The below news is from Sign & Digital Graphics.
The word “plastic” used to have very negative connotations. It meant cheap, fake and fragile. But that has all changed. Our current state of consumer goods would not be possible without modern plastics. Most of the items manufactured today make use of the easy conformability and durability of plastic.
The sign industry is a premier example of the importance of plastic. Its light-transmissive qualities make it ideal for illuminated signs. Plastic’s light weight makes it perfect for indoor displays and its ease of molding and forming fit perfectly for the graphics industry.
Acrylic
The original sign sheet was acrylic. The most common form of this ubiquitous material is the extruded sheet. Liquid plastic is extruded into long rolls of plastic, which are converted into the standard sheets we see so often today. The more expensive cell cast acrylic is poured into individual sheets in a mold. Cell cast plastics are easier to form and have superior optical clarity as compared with less expensive extruded acrylics.
The relatively low cost of acrylics and their ease of use have made them the main plastic to use for indoor signs, especially backlit or high-end signage. Acrylics can be easily thermoformed, heat bent and glued. They are, however, somewhat brittle and will break on impact, especially in the cold. This makes them less suitable for outdoor signage.
The advent of LED lighting technology for illuminated signage brought benefits as well as challenges. When first introduced, the small, energy efficient light sources provided long-lasting, high intensity illumination, but signs tended to look like thousands of pinpoints of light instead of an evenly illuminated graphic. In order to solve this problem, new diffusion techniques had to be invented and acrylics became available from different manufacturers using different technologies to solve the problem by diffusing the light more evenly across the plastic surface.
There are also lots of specialty applications for acrylics. "Edge-lit" technology or "edge glow" is an effect created when light focusing on a material's edge is evenly diffused across its surface. Rowmark’s ColorHues product provides the light transmissive benefits of glass in a lightweight, scratch resistant material that includes 35 bright colors. The translucency of the products make them well suited for edge lighting applications.
Engravable plastic stock usually comes in layers of different colors. Engraving through the top layer exposes the bottom layer in a contrasting color. Now available specifically for backlighting applications is Rowmark’s two-ply Color ColorHues EFX product line, featuring a black cap over translucent colors. Engraving through the black cap leaves the brilliant translucent colors showcased on the opaque black background.
Durability has always been a major Achilles heel with acrylic plastics. However, today’s strengthened acrylics have partially solved that problem by increasing the outdoor durability of the product. But of course the price goes up and it is still not as strong as polycarbonate.
Polycarbonate
Polycarbonate is the king of tough. It is used for everything from riot shields to jet fighter windows. This extreme durability originally came at a price. Early polycarbonates yellowed quickly and were prone to scratching, but those days are gone. The first commercially viable polycarbonate was patented by Bayer in 1953. Bayer MaterialScience now bonds a UV topcoat directly onto the polycarbonate during the extrusion process as an integral layer. They are so confidant in their product that Bayer Makrolon sheets have a 10-year guarantee against breakage or loss of light transmission.
Another problem traditionally experienced with polycarbonates was the soft surface that scratched easily. Using Makrolon as an example again, we can look at their two solutions. One is to coat the polycarbonate with a gloss, scratch-resistant surface and the other solution is to offer a matte, textured surface. The textured surface is the strongest defense against scratching and has the added bonus of making fingerprints hard to see. It is, however, not as optically clear as the gloss products. The gloss scratch resistant coating is not as tough, shows fingerprints easily and is subject to glare, but features enhanced clarity and color brilliance.
Polycarbonates are also very easy to form and shape. They can be cold formed in a break, unlike their acrylic cousins which just shatter. Polycarbonates also maintain their strength after thermoforming and have a faster cool-down time than acrylics, reducing production times. Their excellent forming characteristics mean uniform light diffusion, even with deep draws or complex corner shapes. Makrolon LD sheet is especially designed for LED lighting with increased diffusion and high heat resistance, which allows the facials to be closer to the lights, which in turn means thinner sign cabinets for a more sleek, modern appearance.
And just when you thought that you’d heard all the advantages of polycarbonate, there’s more. While acrylic traditionally just comes in a few stock sheet sizes, polycarbonates come in sheets and/or rolls. For example, Bayer MaterialScience offers sheets as large as 75” x 125” and their roll stock is available up to 100” wide!
In Summation
So acrylics are less expensive than polycarbonates, but not as strong. Both products form easily, but acrylic bonds better. There are a wider variety of specialty acrylic products but polycarbonate comes in larger sign-friendly sizes. Is one better than the other? Well, that depends on what you want to do with it.