. They can be injected into molds and are easy to recycle.
The opposite of thermoplastics is thermoset plastics. These plastics can only be heated just the once, often when being injected into a mold. A thermoset plastic sets after being heated, which is an irreversible chemical change. Trying to reheat a thermoset plastic to another high temperature will cause it to burn. As such, thermoset plastics are not as good as thermoplastics for recycling.
Why is Acrylic so Widely Used?
Acrylic is great for when being transparent is more important than being able to resist impact. It is highly scratch resistant when compared to other kinds of plastics. Acrylic is lighter than glass and is more economic than polycarbonates, making it the better choice when one does not require the resistance and strength a polycarbonate provides. Acrylic can be molded into precise and fine shapes through laser cutting as it vaporizes when hit by the laser. Acrylic can also be cut and molded by hand. It generally has to be polished after being cut by a machine in order to eliminate any marks and restore natural optical clarity. Some of the primary uses for acrylic are:
- For lenses
- An alternative to glass
- For fashion accessories such as bracelets and beads
- Display products such as phone cases
Different Varieties of Acrylic
The journey to acrylic plastic began all the way back in 1843, which was when acrylic acid was first created. Around a century later, in 1933, the German chemist patented the trade name “plexiglass”, which is another name for acrylic plastic. These days, plexiglass is manufactured by many different companies, most of which have their own unique formula and production process for making it. The most common trade names for acrylic plastic now are Plexiglas ® by ELF Atochem and Lucite ®by DuPont.
How is Acrylic Produced?
Much like other plastics, acrylic production begins with distilling hydrocarbon fuels into lighter groups known as “fractions”. These fractions are then combined with catalysts to create the different kinds of plastics, a process that generally involves polymerization.
Acrylic for 3D Printers and CNC Machines
Acrylic can be purchased in sheet and round stock, which makes it suitable for subtractive machining processes. It is available in a variety of different colors, including some fluorescent colors. These are sometimes known as “edge-lit” acrylics. The different colors of a sheet might not be noticeable when one looks directly at it, but it is very apparent along the edges of the acrylic. It looks almost as if it is illuminated without any light source.
The acrylic parts machined from clear stock generally need to be sanded and polished to eliminate tool marks and restore their transparency. It is relatively easy to heat acrylic sheets and turn them into the desired shape. Bends can be made in acrylic with the use of a wire heater. It is also possible to simply heat the entire sheet and force it into the required shape. Parts created with several pieces of acrylic are joined together with solvents that melt the surface. The acrylic cools in a single piece with barely any visible joints.
Is Acrylic Toxic or Not?
One great advantage of using acrylic is that it is free from bisphenol-A (BPA). It neither contains BPA nor releases it during hydrolysis (when material degrades after coming into contact with water). Polycarbonate, on the other hand, contains BPA. While tests into the toxicity of BPA are inconclusive, there are no problems at all when using acrylic. Many studies funded by governments have shown that BPA is hazardous to health, while those funded by private industries suggested that there was a reduced, if not non-existent, medical risk to BPA. No matter what the risks of BPA are or – or aren’t – it’s impossible to deny that certain kinds of polycarbonate have been shown to contain and release BPA. As such, there are now several “BPA-free” polycarbonates on the market, used with consumer products like canning jars. With all that said, the fumes released when 3D printing acrylic and the fumes from the molten material used with injection molding should never be inhaled. These manufacturing processes must be performed in well-ventilated facilities to reduce the potentially harmful effects of the gaseous polymer.
The Disadvantages of Acrylic
As impressive as acrylics are, there are some disadvantages to them. For example, they lack the strength and impact resistance of polycarbonate. This makes polycarbonate the better choice when you need something strong. Acrylic is prone to brittle failure, meaning that it doesn’t take much to make it crack.