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The "Scoop" on Plastic Substrates

Copyright © 2015 by Davis Multimedia, Int'l. All Rights Reserved.
As Printed in July 2016, Volume 42, No. 1 of The Engravers Journal
A UV-LED printer allows you to print full-color photos on plastic sheet materials. Photo courtesy of GoVivid, a division of Rowmark.

   Engraving plastic is found in some form or another in virtually every shop in the recognition and personalization industry. We use it all the time for different purposes, ranging from signs and badges to control panels to ID tags to awards to desk plates… the list goes on and on. In fact, the ways in which you can use a sheet of plastic could probably fill up every issue of EJ for a very long time.
   So what do we mean when we say engraving plastic? There are literally thousands of types of plastic made today with different chemical and physical properties. As a simple definition, think of engraving plastics as having two main characteristics. The first is that they are formulated to be “friendly” to the engraving or personalization process you are using. Generally, that means they cut cleanly and don’t melt or chip, and they don’t present a hazard to either human health or to your equipment. The second characteristic is most materials are constructed with a multi-layer composition with the layers typically having different contrasting colors. This allows you to get a rainbow of surface colors contrasting against a rainbow of core colors.
   Some plastics, e.g. traditional acrylic materials, have excellent engraving properties for both laser and rotary engraving, but for a lot of jobs requiring color or color density in the graphics, you generally have to resort to paint filling to get the color and contrast.
   In this industry, you can buy plastic by the sheet and fabricate it into trophy plates, plaque plates, badges, nameplates, signs and other custom products. As another option, most suppliers offer fabrication services for the materials they sell. They will cut material into custom sizes and shapes, and can add beveling, polishing, radius corners, hole drilling, bending, findings, screen printing, hot stamping, adhesive, etc. Some suppliers, such as Rowmark, Gravotech and Gemini (and others), also offer custom color options for the plastic materials they sell. (See the sidebar accompanying this article for a list of plastic suppliers.)
   Years ago, options in plastic were pretty much limited to phenolic, clear acrylic and conventional “laminated” plastic engraving stock in two or three thicknesses and in a few colors and woodgrains. Laminated flexible engraving stock was manufactured using a heat fusion process which produced a relatively thick “cap layer.” That was problematical for some jobs because deep rotary engraving is not conducive to achieving fine detail. These thick cap laminates were also developed before lasers, and laser users often experienced melting and an unacceptable cut.
   In more recent years, we’ve seen a virtual explosion in the types of plastic available, in addition to an incredible selection of colors, patterns, finishes, gauges, etc. Acrylic, for instance, is now available from suppliers in many colors and thicknesses. You can purchase plastic that closely resembles granite or metal, combining the look of the real thing with the ease of engraving plastic. Microsurface plastic engraving stocks, with an exceptionally thin cap layer of about .003", are available which allow you to engrave amazingly detailed designs. Reverse engravable substrates are available for projects like subsurface and backlit signage. Today, there is also plastic available that has been designed for specific marking methods, such as laser engraving and sublimation, in addition to plastics for making ADA signage and exterior signage. And that’s just the tip of the iceberg! Here’s the “scoop” on the many options available in plastic today.



DuetsContours is an ultra-thin flexible engraving stock that can be used for many applications, including curved surfaces. Photo courtesy of B.F. Plastics, Inc. This sign from Delvie’s Plastics was reverse laser engraved on ¼” acrylic and lit with an LED edge light fixture.

 


Traditional Acrylic
   Traditional acrylic has sleek, upscale, modern qualities that make it a very popular choice for awards, gifts and fabrication applications. Traditional clear or single-color acrylic (Plexiglas, Lucite) is often noted as a lightweight, scratch-resistant and less expensive alternative to glass and with better optical clarity. An advantage of acrylic over some other plastics is its UV stability (meaning it’s able to withstand exposure to UV light) and weatherability (meaning it’s able to withstand the elements, such as sunshine, hot, cold, rain, snow, etc.).
   Both cast and extruded acrylic are used in this industry. Cast acrylic sheets are manufactured by pouring a liquid monomer into a mold made of two sheets of glass. This type of acrylic is known for its optical clarity, strength and impact resistance, and it is easier to machine than extruded acrylic. Engraved lettering and designs on clear cast acrylic will turn frosty white, providing nice contrast. Extruded acrylic, on the other hand, is manufactured by a continuous production process, which results in a more consistent gauge tolerance across the sheet. This type of acrylic is less expensive than cast acrylic and remains clear when engraved. Both cast and extruded acrylics offer UV stability, weatherability, moderate chemical resistance and will withstand heat up to 180º F.
   Traditional acrylic sheets (the materials used for sign blanks) are available as a single-ply sheet typically in 1/8" and 1/4" thicknesses, although suppliers indicate that the material can be produced in just about any thickness. Gemini, for example, produces acrylic in thicknesses from .020" up to 1.5" and Delvie’s Plastics offers clear acrylic in .030"-2" thicknesses.
   Today, acrylic manufactured for engraving is available in a range of optical appearances (clear, opaque, translucent, mirrored, fluorescent, frosted), a variety of finishes (matte, gloss, satin, textured) and a wide range of colors, making it suitable for a variety of applications.
   Popular applications for acrylic include interior and exterior sign-age, badges, awards, industrial applications, channel lettering, etc. An emerging trend in the industry is backlit signage, and acrylic is an excellent material for this application. Delvie’s Plastics, a supplier specializing in acrylic sheet materials, recently developed a line of table standing and wall hanging LED light bars for creating backlit signage. Acrylic can also be formed into many different types of products, such as tent signs, display fixtures, desk accessories and personalized gift items (trays, coasters ornaments, picture frames, etc.).
   Of course, as stated earlier, one of the main disadvantages to traditional acrylics as an engraving stock is their uniform color construction throughout. If you want contrasting color in the engraved graphics, you are adding an extra step of color filling the material using paint or another filler.


Duets by Gemini Laser XT is a UV-stable and weatherable engraving stock. Photo courtesy of B.F. Plastics, Inc. This sign was made using color frosted acrylic, standoff mounts and white ADA engraving stock. Photo courtesy of Delvie’s Plastics. Plastic can be used to create ADA-compliant signage that includes raised lettering and Braille. Photo courtesy of Gravotech.

Modified Acrylic Laminates
   In addition to single-ply acrylic substrates, manufacturers have created acrylic blends containing ingredients such as fillers, pigments and additives that vary the physical properties of the material to create “modified” and “impact modified” acrylics. These acrylic blends are used to manufacture two- and three-ply materials with contrasting core and surface colors through co-extrusion, lamination or by adding a foil cap. The idea here is to utilize the advantages of traditional acrylic (weatherabiity) with the performance characteristics of multi-ply, multi-colored engraving stocks.
   Modified acrylic materials are available in an extensive number of color combinations and finish options, and can be fabricated using many different methods, including both rotary and laser engraving. In addition, the use of modified acrylic in these two- and three-ply substrates makes most of them UV stable and weatherable so they can be used for both interior and exterior applications.
   Suppliers also offer cast and extruded acrylic sheets specifically designed for reverse engraving. This two-ply material consists of a thick clear surface (as viewed from the front) and a thin colored layer on the back. When the thin colored layer is engraved with a reverse-reading design, the letters and graphics show through the clear base material which can then be color filled or back lit for a number of unique applications, including subsurface signage.
   As mentioned, acrylic is a versatile material that can be marked using a variety of methods, including rotary engraving, laser engraving, hot stamping, screen printing, pad printing, UV-LED/direct printing and sandblasting. It can also be fabricated by sawing, routing, thermobending, laser vector cutting, beveling and drilling.

One of the great qualities of acrylic is that it can be fabricated into many different products. Photo courtesy of Gravotech. This plastic directional sign was created with a UV-LED printer. Photo courtesy of GoVivid, a division of Rowmark.

Phenolic
   Some people will say that phenolic is not really “plastic” because it’s what’s called a thermosetting material. More about this shortly, but for now let’s say it’s truly in a different “class” than acrylic and the flexible plastics used in this industry. Phenolic is a hard, dense material made by applying heat and pressure to layers of paper or glass cloth impregnated with synthetic resin. These layers of laminations usually consist of cellulose paper, cotton fabrics, synthetic yarn fabrics, glass fabrics or unwoven fabrics. When heat and pressure are applied to the layers, a chemical reaction (polymerization) transforms the layers into a high-pressure thermoset industrial laminated plastic. Chemically, phenolic is in the same family as “melamine” countertop laminates, e.g. “Formica.”
   Although “thermoset plastics” (phenolic) and “thermoplastics” (flexible engraving stock and acrylic) sound similar, they have very different properties and applications. The primary physical difference is that thermoplastics have a softening temperature of 180° F and can be formed with heat and re-melted back into a liquid, whereas thermoset plastics don’t soften or melt when heated and are able to withstand temperatures of 200º-250º F.
   Phenolic is a hard, rigid plastic that is abrasion resistant, heat resistant, strong and chemically inert which is why it is used for very specialized applications in demanding environments. Its ability to resist harsh and extreme environments make it a good choice for industrial applications like machine control panels, data plates, ring tags and legend plates. It is also used for military applications in equipment or vehicles that need to withstand fire or intense abuse and still be readable or able to display information. It can also be used for products like signs and badges, especially when the item needs to look good for a long period of time. However, most shops avoid phenolic whenever possible because it is not considered laserable and its hardness and abrasiveness make it wear carbide (rotary) cutters. It also chips when it’s sawed or drilled.
   Phenolic is typically available from industry suppliers as a three-ply laminate in 1/16" and 1/8" thicknesses in a limited selection of colors. These materials typically have a matte finish on one side and a gloss finish on the other.
   Because phenolic is hard and rigid, it cannot be sheared, die stamped or punched. To cut this material, you will need to saw it; it can also be drilled using carbide drill bits. Rotary engraving with sharp carbide-tipped tools works well on phenolic, but the material should not be laser engraved as it emits toxic, flammable vapors. Standard industrial safety practices should always be used when fabricating phenolic.

Plastic can be cut into different shapes to make useful products. Photo courtesy of Rowmark LLC.

 



Conventional Flexible Engraving Stock
   Conventional plastic engraving stock began replacing phenolic circa 1963 and became a mainstay in the industry for many years. It is a pliable material typically made up of modified acrylic or ABS (Acrylonitrile Butadiene Styrene). In its usual configuration, this thermoplastic consists of two separate extruded sheets, a relatively thin cap layer and a thick core which are then “laminated” together in a large heat press. The cap layer is .008"-.010" thick and is laminated to a contrasting colored core material so that when you engrave through the cap you see the underlying color. Common thicknesses include 1/32", 1/16", 3/32" and 1/8". Three-ply materials are available in 1/16", 1/8" and 1/4" and there is a wide variety of colors and finishes to choose from, including satin, gloss, matte, textured, woodgrains and metallics. Reverse engravable conventional plastic is also available.
   Traditional laminated plastics are prone to variations in thickness. That’s not much of a problem for rotary engraving using a depth nose, but without a nose, you’re likely to experience cutting depth variations.
   A big advantage of this flexible material is that you can easily fabricate it by shearing, die cutting, hole punching, thermobending, heat fusing, solvent welding, etc. The ABS sheet materials are recommended for interior applications while the acrylic-based plastics are UV stable, meaning they will maintain colorfastness in UV conditions for a limited period time, and are able to withstand exterior weather conditions. Since ABS materials are manufactured with a slightly softer resin than acrylic, they have the features of added flexibility and excellent electrical insulation properties in addition to impact resistance and durability.
   Conventional plastic engraving stock is primarily designed for rotary engraving with a carbide cutter. The laminated acrylic materials can be laser engraved, but the ABS materials are not recommended for laser engraving. ABS has a lower melting point which can cause it to warp and burn and, more importantly, it emits toxic fumes when engraved with a laser. Also, the relatively thick cap necessitates deeper engraving so it’s not well-suited for super fine detail or laser engraving since a relatively high power and low speed setting are required to cut through the cap which can result in melting, burning and discoloration. This material can also be marked by hot stamping, screen printing, pad printing and UV-LED/direct printing.
Microsurface Flexible Engraving Stock
   Microsurface flexible engraving stock came onto the scene in the mid-1970s. It is very similar to conventional laminated flexible engraving stocks except that it has a very thin cap layer, typically about .003" thick as opposed to .008"- .010". The manufacturing process is basically a hot stamping operation which involves using heat and pressure to fuse a thin color or pattern coating to the contrasting core material, which is typically made of ABS or modified acrylic. The micro-thin cap on these plastics means you don’t need to engrave very deep (just slightly deeper than .003"), which allows you to engrave more easily and achieve exceptionally fine detail. The thin cap also makes the acrylic microsurface stock very laser friendly since lower power and higher speeds can be used to penetrate the cap. As mentioned, ABS materials are only recommended for rotary engraving. In addition, the microsurface acrylic materials are UV-stable and weatherable, but the microsurface ABS materials are not recommended for exterior applications.
   Nowadays, there is an enormous selection of colors available in microsurface plastics, including metallics, woodgrains and geometric patterns in a variety of different finishes. New “trending” colors are continuously being introduced by manufacturers, so there is always plenty to choose from and new varieties are being introduced all the time.
   Microsurface plastic is available as a two-ply (1/32", 1/16", 3/32", 1/8") and three-ply (1/8") material. Reverse engravable microsurface plastic is also available. In terms of fabricating and marking, you can use all of the same techniques used for conventional laminated flexible engraving stocks.


The color selection in plastic materials today is enormous. Photo courtesy of Rowmark LLC.

Ultra-Thin Flexible Engraving Stock
   This unique plastic is a two-ply material with a very thin impact acrylic core and a very thin cap, typically .003" or less. The overall thickness of these materials is only about .004"-.030". Some of these products also have a pressure-sensitive self-adhesive backing.
   Ultra-thin engraving stock is available in brass and aluminum look-alikes and several colors, woodgrains and marbles, and are mostly sold in sheets although some varieites are available in rolls. The notable characteristic about all of these materials is that they are extremely thin, flexible and bendable so that they can be put on nearly anything, including curved and tapered surfaces like a flashlight or coffee mug. These characteristics also make these materials well-suited for labeling applications. Ultra-thin plastics are usually intended for interior use only.
   Ultra-thin plastic can be rotary engraved or lasered (as long as they are acrylic-based), and they can be fabricated like other plastics through shearing, sawing, drilling, thermobending, etc. Because they are so thin, they can also be cut with simple tools like scissors, a paper cutter or a scoring knife.
Sublimation Plastic
   These “plastics” are designed to withstand temperatures up to 400º F so that full-color images can be sublimated onto the material with a heat press. There are two types of sublimatable plastic available: fiber glass reinforced plastic (FRP) and Subliflex. FRP is 3/32" thick and Subliflex is offered in .030" thickness. Both are available in white with gloss and matte finishes to show off sublimation’s colors.
   FRP is rotary engravable but cannot be laser engraved due to the fiberglass content. This is a rigid material that needs to be cut with a rotary engraving machine or a saw. It is primarily intended for interior use but can be used for short-term exterior applications.
   The thin Subliflex is a flexible material similar to that used for plastic hotel key cards or plastic ID cards, but it doesn’t contain PVC. This is a more versatile material as it can be rotary engraved, laser engraved, sheared and even cut with scissors. The flexible plastic material can also be thermobent into products such as tent signs and is popular for applications such as ID cards. This material is actually two-sided, with one side having a matte finish and the other having a gloss finish.
   Sublimatable plastic in general offers many different applications. Name badges, interior design, personal identification, signage, holiday decorations, key chains and picture frames are just a few of the many sublimatable plastic product applications.



UV-LED/Direct Print Plastics
   Ok, anyone who is looking into direct print knows that since it’s an ink deposition process, you can print on all kinds of things, including paper and cardboard. However, when you’re looking to do a more permanent personalization job, you might want to be confident that the ink will stay on the material!
   UV-LED/direct printing is making waves in the industry as a new method for direct printing color images on a variety of materials, including plastic. Theoretically, you can use a UV-LED/direct printer to print on any of the plastics mentioned in this article, although you will most likely need to use an adhesion promotor to ensure that the ink adheres well. Rowmark says it has done extensive research and testing on its acrylic products to determine which materials are most suitable for UV-LED printing, and the company now identifies which products it recommends for UV print applications (using an adhesion promotor) in its 2016 color chart. Similarly, Gravotech lists printability for its line of plastic and metal materials in The Engraving Source Book (v. 1-29.2).
ADA Flexible Engraving Stock
   This plastic is primarily used to create ADA-compliant signs, including raised lettering and Braille, for the visually impaired. The system consists of two sheets of single-ply modified acrylic plastic, a 1/32" self-adhesive material used for profiling (the raised graphics) and a 1/32", 1/16", 1/8" or 1/4" material used for the back plate. To create raised lettering, you adhere the profile material on top of the back plate, cut through the profile material and weed the excess, leaving raised letters adhered to the back plate. You can then engrave Braille directly into the back plate or apply Braille balls.
   These materials are offered in many different colors with a matte non-glare finish designed to meet the ADA requirements. Rowmark also offers transparent materials for custom color matching needs. ADA materials are UV stable and outdoor weatherable, and can be laser or rotary engraved. You can also use the same fabricating and marking methods you would use with conventional and microsurface stocks.



Conclusion
   As you can see, the choices in plastic are quite vast—maybe even a little overwhelming. It’s a good idea to check the MSDS and ask your supplier for assistance to be sure you are purchasing the right plastic for your application. This is particularly important when the job needs to meet specific criteria, such as ADA-compliance, weatherability, chemical/solvent resistance, military specifications, etc. You’ll also want to make sure the plastic is compatible with the method you will use to mark it. Your equipment supplier(s) will be of help here as well.
   Most of the manufacturers and leading distributors have come out with extensive material selection guides which provide not only color options and thicknesses, but also personalization process compatibility recommendations. Additionally, most of the manufacturers and distributors have knowledgeable people available to discuss material selection for customer applications.
   In an industry that is becoming increasingly creative, having such an extensive selection of plastic substrates can be a great asset to recognition and personalization businesses. You can see from the photos accompanying this article how using different materials and marking methods can produce some fantastic products.
   Take a good look at all of your options—and let your creativity flow.

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