By Amber E. Watson
A good balance of initial tack and permanent adhesion make for the best vehicle wrap media. Repositionability allows installers to correctly position a graphic to avoid wrinkles, creases, and bubbling by expertly manipulating the substrate. Understanding what influences repositionable media composition, the characteristics of the adhesive, and outside forces that affect application aid in successful installs.
A number of components are found in the chemical makeup of both vinyl and film that make them repositionable. What a print service provider (PSP) or installer should look for varies based on the complexity of the job and the experience level of the installer.
A general rule of thumb, according to Nathan Hurst, marketing specialist, FDC Graphic Films, Inc., is the media should adhere to a surface, lift, and reapply without damaging the adhesive or distorting the film.
The size of the graphic should be considered. “This is especially important if you are a one person operation. If you are applying a 4×8-foot graphic, the repositionable adhesive will allow more forgiveness during application versus a standard permanent adhesive that will have an immediate bond,” explains Craig Campbell, graphic products market manager, ORAFOL Americas.
“Understand the durability requirements. What is the expected life of the wrap? Select the materials that best match your durability requirements and make sure to use an overlaminating film that will protect the graphic and assure the advertiser’s message continues to impress,” shares Jodi Sawyer, market development specialist, product branding, FLEXcon.
Jaimie Mask, product manager, LexJet Corporation, recommends a polymeric vinyl over a monomeric vinyl, or a high-performance cast vinyl. Mask explains that a polymeric vinyl uses higher quality plasticizers that provide durability on more basic wrap projects without having to move to a more expensive cast vinyl. Polymeric vinyl offers stability, and can be used over varying surfaces such as rivets, corrugations, and moderate curves, as well as on flat planes.
Linda Ebbinghaus, car wraps training coordinator, Avery Dennison Graphics Solutions, says that print providers should look for material with low initial tack, and the ability to slide the graphics into place fairly easily. “In addition, the adhesion of the graphic must build so the graphic does not lift in deep channels or compound curves. This combination provides for quicker application,” she notes.
There is a difference between repositionability—snap up—features and slideability, cautions Tim Boxeth, business manager, 3M Commercial Graphics. “PSPs should make sure that the film is truly repositionable, meaning it has the ability to snap up and reposition after being lightly applied to the substrate. Both are critical. Snap up saves time and costly mistakes because the installer is afforded attempts at getting it right.”
The stickiness or adhesiveness of a repositionable substrate must walk a fine line between staying in place once a wrap is completed, while simultaneously providing enough snap up in its initial tack. The lower the initial tack, the longer it takes for the wrap to permanently adhere to the surface.
“Hardness, smoothness, texture, and coating type all play a role in determining an adhesive’s initial tack,” explains Jason Yard, marketing manager, MACtac Distributor Products. “Usually a removable or repositionable adhesive is harder and more costly to develop.” Adhesives are made of various polymers, flow agents, and tackifiers. Proprietary technologies allow for slideability as well.
Campbell classifies a repositionable media as featuring a progressively setting permanent adhesive. “In other words, the adhesive is designed not to reach its permanent state until after a designated period of time.”
Many factors make a media repositionable. “Polymers, such as pigments, act as fillers, reducing the initial tack level of an adhesive,” explains Ritchie Daize, business development manager, Arlon Graphics, LLC. Or an air egress pattern limits the amount of adhesive that makes initial contact with the substrate. A third method involves using a substrate laminate. “Substrate laminates add a layer of vinyl, making the overall graphic thicker and stiffer; this makes it easier to snap up, giving the applicator a sense of greater repositionability,” he adds.
Hexis S.A. uses a structured adhesive with a pyramidal pattern. When the vinyl is applied initially only the peaks of the pyramids are in contact with the surface, thus the initial contact surface is small with a consequently lower tack. Once the structure in the adhesive is flattened by squeegeeing, full adhesion is achieved. Hexis adhesives are specifically pressure sensitive, rather than pressure activated, which simplifies the work of the installer.
Ritrama mainly uses solvent-based adhesives on repositionable clear films to aid in repositionability, as solvent-based adhesives can be applied with a wet application method. This also aids in cleaning any debris that may have found its way into the adhesive.
Although repositionable media provides an almost error-free wrap, it is not without challenges. Ensuring adhesion once a wrap is final involves careful work and observation by the installation team. By nature, repositionable media presents more opportunity to overstretch the material while in use.
“As stretchability increases, it becomes more difficult to reposition the film without distorting the graphic design,” cautions Martin Kugler, corporate communications manager, Hexis. “The ratio between stretchability and repositionability is always a compromise.”
Daize warns that if the adhesive has an extremely low initial tack, it takes a lot of post heating to activate the adhesive and make the bond permanent. “Many adhesion failures are due to applicators not knowing if they have post heated extremely repositionable adhesives enough to activate permanent adhesion levels,” he says.
The installation surface affects how well the media adheres to it. “Rough surfaces often lower the amount of contact; therefore lowering the initial tack on the surface. Conversely, very smooth surfaces, like glass, usually form a stronger initial bond making the film less repositionable,” explains Hurst.
During installation, if a blemish is noticed, avoid the costly mistake of snapping up the whole panel to fix it. Daize recommends using a heat source to heat a small section of vinyl six inches beyond the blemish. Re-squeegee this area firmly and let cool. Doing so it creates an anchor point with permanent adhesion values. The last step is to snap up the vinyl necessary to fix the blemish; the vinyl should hold at the anchor point preventing the entire panel from lifting up.
Robert Rundle, viscom market manager, Ritrama, also warns against static when repositioning a graphic, as it attracts dirt and debris. “This reduces the adhesion area and can potentially lead to a failure, especially if the vinyl is a lower grade and susceptible to shrinkage.”
In terms of removing or changing out a graphic created with repositionable media, Mask reminds PSPs that beyond one year, the adhesive becomes permanent and more durable. “Remove the graphic prior to one year for ease of removal and no residue. If after a year, use a heat source to help soften the adhesive. This will aid in removing the graphic with little to no residue.”
Vehicle wraps are a prime application for repositionable media. The many surface challenges presented necessitate a conformable and forgiving substrate.
Typically more experienced installers require less repositionability and prefer a higher initial tack. Novice installers require more repositionability, but no one is perfect when it comes to lining up graphics. The benefit of a repositionable adhesive is crucial.
Apr2014, Digital Output