Signs are one of the most common uses for outdoor plastics. When it comes to selecting plastic for outdoor signs, there are a number of elements to consider about the signage in question such as size, weight, color, and illumination; but one element above all needs to be taken into account: the weather. Come rain or shine, snow and hail, at the end of the day your sign needs to keep looking as new as the day it was put up.
One of the best plastics for this application is Poly(methyl methacrylate) or PMMA, which is best known as acrylic. Acrylic is one of the engineering plastics we mention in one article on mechanical parts here. Let’s have a closer look at acrylic.
Acrylic as Plastic Glass
Acrylic glass is often referred to as ‘plastic glass’ due to its excellent transparent properties and, therefore, is often used as a glass replacement. It also has good strength and toughness characteristics making it durable and able to withstand storms and impacts from hailstones. It also has great abrasion resistance and will not scratch very easily over a long exposure to the weather.
Acrylic is also UV resistant and will not yellow or discolor, even after years of exposure to bright sunlight.
As a glass replacement, it is considerably lighter than glass itself and has the added advantage of being molded and formed into different shapes. If you are creating a sign, the panels would likely be formed from sheets of acrylic.
Acrylic plastic glass can be colored, but it’s best if that is just a tint, making the plastic translucent or slightly opaque. When used like this, acrylic has a stained glass window effect and can look very artistic and aesthetically pleasing.
Acrylic is perfect for signs that are illuminated with LEDs and shine bright at night, commonly known as lightboxes. The legendary ‘Welcome to fabulous Las Vegas’ sign is a good example of a similar kind of outdoor sign:
From a costing point of view, acrylic is currently $1.97/lb in mid-2022 making this a very affordable material for outdoor sign production.
Advantages of Acrylic
- Excellent transparency properties, glass replacement qualities
- Has a wide temperature operating window making it suitable for all weather conditions
- About half the weight of glass
- Good impact resistance
- High scratch resistance
- Weather resistance including UV resistance and the ability to withstand long exposure to the sun without yellowing or discoloration
Disadvantages of Acrylic
- Impact resistance is not as high as some other materials
- Generally requires alternative materials to complete the sign, such as an aluminum frame
- Less rigidity than other materials and often needs additional support or frames to maintain its position over a long time
Polycarbonate (PC) – the Tough Glass
Polycarbonate has similar properties to acrylic, however, it has around five times the impact resistance making this an even more durable and tougher plastic option in a lot of instances. Because of its excellent impact resistance properties, it is often referred to as ‘tough glass.’ For this reason, as well as for outdoor signs, polycarbonate is used in other applications where toughness is required, such as bus shelters and bulletproof glass!
Polycarbonate also has the added advantage that it can be produced in any color you desire as well as to different opacity levels including full transparency. This makes it more suitable for solid color signs that will not fade in extended sunlight, as polycarbonate is UV resistant.
Manufacturing processes allow for injection molded parts as well as in sheet form which can then be shaped and formed to the desired dimensions.
The toughness of polycarbonate gives it the ability to withstand the most extreme weather conditions far better than acrylic. Its superior impact strength means it is able to withstand rougher conditions, more general abuse and wear and tear.
You might see outdoor signs for companies like banks made from polycarbonate tough glass, for example:
Like acrylic, polycarbonate is also a lightweight plastic, around half the weight of conventional glass. However, the cost of polycarbonate is higher than acrylic at $2.66/lb in mid-2022 making it a less cost-effective plastic than acrylic for importers manufacturing new outdoor products.
Advantages of Polycarbonate
- Excellent transparency properties, glass replacement qualities
- Has a wide temperature operating window making it suitable for all weather conditions
- Has a higher operating temperature than acrylic
- About half the weight of glass and lighter than acrylic
- Excellent impact resistance – better than acrylic
- Can be fully colored
- Weather resistance including UV resistance and able to withstand long exposure to the sun without yellowing or discoloration
Disadvantages of Polycarbonate
- Can be scratched relatively easily
- High price, making it less cost-effective than other outdoor plastics
- Low resistance to chemicals, such as alkaline cleaners and solvents
Conclusion for when sourcing plastic for outdoor signs
If there is one thing signs are designed to do, it is to convey a message or provide information. That information needs to be clear and comprehendible at all times. The materials used in the construction of outdoor signs play a major role in how signs manage to provide this function and so selecting the correct plastic is key.
Plastic for outdoor signs has to withstand the elements that mother nature throws at it, looking as new and fresh as the day it was erected even after years of exposure to UV light, hot and cold temperatures, and torrential rain. It literally needs to be ‘tough glass’.
There are two predominant plastics that are used in the construction of signs, Acrylic and Polycarbonate.
Illuminated signs used above storefronts are generally acrylic and have all the attributes and mechanical properties that a sign such as this requires to function and last a long time.
However, for signs that are larger or more exposed to the elements, such as billboard signs, polycarbonate would be a better choice as this is more suitable for sustaining higher impacts and more extreme weather conditions. As mentioned, Polycarbonate is also commonly used as bulletproof glass so you can see how tough it is!
