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March 11th 2019

When white plastic isn’t just white plastic

Durable. Waterproof.  Tear resistant.  These are just a few of the ways printed plastics impact our life each day, often without us being aware of it!  From the bank cards that we use daily to pay for goods, to the safety signs that warn us about dangerous situations, synthetic materials surround us and provide us printed information, tools, and vital components that power so much of our interactions with the world around us.  Whether it’s the menu at your favorite café that can be disinfected quickly or the label that helps a lab technician identify an infectious bacteria sample, it’s the properties of synthetics and plastics that make these applications possible.

With such a wide range of uses and nearly unlimited applications, plastics must come in an equally broad and diverse range of properties, characteristics, and functions. While many people may not know what makes a sheet of plastic used for credit cards different from a sheet of plastic used for medical tags, or why one would use a white polystyrene vs white polyester, it’s the different ways these plastics perform that makes each of them specially designed to help solve challenges that printing applications present.  Some of these synthetic films may be excellent for rigid applications such as a store sign, but rapidly dissolve when exposed to common chemicals.  Others might be able to tolerate the high temperatures encountered in a factory environment, but not want to fold down flat for the safety manual used by a fight mechanic.

It’s these different characteristics that we’re going to explore. While there are hundreds of different types of synthetic polymers, plastics, and specialty films designed to target applications ranging from children’s toys to adhesive labels applied in the harsh environments of space, we’re going to look at five of the more common synthetics encountered in the day to day operations of many print shops: high-impact polystyrene (HIPS), vinyl’s (PVC), polycarbonate (PC), polypropylene (PP), and polyester (PET).

 

High-Impact Polystyrene

High-Impact Polystyrene, more commonly known simply as styrene or HIPS, is a low-cost, very rigid, and easy to work with plastic for a wide range of applications where customers need something that is stiff, durable, and water resistant. Some of the common applications include point-of purchase displays, shelving strips, and indoor signs where the printed piece needs to stand up either on its own or in a frame.

This film is what’s known as an amorphous thermoplastic. These types of plastics all share some common features that make them great for many applications.  One of the key features of films such as polystyrene is that they don’t melt rapidly, but instead soften over a wide range of temperatures.  This allows them to be formed into three dimensional shapes quickly.  It also allows the film the be easily printed, easily cut, and easy to glue or bond.  As its name implies, high-impact polystyrene has exceptional impact resistance, which is why it’s excellent for store signs that might get bumped, knocked, or nudged by shoppers.  As an added benefit, high-impact polystyrene is FDA compliant for applications that are around food!

There are some things you should look out for when using polystyrenes, however. First, high-impact polystyrene does not hold up well to many solvents.  When exposed to solvent chemicals, styrene can rapidly dissolve making  it unsuitable for any application where these chemicals may encounter it.  Additionally, styrene, like most amorphous thermoplastics, can crack easily under stress or fatigue such as folding or repeated flexing.  Lastly, high-impact polystyrene can be highly flammable and therefore not used in applications where it may be exposed to an open flame.

 

Vinyls

One of the most commonly heard plastics names is vinyl, also known as PVC. This commodity plastic can be found in a wide range of applications in daily use, ranging from credit cards to industrial signage.  With its good thermal properties, excellent corrosion resistance and stiffness, it’s been used for menus, fuel-pump signs, and safety tags.

Like high-impact polystyrene, PVC is an amorphous thermoplastic and shares many of the same characteristics. It’s easy to machine, bonds well with adhesives for things like lamination, and works very well in applications such as credit card and bank card manufacturing since it can be platen laminated and embossed with raised numbers.  It has great UV resistance that makes it suitable for outdoor use.  One of the unique features of PVC is that when exposed to flames, it will self-extinguish, making it ideal for applications where the spread of fire needs to be contained.

Unfortunately, for all the benefits of PVC, there are some strong downsides that should be considered before using this film in your applications. Most notably, there is a very strong case against the environmental impacts of PVC.  Some grades of PVC may contain toxic chemicals known as phthalates.  In addition, PVC produces several potentially hazardous by-products as it breaks down or ir burned and there have been several initiatives worldwide to limit PVC usages and disposal.

 

Polycarbonate

Polycarbonate is one of those plastics that you may or may not have heard of, but you likely interact with on a regular basis. This engineering thermoplastic is strong, tough, durable, and works exceptionally well in applications where a sign needs to hold up to just about anything thrown at it.  You’ve likely encountered polycarbonate on button panels such on those found on machinery or screen overlays on electronic devices.  It’s used in shatter resistant protective covers and even point-of-purchase displays where the extreme durability helps keep the display looking great for years to come!

This synthetic takes all the great features of the amorphous plastics and ramps them up. The outstanding strength and exceptional resistance to impacts (it’s over 250 times stronger than glass!) make it excellent in printed screen overlays and membrane switches that are handled regularly.  For customers needing high-security cards, polycarbonate often replaces PVC due to its toughness.  Being amorphous, it can still be easily thermoformed into three-dimensional pieces.  There are a wide variety of polycarbonates, ranging from flame retardant to UV inhibiting, with an equally wide range of surface finishes.

While polycarbonate does an exceptional job at many things, it does have some weaknesses that should be taken into consideration. First, it can fail due to stress cracking, such as being mounted with screws or put into situations where it is put under pressure or flexing.  It also has much less fatigue resistance than other engineering films such as polyester.  This can lead to some button panels cracking over time after repeated use.  And while it has good chemical resistance, it can still be attacked by many solvents.

 

Polypropylene

Polypropylene, like PVC, is one of those plastics you’ve probably heard of, use regularly, and could identify if you were to touch it. It’s one of the most common types of plastics in the print business due to its soft and flexible feel that helps it feel more like paper than a rigid plastic.  It’s low cost, low rigidity, and soft feel make it commonplace in applications such as menus, book covers, manuals, hang tags, and product labels.

 

Unlike the amorphous thermoplastics such as HIPS, PVC, and polycarbonate, polypropylene is what is called a semi-crystalline thermoplastic. While amorphous films are very easy to shape into three-dimensional buttons and signs, but can crack under stress or fail with fatigue, semi-crystalline thermoplastics like polypropylene are better suited for applications where they don’t need to be thermoformed, and instead need to stand up to lots of stress, repeated folding, and longer-term wear.  The high flexibility of polypropylene makes it exceptional in applications that have a hinge or fold that will be repeatedly moved back and forth over time.  Its soft feel makes it incredible for consumer applications and its FDA compliance make it suitable around foods.  It’s lower cost, high resistance to acid, solvents, and chemicals, combined with its visual appearance make it a popular choice for both consumer and industrial labels, tags, and signage.

 

The largest drawback to polypropylene is its lack of rigidity. Thin polypropylene films used in printing have a very soft feel that prevents them from standing up properly in applications such as sign frames.  Customers looking for a table tent or bi-fold menu that need to stand upright on a table may find that the polypropylene films simply won’t perform like they wish.  In addition, semi-crystalline thermoplastics can be difficult to shape using thermoforming, leaving them best for applications that are folded or lay-flat.  Finally, polypropylene can be difficult to bond with adhesives.  While this is great for applications that need to be easily cleaned off, customers needing to apply a glue, adhesive, or another label to the printed piece may run into challenges.

 

Polyester

When it comes to a synthetic that does a lot of things very well, it’s hard to look much past polyester films. The durability, chemical resistance, and wide-ranging use of this engineering film make it suitable it an exceedingly broad range of applications.  Polyester films can be found in everything from tear-resistant store catalogues to safety-critical signage used in military and lab environments.  It’s rigidity, heat resistance, and ease of use make it ideal in the widest range of print technology, including high-heat laser and toner printing.

 

As a semi-crystalline engineering film, polyester stands out for its excellent chemical resistance and thermal stability. It has one of the highest short-term and long-term operating temperatures outside of high-end, high cost engineered plastics, making it an excellent choice for applications that might be exposed to high temperatures such as those found in a hot-foods deli counter or even tagging products in a heat-based manufacturing environment.  Polyester also has an extremely high actuation life, meaning it can be folded, pushed, and flexed repeatedly without worry about cracking, breaking, or failing.  This allows it to perform better than polycarbonates in button panel applications where repeated button presses could cause polycarbonate to fail.  Polyester can be thermoformed and is excellent when used in parts that have a hinge.  This non-toxic film is benign to the environment and can be recycled.  In addition, polyester has a very high tensile strength that lends itself well to applications where customers need very high tear resistance and durability, such as customer loyalty key ring tags.  Other common applications include safety manuals for flight crews, maps for the military, and menus that need to last repeated handling and cleaning.

For all the benefits of polyester, there are a few things to look out for. Compared to polycarbonate, it has a much lower impact strength.  It’s less easy to easy to die-cut and emboss than polycarbonate in applications such as overlays.  In addition, the high rigidity and dimensional stability of polyester can make folded applications a challenge on the thicker calipers.  While the hinge will last a very long time, the fold will have a higher tendency to want to open than with a softer film such as polypropylene.

With the growing range of synthetics being used in printing, it’s easy to fall into the idea that plastic is plastic. After all, it’s all synthetic, it’s all water resistant, and it’s all designed to be more durable than paper.  Hopefully, however, this guide has helped you understand the applications, ranges, and different types of common printing plastics found in the industry.  The features, benefits, and drawbacks of every synthetic on the market are as diverse as the applications themselves.  By choosing the correct synthetic for your specific application, you can deliver higher quality, higher satisfaction, and more profitable services to your customers.

At Kernow Coatings, we specialize in the development and consultation of printable synthetic applications. If you have questions about which film is best for your application, don’t hesitate to give one of our material experts a call.  We can help guide you through the features of each film that best fit your needs and make sure you have the right type of film for your customer!

– Kernow Sales Team

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