Avoiding Vinyl Failure Part 1: Surface Contimination
By Denise Nathan
Self adhesive failure on any campaign is a costly exercise and can put unnecessary strain on client relations. Today there is a myriad of vinyls to choose from for all types of applications. The sign professional can easily choose the right vinyl and adhesive for the job based on his knowledge and experience and with the help of a sign material supplier, however one factor that is often not determined or controlled by the sign professional is the surface being applied to.
The substrate is often predetermined or specified by the client. Many graphic failures can be caused by an incompatibility with the surface and/or incorrect surface preparation.
Therefore is critical to have an understanding of the surface you are applying to and possible threats to adhesion both short and long term before choosing your media. Surface contaminants can be pre-existing, develop over time or be introduced by the applicator.
Pre-existing surface contaminants such as dirt, grime, grease etc are obvious contaminants and by following recommended cleaning procedures can easily be eliminated. Less obvious are “cure contaminants” which develop over time. Cure contaminants are water or chemicals that exist within a substrate that migrate to the surface and are released as a substrate reaches its ultimate physical property. The time taken for this chemical reaction to be completed is known as cure time. Curing typically occurs with manufactured substrates such as MDO board, fibreglass etc. and painted surfaces. If vinyl is applied before the curing is complete then water/chemicals remain trapped between the surface of the substrate and adhesive and compromise the adhesion or the graphic performance over time.
Contaminants can be introduced during the installation process. Some cleaners and soaps may appear to clean the surface of a substrate but upon evaporation and drying they can actually leave a chemical or soapy residue behind. Soaps containing creams or lotions can lead to further contamination of the surface. When using solvents cleaners, make sure they are fully cleaned off the surface and not just allowed to evaporate leaving dirt behind. Any solvent residue can also interfere with graphic adhesion.
Cleaning tools are also important. Wiping your surface with cloth towels can leave lint and dust behind. Commercial paper towels can also contain chemicals. Many experts recommend plain domestic paper towels.
Applying vinyl to a contaminated surface can lead to obvious problems such as failure of the graphic to adhere, lifting or shrinking. When applying to surfaces affected by cure contaminants the consequences are bleeding and out gassing. Bleeding occurs when a natural property of the substrate like oil or resin rises to the surface. This can result in application difficulties, failure of the adhesive, lifting and peeling and dirt and air becoming trapped under the surface of the vinyl.
Out gassing is similar to bleeding but in this case moisture is released in a gaseous statefrom the substrate. The gases are trapped between the substrate and adhesive layer and cause the appearance of tiny bubbles. Not only does this look unsightly but if the gas is of a chemical nature it can also lead to adhesive failure. Painted substrates may look and feel dry but if you can still smell the solvents then out gassing is still occurring. Some paint manufacturers recommend waiting for three weeks to apply graphics to newly painted vehicles. With so many paints on the market checking with your paint supplier and testing is the best option as what might be three weeks for one paint, may be shorter or longer for another. To determine if the surface is properly cured apply a small piece of film to the surface for 24 hours. If bubbles appear, water or chemical cure is still occurring.
Having an awareness of your substrate and following recommended cleaning procedures is the first step to ensure the best performance of your graphics.