When it comes to printing on plastic, most consumers can quickly find themselves overwhelmed by the sheer number of different plastic substrates available to them. The average person will simply Google “plastic printing” and go with whatever option is the cheapest. I mean, plastic is plastic right? The short answer is no. The long answer is that while the average consumer can get by with only a cursory knowledge of plastic substrates, there is an incredible variety of plastics which are suitable for printing with an infinite number of applications, each with their own advantages and disadvantages.
If you’re creating signs to advertise a clearance sale that are only going to be outside for a few weeks, you probably don’t need a super high-grade, UV resistant plastic for your signs. If strength and durability are extremely important to the job at hand, it might be better to invest in a higher-quality plastic. So how do you choose? Luckily, finding the right plastic for the job is not as complicated as it might seem. It all boils down to understanding two things: what you need, and what options are available. We can’t help you with the first, but by the end of this article you will be have a much better understanding of your options.
H.I.P.S., or High Impact Polystyrene, is a commonly used, low cost, and tough form of styrene (the same material that goes into making Styrofoam) with excellent thermoforming and fabrication characteristics. It is normally found in retail displays, indoor banners and signage, and disposable cutlery. While cheap, it offers a fairly print-friendly surface, making it suitable for many applications where high durability and precision are not required. It is extremely brittle, and so it does not die-cut as well as other plastics. It is also very sensitive to UV and heat, causing it to yellow easily if left outdoors for extended periods of time.
While styrene might not be ideal all of the time due to its structural weaknesses, these weaknesses can and often are mitigated by introducing modifiers into the styrene. The result is a modified form of styrene consisting of approximately 78% styrene and 28% modifiers, with higher tear-strength and rigidity, and increased die-cutting capabilities. Transilwrap Co., Inc refers to these upgraded styrenes as Transalloys, which come in several different grades, including: P260, with a higher rigity; and P300, with higher tear-strength. The downsides to these Transalloys are increased cost, as well as the fact that they only come in shades of white.
HDPE (High Density Polyethylene), the type of plastic that milk jugs and bottle caps are made of, has a cost comparable to that of polystyrene. Due to the fact that it is mainly used in industrial applications, such as piping and plastic lumber, it is not normally made with high-quality in mind and so would probably not be ideal for most printing.
Polyvinyl Chloride, widely known as PVC, is used in everything from sewage pipes to bank cards to vinyl records. It is very strong and is easy to die cut making it suitable for a huge range of applications. It is typically either cast (dried on a sheet) or calendared (extruded through a roller) which offer different qualities and characteristics. Despite its many advantages, PVC is not without its drawbacks. PVC has a large reputation for being one of the dirtiest plastics on the market today. This reputation is not unwarranted, as the production of PVC creates volatile organic byproducts, and this type of plastic is almost never recycled. It is also more costly than other plastics, and offers little in the way of opacity and color choices.
A cheaper alternative to PVC, Proprine (short for Polypropylene) is a type of plastic frequently utilized in stationary folders, packaging, restaurant menus, and storage boxes. Proprine is very rugged and resistant, but is liable to cracking and crazing when exposed to UV radiation and heat for extended periods of time.
Despite this, it does have many advantages over more durable plastics such as PVC. It is strong and die-cuts extremely well, and is much cleaner to make than PVC, as it has a more environmentally friendly production process and is more commonly recycled. There are multiple domestic sources of proprine, resulting in a faster delivery time for rush jobs. It offers a wide array of colors and opacities, and is therefore very easy to customize. It comes in a variety of qualities and costs which vary by grade; Proprine + UPO has a cost, strength, and quality similar to PVC while lower-grade proprine is comparable to polystyrene.
The last alternative we’ll be examining is polyester. Polyester (that is, sheet polyester as opposed to polyester used in fabrics) is a very good alternative to other plastics. It retains most of the good characteristics found in other materials, and is very heat stable. It is strong, tear resistant, and is easy to die-cut. It possesses the ability to be made more optically clear when compared with glossy clear vinyl. The downside to polyester is, however, that it is very expensive.
Polyester used for printing typically comes in two varieties: oriented and extruded. Oriented polyester is stretched as it exits the extruding machine, resulting in increased strength and optical clarity. Extruded polyester on the other hand (also known as APETG) is not stretched. This gives it a lower grade, and it is mostly used for packaging applications.
While there are an incredible number of plastics available, you should now have a fairly good understanding of the ones most commonly used in printing, as well as of their various strengths and weaknesses. Below, you'll find a table of all the information contained in this article, along with the number they are associated with when recycled.